N. F. Bourne, G. D. Heritage, and G. Cawdell Department of Fisheries and Oceans...

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Scientific Excellence • Resource Protection & Conservation • Benefits for Canadians Excellence scientifique • Protection et conservation des ressources • Benefices aux Canadiens

Intertidal Clam Surveys of British Columbia -1991

N. F. Bourne, G. D. Heritage, and G. Cawdell

Biological Sciences Branch Department of Fisheries and Oceans Pacific Biological Station Nanaimo, British Columbia V9R 5K6

1994

Canadian Technical Report of Fisheries and Aquatic Sciences 1972

Fisheries and Oceans

Peches et Oceans Canada

Canadian Technical Report of Fisheries and Aquatic Sciences

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Canadian Technical Report of

Fisheries and Aquatic Sciences 1972

1994

INTERTIDAL CLAM SURVEYS OF BRITISH COLUMBIA - 1991

by

N. F. Bourne, G. D. Heritage and G. Cawdell 1

Biological Sciences Branch Department of Fisheries and Oceans

Pacific Biological Station Nanaimo, British Columbia

V9R 5K6

1Present address: 205-254 Gorge Road East Victoria, B.C. Canada V9A 6W4

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~ Minister of Supply and Services Canada 1994 Cat. No. Fs 97-6/1972E ISSN 0706-6457

Correct citation for this publication:

Bourne, N. F., G. D. Heritage, and G. Cawdell. 1994. Intertidal clam surveys of British Columbia - 1991. Can. Tech. Rep. Fish. Aquat. Sci. 1972: 155 p.

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TABLE OF CONTENTS

Page

LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii

ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix

PART I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 CAMPBELL RIVER AREA SURVEY . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Von Donop Inlet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Physical Description of Beaches . . . . . . . . . . . . . . . . . . . 3 Clam Populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Marina Island . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Physical Description of the Beach . . . . . . . . . . . . . . . . . . 5 Clam Populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Kanish Bay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Physical Description of Beaches . . . . . . . . . . . . . . . . . . . 6 Clam Populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Cameleon Harbour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

PART II ................................................ . BELLA BELLA TO QUEEN CHARLOTTE STRAIT SURVEY .......... .

8 8

Seaforth-Spiller-Return Channel Area . . . . . . . . . . . . . . . . . . . . 8 Physical Description of Beaches . . . . . . . . . . . . . . . . . . . 8 Clam Populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Other Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0

Gale Passage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0 Physical Description of Beaches . . . . . . . . . . . . . . . . . . . 1 0 Clam Populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Other Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Thompson Bay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Physical Description of Beaches . . . . . . . . . . . . . . . . . . . 13 Clam Populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Other Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Stryker Island . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Physical Description of Beaches . . . . . . . . . . . . . . . . . . . 14 Clam Populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Other Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Spider Anchorage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

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Physical Description of Beaches . . . . . . . . . . . . . . . . . . . 17 Clam Populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 7

Kwakshua Channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Physical Description of Beaches . . . . . . . . . . . . . . . . . . . 19 Clam Populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Rivers Inlet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Physical Description of Beaches . . . . . . . . . . . . . . . . . . . 21 Clam Populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Other Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

West Gilford Island . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Physical Description of Beaches . . . . . . . . . . . . . . . . . . . 22 Clam Populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Indian Channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Physical Description of Beaches . . . . . . . . . . . . . . . . . . . 24 Clams Populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 BUTTER CLAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 LITTLENECK CLAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 MANILA CLAMS ...................................... 26 STUNTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 COMMERCIAL POTENTIAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

. OTHER SPECIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

GENERAL SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

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LIST OF FIGURES

Page

Fig. 1. landings of intertidal clams, razor, butter, littleneck, manila and mixed, in commercial fisheries in British Columbia 1951-1991. . . . . . . . 49

Fig. 2. Map of northern Strait of Georgia showing location of beaches sampled in May, 1991 ................................... 51

Fig. 3. Map of the British Columbia coast, from Bella Bella to Alert Bay, showing the location of beaches (circled numbers) surveyed in July 1991. 1. Seaforth-Spiller Return Channel, 2. Gale Passage, 3. Thompson Bay, 4. Stryker Island, 5. Spider Anchorage, 6. Kwakshua Channel, 7. Rivers Inlet, 8. West Gilford Island, 9. Indian Channel. . . . . 53

Fig. 4. Map of Von Donop Inlet showing location of three beaches surveyed, May 28, 1991. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Fig. 5. length frequency of butter clams from Von Donop Inlet and Kanish Bay, May 28-29, 1991. . ................................ 57

Fig. 6. length and age frequencies of littleneck clams from Von Donop Inlet, May 28, 1991. . ...................................... 59

Fig. 7. Growth rate of littleneck clams from Von Donop Inlet and Kanish Bay, May 28-29, 1991. . ................................ 61

Fig. 8. length and age frequencies of manila clams from Von Donop Inlet, May 28, 1991. . ...................................... 63

Fig. 9. Growth rate of manila clams from Von Donop Inlet and Kanish Bay, May 28-29, 1991 ...................................... 65

Fig. 10. Map of Marina Island showing sampling location, May 28, 1991 .... 67 Fig. 11. Length and age frequencies of littleneck clams from Marina Island,

May 28, 1991. . ...................................... 69 Fig. 12. Length and age frequencies of manila clams from Marina Island,

May 28, 1991. . ...................................... 71 Fig. 13. Map of Kanish Bay showing the location of three beaches surveyed,

May 29, 1991. . .. ' .................................... 73 Fig. 14. Length and age frequencies of littleneck clams from Kanish Bay,

May 29, 1991. . ...................................... 75 Fig. 15. length and age frequencies of manila clams surveyed from Kanish

Bay, May 29, 1991 ..................................... 77 Fig. 16. Map of the Cameleon Harbour showing the beach visited, May 29,

1991. 0 •••••••••••••••••••••••••••••••••••••••••••• 79 Fig. 17. Map of the Seaforth-Spiller-Return Channel area showing the

location of beaches surveyed July 8, 1991 ..................... 81 Fig. 18. Length and age frequencies of littleneck clams from the Seaforth

Spiller-Return Channel area, July 8, 1991. . . . . . . . . . . . . . . . . . . . . . 83 Fig. 19. Length and age frequencies of manila clams from the Seaforth

Spiller-Return Channel area, July 8, 1991. . . . . . . . . . . . . . . . . . . . . . 85

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Fig. 20. Growth rate of manila clams from the Seaforth-Spiller- Return Channel area, July 8, 1991. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

Fig. 21. Map of Gale Passage showing the location of beaches surveyed July 9-10, 1991 ....................................... 89

Fig. 22. Length and age frequencies of butter clams from Gale Passage, July 9-10, 1991 ....................................... 91

Fig. 23. Length and age frequencies of littleneck clams from Gale Passage, July 9-10, 1991 ....................................... 94

Fig. 24. Length and age frequencies of manila clams from Gale Passage, July9-10,1991 ....................................... 95

Fig. 25. Growth rates of manila clams from North Gale Passage, and from the South Gale Passage-Thompson Bay area, July 9-1 0, 1991. . . . . . . 97

Fig. 26. Map of the Thompson Bay area showing the location of beaches surveyed, July 10, 1991. . ............................... 99

Fig. 27. Length and age frequencies of butter clams from the Thompson Bay area, July 10, 1991 ................................... 101

Fig. 28. Length and age frequencies of littleneck clams from the Thompson Bay area, July 10, 1991. . .............................. 103

Fig. 29. Length and age frequencies of manila clams from the Thompson Bay area, July 10, 1991 ................................ 105

Fig. 30. Map of the Stryker Island area showing the location of beaches surveyed July 11, 1991 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 07

Fig. 31. Length and age frequencies of butter clams from the Stryker Island area,July11,1991 ................................... 109

Fig. 32. Length and age frequencies of littleneck clams from the Stryker Island area, July 11, 1991. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

Fig. 33. Length and age frequencies of manila clams from the Stryker Island area, July 11, 1991 ................................... 113

Fig. 35. Map of the Spider Anchorage area showing the location of beaches surveyed, July 4-6 and 12, 1991. . . . . . . . . . . . . . . . . . . . . . . . . . 117

Fig. 36. Length and age frequencies of butter clams from the Spider Anchorage area, July 12, 1991. . . . . . . . . . . . . . . . . . . . . . . . . . . 119

Fig. 37. Length and age frequencies of littleneck clams from the Spider Anchorage area, July 12, 1991 . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

Fig. 38. Length and age frequencies of manila clams from the Spider Anchorage area, July 12, 1991. . . . . . . . . . . . . . . . . . . . . . . . . . . 123

Fig. 39. Growth rate of manila clams sampled in the Spider Anchorage area, July 12, 1991 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

Fig. 40. Map of the Kwakshua Channel area showing the location of beaches surveyed, July 13, 1991. . . . . . . . . . . . . . . . . . . . . . . . . . 127

Fig. 41. Length and age frequencies of butter clams from the Kwakshua Channel area, July 13, 1991. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

Fig. 42. Length and age frequencies of littleneck clams from the Kwakshua Channel area, July 13, 1991 ............................. 131

Fig. 43. Length and age frequencies of manila clams from the Kwakshua Channel area, July 13, 1991. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

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MISSING PAGE

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LIST OF TABLES

Page

Table 1 . Location of four areas in the Campbell River area sampled during an intertidal clam survey, May 28 and 29, 1991. . . . . . . . . . . . . . . . . . . 33

Table 3. Location of intertidal beaches sampled during an intertidal clam survey in the Central Coast and Alert Bay areas of British Columbia, 4 - 16 July, 1991 ....................................... 35

Table 4. Denisties of butter, littleneck and manila clams, expressed as clams per square meter, on beaches surveyed in the Central Coast and Alert Bay areas, July 8-16,1991. R = dug with rake or scraper, F = dug with potato fork ....................................... 36

Table 5. Number, shell length or height and age of horse clams, cockles and soft-shell clams on beaches surveyed in the Central Coast and Alert Bay areas, 4-16 July, 1991. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Table 6. Stages in gonadal development in manila clams in the SeaforthSpiller-Return Channel and South Gale Passage-Thompson Bay areas in the north coast district of British Columbia, 1991. . . . . . . . . . . . . . . 47

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ABSTRACT


Results of 1991 surveys to assess populations of commercially important intertidal clams on selected beaches in the Strait of Georgia, north coast district and Queen Charlotte Strait areas of British Columbia are presented.

Butter clams, Saxidomus giganteus, were widely distributed on beaches throughout the sampling area. In general, a wide distribution of size and age classes indicated recruitment has been consistent in recent years.

Littleneck clams, Protothaca staminea, were the most common clam species found in all sampling areas. A wide distribution of size and age classes indicated consistent recruitment in recent years.

Manila clams, Tapes philippinarum, were found in the Strait of Georgia and Bella Bella areas but were scarce elsewhere. The northern boundary for manila clam populations in British Columbia is the SeaforthMathieson Channel area. Manila clams were not found in abundance south of the Bella Bella area (statistical area 7) and were rare in the Queen Charlotte Strait area. In locations where manila clams were found there was a preponderance of larger, older clams which may indicate erratic recruitment.

Limited information is also presented on populations of cockles, Clinocardium nuttallii, horse clams, Tresus capax, and soft-shell clams, Mya arenaria found during the surveys.

The potential for commercial exploitation of clam species found in the survey area is discussed.

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RESUME


Nous presentons ici les resultats des releves menes en 1991 pour evaluer les populations de bivalves fouisseurs commercialement importants sur certaines plages du detroit de Ia Reine-Charlotte, en Colombie-Britannique.

Les palourdes jaunes, Saxidomus giganteus, etaient largement reparties sur les plages dans toute Ia zone echantillonnee. De fac;on generale, on observe une large distribution des classes de taille et d'age, ce qui indique un recrutement equilibre ces dernieres annees.

La palourde du Pacifique, Protothaca staminea, etait l'espece trouvee Ia plus communement dans toutes les zones echantillonees. La large distribution des classes de taille et d'age indiquait un recrutement equilibre ces demieres annees.

On a trouve des palourdes janonaises, Tapes philippinarum, dans les regions du detroit de Georgie et de Bella Bella, mais l'espece etait rare ailleurs. La limite septentroinale des populations de cette espece en Colombie-Britannique est Ia region des passages Seaforth-Mathieson. Les palourdes japonaises n'etaient pas abondantes au sud de Ia region de Bella Bella (district statistique 7), et elles etaient rares dans Ia region du detroit de Ia Reine-Charlotte. Dans les zones ou se trouvaient des palourdes japonaises, on observait une predominance de coquillages ages et de grande taille, ce qui peut indiquer un recrutement erratique.

Nous presentons aussi quelques donnees limitees sur les populations de coque, Clinocardium nuttallii, de fausse-mactre, Tresus capax, et de mye, Mya arenaria, observees pendant les releves.

Nous analysons le potentiel d'exploitation commerciale des coquillages trouves dans Ia zone d'etude.

INTRODUCTION

British Columbia intertidal clam resources have supported commercial fisheries for over one hundred years (Quayle and Bourne 1972). Four clam species have comprised almost all the landings: razor, Siligua patula; butter, Saxidomus giganteus; littleneck, Protothaca staminea; and manila, Tapes philippinarum. Occasionally there have been minor landings of other species including: horse clams, Tresus capax and T. nuttallii; cockles, Clinocardium nuttallii and soft-shell clams, Mya arenaria.

The razor clam fishery has been small and located almost entirely on oceanic beaches between Masset Inlet and Rose Spit on Graham Island, Queen Charlotte Islands. Annual landings have never been large and were generally under 100 t (tonnes) until recently, when they reached about 140 t (Fig 1).

