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BRISIDL BAY D!\.TA REEORT NO. 105

Wood River Lake System Studies, 1975-77

Resume of the Creel Census of Recreational Anglers; Investigation of the Association between Northern Pike Arctic Char, and Sockeye SaliWn as related to I. crassus, December 1975 and January 1977; Pike Investigation

by

Agencies Under Oontract University of Alaska

Washington co-op Fishery Research Unit

Alaska Department of Fish and Game Division of Oomrnercial Fisheries

Dillingham, Alaska

December, 1983

·ARLIS· · ·-1.-l&Ska;R,esourc_cs Lihrars ~\ Information Service~

· , ·LibrarY Bui!Jing. Suite 111 · ·: .· 3211 Providcnc·c Drive

-\m:hnragc. r'\K 995flR-Uil-l

S-H ~~2

ALJ Vl1

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I, 1 .• A R,esume o£

The Creel Census of Recreational Anglers in the Wood River System

1975--1976

A creel census of recreational angling effort in specific areas of the.

Wood River System was accomplished in 1975 and 1976 by the Sport Fish

Division, as one segment of an overall departmental "char investigational

program".

The 1976 census of sport anglers differed from the previous year in that

sampling was intensified and extended into areas not sampled in 1975. The

program also differed in design, the 1976 census-employing a statistically

designed sampling scheme, which provided very good estimates of recreational

fishing effort and harvest of Arctic char.

The goal of the two year recreational creel census was, "to define.the

level of recreational angling, the species and populations used, and the

. timing and specific locations of sport fisheries in the Wood River systems".

Determinations were also made in 1976 as to the residency status of parti­

cipating anglers, i.e., which areas within the system are fished by Alaska

resident-s and nonresidents, respectively.

Table 1 defines the 1976 sport harvest of Arctic char ~nd distribution of

angler effort in the Wood River Lakes system for the June 14-September 6

period.

During a similar period in 1975 (June 8 - September ZO) an estimated total

of 700 anglers fished the Agulowak River mouth, and captured 1,089 Arctic

char.

While angler effort at the mouth of the Agulowak River is quite comparable . .

for both years, the harvest appears substantially less in 1975. The dis-

parity in magnitude of harvest is thought to be a product of different

sampling designs, resulting in a low estimate of harvest for 1975.

The 1976 distribution of anglers, throughout the system, was determined by

enumeration of anglers during a series of randomly· selected flights. In the

areas where angler numbers observed during these flights were correlated

with C.P.U.E. obtained from "on the water" angler interviews, estimates of

harvest are calculated and shown. Those fishing areas that appear without

harvest estimates in Table 1 reflect areas which were not actually creel

censused.

Timing or distribution of angler participation through the 1976 seasson is

represented in Table 2 for the Agulowak River mouth. While only the single

census area is shown, this is. the site within the system where the greatest

sport effort and harvest of Arctic char occurs, and timing is thought to be

generally representative of other areas.

-3-

•

Table 2. Timing of Sport Fi.shery Effort at the Mouth Of the Agulowak River, 1976 •.

Date ..

6/14-6/27

6/28-7/11

7/12-7/25

7/26-8/8

8/9 -8/22

8/23-9/6

. . . . . - .

--·Man-Days··

182

145

212

193

63

.. "15

810

Comparative Use by 2-1'/eek Period-

22.5%

17.9%

26.2%

23.8%

7.8%

'1~8%

100. 0%

A sample of anglers was interviewed at three separate census sites, for

determinations of residency status. Considerable difference in comparative

numbers of participating resident and non-resident anglers was shown

depending upon location within the Wood River system.

The information presented in Table 3 indicates a higher percentage of non-

resident anglers at Agulukpak River, while the outlet of Nerka Lake, the

Agulowak River, and it's mouth were utilized largely by resident anglers. The

close proximity to the village Of·Aleknagik and the accessibility of the

latter two areas by boat likely explain th.ese d;i:.fferences •

. -4-

Table 3. Residency of Sport Fishermen in the Wood River System, June 14, 1976 - September, 6, 1976.

