J., S., Dawe E., D., J. Snook - Torngat Secretariat · 2015. 9. 15. · TJFB‐DFO 2013...

TJFB‐DFO 2013 Collaborative Post‐Season Trap Survey for

Snow Crab in NAFO Division 2H and 2J North

Whalen, J., Boudreau S., Dawe E., Mullowney D., and J. Snook

Torngat Wildlife, Plants and Fisheries Secretariat,

217 Hamilton River Rd., P.O. Box 2050 Stn. B

Happy Valley‐Goose Bay, NL A0P 1E0

2013

Torngat Joint Fisheries Board

Torngat Wildlife, Plants & Fisheries Secretariat 2013/02

Torngat Wildlife, Plants and Fisheries Secretariat

The primary responsibilities of the Torngat Wildlife and Plants Co‐management Board

and the Torngat Joint Fisheries Board are to establish total allowable harvests for non‐

migratory species of wildlife and for plants, recommend conservation and management

measures for wildlife, plants, and habitat in the Labrador Inuit Settlement Area (LISA)

and to make recommendations in relation to the conservation of species, stocks of fish,

aquatic plants, fish habitat, and the management of fisheries in the Labrador Inuit

Settlement Area.

The Secretariat is the implementation agent of the Torngat Joint Fisheries Board and the

Torngat Wildlife and Plants Co‐Management Board. The Secretariat is a team of

professionals based in Happy Valley‐Goose Bay that provide financial management,

logistical, project management and analytical support to both boards.

Torngat Omajunik, Piguttunik Oganniaganillu Suliangit

Suliagigumajangit Torngat Omajunik, Piguttunillu AulatsiKatigengita

AngajukKauKatigengit ammalu Torngat Ikajuttiget Oganniatuligijingita

AngajukKauKatigengit sakKititsigiamut pijaugunnatunik katillugit aullaigatsatagiamut

nokataKattangitunik omajunik ammalu piguttunik, uKautjigiajut asikKitailigiamut

ammalu aulatsigiamut omajunik, piguttunik, ammalu inigiKattajanginnik Labradorimi

Inuit Satusasimajanginni Nunani (LISA) ammalu uKautjigiagutinik ilingajunik

asikKitailigiamut omajunik, oganniaganik, piguttunik, oganik, ammalu aulatsigiamut

oganniaganik Labradorimi Inuit Satusasimajanginni Nunani. SuliaKattet atuliaKititsigumajut kiggatuttinganik Torngat Ikajuttiget

Oganniatuligijingita AngajukKauKatigenginnik ammalu Torngat Omajuligijinginnik

Piguttunillu AulatsiKattajut AngajukKauKatigenginnik, sunatuinnanik, suliatsanik

aulatsigiamut ammalu ikajutsitaullutik tamâginnut angajukKauKatigenut.

i

Torngat Wildlife, Plants & Fisheries Secretariat Series

2013

TJFB‐DFO Post‐Season Trap Survey:

Snow Crab in NAFO Division 2H and 2J North

Whalen, J.,1 Boudreau S.,1 Dawe E.,2 Mullowney D.,2 and J. Snook1

1Torngat Wildlife Plants and Fisheries Secretariat

217 Hamilton River Rd., P.O. Box 2050 Station B,

Happy Valley‐Goose bay, NL

A0P 1E0

2Department of Fisheries and Oceans

Northwest Atlantic Fisheries Centre

PO Box 5667, 80 East White Hills

St. John’s, Newfoundland and Labrador

A1C 5X1

ii

Published by:

Torngat Wildlife, Plants and Fisheries Secretariat

217 Hamilton River Rd., P.O. Box 2050 Stn. B

Happy Valley‐Goose bay, NL

A0P 1E0

Whalen, J., Boudreau, S., Dawe, E., Mullowney, D., and J Snook. 2013. TJFB‐DFO

Collaborative Post‐Season Trap Survey: Snow Crab in NAFO division 2H and 2J North.