For many years butter clams were the main species harvested in the commercial fishery. Approximately half the coast-wide catch came from the north coast district until 1963 when that fishery for intertidal clams was closed because chronic low levels of PSP (paralytic shellfish poisoning) were found in butter clams in many north coast areas (Quayle 1969). Although a monitoring system was established to allow harvest of butter clams under permit, the north coast fishery was never re-established. Recently the harvest of butter clams has become economically unattractive because of high processing costs and coast-wide landings have declined to low levels (Fig 1 ).

Since the mid 1970's, the main species of intertidal clams harvested in commercial fisheries have been steamer clams, littleneck and manila clams, (Fig 1) and until 1992 all landings were from the south coast district. In recent years manila clams have been the main target species and have accounted for over 90% of annual intertidal clam landings in some years (Fig 1 ). This led to increased harvesting pressure on many beaches in the south coast district as the industry tried to meet market demand. New management policies were initiated to reduce effort and surveys of some beaches were undertaken to assess the status of existing stocks to determine if beaches could be opened to annual harvesting. In addition, industry and managers enquired whether beaches in the north coast district could be opened for commercial harvest of intertidal clams, particularly steamer clams.

In 1991 two surveys were carried out to assess intertidal clam resources in selected areas. In May, a two day survey was undertaken in the Campbell River area, statistical areas 13 and 15 (Fig 2) and in July a two week survey was carried out from the Bella Bella area (statistical area 7) south to the Alert Bay area (area 12). The second survey also determined distribution and abundance of manila clams in that area (Fig 3).

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Results of both surveys are presented separately. A brief description of the physical characteristics of each beach is presented, followed by observations of clam populations in both areas.

SURVEY METHODS

Beaches selected for sampling in both surveys were chosen from chart surveys, previous experience or from information supplied by Fishery Officers.

Sampling was undertaken after the manner described by Bourne and Cawdell ( 1992). A brief survey was made of each beach to assess the presence or absence of intertidal clams and determine the area of the clam bearing part of the beach prior to sampling. Slope of the beach and substrate type were recorded. As in the 1990 survey, it was decided to survey as many beaches as possible in an area rather than sample one or two beaches intensively, in order to obtain a general estimate of clam distribution and abundance.

Two types of samples were taken during the surveys. The first was undertaken primarily to assess butter and littleneck clam populations. Random plots of 0.25 or 1.0 m2 (square meter) were marked out in the clam bearing part of the lower third of the intertidal beach. The plots were dug with forks to a depth of about 35 em. The soil was worked through the fingers and reworked back into the plots and all clams removed. All sampled clams were placed in plastic bags and labelled for later measurement. The second type of sampling was undertaken primarily to assess manila clam populations. Random plots of 0.25m2 were marked out in sand-gravel areas of the central part of intertidal beaches amd dug with rakes, or scrapers, to a depth of about 15 em. The soil was worked through the fingers and reworked back into the plots. All sampled clams were placed in plastic bags and labelled for later measurement.

In addition, many other beaches in the survey areas were visited briefly to assess for the presence or absence of manila clams. Numerous exploratory plots were dug on these beaches. Numbers of clams were recorded but no samples were retained. In addition observations were made on many beaches for the presence or absence of manila clam shell at the high tide line and on large rocks where birds drop and break clams.

Shell length of each sampled clam was measured to the nearest mm with vernier calipers. Age of most clams was determined by counting annuli (Quayle and Bourne 1972). In addition, samples of butter and littleneck clams from some areas, and a sample of manila clams from most areas were taken and the

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shell length at each annuli measured to the nearest mm. Means of shell lengths at annuli were calculated to provide a measurement of age distribution and growth rates of populations of butter, littleneck and manila clams at most locations.

PART I

CAMPBELL RIVER AREA SURVEY

Four locations were surveyed in the Campbell River area on May 28 and 29, 1991: Von Donop Inlet, Marina Island, Kanish Bay and Cameleon Harbour (Fig 2, Table 1). At Von Donop Inlet and Marina Island, sampling was confined to assessment of steamer clam populations. Sampling in Kanish Bay included assessment of butter, littleneck and manila clam populations. No sampling was undertaken at Cameleon Harbour because the tide was too high to permit adequate sampling.

Von Donop Inlet

Three beaches were sampled in Von Donop Inlet (Fig 4).

Physical Description of Beaches

Beach 1 . A beach with a gentle slope located on the south side of the entrance to Von Donop Inlet that was about 0. 75 ha (hectares) in area (Fig 4). Substrate of the lower beach was mud-gravel-shell that was good habitat for butter clams. Substrate of the upper portion was mostly sand-gravel with some rock. There was evidence of previous digging.

Beach 2. An extensive beach with a gentle slope located at the head of the west arm of Von Donop Inlet. Total area of this beach was about 2 ha but only about 10-15% was suitable as clam habitat (Fig 4). Most substrate was soft mud with some patches of firmer gravel substrate. Considerable organic material was present in the substrate and the smell of hydrogen sulphide was evident during digging. There was evidence of past digging.

Beach 3. A beach with a moderate slope located at the end of the Inlet that was really two beaches separated by a large rock outcrop. The area was about 1.5 ha and the part of the beach on the other side of the rock outcrop had a

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similar area. Substrate of the lower portion was soft mud; the upper part had a firmer substrate with gravel. There was evidence of extensive past digging.

Clam Populations

Six 0.25 m2 plots were dug at the first two beaches and seven 0.25 m2 plots were dug at the third beach.

Butter Clams. Butter clams were found only at the first beach and all were sublegal size, < 63 mm shell length and ranged from 28-61 mm (Table 2; Fig 5). This was not surprising since the main area of butter clam abundance is the lower third of the intertidal beach and sampling was confined to the upper part of the beach. Further, sampling was done with rakes and scrapers only to a depth of 15 em and most butter clams were probably missed because of shallow digging. The lower portion of the beach was good butter clam habitat. One incidental 0.25 m2 plot on the lower portion of the beach had 20 butter clams.

Littleneck Clams. Littleneck clams were common at the first and third beaches but not at the second, densities ranged from 0-140 m-2 (Table 2). Most littleneck clams (88% and 86%) at beaches 1 and 2 were sublegal size, < 38 mm shell length; at beach 3, 62% were legal size, ~ 38 mm shell length (Fig 6). The low number of littleneck clams at beach 2 was not unexpected because most of this beach was poor habitat for littleneck clams. The wide age class distribution indicated good recent recruitment (Fig 6).

Growth of littleneck clams was similar to that observed in other areas of the Strait of Georgia (Quayle and Bourne 1972); it required 3.5-4 years to attain the legal size (Fig 7).

Manila Clams. Densities of manila clams ranged from 0-408 clams m-· (Table 2). Clams were more abundant at the first beach. Low densities occurred in some plots at beach 3 because they were dug on the lower portion of the beach. Plots dug in the upper portion of this beach had good numbers of manila clams. Most manila clams at Beach 1 were sublegal size (81 %) but at Beaches 2 and 3 legal sized clams were more prevalent (58% and 57%) (Table 2; Fig 8). A wide size and age distribution of manila clams indicated good recent recruitment (Fig 8).

Growth of manila clams was similar to that observed at other locations in the Strait of Georgia; it required about 3.5 years to attain the legal size (Fig 9).

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Marina Island

There was an extensive beach along the west side of Marina Island that was exposed to northwest winds (Fig 1 0). A 2 km expanse from Shark Spit southward along the west side of the Island was sampled.

Physical Description of the Beach

The beach along the northwest side of Marina Island varied in width from about 100-300 m and had a gentle slope. The substrate was mostly sandgravel, but there were large numbers of huge boulders along the beach. An oyster lease was present on one part of the beach.

Clam Populations

Over thirty sample plots were dug with rakes or scrapers. Plots were dug in sand-gravel areas between the large rocks in the mid to upper portion of the beach. Very few clams of any species were found in most samples, although patches of manila and littleneck clams were scattered along the upper part of the beach in the sand-gravel substrate. It was difficult to estimate the area of these clam bearing areas, but it was probably about 0.2 ha. Four plots were dug in these clam bearing patches.

Butter Clams. No butter clams were found on this beach. This was expected because of the exposed nature of the beach and the fact that most sampling occurred in the mid and upper part of the beach.

Littleneck Clams. Densities of littleneck clams were low and ranged from 0-40 clams m-2 (Table 2). The low number of littleneck clams was probably due to sampling being confined to the high intertidal area. Most littlenecks (59%) were sublegal size. Random sampling in lower parts of the beach did not produce large numbers of littleneck clams. Length and age frequencies showed most clams were between 30-40 mm shell length and 3-5 years in age (Fig 11 ). Many littleneck clams were stunted probably because of high beach location.

Growth rate was not determined because of the severe stunting.

Manila Clams. Four plots were dug in the small area where manila clams were found; densities ranged from 60-248 clams m-2 (Table 2). Most manila clams (63%) were sublegal size and many were stunted (Fig 12). Fishery Officers reported that commercial harvesting had occurred on this beach during the previous season. However, except for these patches, no other concentrations of manila clam were found in the beach. Length and age frequencies showed most clams were between 30-40 mm shell length and 3-5 years in age (Fig 1 2).

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Growth rate of manila clams was not determined because of severe stunting.

Kanish Bay

Three beaches were surveyed in this area north of Seymour Narrows, although sampling was confined to the first and third beaches (Fig 13).


Beach 1 . An extensive beach located at the head of Kanish Bay (Small Inlet) which had a clam bearing area of about 1.5 ha (Fig 13). Most of the substrate was soft mud but there were areas with firmer sand-gravel substrate scattered throughout the beach and around the perimeter which was good habitat for butter and littleneck clams. There was a considerable amount of rock along the sides and in other parts of the beach.

Beach 2. A beach located outside Small Inlet between an island and a peninsula of Quadra Island with a clam bearing area of about 0.5 ha (Fig 13). There was evidence of logging activity above and on this beach. Most of the beach was soft mud but there were a few firm sand-gravel areas that were suitable habitat for clams. Much rock made digging difficult. A few test plots were dug but no samples were retained.

Beach 3. A beach in a bay on the north side of Kanish Bay west of beach 2 with an area of about 1 ha (Fig 13). Logging activities had occurred above and on the beach and much of the subsurface substrate had logging debris. The substrate was soft mud, but there were firm sand-gravel patches that were good clam habitat. Much rock made digging difficult. Fishery Officers reported past commercial harvesting on this beach. Two plots were sampled by fork from the lower third of the beach and two plots were sampled by rake in the upper beach to assess manila clam populations.

Clam Populations

Butter Clams. Butter clams were moderately abundant at Beach 1 but few were found at Beach 3 (Table 2). All were legal size which indicated no recruitment in recent years (Fig 5).

Littleneck Clams. Littleneck clams were common at both Beaches 1 and 3; densities ranged from 0-120 clams m-2 (Table 2). At Beach 1 all clams were large, but at Beach 3 both legal and sublegal sized clams were present (Fig 14). Length and age frequencies showed a preponderance of larger and older clams.

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Growth of littleneck clams in Kanish Bay was similar to that at Von Donop Inlet and other parts of the Strait of Georgia (Fig 7).

Manila Clams. No live manila clams were found on Beaches 1 and 2, however, some old dead shells were found at the high tide line. Live manilas were found in two small gravel patches high in the intertidal area at Beach 3. These gravel patches had a combined area of about 500 m2

• Densities were 48 and 112 clams m-2 (Table 2). Shell lengths ranged from 25-49 mm and age from 2-5 years; most were 4 and 5 years old (Fig 15).

Growth of manila clams in Kanish Bay was slower than recorded in Von Donop Inlet; it required 4-4.5 years to attain legal size (Fig 9).

Cameleon Harbour

A brief visit was made to a beach in Cameleon Harbour on the north side of Sonora Island in Nodales Channel (Fig 16). The tide was too high to adequately sample for manila clams. However, recent dead manila clam shell was found there along with one live Pacific oyster, Crassostrea ~·

DISCUSSION

Extensive commercial harvesting, mostly for manila clams, has occurred in Von Donop Inlet and on the northwest side of Marina Island in recent years. Results of this survey showed that harvestable populations of littleneck and manila clams remain in both areas. lnidcations were found of recent recruitment of both species that would insure continued stocks for commercial harvest in future years. There were harvestable populations of littleneck clams in Kanish Bay, however, populations of manila clams appeared to be too limited to support commercial harvest even at todays prices.

It is interesting to note that manila clams were found in Kanish Bay and recently dead shell in Came leon Harbour. Both areas are north of Seymour Narrows, which was thought to be a biological barrier to northward spread of this species (Quayle and Bourne 1972; Bourne 1982). Whether manila clams have actually bred in these areas, or the areas were continually supplied with larvae from areas south of Seymour Narrows, is unknown. There were five year classes in Kanish Bay which indicated that local breeding had probably occurred.

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PART II

BELLA BELLA TO QUEEN CHARLOTTE STRAIT SURVEY

The 1991 Bella Bella to Queen Charlotte Strait survey was a continuation of 1990 work that assessed intertidal clam populations and determined manila clam distribution in the north coast district. In 1991, over ninety beaches were sampled in nine areas that extended from Seaforth Channel in Fishery Statistical Area 7 (FSA 7) to the Alert Bay area in FSA 12 during the period July 8-16, 1991 (Table 3; Fig 3). Sampling was by rakes, scrapers and forks.

Seaforth-Spiller-Return Channel Area

Five beaches were sampled and another five visited in the SeaforthSpiller-Return Channel area (Fig 17). The clam bearing area of beaches and extent of clam populations in this area was probably larger than recorded because the flooding tide curtailed sampling. This could lead to underestimation of clam populations.

The lower portion of many beaches appeared to have soft substrates and many eel grass beds.


Beach 1 . Several small beaches with steep to gentle slopes located among the Foote Islands with a total area of about 0.2 ha (Fig 17). The substrate was shell-sand-gravel sometimes forming shallow layers over rock outcrops.

Beach 2. A gently sloped beach located on the south side of Morehouse Bay with an area of about 1 ha (Fig 17). The substrate was gravel-mudsmall stones.