Lake Aleknagik, including Agulciwak River Mouth

Agulowak River, including Lake Nerka Outlet

Agulukpak River Mouth, Lake Nerka

In Swmnation:

Percentage of Alaskan Residents

77

60

24

During 1976 more recreational fishing for Arctic char occurred at the

Agulowak River mouth than at any other location censused within the Wood

River system.

"Catch per Unit of Effort" for Arctic char was far greater at the Agulowak

and Agulukpak River mouths than at any other area.

The third most intensively fished location in the system was the Wood River

at the village of Aleknagik, although the harvest and C.P.U.E. was relatively

low.

The total recreational harvest for all areas censused in 1976 was estimated

at 4,800 char. Approximately 3,000 man/days of sport fishing effort occurred.

It is considered unlikely that the total system-wide sport harvest of Arctic

char exceeded 6,000 fish in 1976.

-5-

!

A greater percentage of sport anglers utilizing the Agulowalc. River and its

mouth are resident anglers than those occurring at other areas higher or

further upstream, in the drainage. Xt is concluded the close proximity of

Aleknagik Village and the accessibility· of the Agulowak River by boat con­

tributes to this phenomenon.

Note: Additional information r_egarding the 1975 and 1976 census programs

will be available for review at the inter-agency meeting. We can at this

time discuss any of the sampling techniques, conclusions, etc., the

attending participants desire.

-6-

....

/ / . -. - .

·- ·•

· ... -.

: -.-.

INVESTIGATION OF THE ASSOCIATION BETWEEN NORTHERN . PIKE, ARCTIC CHAR, AND SOCKEYE. SALMON AS RE­

LATED TO THE CESTODE Triaenophorus crassus

A Preliminary Report To Alaska Department of Fish and Game

"by

··.John Burke .·.

· Washington Cooperative Fishery Research Unit College of Fisheries

University of Washington Seattle, Washington 98195

. '.

. . ' .. :

DECEMBER,. 1975

. ·'-'

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-.

.·INVESTIGATION OF THE ASSOCIATION BETWEEN NORTHERN PIKE, ARCTIC CHAR, AND SOCKEYE SALMON AS RELATED TO THE CESTODE Triaenophorus crassus

· INTRODUCTION

It is possible that increasing the health of sockeye salmon juveniles

would increase their survival and subsequently the abundance of returning

adults. A reduction of parasites could serve this end. There is one par­

--ticularly abundant and obvious parasite of juvenile sockeye in the Wood

River system, Triaenophorus crassus. Through management of different hosts

of the parasite, it might be possible to reduce the incidence of infection .. :1il sockeye.

Objectives

.. 1. Determine the abundance and distribution ofT. crassus

in Arctic Char (Salvelinus alpinus), sock7ye salmon (Oncorhynchus

~rka), northern pike (Essox lucius), and certain cyclopoid copepods.

2. Determine the critical· life history segments of- adul~ and juvenile

·stages of the above mentioned animals. useful for possible parasite

control-·opera tions.

3. Determine the detailed effects of !· crassus parasitism by histo-

pathological examination of sockeye salmon, Arctic char, and northern

pike.

T. crassus Life Cycle, Abundance, and Distribution

The adult cestode lives in the intestine of northern pike, where it

matures and releases its eggs in the spring. The eggs hatch in the water

and infect minute crustaceans, cyclopoid copepods. Infected copepods, when

eaten by sockeye juveniles, carry the parasite to these fish where they de-

velop into cysts. The sockeye are subsequently eaten by the pike and the

2

parasite reaches its definitive host. In the·Wood River system there are

probably other intermediate and accidental hosts of the parasite. Certain

details of the cycle remain to be thoroughly worked out.