Torngat Wildlife, Plants & Fisheries Secretariat. Ser. 2013/02 + 54 p

TABLE OF CONTENTS Executive Summary .................................................................................................................... 1

Introduction ................................................................................................................................. 3

Objective of Post‐Season Trap Survey ................................................................................ 10

Methods ...................................................................................................................................... 11

Recommendation from past year’s survey ......................................................................... 11

Application Process ............................................................................................................... 11

Study Areas ............................................................................................................................. 12

Gear and Survey Design ....................................................................................................... 13

Sampling Procedure .............................................................................................................. 14

Results ......................................................................................................................................... 18

Survey summary .................................................................................................................... 18

Temperature ........................................................................................................................... 23

Depth ....................................................................................................................................... 26

Soak time ................................................................................................................................. 27

Sampled pots .......................................................................................................................... 29

Station 320 (Tagged crab) ...................................................................................................... 37

Shell Condition ....................................................................................................................... 40

Bycatch ..................................................................................................................................... 43

Summary and Discussion ........................................................................................................ 46

Recommendations .................................................................................................................... 47

Conclusions ................................................................................................................................ 48

Acknowledgements .................................................................................................................. 48

References .................................................................................................................................. 49

LIST OF FIGURES

Figure 1. Life cycle of snow crab ................................................................................................ 5

Figure 2. Female crabs ................................................................................................................. 7

Figure 3. Immature and mature female crabs .......................................................................... 8

Figure 4: Male crab ....................................................................................................................... 9

Figure 5. The survey stations in NAFO Division 2H‐J North. ............................................ 12

Figure 6. Fishery catch per unit effort (CPUE) in NAFO 2J ................................................. 13

Figure 7. Tagged crabs .............................................................................................................. 15

Figure 8: Measuring carapace width (CW) ............................................................................ 16

Figure 9. Shell ages .................................................................................................................... 17

Figure 10: Claw sizes ................................................................................................................. 18

Figure 11. Sampled stations in 2013. ....................................................................................... 19

Figure 12. The number of males and females caught at each station. ................................ 21

Figure 13. The number of crab per trap at each station ........................................................ 21

Figure 14. Map of the proportional catch rate of male and female crab. ........................... 22

Figure 15. Average temperature (oC) at each station. ........................................................... 23

Figure 16: The average temperature (oC) at each corresponding average depth

(fathoms). .................................................................................................................................... 24

Figure 17. Number of crab captured at each average temperature. ................................... 24

Figure 18: The number of crab per trap (effort) at each average temperature (oC), from

coldest to warmest. .................................................................................................................... 25

Figure 20. The total catch and male/female proportion with average temperature. ....... 25

Figure 20. The number of males and females recorded at each depth (fathoms), from

shallow to deep. ......................................................................................................................... 26

Figure 21. Number of crab per trap by depth, shallowest to deepest. ............................... 26

Figure 22. Map of the total catch and male/female proportion with average depth. ...... 27

Figure 23. The number of crab captured with each soak time, shortest to longest. ......... 27

Figure 24. Number of crab per trap by soak time, shortest to longest. .............................. 28

Figure 25. Shell condition and carapace width (CW) of station 307 measured males in

small mesh pot, N=5. ................................................................................................................. 30

Figure 26. Shell condition and carapace width (CW) of station 308 measured males from

a large mesh pot, N=17. ............................................................................................................. 30

Figure 27. Shell condition and carapace width (CW) of station 309 males measured in

the large mesh pot, N=27. ......................................................................................................... 31


large mesh pot, N=41 ................................................................................................................. 32

Figure 29. Shell condition and carapace width (CW) of station 312 measured male ....... 32

Figure 30. Shell condition and carapace width (CW) of station 312 females measured in

the small mesh pot. .................................................................................................................... 33


the small mesh pot, N= 20. ........................................................................................................ 33



Figure 33. Shell condition and carapace width (CW) of station 313 females measured in

the small mesh pot, N=5. ........................................................................................................... 34


the small mesh pot, N=9. ........................................................................................................... 35




the large mesh pot, N= 32. ........................................................................................................ 36

Figure 37. Frequency distribution of tagged crab carapace widths (CW) and their shell

condition, N=76 .......................................................................................................................... 37

Figure 38. Frequency distribution of all measured male crab from large mesh pot 3 of all

stations to examine the proportion of shell conditions present, N=180 (there was only 1

crab present and measured in pot 3 of station 20). ............................................................... 40

Figure 39. Frequency distribution of all measured male crab from small mesh pots (pot

7) of all small mesh pot stations (crab were caught at stations 307, 312, and 313) to

examine the proportion of shell conditions present, N=34. ................................................. 41

Figure 40. Map of proportion of male crab by shell condition from large mesh pot 3. ... 41