Beach 3. A beach with a gentle slope situated on the east side of Raven Cove with an area of about 0.5 ha (Fig 17). The substrate was mostly gravel-mud with some small rock.

Beach 4. A gently sloped beach located on the west side of Wigham Cove with an area of about 0.5 ha (Fig 17). The substrate was gravel-shell-mud with some rock.

Beach 5. A small beach with a gentle slope located on the north side

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of Yeo Cove with an area of about 0.2 ha (Fig 17). The substrate was loose gravelsand that made digging easy.

Clam Populations

Surveys in this area were confined mainly to assessment of manila clam populations and all sampling was done with rakes or scrapers. The flooding tide permitted sampling for only about 2. 5 hours.

Butter Clams. Only a few sublegal sized butter clams were found in one plot at Beach 4 and in two plots at Beach 5, (Table 4). This was not surprising because sampling was by rakes and scrapers to shallow depths in the substrate and confined to the upper part of beaches.

Littleneck Clams. Littleneck clams were common at all sampling sites; densities ranged from 4-284 m-2 (Table 4). Most littleneck clams (81.7 to 100%) were sublegal size (Fig 18). All littleneck clams were pale brown and many were badly stunted, making aging difficult. Severe stunting may have been due to sampling being confined to the upper portion of intertidal beaches rather than sampling in more optimum habitats in lower parts of the beach.

Shell lengths of littlenecks ranged from 14-44 mm, however, there was a preponderance of older year classes, 5-8 years (Fig 18). This indicated slow growth, probably caused by stunting.

Manila Clams. Manila clams were found at all sampling sites and densities ranged from 4-304 clams m-2 (Table 4). Densities were low in the Foote Islands but high elsewhere, and high on beaches 3-5.

Most manila clams (50 to 90.6%) were legal size or larger; the largest was 57 mm shell length (Table 4 and Fig 19). Age distribution showed most manilas were 4-7 years of age. The absence of small manilas indicated that recruitment had been restricted in this area in recent years.

Growth of manila clams in the Seaforth-Spiller-Return Channel area was slightly slower than observed under optimum conditions in the Strait of Georgia. It required about 4 years to attain a shell length of 38 mm (Fig 20).

Five other beaches (marked Von Fig 17) were visited briefly. In areas, other than the Foote Islands (Beach 1 ), there was much dead manila clam shell on the beaches. Limited sampling indicated manila clams were present in all areas, probably in sufficient quantities to support commercial harvesting. Manila clams have been present in this general area for at least ten to fifteen years.

Other Species. One cockle was found at Beach 2 and one soft-shell

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clam at Beach 2 and four at Beach 4 (Table 5). Soft-shell clams were common at higher beach levels.

Other Observations

Samples of gonads from 25 manila clams were preserved, sectioned and examined microscopically to determine the state of gonadal development. Gonads of almost all males were ripe; those of females were mostly ripe but some were partially spawned and two were spawned out (Table 6).

Surface water temperatures and five minute surface plankton tows were made in Yeo and Wigham Coves during the afternoon of July 8, 1991. Surface water temperatures were 17.8oC and 15.6oC respectively. Most bivalve larvae at Yeo Cove were blue mussels, Mytilus edulis, nestling saxicaves, Hiatella sp. and a few littlenecks Protothaca staminea. There were few bivalve larvae in the tow at Wigham Cove but f. staminea larvae were the most abundant species. No manila clam larvae were identified in either tow.

Gale Passage

Sampling in Gale Passage was carried out on two days because a tidal falls at the narrows in the Passage prevents small boat travel through the Passage at low water (Table 3; Fig 21 ). The northern part was sampled on July 9 and the southern part on July 1 0. A second tidal falls in the southern part of the Passage prevented sampling in the main basin.

Sampling was undertaken on seven beaches and visits made to six others.


Numerous beaches lined the sides of the northern part of Gale Passage. Most were steeply sloped and the substrate was mainly small gravel-mud which appeared to be good habitat for steamer clams. Beaches in the southern part were small, typical of the north coast district.

Beach 1. A beach with a gentle slope located at the southwest end of the northern part of Gale Passage with a clam bearing area of about 1 ha (Fig 21). A stream ran through the centre of the beach and the substrate was gravel-sandmud with some small rock.

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Beach 2. An extensive saddle beach situated between Athlone Island and a small island at the northern end of Gale Passage (Fig 21). There was a berm about 1 ha in area with a substrate of gravel-sand-mud.

Beach 3. A gently sloped beach located on the east side of the north entrance to Gale Passage with an area of about 1 ha (Fig 21 ). The substrate was gravel-sand-mud with some small rock.

Beach 4. A small beach with an area of about 0.25 ha located at the head of the south Passage (Fig 21). The substrate was sand-gravel-shell which made digging easy.

· Beach 5. An extensive beach with a gentle slope located southwest of Beach 4 at the north end of the main basin of Gale Passage with a clam bearing area of about 0.2 ha (Fig 21 ). The substrate was gravel-sand which made digging easy. There was a large tidal pool in the middle of the beach.

Beach 6. A steeply sloped beach located to the east of the previous beach with an area of about 0.1 ha (Fig 21 ). The substrate was sand-gravel which made digging easy.

Beach 7. A beach located in the northeast part of southern Gale Passage (Fig 21 ). The beach had a strip of clam bearing area around a lagoon that had a substrate of sand-gravel.

Clam Populations

Sampling was undertaken to assess butter, littleneck and manila clams. Although there appeared to be excellent habitat for intertidal clams throughout Gale Passage, clam populations were limited.

Butter Clams. Sampling for butter clams (with forks) was undertaken only at Beaches 1 and 3 where densities ranged from 48-156 clams m-2 (Table 4). Most butter clams at Beach 1 were sublegal size (96%) and at Beach 3 most were legal size (76%), the largest was 78 mm shell length (Fig 22). Age frequency distribution showed most butter clams were 8-12 years old.

Growth rate was not determined but many of the butter clams were stunted and growth appeared to have been slow.

Littleneck Clams. Littleneck clams were not particularly abundant in either the northern or southern parts of Gale Passage; densities ranged from 0-112 clams m-2 (Table 4). Most littlenecks were sublegal size (88%) and only a few were over 45 mm shell length (Fig 23). Ages of most littlenecks were not calculated because most of the larger, older clams were badly stunted and difficult

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to age.

Growth rate was not determined but it appeared that it was slow.

Manila Clams. Manila clams were moderately abundant in both the northern and southern parts of Gale Passage and density ranged from 28-500 m-2

in plots dug with rakes and scrapers (Table 4). Most manila clams were above the legal size (94%) with the largest being 63 mm (Table 4 and Fig 24). Age frequency distribution showed most manila clams were 5-7 years old. The lack of smaller, younger manila clams indicated that recruitment had been limited in recent years.

Growth of manila clams in the northern part of Gale Passage was ·slightly faster than in the Seaforth-Spiller-Return Channel area. It required 3.5-4 years for manilas to reach 38 mm (Fig 25). Manila clams used to measure shell length at annuli in south Gale Passage were inadvertently mixed with those from Thompson Bay. Growth rate shown in Fig 25 for South Gale Passage is actually a pooled growth rate of clams from this area and Thompson Bay. The growth rate was similar to that observed in North Gale Passage.

Six other beaches were visited in Gale Passage (Fig 21). Considerable amounts of dead manila clam shell were found on many beaches. Some of the shell was old which indicated manila clams had been present in this area for many years. Other shell was more recent and may have resulted from winter kill during the preceding winter (Bower 1992; Bower et al. 1986).

Clam abundance, particularly of manila clams, was less than expected in north part of Gale Passage. There were many beaches there with excellent gravel-sand substrate but few, if any, manila clams were found.

Two beaches located on the east and west sides of the northern part of Gale Passage, immediately north of the tidal falls were of interest. Both beaches had extensive areas of gravel-mud substrate but few littlenecks and manilas were found. Lagoons were present on both beaches at levels that were within 1 m of maximum high tide and each was about 0.5 ha in area. Both lagoons had large numbers of manila clams, however, it was difficult to sample them. These manila clams were permanently covered with water throughout the tidal cycle and might be considered as "subtidal populations."

Other Species. Six small cockles were found at Beach 3 (Table 5). Soft-shell clams were found at Beaches 1 and 3 (Table 5).

Other Observations

Samples of gonads of 25 manila clams from the south Gale PassageThompson Bay area were preserved for microscopic examination. Gonads of 10

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males were ripe and one was spent. Gonads of 1 0 females were ripe, one was partially spent and three were spent {Table 6).

A five minute surface plankton tow was made in south Gale Passage. There were large numbers of gastropod larvae. Most bivalve larvae were M. edulis, Hiatella sp. and ,E. staminea.

Thompson Bay

Three beaches were sampled and three others visited at the northern end of Thompson Bay (Fig 26).


Beach 1 . Two small beaches with gentle slopes, one a saddle beach between two islands, located at the northern end of Thompson Bay with a total area of about 400 m2 (Fig 26). The substrate was sand-gravel, sometimes over shale which made digging easy. There was much old dead manila clam shell on the beach.

Beach 2. A beach between Thompson Bay and Joassa Channel with an area of about 1 ha but the clam bearing part was about 0.1 ha (Fig 26). Most of the beach was quite flat and at a low intertidal level. The substrate was sandgravel with some rock.

Beach 3. An extensive gently sloped beach located at the northern end of Potts Island (Fig 26). The lower part was soft mud but there was a clam bearing area, a strip about 30-40 m wide, in the middle part of the beach. The substrate was sand-gravel.

Clam Populations

Sampling included assessment of butter, littleneck and manila clams. Although there were several small beaches in the area with good clam habitat, clams were only found on a few beaches.

Butter Clams. Butter clams were found on all three beaches and were abundant at Beach 2 where digging was by fork. Densities ranged from 52-92 clams-m2 (Table 4). Most butter clams on this beach (74%) were smaller than the legal size and 5-7 years old (Table 4; Fig 27).

Littleneck Clams. littlenecks were present at Beach 2 and abundant at Beaches 1 and 3 where sampling was by rake. Densities ranged from 4-252

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clams m- 2 (Table 4). Most littlenecks at this location were sublegal size (85%) which indicated good recruitment in recent years (Fig 28). Few littlenecks were aged because many larger clams were badly stunted.

Manila Clams. Manila clams were found at Beaches 1 and 3 where sampling was by rake; densities ranged from 12-208 clams m-2 (Table 4). Most clams were 5-7 years old and larger than the legal size (85%) which indicated limited recent recruitment (Fig 29). Many of the manila clams in this area were dull brown with no colour patterns on the shells.

As stated above, growth shown in Fig 25 was for manila clams collected in south Gale Passage and Thompson Bay.

Three other beaches were visited in this area (Fig 26). Although they appeared to have good clam habitat there were generally few clams. Small numbers of manila clam shell were found.

Other Species. Two cockles were found, one at beach 1 and one at Beach 2 (Table 5).

Horse clams were abundant in plots dug with forks at Beach 2; densities were 14 and 15 m- 2 (Table 5). Most were small, which indicated good recruitment in recent years.

Moonsnails, Polinices lewisii, and their egg collars were abundant on most beaches.

Other Observations

Surface water temperature near Beach 2 was 15 °C.

Stryker Island

There were numerous small beaches with good clam habitat around Stryker Island. Large amounts of old clam shell were found on many beaches. Five beaches were sampled and brief visits were made to an additional seven (Fig 30).


Beach 1 . A gently sloped beach located at the southeast corner of Stryker Island with an area of about 0.25 ha (Fig 30). The substrate was sand and shell with rock. Most clam habitat was at the low intertidal level.

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Beach 2. An extensive beach with a gentle slope situated on the south side of Stryker Island with an area of about 2 ha (Fig 30). The substrate was sand-pebbles with small amounts of old clam shell on the west side and coarse sand on the east side.

Beach 3. A gently sloped beach located on the west side of Louise Channel with an area of about 0. 75 ha (Fig 30). The substrate was sand with occasional cobble.

Beach 4. A beach with a gentle slope situated at the north end of Louise Channel with an area of about 2 ha, however, the clam bearing part was about 0.5 ha (Fig 30). The substrate of the lower part was soft mud with much eel grass. At higher levels the substrate was pea gravel overlying sand-mud. There was considerable debris on the beach.

Beach 5. A beach located at the northeast corner of Stryker Island (Fig 30). At the southern end there were large boulders that appeared to have been a fish weir. There was a steep rise to a berm about 1.3 m below high tide. A lagoon, which could not completely drain during low tide, occupied much of the berm. Total area of the berm was about 2 ha. The substrate was pea gravel and sand, id,aal habitat for manila clams .

.Clam Populations

Most beaches in this area had abundant populations of clams.

Butter Clams. Butter clams were found on Beaches 1 to 5 and were more abundant on beaches 1 and 3 where digging was by fork; densities ranged from 48-104 m-2 (Table 4). Size frequency distribution showed 85% of the butter clams were above legal size, the largest was 1 00 mm (Fig 31). Most clams were over 12 years old and recent poor recruitment was indicated by the lack of small clams.

Littleneck Clams. Littleneck clams were found on Beaches 1-5 and were particularly abundant on Beach 2 where densities ranged from 28-376 m-2

(Table 4). Size frequency distribution showed that 60% of little necks were below the legal size; the largest was 67 mm shell length (Fig 32). However, age frequency distribution showed most were over 5 years old indicating slow growth (Fig 32). Many littlenecks were stunted. The lack of younger clams indicated limited recent recruitment.

Manila Clams. Manila clams WHre found on Beaches 2-5 where digging occurred in areas with suitable habitat (Table 4). They were particularly abundant on Beaches 4 and 5 where densit\es ranged from 12-368 m-2

• There was considerable organic fouling in the substrate on Beach 4 and manila clams

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there were very dark in colour. Size frequency distribution showed most manila clams (91 %) were legal size; the largest was 63 mm (Fig 33). Most clams were 5-7 years old. The low number of small clams indicated poor recruitment in recent years.