: T. crassus is extruded from northern pike during spawning in the early

summer. In personal communication with Mike Chihuly, a graduate student

(University of Alaska) studying pike in the Wood River system, he said that

during .his sampling in Lake Aleknagik he. noted worms being extruded through­

out June. By the end of ~he first week of July the worms were no longer seen.

When I examined these fish in the first two weeks of July, most of the pro-

glottids had been shed, Only vestiges of attachments remained in the pike

intestine at this time, \

Field time spent with Chihuly was used to observe the seasonal pike

·:habitat thr~ugh sprin.g and early summer. Tliis specific habi'tat inay serve·

as a focal point of~· crassus.

,/ TABLE 1.. Pike samples from Lake Aleknagik.

Date No. of :{1975) Pike Method Remarks Use

July 2 3 hook and line Formalin

,.

.:.. " 7 16 pike trap

3 extruding T, crassus

1 extruding T, crassus Tag & releasl-

II 8

. . . •• 9

II lQ.

II 12

II 13

II 14

.. 134

1

3

47

3

31

70

67

28

25

15

gill net

natural mortality

mortalities from 7/7 sample

gill net

hook and line

" " gill net

hook and line

" II

gill net II "

0. II .. · heavy T, crassus inf,

0 extruding T, cra:ssus

0 " " ·o 11 It

0 11 " 0 .. II

killed for pike study

" 11 " " 0 extruding T, crassus

" Formalin

Bouins

II

Tag & releaso c .•

Bouins

Tag & releas.

" " " II

Tag & releasL.

--

-

3

After July 7, very few T. crassus were seen being extruded by the pike

in Aleknagik. On. about the lOth of July the pike began to leave the weedy

areas in the lake. The focus of T. crassus coracidia should be the weedy

areas of the lake where pike were congregated throughout June and early July.

·Every pike examined internally showed vest:i:ges of heavy !.· crassus

infection.

It would be beneficial in 1976 to examine the pike population earlier

in the season and perhaps under the ice. The total parasite should be ob­

servable at several life stages in the definitive host at this time, and ·

accurate numbers of parasites per pike could be obtained, It would also

be interesting to examine the pike at various_ points in the lake system

to compare infection rates.

·In sockeye smelt, T. crassus forms a cyst which is easily seen as an

· . _external lump on many outward migrating fish.' Sockeye most probably rep­

resent an intermediate host for the parasite. To confirm this, the eating

habits of pike must be known. If pike da not eat sockeY.e, it is possible

that sockeye smelt represent an accidental host,

Infection ra~es in smelt vary with the origin of the smelt, These

rates probably correspond to relative amounts and locations of pike habitats

·.in the different lakes •

. · From June 19 to June 22, 1975, I sampled 130 sockeye smelt from the

Little Togiak River. At the time I felt that none of these fish were in-

fected, but I now have some question:about this observation. My methods

~ere not perfected at that time. I would speculate that Little Togiak is

one of the least infected lakes in the system.

Other smelt samples were taken at Lake Aleknagik during the period of

the pike study (7/1- 7/15/75). All of these fish were infected by T.

4.

erassus and were selected because of this, Some samples were taken from

ehar gullets, others with a beach seine, These samples were taken for

histopathological study, The location, the Agulowak River, is a more

representative sampling site for the entire system than the Little Togiak

R1.ver.

In 1976, I will examine sockeye smelt from the mouth of the Agulowak

to establish a more representative infection rate •. It would be beneficial

to also check several other points in the system to compare infection rates

(Lit~e Togiak, Wind, Agulopak, and Wood Rivers?).

-From August 23 to September 1, 1975, I was part of the FRI tow net .. erew. · The purpose was to examine juvenile sockeye throughout the system

for T. crassus~

7ABLE 2. Tow net sample of juvenile sockeye.