Figure 41. Frequency distribution of all measured female crab from all stations to

examine the proportion of shell conditions present, N=148. We note that two of the

female crab included here, a 56 mm CW new‐shelled and a 59 mm CW old‐shelled,

were measured from the large mesh pot sampled at station 308 (no small mesh pot at

this station). The remainder of the females were from small mesh pots. .......................... 42

Figure 42. The total bycatch in number by species recorded from the survey. ................ 43

Figure 43. Map of proportion of different bycatch types. .................................................... 45

Figure 44. Map shows proportion of Wolffish species caught by station. ......................... 45

LIST OF TABLES

Table 1. Quota reports by year ................................................................................................... 4

Table 2. Summarized data from each sampled string presented by each station. ........... 20

Table 3. Summary of pots sampled for length measurements. ........................................... 29

Table 4. Tagged crab details from station 320 including the tag number. ......................... 38

Table 5. Bycatch species, listed alphabetically, broken down by each station. ................. 44

1

Executive Summary

Under the Torngat Joint Fisheries Board’s (TJFB) research program, the Torngat Wildlife, Plants

& Fisheries Secretariat collaborated with Fisheries and Oceans Canada (DFO) to develop and

implement the TJFB‐DFO Collaborative Post‐Season Trap Survey for Snow Crab in NAFO

Division 2H and 2J North in 2013. The objective of the Survey is to infer the continued health of

the Nunatsiavut snow crab resource in NAFO Division 2H and 2J North (Crab Management

Area 1) by obtaining data on the recruitment, mortality and abundance of the crabs within

commercially fished areas. There are several components to the survey: a tag and release

program that will provide indications on mortality rates and abundance; a small meshed pot

sampling program that targets the capture of females and juvenile males to give an indication of

recruitment prospects and larval production; and commercial sized pot sampling program that

provides additional trends analysis for snow crab and bycatch.

The Survey sampled 20 stations where all crabs and bycatch were counted. In 2013, crabs were

measured from 19 large mesh pots across 10 stations and 10 small mesh pots. Ten large mesh

pots were sampled at station 320 where 76 commercial sized male crabs were successfully

tagged. No crabs (or very few) were caught at the northern stations (301 to 306) and some more

southern stations (310, 315 and 317). Overall, most crabs sampled were recently molted (soft‐

and new‐hard‐shelled). The largest proportion of soft shelled crab was found at station 313.

Soak times ranged from 13.5 to 29 hours with the majority of the crabs captured in stations with

soak times less than 24 hours. In general, females were caught at shallow cold areas and the

largest males in deep warm areas, and the majority of crabs are found around the Cartwright

Channel.

It is recommended to continue the survey for a minimum of three years, so that trends in crab

catch rates, male size composition, shell condition, maturity of females and males, depth and

temperature, as well as bycatch may be examined. Other recommendations included: bringing

stations 304 and 317 east to a depth of 50‐60 fathom; keeping the northernmost stations to detect

a recruitment signal in the future; add four unbaited pots to each end of the string to prevent

movements from current; and expand the tag and release program to all survey stations. In

conclusion, the collaborative post‐season trap survey was successful in completing the first year

of the time series.

2

AngajukKaunet Naillitisimajanga

Atâni Torngat Ikajuttiget Oganniatingita AngajukKauKatigenginni (TJFB)

Kaujisannigisimajangit, Torngat Omajunik, Piguttunik Oganniaganillu Aulatsijingit

ikajuttiKadlutik Oganniaganik Imappimilu Canadami kamajinik (DFO) âkKisuilauttut

atuttauliaKititsidlutillu TJFB‐DFO Ikajuttigetillugit Jârimi Tarâpinik atudlutik Kaujisasimajut

Putjotivannik NAFO Nalunaikkutak 2H‐mi ammalu 2J Taggâni 2013‐mi. Tugâguringit

Kaujisannimut Kaujimattisigiamik kajusijumik inositsiagittotitsigasuannimut Nunatsiavut

putjotivangit atuttautillugit NAFO SuliaKapvinginni 2H ammalu 2J Taggâni (Putjotivannik

Aulatsijet Nunangani 1) Kaujisallutik pitâsongugiamut, tuKuKattajunik ammalu

ununninginnik putjotivait aullaigatsaulittilugit oganniataullutik. Unuttunik piusiKagunnatut

Kaujisagiamut: nalunaikkutattâlugit aullatiniammilugit takutitsigunnalâmmata

tuKuKattajunik kititanginnik ammalu ununninginnik; mikijumik nullualimmik nuluamik

atullutik kamagiluallugit annangit ammalu pigugiasitainnatuit angutet takutitsigiamut

pijaugunnagajattunik ammalu piagatsangit kamagillugit; ammalu aullaigatsatallutik angijunik

putjotinniagutinik atullutik Kaujisagiamut pivitsaKattisigajattuk Kaujisagiamut putjotivanik

ammalu pijauKattajunik.