Growth of manilas at Stryker Island was similar to that observed at Gale Passage-Thompson Bay. It required about 3.5 years to attain a shell length of 38 mm (Fig 34).

In addition to the above sampling, seven other beaches were visited. Manila clams were found on most of these beaches. There were considerable amounts of dead manila clam shells on most beaches. Some shells were old, but many were recent indicating extensive mortalities possibly caused by cold temperatures during the previous winter.

Other Species. Cockles were found on all beaches; most were small and ranged in age from 1-1 0 years (Table 5).

Horse clams were found at Beaches 1 and 3 in plots dug with forks; most were large (Table 5). At Beach 1 all were large but at Beach 3 all were small.

Soft-shell clams were found on Beaches 3 and 4 and were common at higher levels (Table 5).

The exotic seaweed, Sargasum muticum, was abundant at the low intertidal and immediate subtidal levels at Beaches 4 and 5.

Other Observations

At Beach 5, surface water temperature in the lagoon was 13.8°C and in the water outside the lagoon it was 13 °C.

Spider Anchorage

Manila clams were first found north of Vancouver Island, British Columbia, in 1972 on the east side of Hurricane Island at Spider Anchorage (Bourne 1982). The area had not been resurveyed for intertidal clam populations since then. Considerable sampling was undertaken there during this survey to assess manila clam distribution and abundance. Sampling was undertaken only for manila clams from July 4-6 when the tide was too high to assess other intertidal clam species. Additional sampling was carried out during a lower tide on July 12. A total of 28 beaches were surveyed and eight were sampled (Fig 35).

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Substrate of the lower portion of many of the beaches was soft mud with eel grass beds.


Beach 1 . A beach with a gentle slope located on the west side of Hurricane Island with an area of about 0.25 ha (Fig 35). The substrate was mudsand at lower levels and sand-pebble at upper part.

Beach 2. A gently sloped beach located on the west side of Hurricane Island with an area of about 0.25 ha (Fig 35). The substrate was sand-gravel.

Beach 3. A beach about 0. 2 ha in area located on the south side of Hunter Island with a lagoon in the middle of it (Fig 35). Substrate on the west side was mostly cobble and boulders with some sand-shell-gravel patches. On the east side there were patches of sand-shell substrate.

Beach 4. A beach with a gentle slope located on the northwest side of Spitfire Island about 0.25 ha in area (Fig 35). The substrate was mostly sand and pebbles.

Beach 5. A moderately sloping beach located on the west side of Spitfire Island with an area about 0.1 ha (Fig 35). The substrate was sand.

Beach 6. A beach located on the south side of Hurricane Island that was about 1.5 ha in area (Fig 35). The substrate of the lower part was mostly mud with eel grass, that of the upper part was sand-gravel.

Beach 7. A beach located on the southern part of Hurricane Island with a lagoon at the upper end. The total beach area was about 0.1 ha (Fig 35) and the substrate was sand-gravel with some shell.

Beach 8. A beach located on the south side of Hunter Island in Spitfire Channel (Fig 35). The lower and central beach was mud with eel grass, that of the remainder was sand-gravel-mud.

Clam Populations

Butter Clams. Butter clams were found on Beaches 1-6 in plots dug with both forks and rakes; densities ranged from 0-388 m-2 (Table 4). There was a wide range of sizes and 58% were under 63 mm (Fig 36). There was a wide range of ages with a preponderance of clams aged 2-5 years (Fig 36), indicating good recruitment in recent years.

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Butter clams were common in the Spider Anchorage area and commercially exploitable populations occurred on many beaches. At Beach 4, 27 butter clam siphon holes were counted in one square meter.

Littleneck Clams. Littleneck clams were found in all plots and densities ranged from 2-346 m-2 (Table 4). There was a wide range of lengths and ages; most (62%) were under 38 mm (Fig 37). Abundance of younger littlenecks indicated good recruitment in recent years (Fig 37).

Littleneck clams occurred in commercially exploitable abundance on many beaches in the Spider Anchorage area.

Manila Clams. In spite of considerable sampling, only a few manila clams were found in the Spider Anchorage area at Beaches 1, 2, 7 and 8 (Table 4). Size distribution showed that 88% were commercial size and from 6-8 years old (Fig 38).

The number of manila clams used to calculate a growth in Spider Anchorage was limited, however, the growth rate calculated was similar to that observed at the previous two sampling locations. It required about 3.5 years to attain a shell length of 38 mm (Fig 39).

Manila clams were found at only a few of the other 20 beaches visited. When they were found in test plots the density was generally less than 2 clams m-2

• Further, few dead shells were observed on any of the beaches, although there was some evidence of winter kill at Beach 6. Although manilas were first found north of Vancouver Island in the Spider Anchorage area it appears that large populations have not accumulated anywhere in the Spider Anchorage area.

Other Species. Cockles were abundant on most beaches with densities as high as 36 m-2 (Table 5). There was a wide height and age distribution, the largest was 75 mm shell height and the oldest 8 years.

A few horse clams were found in plots mostly dug by fork. Most were small and ranged from 1-4 years old (Table 5).

Soft-shell clams were common on some beaches, particularly at the higher intertidal levels.

Moonsnails and their egg cases were common at lower levels on many beaches.

Jingle shells, Pododesmus macroschisma, and native oysters, Ostrea conchaphila (lurida), were found in a lagoon at the head of a bay on the southeast side of Watt Bay.

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Kwakshua Channel

In previous years the Kwakshua Channel area was important for butter clam harvesting. There are several clam beaches in the area but some may now be unsuitable for clam harvesting because of the presence of fish camps. Littleneck clams were known to be common in Kwakshua Channel but manila clams had not been reported from this area (Bourne Unpub. MS). Sampling was undertaken on five beaches and another five were visited (Fig 40).


Beach 1 . An extensive beach located on the north side of Pruth Bay with an area of about 5-6 ha, however, the clam bearing area was about 2-3 ha (Fig 40). Substrate at lower beach levels was firm sand with eel grass and there was a gentle rise to an area with large boulders. Above this was a larger beach with much gravel on the west side.

Beach 2. An extensive beach located on the west side of Keith Anchorage with an area of about 2-3 ha (Fig 40). The lower part was soft mud with eel grass. In the middle and along the edge, the substrate was mostly sandgravel and good clam habitat.

Beach 3. An extensive beach located on the east side of Keith Anchorage with an area of about 3-4 ha (Fig 40). The lower part was soft mud with eel grass. The central part and edges had a firmer substrate of sand-gravel.

Beach 4. A beach located on the west side of the channel leading north from Kwakshua Channel (Fig 40). There were large boulders at the lower beach level. Above this was a fairly flat beach with a clam bearing area of about 1-2 ha. The substrate was sand-gravel with some shell.

Beach 5. A large beach located on Hecate Island across from the previous site with an area of about 1-2 ha (Fig 40). The lower part was soft mud with eel grass. The beach rose to an extensive gently sloping berm with sandgravel patches. An extensive area of sand-gravel substrate was present around the edges of the beach.

Clam Populations

Butter Clams. Butter clams were common on beaches in Kwakshua Channel, even in plots dug with rakes or scrapers. Densities ranged from 0-88 m-2

(Table 4). Most butter clams (70%) were larger than 63 mm and there was a preponderance of clams aged 7-12 years (Fig 41). At Beaches 4 and 5 in 1 m2

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quadrats, 25 and 30 butter clam siphon holes were counted respectively. The number of smaller clams indicated moderate recruitment in recent years. Commercially exploitable populations of butter clams were present in this area.

Littleneck Clams. Littleneck clams were common on beaches in this area and were particularly abundant on Beaches 1 and 2 where densities ranged from 12-904 m-2 (Table 4). Most littlenecks (72%) were smaller than 38 mm and age classes 3 and 4 and 6-8 were common (Fig 42). The abundance of small littlenecks indicated good recent recruitment. Many were stunted. Littleneck clams occurred in commercially exploitable populations in this area.

Manila Clams. Manila clams were uncommon in the Kwakshua Channel area and were found only on Beaches 1-3 where densities ranged from 0-36 m-2 (Table 4). There were few manila clam shells on the beaches sampled. Two 1 00 m transects were established on Beach 1 to look for dead manila clam shell; three were found on one transect and one on the second. All manila clams found in plots, except one, were over 38 mm and most were 6-1 0 years old (Fig 43). The low number of small manila clams indicated little successful breeding in recent years.

The number of manila clams found in the Kwakshua Channel area was too low to permit assessment of a growth rate.

Five other beaches were visited in the Kwakshua Channel area but few live manilas and little old shells were found. The conclusion was that manila clam populations in this area were too small to support commercial exploitation.

Other Species. West Beach was visited (Fig 40). No live razor clams, Siligua patula, but some dead shells were found. A resident of the area said razor clams were still present on this beach, at the lowest intertidal levels.

Cockles were found at Beaches 1 and 2. They ranged in shell height from 22-64 mm and in age from 1-6 years (Table 5).

Soft-shell clams were common on most of the beaches. At Beaches 3 and 4 they ranged in shell length from 25-76 mm (Table 5).

Horse mussels, Modiolus sp. were found at lower intertidal levels at Beach 1.

Rivers Inlet

Extensive sampling was undertaken on beaches among islands located on the north side of the mouth of Rivers Inlet. There were numerous small beaches in the area but some could not be sampled because the presence of fish camps

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blocked access. Sampling was undertaken on four beaches and an additional eight were visited (Fig 44).


Beach 1 . A small steeply sloped beach located at the southwest corner of Ripon Island, about 300 m2 in area (Fig 44). The substrate was sandshell.

Beach 2. A small beach with a steep slope located on the northeast side of Penrose Island, about 150 m2 in area (Fig 44). The substrate was mostly sand-shell.

Beach 3. A fragmented beach with a steep slope fronting the Indian Reserve at the northern entrance to Klaquaek Channel with a total area of about 1 ha (Fig 44). The substrate was mostly sand-shell.

Beach 4. A small beach located at the southeast corner of Penrose Island among several small islands about 100m2 in area (Fig 44). The substrate was mostly mud with eel grass and patches of sand-shell that were good clam habitat.

Clam Populations

Sampling was undertaken for butter, littleneck and manila clams with forks, rakes and scrapers.

Butter Clams. Butter clams were found in all plots except those sampled by rake; abundance ranged from 60-192 m-2 (Table 4). There was a wide size range of butter clams, although 65% were above 63 mm (Fig 45). Butter clams as young as two years were found but most were 7-10 years (Fig 45). As many as 50 butter clam siphon holes m-2 were observed on Beach 4. Commercially exploitable populations of butter clams were present in this area.

Littleneck Clams. Littleneck clams were common and found on all beaches; densities ranged from 8-284 m-2 (Table 4). Most littlenecks (68%) were smaller than 38 mm and from 3-5 years old, indicating successful recruitment in recent years (Fig 46). Many littlenecks found in this area were stunted. Commercially exploitable populations of littleneck clams occurred in this area.

Manila Clams. No live manila clams, or dead shell, were found on any beaches sampled in this area. Many beaches had poor manila clam habitat, however, there was sufficient suitable habitat on some beaches.

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Butters and littlenecks were common on the other eight beaches visited but no live manilas or dead shell were found on them. The conclusion was that manila clams were not present in this area.

Other Species. Cockles were found on Beaches 1, 3 and 4. Shell height ranged from 20-69 mm and age from 1-5 years (Table 5).

Horse clams were common at Beaches 1 and 3. They ranged in shell length from 41-125 mm and in age from 1-11 years (Table 5).

Soft-shell clams were common at higher beach levels.

The small black sea cucumber, Cucumaria pseudocurata was extremely common on rocks at Beaches 2 and 3. The echiurid worm, Arhymohite pugettensis, was common at Beach 3 as was the orange sea cucumber, Eupentacta guinguesemate.

Other Observations

Surface water temperature near Beach 3 was 13°C.

West Gilford Island

The Alert Bay area (FSA 12) is an important commercial clam harvesting area (Quayle and Bourne 1972). In past years most of the harvest was butter clams but recently it has become an important area for harvesting littleneck clams. Since 1970 small landings of manila clams have been reported from area 12, however, the exact location of harvested stocks is unknown (Anon 1992). The primary intent of this part of the survey was to obtain information about the extent of manila clam populations in the Queen Charolotte Strait area. Information on butter and littleneck clam populations was also obtained. Sampling took place on six beaches and included extensive exploratory assessments (Fig 4 7).


Beach 1 . Two small beaches with moderate slopes located on the north side of the entrance to Monday Anchorage with an area of about 0.25 ha (Fig 4 7). The substrate at the lower beach level was mud with eel grass. At higher levels the substrate was mud-gravel-shell and rock with a few firm gravel patches.

Beach 2. Several small beaches with generally gentle slopes located at the head of Viner Sound (Fig 47). The substrate was sand-shell with some mud. Eel grass covered the lower portion of the beaches.

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Beach 3. A small beach located in the Fox Island Group with an area of about 200m2 (Fig 47). There were several other similar beaches in this area. The beach was generally flat and the substrate mostly shell.

Beach 4. A beach with moderate slope located just inside the south side of Shoal Harbour that had an area of about 0. 5 ha (Fig 4 7). The beach was more or less continuous around the perimeter of this Harbour. The substrate was mostly mud-gravel with a fair amount of rock.

Beach 5. Two gently sloped beaches located in the Burdwood Group with a total area of about 0.15 ha (Fig 47). The substrate was mostly sand-shell.

Beach 6. Two beaches with gentle slopes located at the entrance to Deep Harbour with a total area of about 0. 75 ha (Fig 4 7). The substrate was sandshell-gravel. The alga, Ulva sp., was abundant.

Clam Populations

Although sampling was undertaken for butters and littlenecks, most sampling was devoted to determining the presence or absence of manila clam populations.