SOCKEYE /. DATE LOCATION NO, USE

-· ,/ 8/23 Lake Kulik (Formalin) / 25

8/24 Lake Beverly 68 (Formalin)

8/27 \

South and Central 40 (Formalin) Lake Nerka 20 (Bouins)

8/28 North and Central 21 (Formalin) Lake Nerka 20~ (Bouins)

8/31 Little Togiak 15 (Formalin)

9/1 Lake. Aleknagik 26 (Formalin)

There were no externally obvious cysts among these juveniles. Few of

the cestodes could be found in the flesh. Subsequent laboratory examination

of the fish preserved in Bouins revealed far fewer parasites than one would

expect. The majority of samples (in formalin) have not yet been_.examined,

-·

s

No account of ~· crassus parasitism in Arctic char could be found in

the literature. It is possible that infection does occur in these fish,

as the eating habits of the char include many infected smolt. The Arctic

char does not serve as a definitive host for the parasite, but could serve

as an intermediate or reservoir host,

I sampled 5 Arctic char from the Little Togiak River to examine for

· macroscopic parasites. The findings included a copepod in the tongue of

one fish, yellowish and white cysts. around and in most internal organs

(usually on the surface of the organs), large numbers of mature cestodes

. in the pylo·dc caeca, and nematodes in the body cavity, The fi"!h were all

heavily parasitized. The internal ·organs of three fish were adhering and

could not be easily separated; .This could be a result of the IllJlllenous

parasitic cysts or migrating nematodes in th~ body cavity. Samples of

these parasi.tes were preserved in bouins and formalin •

.Other adult Arctic.: char were. examined through the summer, The results

were very similar. Two juvenile char were captured in a pike trap. The

juveniles showed no evidence of encysted parasites which probably reflects

-·' the fact they do not feed on sockeye or other small fish as do the juveniles.

It· is difficult to identify encysted parasites. Hopefully it will be

possible to determine what the different cysts in the char represent. Cyclo-

poid copepods, an intermediate host, were not examined in 1975.

T. crassus could parasitize other fish in the lake system, This is not

known at the present time, but it is likely to be found true for whitefish

and possibly other fish~

- ...... -~ -:... ..... ·. • :<- ·~----- -. ~

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·.·.

6

Life History Segments of Adult and Juvenile Stages of T. crassus and

its Hosts Useful for Possible Parasite Control Operations

One obvious point in the cycle of the parasite which could be used

for control is when pike are concentrated during spawning and the eggs of

the parasite are released. Pike spawning habitat represents a concentrated

focus of the infection. In these areas, control could be attempted on the

definitive host, the parasite itself (eggs and coracidia), or the first . . intermediate host, cyciopoid copepods.

,·

An effort will be made in 1976 to determine the timing of proglottid'

release and egg to coracidia development. It: might also be possible to

examine the-infectivity of diff~rent areas by. looking at the infection

rates of copepods,· if this·can_be. accomplished. In terms of how the in-

fection spreads, it would also .be beneficial .to know what physically

happens to these eggs in water.

Effects of T·. crassus Parasitism Shown by His-topathological Examination of

Sockeye Salmon, Northern Pike, and Arctic Char

Most of the effort in Alaska between sampling periods, and all of the

time at the University of Washington, has been spent toward evaluating the

histopathological effect of the parasite. on each of the study fish. The

initial work in Anchorage concerned the principles of fixing, dehydration,

clearing, and infiltration of tissue. These histological operations were

accomplished with the tissuematon. The result of the operation is a block

of paraffin containing the tissue to be examined. Paraffin blocks of char

cysts, pike intestine attachment sites, and sockeye smolt and juveniles (in-

fected and uninfected) will be examined for any histopathology.

The next steps in histopathological examination are the use of the micro-·,

tome and staining procedures. This process is ongoing at the University of

,.

. ·· ~-.... ··

./

7

Washington. There have been several difficulties with the staining pro-

cedure, which. has not been standardized,as methods useful for mammals

.are not always appropriate for aquatic organisms. Several individual

slides of the. various tissues have been adequate. I have not made detailed

l'athological observations; however, casual·. observations of these slides to

evaluate staining have shown the attachment of T. crassus. in pike intestine ·

is a deep penetration, causing extensive. pathology. The worm passes be-

tween the villi and burrows well into the smooth muscle surrounding the

intestine. At this time, a complete evaluation of the damage to host tis­

sue or the pike 2tself is not appropriate.

There are more encysted .1· crassus in a so.ckeye smelt than the tell-

tale exterior-lumps would indicate. If the cysts are very small, or located

deep in the muscle, they show no exterior evidence. In one extreme case

the cysts took up approximately 30~ of the white muscle·area in a ·single

cross section of sockeye smelt. Several of these cysts could not be noted

externally •

.There are vacant or necrotic areas in the liver tissue of these sockeye

.smelt. This is .. not normal. It is not probable that this _is the result of

T. crassus infection, but the situation needs to be explained, if possible.

These could be artifacts of poor histological technique, and nothing more,

Determine the abundance of .1• crassus in sockeye smelt at several

locations in the system.· ·

Examine the infection from proglottid release through the copepod

to determine relative infectivity of different areas.

Possible laboratory examination of eggs, coracidia, and copepods

related to parasite control.

-·

/

8

Examine relationship of T. crassus and Arctic char.

Examine relative predation of Arctic char on infected vs. uninfected

sockeye smolt.

Examine migration time through rivers (daily cycle) of infected vs.

uninfected smolt (might relate to predation) .•

Histopathological study of the infection.

.•·.

,----

INVESTIGATION OF THE ASSOCIATION BET'wEEN NORTHERN PIKE, ARCTIC CHAR, AND SOCKEYE SALNON AS RE­_LATED TO THE CESTODE Triaenophorus crassus

(PATHOLOGICAL EFFECTS ON SOCKEYE SALHON)

A Preliminary Report · To Alaska Department of Fish and Game

by

John Burke

Washington Cooperative Fisher; Research Unit College of Fisheries

Universtiy of lvashington Seattle, Washington 98195

JANUARY, 1977

PATHOLOGICAL EFFECTS OF Triaenophorus crassus INFECTION IN SOCKEYE SAL.I.!ON

OBJECTIVES WERE:

1 •. To determine the infection rate of T. crassus in the different Wood River Lakes.

2. To make general. pathological investigations-of infected sockeye smelt; infection vs. length and weight, location and description of cysts, and extreme situations of infection.

3. A histopathological investigation of the infection in sockeye smelt and northern pike.

4. Tb determine possible variable effects of char predation on infected and uninfected sockeye smelt.

5. A laboratory experimental infection of juvenile sockeye.

6. A statistical evaluation of infection rate data as possible indirect evidence of survival differences between infected and uninfected sockeye smelt during outmigration.

' SUMMARY OF PRELIMINARY RESULTS

Samples of discrete smelt populations were obtained from Lakes, Kulik,

Little Togiak, Aleknagik, and Beverly. The infection•rates from lake to

lake were not constant. This is contrary to the statistical implications

and assumptions from the Wood River Smelt program:in 1975 •.

The number of encysted ~ crassus was determined for each fish examined.

This number reflects the intensity of infection per fish. Since this

evaluation deals with the actual numbers of parasites carried by a group

of fish it should prove a more useful measurement for comparing infection

in different populations.

-2-

Place Period Smolt Infected " Infected T. crassus/fish "

Aleknagik 6/4-6/11 77 33 43 .90

Little Togiak 6/29-7/8 220 6 3 .03

Beverly 6/20-6/26 275 175 64 1.35

Kulik 7/3-7/4 111 18 16 .19

General pathological investigations are not complete, but I can make

some preliminary comments. Wood River Smolt data from 1975 suggested

that ~ crassus infection does not affect grovth in length of juvenile

sockeye. Many of the smolt collected in 1976 ve·re veighed and measured

and grovth vill be evaluated related to the intensity of infection.