Butter Clams. Butter clams were common and were found in all samples dug with forks; densities ranged from 20-296 m-2 (Table 4). There was a wide range in shell lengths of butter clams from 18-11 0 mm and in ages from 1-24 years (Fig 48). The large number of smaller, younger butter clams indicated successful recent recruitment. Commercially exploitable butter clam populations were present on many beaches sampled in this area.

Littleneck Clams. Littleneck clams were abundant and densities ranged from 0-360 m- 2 (Table 4). Most littlenecks (67%) were larger than 38 mm and most were 4-8 years old (Fig 49). The low number of small, young clams indicated limited recruitment in recent years. Commercially exploitable populations of littleneck clams occurred in this area.

Manila Clams. Manila clams were rare in this area. They were found only at Beach 2 where densities ranged from 0-16 m- 2 (Table 4). Most were larger than 38 mm and all were over 4 years old (Fig 50). Some old dead shell was found on Beach 4 and on Beaches 2 and 6 on rocks where birds had dropped them.

In spite of extensive sampling on all twelve beaches few manila clams were found. No commercially exploitable manila clam populations were found in the area surveyed.

Other Species. Cockles were abundant in the area and ranged in size

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from 15-69 mm shell height and in age from 1-5 years (Table 5).

Horse clams were common in samples dug with forks. All were large and ranged in age from 8-15 years (Table 5).

Indian Channel

The survey in the Indian Channel continued work in the Queen Charlotte Strait area and concentrated on beaches in the southern part of the Alert Bay area. Five beaches were sampled and another four were visited (Fig 51).


Beach 1. A small, moderately sloped, beach located at the northwest tip of Harbledown Island with an area of about 0.5 ha (Fig 51). The substrate was sand-shell-gravel.

Beach 2. A beach with a gentle slope located on the northern side of the west end of Harbledown Island with an area of about 0. 25 ha (Fig 51). The substrate was sand-gravel with some rock.

Beach 3. A gently sloped beach located at the east end of Mound Island with an area of about 0.25 ha (Fig 51). The substrate was sand-gravel-shell.

Beach 4. A beach with a gentle slope located near Karlukwees on the southwest side of Tumour Island with an area of about 0.3 ha (Fig 51). The substrate was sand-gravel-shell. The beach was covered with Ulva sp.

Beach 5. A saddle beach with a gentle slope located in the northern part of the Carey Group with an area of about 1 ha (Fig 51). The substrate was cobble and rock outcrop with patches of sand-gravel.

Clams Populations

Butter Clams. Butter clams were found at Beaches 2, 4 and 5; densities ranged from 0-84 m- 2 (Table 4). There was a wide range in shell length, 39-90 mm, and in age, 4-16 years (Fig 52). Butters were present in the lower third of most beaches where suitable habitat existed.

Littleneck Clams. Littleneck clams were present on all beaches and densities ranged from 4-184 m-2 (Table 4). There was a wide range in sizes and ages of littleneck clams (Fig 53). The large number of smaller, younger littlenecks indicated good recruitment in recent years.

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Manila Clams. No live manila clams, or dead shell, were found on any sampled beaches.

Extensive sampling for manila clams was carried out on four other beaches visited in this area. A lagoon was present at the upper tidal level on the sand-shell beach between Parsons and Harbledown Islands. Three dead manila clam shells were found there, but no live animals. This was the only evidence of manila clams found during this day of sampling.

Other Soecies. One cockle was found at Beach 4 (Table 5).

DISCUSSION

In 1991 clam populations in the north coast district were essentially unexploited. Although minor harvest of clams probably occurred in native food and recreational fisheries there has been no real commercial harvest of butter clams there since 1980. Littleneck and manila clams have never been harvested commercially in this district. Annual commercial landings of both butters and littlenecks have occurred in the Alert Bay area (area 12) and small landings of manila clams have been reported (Anon 1992) but it is believed these are in error. If manilas have been harvested from FSA 1 2, the exact location of the harvested stocks is unknown.

Although this survey focused on an assessment of manila clam populations, information was gathered on both butter and littleneck clams.

BUTTER CLAMS

Butter clams were widely distributed and found in all areas during the survey when sampling was by fork in suitable habitat in the lower third of intertidal beaches. Densities as high as 296 clams m-2 were recorded (Table 4). Differences in abundance at various locations were probably due to variations in recruitment patterns, predation, habitat type or sampling error, rather than environmental factors.

Generally, there were wide ranges in size and age distribution of butter clams indicating there had been consistent recruitment in recent years. The dominance of the 1987 year class, observed in the 1990 survey, was not observed

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slow. It required 6-8 years to attain the legal commercial size of 63 mm shell length compared to 5-6 years in the Strait of Georgia (Quayle and Bourne 1972). Many butters were stunted and would have an even slower growth rate than nonstunted individuals.

Littleneck Clams

Littleneck clams were the most common clam species found during the survey and formed the largest bivalve biomass on many beaches. Densities as high as 904 clams m-2 were recorded (Table 4). Littlenecks occurred on virtually all beaches where a firmer more gravelly substrate was present from the lower third to the mid intertidal level. Populations were probably higher than recorded since sampling did not target on assessment of this species.

At all locations, except the Alert Bay area, most littlenecks were smaller than the legal size, of 38 mm shell length. This indicated consistent recruitment in recent years. No single year class dominated littleneck populations throughout the survey area.

Most littlenecks sampled were aged but growth rates were not calculated. Growth throughout the area was slow and required 4-4.5 years to attain the commercial size of 38 mm shell length compared to 3-4 years in the Strait of Georgia (Quayle and Bourne 1972).

As observed with butter clams, many littleneck clams were badly stunted.

Manila Clams

Results of this survey provided further information on the distribution and population structure of manila clams in British Columbia. The 1990 survey (Bourne and Cawdell 1992) showed manila clams had not spread northward of the Seaforth Channei-Mathieson Channel area. The present survey showed significant populations of manila clams were present at least as far north as the north side of Seaforth Channel.

The southern distribution of manila clams from the Bella Bella area is of interest. Significant, and presumably, commercially exploitable populations of manilas were found in protected bays on the north side of Seaforth Channel, in Gale Passage, in Thompson Bay and around Stryker Island. All these locations are exposed to oceanic conditions (Dodimead 1980; Thomson 1981 ). In spite of extensive sampling only minor populations were found in Spider Anchorage and Kwakshua Channel although suitable habitat occurred in both areas. Neither live manilas nor dead shell were found at the northern entrance to Rivers Inlet

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indicating the species was not present in this area. Only a few manila clams were found in the Alert Bay area. Enquiries of local residents in this area indicated they were not familiar with manila clams and hence it is believed they are not common in the Alert Bay area. The small landings of manila clams reported from Area 12 in the DFO annual statistics since 1970 have probably come from small isolated populations. Results of the 1990 and 1991 surveys indicated the major concentration of manila clams in the north coast district occurred in the Bella Bella area (Fig 54).

When present on beaches, manila clams were found from approximately the lower third to well above the mid intertidal level, mostly in a substrate of firm sand-gravel. This is similar to the habitat occupied by manila clams in other areas of the west coast of North America (Quayle and Bourne 1972; Schink et al 1983).

Densities varied greatly with location. In areas of abundance, densities as high as 500 clams m- 2 were found (Table 4). In the Spider Anchorage and Kwakshua Channel areas, maximum densities were only 60 and 36 clams m-2

respectively (Table 4). In the Alert Bay area maximum density was only 16 clams m-2.1t is believed these density levels reflect true densities of manila clams in these areas. Variations within a site were probably due to differences in recruitment, habitat, natural mortality and sampling error.

Large quantities of old dead shell were observed only at the first four sampling locations where extensive populations of live manila clams occurred. Old shell at the other locations was either scarce or nonexistant. This provides further evidence of sparse manila clam populations in other areas. Some dead shell at the first four sites was recent and probably had resulted from winter kill caused by low temperatures during the previous winter (Bower et al 1986; Bower 1992). Much of the dead shell was old and had been on the beach for several years which indicated manila clams had been present in this area for at least 10-15 years.

As observed in the 1990 survey (Bourne and Cawdell 1992), there was a preponderance of larger, older manila clams on many beaches. Manila clams larger than the legal size of 38 mm shell length comprised 85-94% of sampled clams (Table 4). Two factors could explain the lack of small manila clams: 1. They have never been harvested commercially in this area and the observed size frequency distribution may reflect an unexploited population with an accumulation of older individuals. 2. They are at the northern periphery of their range in the Bella Bella area and recruitment may be erratic.

Local recruitment of manila clams has occurred in the Bella Bella area. Evidence for this comes from two sources: ( 1) Several year classes were present at most sampling sites Which indicated recruitment has occurred over several years. (2) Results of histological examination of manila clam gonads from the Seaforth-Spiller-Return Channel and Gale Passage-Thompson Bay areas showed

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most of the gonads were either ripe or partially spawned (Table 6). Mann (1979) stated a temperature of 14°C was required for gonadal development and a temperature of 15 °C for spawning and larval development of manila clams. These temperatures are seldom recorded from exposed lighthouse monitoring sites in this area (Hollister and Sandes 1972; Dodimead 1980)), however, water temperatures in protected areas and coves, where manila clams occur, can be higher than recorded at monitoring sites, and indeed, surface water temperatures as high as 17 .8°C were observed during this survey. These water temperatures would be sufficient to permit successful breeding in this area. Such water temperatures probably occur only locally and may not occur every year which would lead to erratic recruitment. No manila clam larvae were found in plankton tows. This may have been due to inadequate sampling, or to the fact that the main manila clam spawning might be in mid to late July and there were few, if any, manila clam larvae in the water at the time of sampling.

Another explanation for poor recruitment could be cold winter temperatures that could virtually eliminate year classes in some years.

If recruitment is erratic then this factor must be taken into consideration for management of any potential fishery.

There was a slight difference in growth between the first area and the second and third areas. Growth was slightly faster in the Gale Passage-Thompson Bay and Stryker Island areas than in the Seaforth-Spiller-Return Channel area (Figs 20, 25 and 34). In the first area it required about 4 years to attain a shell length of 38 mm but only 3.5 in the second two areas. Growth in the latter areas was similar to that observed in the Strait of Georgia area (Bourne 1982). Differences in growth rates were probably caused by slight differences in temperatures and other environmental factors between the areas.

Stunting

As observed in the 1990 survey (Bourne and Cawdell 1992) many butter and littleneck clams were found to be stunted. The shells were thick and heavy and the ventral margins thickened. The posterior and anterior edges of the shells tended to be involuted. Colour of the outer surface of the shells was generally an uncharacteristic pale brown for both species.

No explanation can be given for stunting or coloration of the shells. Stunting did not appear to be due entirely to density or substrate. Some stunting may have been due to high beach location.

It is of interest to note that in both the 1991 and 1990 surveys, no stunting of manila clams was observed.

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Commercial Potential

Whether populations of butter, littleneck and manila clams in the survey area can be harvested commercially will depend on the economics of harvesting, processing and markets.

Butter and littleneck clams are harvested commercially in the Alert Bay area (area 12). Stocks appear sufficient to support continued harvest of both species. Manila clam stocks appear to be too small to support commercial harvest in this area.

Approximately half the coastal landings of butter clams formerly came from the north coast district (Quayle and Bourne 1972). However, landings of butter clams have declined severely in recent years because of high processing costs. Extensive butter clam populations occur in the north coast district, but it appears the economics of harvesting and processing will have to improve before extensive commercial harvesting of this species can occur.

Markets for steamer clams, particularly manila clams, have been strong in recent years and industry is interested in harvesting manilas from the north coast area. Manila clam stocks sampled on some beaches during this survey were sufficient to support commercial harvesting provided the economics is suitable. A major problem for a continuing fishery might be recruitment of manila clams which may be inconsistent in some areas.

Large stocks of littlenecks occur in many areas in the north coast district, however, the current market is not as strong for this species as for manilas. If the economics for harvesting littlenecks improves then a fishery could develop in the north coast district since extensive populations occur there.

Other Species

Cockles, horse and soft-shell clams were present in most of the sampling areas (Table 5). All horse clams were Tresus capax. Populations of the three species were probably higher than recorded since sampling was not designed to adequately assess these species. It is doubtful that intertidal stocks of these three species are sufficient to support commercial harvesting, although they could be harvested with other species.

A small population of razor clams continues to exist at West Beach on the west side of Calvert Island.

Moon snails and their egg collars were abundant at a few locations.

The exotic seaweed, Sargasum muticum, was only observed on

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beaches off Stryker Island. It was well established and may have arrived about the same time as manila clams.

Of interest was the extremely abundant population of the small black sea cucumber, Cumcumaria pseudoocurata, at the mouth of Rivers Inlet. It was only found in this area during the survey.

GENERAL SUMMARY

Intertidal clam surveys in 1991 added considerably to our knowledge of butter, littleneck and manila clam stocks in British Columbia.

In the Campbell River area stocks of manilas are sufficient to support continued commercial harvest in Von Donop Inlet and on Marina Island areas. Stocks of littleneck and butter clams could also be harvested.

Populations of manila clams now extend north of Discovery Passage and appear to be well established in Kanish Bay where a breeding population exists. It appears this species now occurs in the Sonora Channel area. Whether a significant stock of manila clams has become established north of Discovery Passage at the southern end of Johnstone Strait merits further investigation.

Extensive stocks of littleneck and butter clams inhabit the north coast district and could support commercial harvest. However, harvesting will be dependent on the economics of harvesting and processing and development of markets.

Results of the 1990 and 1991 surveys indicated stocks of manila clams in the north coast district are concentrated in the Bella Bella area, from the Seaforth Channel area in the north, south to the Stryker Island-Sans Peur Passage area (Fig 54). No explanation can be given for the lack of extensive manila clam stocks south of this area. Further surveys are warranted to determine if extensive manila stocks occur in areas south of the Sans-Peur Passage area that were not included in the 1991 survey.