The primary site of infection is the anterior dorsal area of vhite •

.•. · muscle. The large majority of infections shov as an external blib or

cyst. ·Rare infections vere noted in the head region, the gills , and the

caudal peduncle.

Histopathological examination suggests sockeye juveniles cope vell

with infection by~ crassus. The plerocercoids are usually surrounded,

encysted, by the fish's inflammatory response. There were instances of

empty (of worms) fluid filled cysts. In these cases the worm had probably

died. In very rare instances the cyst vall seemed neoplastic.

In a more gross vay histopathological examination revealed that a

large amount of white muscle was often replaced by several encysted vorms

in the same cross section. This could lead to the assumption that these

fish are partially handicapped when using these muscles. These muscles

are used for the svift bursts of speed necessary to escape predation.

-3-

Statistical comparison of infection rates in sockeye smolt taken by

~ke net and from char· stomachs is not complete. The data from the two

areas examined,:!.Agulowak.·.River:mouth:.and Agulopak River mouth, is somewhat

contradictory. Preliminary trend graphs would show differences in infection

rates from char vs. nets, but these differences.are not similar in the

two areas.

The attempt to infect juvenile sockeye in the laboratory was not a success .

. The statistical evaluation of infection data through· the system during

smolt outmigration is not complete.

•

FrojBct Objectivesr

PIKE IJ>VESTIGATIOl~S

A Summary Report

1977

1. Determine dist~ibution of the northern pike and define the amount of northern pike hal:•it2.t in the Hood River lakes.

2. Define the population st:ructuro; of pike populations of the 1-iooci River lakes with emphasis on Lake Aleknagik,

), Estimate the discreteness of pike populations in Lake Aleknagik,

4. Assist in conducting an an~ler harvest survey ·of northern pike in the Hood River lakes,

5. Conduct a stcm.:-;.ch ::.naly·sis of northern pike in Lake Aleknagik with emphasis on the _!. crassus life cycle.

Progress:

Over 500 northern pike from the \·lood River lakls were aged and their

lengths at each annulus back-calculated using opercular bones, The

back-calculations Here done using a simple photographic enlarger to

project a magnified image for measurement, The bones were placed in

a glass dish of xylene during projection to enhance clarity, Opercular

bones were read three times, twice before projection and once during

the back-calculation procedure, Most of the bones could be read using

a laree magnifyine glass while small bones were inspected under a

· binocular dissecting scope, . Often the lart:;er opercular bones have a

thick, sr.ongy, r;luti.r.ous base which may o"bl'cure the "first and second

;tnnuli (rr.r?.ly three), Hhen suspicion of missing anntili !'irtS encountered,

'.~alford plots were used to find. the missint; annuli if they occurred,

The Halford plot is a graph of "length at age n" on "length at age

n + I", Eack-calculn ted values a_re plotted aiid the result is a re:ore.s­

sion who:<e y-intercept is length at age I,

Over 100 total lengths of northern pike of all sizes were re:oressed.on

opercular bone lengths and gave the relationship: y = -2,5 + .322x,

Otoliths from 77 northern pike of all sizes were prer~red and aged

to give a oomparison of readings with or~rcular bones, Of the 77 com­

parisons, 58 11ere in agreement, 13 va.ried by one year, four varied 'cy

two years, and t-•o Yaried by three years,

A general conclusion dealing in aging techni<;.ues for northerns

is that opercular bones are far superior to other methods, Briefly,

the disndvantages are (1) the nead to sacrifice the fish, and (2)

they can be used for age and grcnth but not age alone(problem of

missing annuli of older fish).

Age, length, weight, sex, location, and other pertinent data. ,;ere

coded, punched on IBN cards, and fed into the computer for analysis,

Regressions of age on length for Lake Aleknagik, Lake Nerka, Little

Togiak Lake, Lake Beverley, and L"ke Kulik were run and tested for

difference, Age on length regressions for males and females, as well

as observed and back-calculated valuesJwere computed and tested for

difference, Regressions of at;e on length for three :;ections of Lake

Aleknagik have been computed and test<?d for· difference,. Length on

wei~ht regressions for males and females have been com1~ted and t~sted

f'oc di.ffQrcnce,

The above regressions have "cecn tested for homoc;e.nei ty of slope

using an F-test (alph::t. = .10). The a.e;e on len~th regression of Lake

Nerka northern pike differed si:I;nificantly from ti1e C'!.gc on lenr;th

regression of northerns from Lake Aleknagik. Tho age on le!l~th rct:;res­

sicn for Le.ke Kulik a.lzo differed si~nificantly from Lake J.l,,kna~ik,

but only for the first threE:: aze claEscs, The ac:;e on length rev:-essions

for observed and tack-calculated values of pike from Lake Aleknae;ik

were significantly different only for the older a~e classes, All

other regression tests were insignificant.

The age-length relationship of northern pike from Lake Aleknagik

is shown in Fiet1re 1.

In· Fj.gure 2, the same relat~.onship is coml"'-red wj_th th?.t of northe:e:n

pike from other Alaskan waters, Canadian lake:;, l·i ieconsin t<a ters, and

Lake: Hindermere in England,

Figure J gives the length-weight relationship of northern pike

from Lake Aleknagik.

Foregut a.n.<tlysis of northern pike from the 1·iood River system

has been completed and wHl be presented at a later date,

A regression of total length on fork lene;th of northern pike from

I.ake Aleknagik gave the relationship: !"1 = -5.458 + .9529 T1 (n =

251, r = .9995).

Plants collected.for habitat evaluation are being identified by

Dr. }!urray a.t the University of AlaskP. herbariun,,

The :r.ethod of external sex determination described by Casselman

(1974) was tested on 311 northern pike from Lake Aleknat~ik, Pike

..... 1l('l"':lo/' fr"m ?~1-r•m to P.!•Q ·r.:~ ~J•d "CCll"~cv v:-r-~i~.:~ l'"""·•t··nn ?,•:! ~11·1 q(·~ J-~ ....... •.• ..... ~-~ .... ,,,. ~.r ... ,,,_, n,. c• ··• J :.• ---U t_..,~l ..... 1 .,..,., l ,.·,~

with time,

The average sport ca.uc:ht northern pl.ke from Lake Aleknagik for the

duration of the project was 526 mm or 20.7 inches (n = 366).

The Futurea

There. are two major asr,ects of the pike investigations that have

yet to be dealt with. They are mainly, (l)·estimate the discreteness·

of pike populations, and (2) determine the distribution and define

the amount of pike ha"oitat :l.n the· system,

The results of our tagging study will be analysed next. If all

goes well, these data ''ill be presented at the upcoming interagency

meeting", Hhen this is complete, all attention 1<ill be given the habitat

and distribut:l.on aspect of the study,

The ev~1uation of all the above data will be concurrent with

preparation of the thesis.

~

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0 -~

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20

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Figure 1

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5

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Year of Life

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. :.

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120

..c:: -Cl c:: 60 .3 0 -~ 40

Figure 2 ..... ··.

. . . : .

. -.. ···~ ... ··-· ___ , .......

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•

o Cree Lake, Saskatchewan • Great Bear Lake, N.W. Territory .:. Lake Aleknagik • Lake Windermere, England o Wisconsin Waters • Minto Flats*

8 10 12 14 16 18 20 22 24 26 28 Year of Life

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5000

Log W= -5.24576 +3.02133 Log L

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500

Figure 3

ARLIS Alaska Resources

Library & Information Service~ Anchorage Alaska