Manila clams appear to be uncommon in the Alert Bay area and no commercially harvestable stocks were found. Further studies are warranted, in Queen Charlotte Strait and Johnstone Strait, to determine if commercially exploitable stocks of manila clams occur in statistical area 1 2 that were not sampled during this survey.

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Most manila clams in the Bella Bella area, where maximum abundance was found, were large and old which may reflect erratic recruitment. If this is true it will have serious implications for management of a fishery since it could lead to a short-lived intense fishery, followed by periods when stocks could be too small to support commercial harvesting.

ACKNOWLEDGEMENTS

Sincere appreciation is extended to Fishery Officer D. Swift for making arrangements to undertake the survey in the Campbell River area and to Captain G. Cadorin and crew of the C.S.S. Vector for their kind hospitality and assistance during the northern survey. Our thanks are extended to the late Dr. D.B. Quayle for his companionship during the north coast survey and for identification of stages of gonadal development in manila clams. The assistance of L. Townsend with the computer work is gratefully acknowledged.

REFERENCES

Anon. 1992. DFO statistics for 1991.

Bourne, N. 1982. Distribution, reproduction and growth of manila clams, Tapes philippinarum (Adams and Reeve), in British Columbia. J. Shellfish Res. 2 (1 ): p 47-54.

Bourne, N. and G. Cawdell. 1992. Intertidal clam survey of the North Coast Area of British Columbia - 1990. Can. Tech. Rep. Fish. Aquatic Sci. 1864: 151 p.

Bower, S. M. 1992. Winter mortalities and histopathology in Japanese littlenecks Tapes philippinarum (A. Adams and Reeve, 1850) in British Columbia due to freezing temperatures. J. Shellfish Res. 11 (2): 255-264.

Bower, S. M., R. Harbo, B. Adkins and N. Bourne. 1986. Investigation of manila clam (Tapes philippinarum) mortalities during the spring of 1985 in the Strait of Georgia, with a detailed study of the problem on Savary Island, British Columbia. Can. Tech. Rep. Fish. Aquatic Sci. 1444: 25 p.

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Dodimead, A. J. 1980. General review of the oceanography of the Queen Charlotte Sound-Hecate Strait-Dixon Entrance region. Can. Ms. Rep. Fish. Aquat. Sci. 1574: 248 p.

Hollister, H. J. and A. M. Sandes. 1972. Sea surface temperatures and salinities at shore stations on the British Columbia coast 1914-1970. Mar. Sci. Directorate, Pacific Region. Pac. Mar. Sci. Rep. Can. 72-13: 93 p.

Mann, R. 1979. The effect of temperature on growth, physiology and gametogenesis in the Manila clam, Tapes philippinarum, Adams and Reeve 1850. J. Exp. Mar. Bioi. Ecol. 38: 121-133.

Quayle, D. B. 1969. Paralytic shellfish poisoning in British Columbia. Fish. Res. Bd. Canada. Bull. 168: 68 p.

Quayle, D. B. and N. Bourne. 1972. The clam fisheries of British Columbia. Fish. Res. Bd. Canada. Bull. 179: 70 p.

Schink T. D., K. A. McGraw, and K. K. Chew. 1983. Pacific coast clam fisheries. Tech. Rept. Washington Sea grant, Univ. Washington HG-30, Seattle, Washington. 72 p.

Thomson, R. E. 1981. Oceanography of the British Columbia coast. Can. Spec. Publ. Fish. Aquat. Sci. 56: 291 p.

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Table 1. Location of four areas in the Campbell River area sampled during an intertidal clam survey, May 28 and 29, 1991.

LOCATION DATE SAMPLED

Von Donop Inlet 28 May

Marina Island 28 May

Kanish Bay 29 May

Cameleon Harbour 29 May

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Table 2. Number of butter, littleneck and manila clams, expressed as clams per square meter (m2

), found on selected beaches in the Campbell River area, 28 and 29.

Beach Plot Digging Butter Clam Littleneck Clam Manila Clam No. No. Method

Legal Sublegal Legal Sub legal Legal Sublegal

VON CONOP INLET

1 R 0 0 0 68 40 220

2 R 0 0 4 136 32 48

3 R 0 12 12 44 40 48

4 R 0 4 40 92 40 236

5 R 0 4 4 80 24 84

6 R 0 0 4 52 20 200

2 1 R 0 0 4 0 36 20

2 2 R 0 0 4 20 12 20

2 3 R 0 0 0 16 48 36

2 4 R 0 0 0 8 56 36

2 5 R 0 0 0 4 32 32

2 6 R 0 0 0 0 12 0

3 R 0 0 8 4 20 4

3 2 R 0 0 12 4 0 0

3 3 R 0 0 24 0 8 0

3 4 R 0 0 24 0 4 0

3 5 R 0 0 0 0 44 20

3 6 R 0 0 4 28 184 104

3 7 R 0 0 0 8 196 212

MARINA ISLAND

R 0 0 20 20 128 104

2 R 0 0 16 12 32 28

3 R 0 0 0 20 96 152

4 R 0 0 0 0 16 188

KANISH BAY

F 12 0 68 0 0 0

2 F 24 0 84 0 0 0

3 F 28 0 20 0 0 0

3 F 0 0 88 32 0 0

3 2 F 8 0 68 12 0 0

3 3 R 0 0 44 16 32 16

3 4 R 0 0 0 0 76 36

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Table 3. Location of intertidal beaches sampled during an intertidal clam survey in the Central Coast and Alert Bay areas of British Columbia, 4- 16 July, 1991.

LOCATION

Spiller and Return Channels

Gale Passage

Thompson Bay

Stryker Island

Spider Anchorage

Kwakshua Channel

River Inlet

West Gilford Island

Indian Channel

DATE SAMPLED

8 July

9 & 10July

10 July

11 July

4-6 and 12 July

13 July

14 July

15 July

16 July

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Table 4. Denisties of butter, littleneck and manila clams, expressed as clams per square meter, on beaches surveyed in the Central Coast and Alert Bay areas, July 8-16,1991. R = dug with rake or scraper, F = dug with potato fork.

Beach Plot Digging Butter clam Littleneck clam Manila clam No. No. Method Legal Sublegal Legal Sublegal Legal Sublegal

SEAFORTH CHANNEL

R 0 0 0 0 0 4

2 R 0 0 0 0 4 0

2 1 R 0 0 8 72 16 4

2 R 0 0 0 4 0 4

3 R 0 0 40 16 0 4

4 R 0 0 12 176 64 24

3 R 0 0 12 92 108 12

2 R 0 0 0 24 56 24

3 R 0 0 0 12 144 12

4 R 0 0 24 96 152 12

2 R 0 4 4 108 116 24

3 R 0 0 64 220 236 16

5 R 0 8 0 132 152 52

2 R 0 8 0 88 252 52

GALE PASSAGE

R 0 0 4 108 160 0

2 R 0 0 16 44 448 52

3 F 2 52 0 6 22 0

2 R 0 0 0 4 48 24

3 F 116 36 4 0 0 0

2 F 140 16 0 8 0 0

3 F 20 28 4 4 0 0

4 R 0 0 0 16 80 0

2 R 0 0 0 0 20 8

3 R 0 0 8 48 64 0

4 R 0 0 8 16 124 0

5 R 0 0 12 12 308 0

5 R 0 0 0 0 84 8

6 R 0 0 0 48 368 20

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Table 4. (cont'd.).

Beach Plot Digging Butter clam Littleneck clam Manila clam No. No. Method Legal Sublegal Legal Sublegal Legal Sublegal

7 R 0 0 0 8 124 12

THOMPSON BAY

1 1 R 0 0 64 188 84 32

2 R 0 4 36 180 164 44

2 F 20 72 4 12 0 0

2 F 20 32 0 0 0 0

3 R 0 0 0 4 96 4

2 R 0 8 4 196 8 4

3 R 0 0 20 136 136 0

STRYKER ISLAND

1 F 80 4 32 0 0 0

2 F 92 12 8 0 0 0

2 1 R 0 0 24 4 0 0

2 R 0 0 56 72 0 0

3 R 4 4 100 276 16 0

3 F 28 20 4 4 0 0

2 R 12 0 16 0 0 0

3 R 0 0 0 0 64 20

4 R 0 0 56 12 44 8

5 F 80 4 12 4 0 0

4 1 R 0 0 0 8 320 20

2 R 4 0 12 32 252 20

3 R 0 0 4 52 272 0

5 1 R 0 8 0 12 304 64

2 R 0 0 0 0 144 8

3 R 0 0 0 0 52 4

4 R 0 0 0 0 8 4

SPIDER ANCHORAGE

1 F 56 0 8 0 0 0

2 R 0 0 0 28 56 4

3 F 44 0 24 0 0 0

- 38-

Table 4. (cont'd.).

Bouch Plot Digging Butter clam Littleneck clam Manila clam Nn. Nn. Mothud

Loyul Su!Jioyul Loyul Su!Jioyul Legal Sublogal

2 F 4 0 32 4 0 0

2 R 0 0 56 36 8 0

3 F 48 340 172 224 0 0

4 R 8 32 36 88 0 0

2 F 13 0 2 2 0 0

3 R 60 20 12 72 0 0

5 F 20 4 0 0

2 R 8 16 84 44 0 0

6 F 72 68 104 48 0 0

2 F 24 20 36 16 0 0

7 F 0 0 4 92 24 8

8 R 0 0 32 312 32 4

KWAKSHUA CHANNEL

1 R 0 4 40 56 4 0

2 F 48 36 328 224 0 0

3 R 40 48 208 408 0 0

4 R 40 8 216 360 0 0

5 R 0 4 4 172 20 0

6 F 17 4 22 10 0 0

7 R 0 0 96 212 0 0

2 R 44 32 108 796 4 0

2 R 0 0 0 12 36 0

3 F 40 4 8 0 0 0

3 R 0 0 32 84 8 4

2 F 32 8 12 0 0 0

3 F 20 0 8 0 0 0

4 F 24 0 8 0 0 0

2 F 44 4 72 8 0 0

5 1 F 16 8 28 140 0 0

2 F 0 0 56 32 0 0

- 39-

Table 4. (cont'd.).

Beach Plot Digging Butter clam Littleneck clam Manila clam No. No. Method

Legal Sub legal Legal Sublegal Legal Sublegal

RIVERS INI,.~T

F 60 20 32 12 0 0

2 F 48 12 24 20 0 0

3 F 48 24 8 0 0 0

2 R 0 8 48 236 0 0

3 R 0 0 64 12 0 0

4 F 92 44 40 120 0 0

4 F 108 84 48 152 0 0

WEST GILFORD ISLAND

F 16 4 20 20 0 0

2 F 36 0 4 4 0 0

3 F 8 4 72 8 0 0

4 R 0 0 80 96 0 0

5 F 28 0 100 8 0 0

6 R 4 0 20 0 0 0

7 R 0 4 52 12 0 0

2 F 60 48 120 68 4 0

2 R 0 0 136 32 0 0

3 R 0 0 20 12 12 4

4 R 0 4 36 76 0 0

5 R 0 0 92 28 12 0

6 R 0 0 52 12 4 0

7 R 0 0 8 32 0 0

3 F 128 4 0 0 0 0

2 F 88 68 0 8 0 0

4 1 F 36 4 4 0 0 0

2 F 80 20 4 0 0 0

5 F 80 0 4 0 0 0

2 F 64 32 44 8 0 0

3 R 8 44 136 48 0 0

- 40-

Table 4. (cont'd.).

Beach Plot Digging Butter clam Littleneck clam Manila clam No. No. Method

Legal Sublegal Legal Sublegal Legal Sublegal

6 1 F 120 176 284 76 0 0

2 R 0 12 24 124 0 0

INDIAN CHANNEL

F 0 0 12 0 0 0

2 R 0 0 76 24 0 0

3 R 0 0 32 12 0 0

2 F 8 0 4 0 0 0

2 F 8 8 16 0 0 0

3 R 0 0 68 0 0 0

4 F 64 20 36 12 0 0

2 R 0 0 16 168 0 0

5 F 8 0 100 8 0 0

2 R 0 0 52 8 0 0

- 41 -

Table 5. Number, shell length or height and age of horse clams, cockles and soft-shell clams on beaches surveyed in the Central Coast and Alert Bay areas, 4-16 July, 1991.

Beach Plot Plot area Cockle Horse clam Soft-shell Clam No. No. 1m2)

Height(mm) Age Length(mm) Age Lengthlmm) Age

SEAFORTH CHANNEL

2 0.25 27 2

3 0.25 30

4 1 0.25 70

2 0.25 37

3 0.25 34

35

GALE PASSAGE

3 1.00 55

66

68

3 0.25 43 3

45 3

2 0.25 21 53

25

25

28

THOMPSON BAY

1 0.25 28 3

2 0.25 24

34

52 2

83 4

90

94 6

95 7

95 7

100 8

100 7

104 7

105 8

106 8

106

2 2 0.25 62 4 30

31

31

- 42-

Table 5. (cont'd.).

Beach Plot Plot area Cockle Horse clam Soft-shall Clam No. No. 1m2

) Height(mml Age Length(mm) Age Length(mml Age

31

31

32

36

41 2

42 2

70 4

74

76 4

86 6

95 7

96 6

105 8

110 70

STRYKER ISLAND

1 0.25 94 10

2 0.25 118 12

138 15

140 15

143 17

2 2 0.25 48 4

38 2

18

3 0.25 15

33

3 0.25 72

4 0.25 38

5 0.50 47 2

70 3

71 3

92 5

83 4

4 2 0.25 27

SPIDER ANCHORAGE

2 0.25 20

23

48

65

- 43-

Table 5. (cont'd.).

Beaoh Plot Plot area Cookie Horse olam Soft-shell Clam No. No. (m2)

Height(mm) Age Length(mm) Age Length(mm) Age

78

3 0.25 54 3

2 0.25 68 6

71 8

2 0.25 21

31

3 0.25 14 30

17 31

18 41 2

19 41 2

19 42 2

21 1 78 4

22 2

25 1

45 3

4 0.25 18 1

24 2

33 3

2 1.00 24

3 0.25 14

19

5 1.00 30 2

48 3

67 6

70 5

70 6

70 6

70 5

2 0.25 38 2

44 3

44 3

44 3

6 0.25 47 3 45 2

48 3

49 3

69 6

73 7

- 44-

Table 5. (cont'd.).


Height(mml Age Length(mml Age Length(mml Age

75 8

2 0.25 52 4

56 4

8 0.25 48 3

KWAKSHUA CHANNEL

2 0.25 53 6

58 6

58 6

4 0.25 32 2

6 1.00 40 2

59 5

64 6

2 0.25 22

37 2

2 0.25 24

30

40

41

41

48

51

58

67

76

3 0.25 25

39

40

51

0.25 28 1 110 9

29 2 112 9

121 10

125 11

2 0.25 75 3

113 10

120

3 0.25 82 4

- 45-

Table 5. (cont'd.).

Beach Plot Plot area Cockle Horse clam Soft-shell Clem No. No. 1m2) Height(mm) Age Length(mm) Age Length(mm) Age

2 0.25 20

21

24

3 0.25 41

41

48 2

4 0.25 37

47 2

53 2

54 4

55 2

56 2

56 2

57 3

57 2

60 3

64 3

65 3

95 6

116 9

117 10

122 11

4 0.25 56 3

60 4

63 4

66 5

69 5

0.25 24

3 0.25 69 5

4 0.25 22 2

50 2

5 0.25 42 2

2 0.25 16 72

20

23 2

44 3

2 0.25 38

70

4 0.25 42 2

5 0.25 28 2

- 46-

Table 5. (cont'd.).


Height(mm) Age Length(mml Age Length(mml Age

36 3

47 3

6 0.25 45 3

3 0.25 105 11

108 10

2 0.25 40

60

4 2 0.25 114 11

s 0.25 116 11

145 15

2 0.25 52 3 105 8

6 0.25 15

18

18

19

20

24

INDIAN CHANNEL

4 1 0.25 76 4

- 47-

Table 6. Stages in gonadal development in manila clams in the Seaforth-Spiller-Return Channel and South Gale Passage-Thompson Bay areas in the north coast district of British Columbia, 1 991 .

STAGE OF DEVELOPMENT

DATE EARLY ACTIVE LATE ACTIVE

SEAFORTH-SPILLER-RETURN CHANNEL AREA

8 July 0 M 0 M

OF OF

SOUTH GALE PASSAGE-THOMPSON BAY

10 July 0 M 0 M

OF OF

RIPE

10M

9F

10M

10 F

PARTIALLY SPENT

OM

4F

OM

1 F

SPENT

1 M

2F

1M

3F

BRITISH COLUMBIA LANDINGS INTERTIDAL CLAMS

Metric Tonnes (Thousands) 5~-----------------------------------------------.

4

3

2

1

0 1951 1956 1961 1966 1971 1976 1981 1986 1991

.. Butter ~Littleneck 1: · >l Manila ~Razor

Fig. 1. Landings of intertidal clams, razor, butter, littleneck, manila and mixed, in commercial fisheries in British Columbia 1951-1991.

I

~ \!)

- 51 -

BRITISH

COLUMBIA

"'-<~ -'ttc QUADRA 0(/ ISLAND v~ --?

<S' <4 -to

~

~ 50°00'

U' ~ ~

0 25 50 G' <///---(<'0

KILOMETRES ~Q 0..<' /..;

Fig. 2. Map of northern Strait of Georgia showing location of beaches sampled in May, 1991.

QUEEN

CHARLOTTE

SOUND

•

0 50

KILOMETRES

- 53-

BRITISH

9

10 .

Fig. 3. Map of the British Columbia coast, from Bella Bella to Alert Bay, showing the location of beaches (circled numbers) surveyed in July 1991. 1. Seaforth-Spiller Return Channel, 2. Gale Passage, 3. Thompson Bay, 4. Stryker Island, 5. Spider Anchorage, 6. Kwakshua Channel, 7. Rivers Inlet, 8. West Gilford Island, 9. Indian Channel.

{j

125°00'

-55-

CORTES

ISLAND

3 4

KILOMETRES

5

Fig. 4. Map of Von Donop Inlet showing location of three beaches surveyed, May 28, 1991.

Number

-57-

VON DONOP INLET Butter Clams

10~--------------------------------~

8 ...... ············································· . ··········· .. ····························-······

I ................................. .

2

o~~~~~~~~~~~~~~~~~~

0 8 ~ • H H ~ M ~ ~ ~ H Length (mm)

Numb•

KANISH BAY Butter Clams

10~----------------------------------

8 ... ..... ·-··················. ······ .................... ····················· ............................................. .

I .... ············ ............ - .. . ... .. - . ·- .......... . .. ·--···- -···--·· - ............ ------ .. --··-·-·---------~

4 ..... ······················································· ········· .... ······························· .......................................... .

2 ··········································································· ........... .

o~~~~~~~~~~~~~~

H ~ M ~ " ~ H ~ H ~ n ~ Length (mm)

Fig. 5. Length frequency of butter clams from Von Donop Inlet and Kanish Bay, May 28-29, 1991.

-59-

VON DONOP INLET Littleneck Clams

10 ..;N=um=b:.::•~----------------,

30-+ .......................................................................................................................................................................... .

20

10 ................................................................................ .

0 4-M-rrf-TTTT+n-l!i"''"fT~ 0 & ~ • m H 30 • ~ ~ 10 H

Length (mm)


~~N=um=b~·~------------------,

eo

20

0 1

..................................................................................................... !

~ .............................................................................................. .

2 3 4 & I 1 8 I ~

Annulus Fig. 6. Length and age frequencies of littleneck clams from Von Donop Inlet, May 28, 1991.

- 61 -


10 ·········································································

40 .................................. .

30

20

10

0~--~--~--~--~---r---r---.---.--_, 1 2 3 4 e a

Annulus 7

KANISH BAY Littleneck Clams

8 • 10

10 TM=••=n~a=•=••~~=~~th~(mm==)-------------------===~

10 ·······································-·················································--······-·····-···

30 ··································· ···············································-·························································································

20 ............................................................................................................................................................................. .

10 ... ······································································-····································································································

0~----------~--~---r---.---.---.--_, 1 2 3 4 8 7 8 • 10

Annulus Fig. 7. Growth rate of littleneck clams from Von Donop Inlet and Kanish Bay, May 28-29, 1991.

Numb•

- 63-

VON OONOP INLET Manila Clams

~~--------------------------------~

eo

ao

20 ····································· ....... .

10 ······················

0 """+"rr"'T"T"t-T'TT"''r+T-T.,..,.....,........

o 1 ~ • m a ao u ~ ~ eo H Length (mm)

Number

VON DONOP INLET Manila Clams

200~--------------------------------~

110 ................................. ..

120 ..........................................................................................................

80 ............... .. .. ....................................................................................... t

40 ..................................................................................

a e 10 Annulus

Fig. 8. Length and age frequencies of manila clams from Von Donop Inlet, May 28, 1991.

- 65-

VON OONOP INLET Manila Clams

Mean 8MII Length (mm) 10~~----~~-----~----------------------------,

10 ····················

ao ·············.

20

10

0+----------~---------------------~----r---~---r--~ 1 2 3 8 8

Annulus 7

KANISH BAY Manila Clams

8 • 10

10 ~M~•=•n~8M~U~Le~ng~th~(=mm~)--------------------------------,

40 ................... .

ao ·························· ··········· .................................................................................................................................... .

20 ····················· ·······················································································································································

10 ..... ·········································································································································································

o+---~------4----~--~---+-------r---~---r--~

1 2 3 4 8 8 Annulus

7 a • 10

Fig. 9. Growth rate of manila clams from Von Donop Inlet and Kanish Bay, May 28-29, 1991.

- 67-

.......;

2 4 6 8 10

KILOMETRES

Fig. 10. Map of Marina Island showing sampling location, May 28, 1991.

Number

- 69-

MARINA ISLAND Littleneck Clams

~~---------------------------------,

4 ................................................................................................................................................................................... ,

a ................................................................................................................................................................... ..

2 ..................................................

1 ....... ···········································

0~~~~~~~~~

0 I ~ • H H • M ~ " ~ H Length (mm)

MARINA ISLAND Littleneck Clams

Numb• 14~~-----------------------------.

12 ................................................ . .............................................................................................................

10 ........................................... .

8

2

1 2 a 4 e e 1 8 • ~

Annulus

Fig. 11. Length and age frequencies of littleneck clams from Marina Island, May 28, 1991.

Numbw

- 71 -

MARINA ISLAND Manila Clams

~~----------------------------------~

30 .............. ······ .... .

20 ································

10

o~~~~~~~~~~

o e ~ ~ m u 30 • ~ ~ ~ H Length (mm)

MARINA ISLAND Manila Clams

Number 120~----------------------------------~

100

80 ......................... .

eo ······································· .. ·

40 ····························································································1

20 .......................... . . ............................................................................. ..

1 7 8 • 10

Annulus

Fig. 12. Length and age frequencies of manila clams from Marina Island, May 28, 1991.

- 73-

OKISOLLO

QUADRA ISLAND

0 2 3 4 5

KILOMETRES

Fig. 13. Map of Kanish Bay showing the location of three beaches surveyed, May 29, 1991.

800ft

lOOt.

400t.

Ott 4-.-r-..r-r+t-t

- 75-


~ H n ~ H ~ ~ ~ H H H ~

Numb•

Length (mm)


~~----------------------------------,

21

20

11

10

I ....

1 2 3 4 I I 1 8 I ~

Annulus

Fig. 14. Length and age frequencies of littleneck clams from Kanish Bay, May 29, 1991.

- 77-


Number 12~---------------------------------------,

10

8

18

14

12

10

8

8

4

2

0

0 S ~ ~ ~ H ~ H ~ " ~ H Length (mm)

Number

.................

....................


s 8 7

Annulus 8 t 10

Fig. 15. Length and age frequencies of manila clams surveyed from Kanish Bay, May 29, 1991.

- 79-

50°22'

0 2

KILOMETRES

125°20'

Fig. 16. Map of the Cameleon Harbour showing the beach visited, May 29, 1991.

0 FOOTE

hiTS. '\.!J'

- 81 -

YEO ISLAND

KILOMETRES

Fig. 17. Map of the Seaforth-Spiller-Return Channel area showing the location of beaches surveyed July 8, 1991.

- 83-

SEAISPI/RET CH, LITTLENECK CLAMS Length Frequencies

LENGTH(mm)

Age Frequencies

10 11 12 13 14 AGE

19 20

Fig. 18. Length and age frequencies of littleneck clams from the Seaforth-SpillerReturn Channel area, July 8, 1991.

- 85-

SEA/SPI/RET CH, MANILA CLAMS Length Frequencies

LENGTH(mm)

Age Frequencies 00>~----------------------------------------------------------~

80· ·····-··-··-········-··

70 ·····-·--·-······--·--·

60 ··--·--·----·····-·····

B5 50 ··········-···-··--·---10 ::E ~ 40 ·····-··-··-··-····

30 ········-····--····

20 ····-······-·--

10 ········--·-··· 1· r····-··-··-·····-··-··-········-·····-·······-··--··-··-·

o~--__,.~•.2..,. a ~or 41.r s"" 6..., 1~-:- 10 11 12 13 14 15 16 11 1a 19 20

AGE

Fig. 19. Length and age frequencies of manila clams from the Seaforth-SpillerReturn Channel area, July 8, 1991.

SEAISPI/RET CH, MANILA CLAMS Length at Annulus

E>C>·············--------------------------------------------------------------------------------·

~ ~·----------------------------------------------------------E E '--'

:r: ~()·------------------------------------~---···-----------------·-·····--·-··----·············· ~ z L1J :3()·-······················--···································································· _J

z Li) ~()·-······-·······1··············-----------------------------------·-··-·········-·--·········· ~

1()········1·····················································································

() 1 ~ :3 ~ 5 E)

ANNULUS 7 8 9 1()

Fig. 20. Growth rate of manila clams from the Seaforth-Spiller- Return Channel area, July 8, 1991.

CX> -...J

0

ATHLONE

ISLAND

CHART 3787

SEAFORTH

TIDAL FALLS

2

- 89-

CHANNEL

DUFFER IN

IS LAND

4

Fig. 21. Map of Gale Passage showing the location of beaches surveyed July 9-10,1991.

a: w co

~

- 91 -

GALE PASSAGE, BUTTER CLAMS Length Frequencies

LENGTH(mm)

Age Frequencies 2•~-----------------------------------------------.

2 3 4 10 11 12 13 14 15 16 17 18 19 20 AGE

Fig. 22. Length and age frequencies of butter clams from Gale Passage, July 9-10, 1991.

a: w

~

- 93-

GALE PASSAGE, LITTLENECK CLAMS Length Frequencies

LENGTH(mm)

Age Frequencies

2 ..................... .

3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 AGE

Fig. 23. Length and age frequencies of littleneck clams from Gale Passage, July 9-10, 1991.

a: UJ m ~ ::::> z

- 95-

GALE PASSAGE, MANILA CLAMS Length Frequencies

LENGTH(mm)

Age Frequencies

7 8 9 10 11 12 13 14 15 16 17 18 19 20 AGE

Fig. 24. Length and age frequencies of manila clams from Gale Passage, July 9-10, 1991.

- 97-

NORTH GALE PASSAGE, MANILA CLAMS Length at Annulus

o~~--~--~--~--~--~--~--~--~---r~ 2 3 4 5 6 7 8 9 10

ANNULUS

SOUTH GALE PASSAGE, MANILA CLAMS Length at Annulus

EK) -----------------------------------------------------------------------

~50 ~40

a5 30 ------------------ ----------------------------------------------------..J

~ 20 ----------- ----------------------------------------------------------~

ANNULUS

Fig. 25. Growth rates of manila clams from North Gale Passage, and from the South Gale Passage-Thompson Bay area, July 9-10, 1991.

0

128°25'

ATHLONE ISLAND

ALICE

ISLAND

·;,~.:~ ·.·

2 3

KILOMETRES CHART 3787

128°20'

,,: ~--~

'\:. :~: .. :<:(yf!j' ':-:::;;·,• "'/':{ v ,,.._ .. : .. - '

J/··:··:·:. (J ' .

:) ~::

THOMPSON BAY

4

Fig. 26. Map of the Thompson Bay area showing the location of beaches surveyed, July 10, 1991.

1.0 1.0

- 101 -

THOMPSON BAY, SUITER CLAMS Length Frequencies

LENGTH(mm)

Age Frequencies 2~------------------------------------------,

1

10 11 12 13 14 15 16 17 18 19 20 AGE

Fig. 27. Length and age frequencies of butter clams from the Thompson Bay area, July 10, 1991.

a: w CD

~ z

a: w CD :::::! ~ z

- 103-

THOMPSON BAY, LITTLENECK CLAMS Length Frequencies

LENGTH(mm)

Age Frequencies

4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 AGE

Fig. 28. Length and age frequencies of littleneck clams from the Thompson Bay area, July 10, 1991.

a: UJ m ~ z

a: UJ m ~

~

- 105-

THOMPSON BAY, MANILA CLAMS Length Frequencies

LENGTH(mm)

Age Frequencies

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 AGE

Fig. 29. Length and age frequencies of manila clams from the Thompson Bay area, July 10, 1991.

0

52°04'

.·· . .... ~:~··

THOMPSON BAY

!!f)_ .•. a:.:·

,· •... _ ..... ,; ._.,.

.

' . • tii}':~;

o\\ m ~

0

0

KILOMETRES

- 107-

·sTRYKER

ISLAND

CHART 3787 ~ ··· .. !:c:, cl:-•

Fig. 30. Map of the Stryker Island area showing the location of beaches surveyed July 11, 1991.

a: w CD ::E ::> z

- 109-

STRYKER IS., BUTTER CLAMS Length Frequencies

1~----------------------------------------------------~

LENGTH(mm)

Age Frequencies

13 15 AGE

0

Fig. 31. Length and age frequencies of butter clams from the Stryker Island area, July 11 , 1991 .

a: w m :a: :::::> z

- 111 -

STRYKER IS., LITTLENECK CLAMS Length Frequencies

LENGTH(mm)

Age Frequencies

2 -----------

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Age

Fig. 32. Length and age frequencies of littleneck clams from the Stryker Island area, July 11, 1991.

a: w m ~ ::> z

- 113 -

STRYKER ISLAND, MANILA CLAMS

ffi m ~ ::::> z

140 13(} 120 110 100 90 80 70 60 50 40 30 20 10 0

Length Frequencies

LENGTH(mm)

Age Frequencies

Fig. 33. Length and age frequencies of manila clams from the Stryker Island area, July 11, 1991.

STRYKER ISLAND, MANILA CLAMS Length at Annulus

E>C>···-·····--·----··--·-··----··--·-----·-········--·--·-··--·-····--·--········-··--·-·---·-··-

- 5()··---.-.. -.. -----------.----.. --. -· ·-.---.. -.--.-.. -... --~·~-.

E E :r: ~()···-·····-·--------------------··---~-------·-··-·-···--·----··-··--·-··--·-·····----------t5 z LLJ ~() ... ··----·--····-----------~----················-········-·····-··························-·-· _J

z < LLJ ~()····-----------~---··--·--···········-····--········-·····-···-···---····--····-··-··--·----

:E

1()·····•••1··················-·····-··-····--··--·-·····-··-································-··-

() 1 ~ ~ ~ 5 E5 7 8 9 ANNULUS

Fig. 34. Growth rate of manila clams from the Stryker Island area, July 11, 1991.

.....

..... 1.11

\0

vs t

:t2 SPIDER

~~o ~ ANCHORAGE

•r!J \J C)

< ~ 0

Cl)

iJ' ~ ;:<(Ji

oDa

I-C) --C)

-J --~

~fJ.. 4° I ti 2 3 4 ~ •

~ til KILOMETRES 5 CHART 3784 128°10'

Fig. 35. Map of the Spider Anchorage area showing the location of beaches surveyed, July 4-6 and 12, 1991.

..... ..... -...]

- 119 -

SPIDER ANCHORAGE, BUTTER CLAMS Length Frequencies

1 --------------------------------- ---------------------- -----------------------

a: UJ Ul ~ :::> z

40

0 LENGTH(mm)

Age Frequencies

~ ---------···-··· . ························································------------

3(} ··•··•·••·••··•· . . ........•..........•.••.....•..•...•..•..•...••.••..•••••••••••••••

25- •..•••.•.• a: UJ ~ 2Q- •••••••••• :::> z

15- ....•.•.•• ••• - •...•........

1Q- ··-······· • ····-···· •

5- ·····-· 1- -,..

3 5 7 9 11 13 AGE

•--15 17 ..

19 21 23' 25

Fig. 36. Length and age frequencies of butter clams from the Spider Anchorage area, July 12, 1991.

- 121 -

SPIDER ANCHORAGE, LITTLENECK CLAMS

a: w m ~ ::::> z

a:

Length Frequencies

LENGTH (mm)

Age Frequencies 401~------------------------------------------~

~ ························---------------------------------------·-··--····

30 ····-·-····----

25 ---------

~ ~ 20 -----::::> z

15

10 ------

5 ------

01+---1 2 3 4 5 6 7 8 9 10~~ 1314151617 1819 20

AGE

Fig. 37. Length and age frequencies of littleneck clams from the Spider Anchorage area, July 12, 1991.

- 123-

SPIDER ANCHORAGE, MANILA CLAMS

a: w ~ :::> z

Length Frequencies

20~----------------------------------------------, 18

16

14

ffi 12

~ 10

~ 8

6 ········-········································

4 ············································

2

0+---~~~hT""~~~~hT~~

LENGTH (mm)

Age Frequencies

Fig. 38. Length and age frequencies of manila clams from the Spider Anchorage area, July 12, 1991.

SPIDER ANCHORAGE, MANILA CLAMS Length at Annulus

€)()·---------------------------------------------------------------------------------------------

~ ~·--------------------------------------------------E E ;c: ~()·---------------------------------r-----------------------------------------------------------6 z LLJ !3()·--------------------·'··---------------------------------------------------------------------~

z Li) ~()·---------------·····-------------------------------------------------------------------------~

1 ()·- -------------------------------------------------------------------------------------------

() 1 ~ !3 ~ 5 E5 7 8 9 1() ANNULUS

Fig. 39. Growth rate of manila clams sampled in the Spider Anchorage area, July 12, 1991.

..... N VI

0

CHART 3784

b~

()

·". p. ' ,

2 3 4

KILOMETRES

.... ~f) ... "" 8 ..• ~

tf)

~ •• It

·'

II fJ

5

. ISLAND

HECATE

ISLAND

51°40'

Fig. 40. Map of the Kwakshua Channel area showing the location of beaches surveyed, July 13, 1991.

...... N -..J

- 129-

KWAKSHUA CHANNEL, BUTTER CLAMS Length Frequencies

1~------------------------------------------------------~

1

Length (mm)

Age Frequencies

9 11 13 AGE

21 23 25

Fig. 41. Length and age frequencies of butter clams from the Kwakshua Channel area, July 13, 1991.

- 131 -

KWAKSHUA CH., LITTLENECK CLAMS Length Frequencies

12~~------------------------------------------------~

LENGTH(mm)

Age Frequencies 2~--------------------------------------------------~

10 11 12 13 14 15 16 17 18 19 20 AGE

Fig. 42. Length and age frequencies of littleneck clams from the Kwakshua Channel area, July 13, 1991.

a: w m ::::!: :::> z

- 133-

KWAKSHUA CH., MANILA CLAMS Length Frequencies

1frr----------------------------------------------------~

2 ·················-········

1 ·•••·••••••••••·••

1 2 3 4

LENGTH(mm)

Age Frequencies

8 10 11 12 13 14 15 16 17 18 19 20 AGE

Fig. 43. Length and age frequencies of manila clams from the Kwakshua Channel area, July 13, 1991.

127°45'

o·

51°30'

ISLAND

...

51 °27' o~!!!!!!!!!!~iiiiiiiiiiiiiiiiiiiiiiiiiii~~~~~iiiiiiiiiiiiiiiiiiiiiiiiiiiiil!!!!!!'!!!!!!!!!!!!!!!!!! 2 3 4


RIPON

ISLAND

Fig. 44. Map of the northern entrance to Rivers Inlet showing the location of beaches surveyed, July 14, 1991.

..... w U1

- 137-

RIVERS INLET, BUTTER CLAMS Length Frequencies

LENGTH(mm)

Age Frequencies

10 11 12 13 14 15 16 17 18 19 20 AGE

Fig. 45. Length and age frequencies of butter clams sampled from Rivers Inlet area, July 14, 1991.

a: w co ~ :::> z

- 139-

RIVERS INLET, LITTLENECK CLAMS Length Frequencies

LENGTH(mm)

Age Frequencies 7"

EX} ·····-·····-···

50 ······---·-----

40 ----------------

30 ---------------

20 -·-------------

10 -----------

o-+-"-----1.,. 2'-r 3'-r 4'-r s'"r 6., 1~'10 11 12 13 14 1s 15'17'1s19 20 AGE

Fig. 46. Length and age frequencies of littleneck clams from the Rivers Inlet area, July 14, 1991 .

ISLAND

BURDWOO~.. r!" .as:J> GROUP < .. ····· ... o ••

~ff,q

GILFORD ISLAND

0 2 4 6 8 10

KILOMETRES

CHART 3596 0

Fig. 47. Map of the area at the western end of Gilford Island showing the location of beaches surveyed, July 15, 1991.

....... ~ .......

a: UJ

- 143-

GILFORD ISLAND, BUTTER CLAMS Length Frequencies

LENGTH(mm)

Age Frequencies "'

~ ···········-··················································-·····-··-··-··-····-···-··

3cr ••••••••••••••••

2sr ·····--------·-·

~ 2<r ---·-···-··-··-· • :::::> z

1sr -------------·-·

1cr ·····-----

& -------. (}

1 3

"llf ~ii----------~----------

5 7 9 11 13 15 17 19 21 23 25 AGE

Fig. 48. length and age frequencies of butter clams from the area at the western end of Gilford Island, 15 July, 1991.

- 145-

GILFORD ISLAND, LITTLENECK CLAMS Length Frequencies

LENGTH (mm)

Age Frequencies 101~DT--------------------------------------------------~

90 ---········-----------------------------------------------------------------····--····-

80 ----------------------

70 ------------------

60 ------------------a: lU co 50 ------------------~ :::> z 40 ------------------ . -

30- ..............

20-

10

0-+-----6 7 ~--8"9 10 11 1213 14 15 161718 19 20

AGE

Fig. 49. Length and age frequencies of littleneck clams from the area at the western end of Gilford Island, July 1 5, 1991 .

a: w ~ ::::> z

- 147-

GILFORD ISLAND, MANILA CLAMS Length Frequencies

10r------------------------------------------------~

9 ----------------------------------------------------------------------------··-8 -------------------------------------------------------------------------····--

7 -------------------------------------------------------------------------------6 -----------------------------------------------------------------------------·-

5 -------------------------------------------------------------------------------

4 --------------------------------------------------------------------·--------·-3 -------------------------------------------------------------------------------

2 -------------------------------------1

Ol+---~1 ~~""nn~mm~~~nn~0~~~nn~~~~0~~ LENGTH(mm)

Age Frequencies

2 ------------------

1 ------------------

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 AGE

Fig. 50. Length and age frequencies of manila clams from the area at the western end of Gilford Island, July 15, 1991.

126°40'

~'c:» ;o "" co .•

C?~o ~~· ...

•

TURNOUR ISLAND

HARBLEDOWN ISLAND

CRACROFT ISLAND - •

JoHNsr0N~ srR4,r

0 2 4 6 8 10


Fig. 51. Map of the Indian Channel area showing the location of beaches surveyed, July 16, 1991.

1-,r,. 1!:·

- 151 -

INDIAN CHANNEL,BUTTER CLAMS

1

1

ffi 1

~ z

Length Frequencies

6 -----------------------------------------------------------------------

4 -------------------------------------2

0+---mmmn~~~mm~~mm~NNmM~~~mmmm--~ 10 20 30 40 50 60 70

LENGTH(mm) 80

Age Frequencies

90 100 110

10~--------------------------------------~

9- -------------------------------------------------------------------------

8- -------------------------------------------------------------------------

7-

a: 6

~ 5

~ 4-

3 ---------------

2 ---------------

0+------.--2 .... '3 ..... 4 "'56 7 8

Fig. 52. Length and age frequencies of butter clams from the Indian Channel area, July 16, 1991.

- 153-

INDIAN CHANNEL, LITTLENECK CLAMS

a: LU m ~ ::::> z

3" ·-

~ ------------------

2(r ------------------

15- -----------

1(r -----------

5- -----------

1'\ v

Length Frequencies

LENGTH(mm)

Age Frequencies

Fig. 53. Length and age frequencies of littleneck clams from the Indian Channel area, July 16, 1991.

0 22!!!_

- 155 -

50 100 150 --===:a KILOMETRES

SOUND

Fig. 54. Area of major concentration of manila clams in the north coast district of British Columbia.

N. F. Bourne, G. D. Heritage, and G. Cawdell Department of Fisheries and Oceans...

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Transcript of N. F. Bourne, G. D. Heritage, and G. Cawdell Department of Fisheries and Oceans...