Kaujisasimajut 20‐nik inigijauKattajunik ilonnainut putjotivannut pijauKattajullu kitidlugit.

2013‐mi, putjotet ottutaulauttut pisimajut 19‐nanit angijunit putjotinniagutinit senani

inigijauKattajuni ammalu senait mikinitsait putjotinniagutet. Senait angijut putjotinniagutet

ottugattaulauttut inigijauKattajuni 320 tamâni 76 angijuit angutet putjotet

nalunaikkutattâtaudlutik. Putjotet (ubvalu ikittuit) pijaulauttut taggâni putjotinniavini (301 –

306) ammalu ilangit siKingani inigijauKattajuni (310, 315 ammalu 317). Ilonnâgut, ilonnagalatik

putjotet ottugattaulauttut mânnaKamik aKittosimajut (aKittunik ammalu nutât

uvilukuttâgiasitainajut). Anginippâk aKittumik uvilukulik putek takujaulauttuk

inigiKattajangani 313‐mi. kinitsitauKattalauttut pigiasidlutik 13.5‐mit 29 sitondinut u nunningit

putjotet tigujautillugit inigiKattajanginnit kinitsitauKattadlutik ikinnisanit 24 sitondinit.

Ilonnâgut, annait tigujausimajut ikkatuni nillinattuni Imani ammalu anginippât angutet itijuni

nigummituni Imani; ammalu ununningit putjotet takujaudlutik saniani Cartwright Imanginni.

UKautjigiagutiKavuk kajusigiamik Kaujisannimik ikinnisaungitunit pingasunit jârinit,

taimaimmat putjotet pijauKattajut kititangit, angutet Kanuk angitigimmangâta, uvilukungit

kamagillugit, piguppalianingit annait angutellu, itiningit onanningillu imait, ammalu

pijauKattajut kamagijaullutik. Asingit uKautjigiagutet ilauttisijut ukuninga: InigijauKattajut

304 ammalu 317 kangiani itininganut 50‐mit 60‐mut isattanik; piulimallugit taggânenitsait

inigijauKattajut Kaujigiamut pijaugunnagajattunik sivunitsatinni; ilallugit sitamanik

nagiaKangitunik putjotinniagutinik atunit nâningani nuluajangita aulattailigiamut

ingigganimmit; ammalu asingit nalunaikkutattâlugit aullatiKattamillugit ilonnainit

Kaujisattaujunit iniuKattatunit. Nâjiusik, ilauKatigennik omajunniavinni tarâpinut

Kaujisallutik pitsiasimajut pijagedlutik sivulliani jârimi taitsumanganit.

3

Introduction

The snow crab (Chionoectes opilio) fishery is presently the most valuable commercial fishery in

Newfoundland and Labrador. In 2012, the Province landed 50,462 metric tonnes (mt) of snow

crab, with a value of $217 Million CAD. By comparison, Atlantic Canadaʹs total snow crab

landings were 92,849 mt at a $429 Million value (DFO 2013 a,b). The Newfoundland and

Labrador snow crab fishery began in 1967 in NAFO Divisions 3KL, south of NAFO Div. 2J.

Since the 1980s, it has expanded to the entire continental shelf and coastal areas surrounding the

entire Province and incorporated many different vessel fleets, including the Nunatsiavut fleet in

the late 1990s. In 2012, the communal licences in fishing area 2HJN (NAFO Div. 2H and 2J

North) landed 52.3 mt, which is 0.1% of the total landings in Newfoundland and Labrador.

The Labrador Inuit Settlement Area (LISA) is a part of the snow crab fishing area 2H and 2J

North which extends in latitude from 54ʹ40ʺto 56ʹ00ʹʹ N. The 2013 Snow Crab post‐season trap

survey took place within this area. The fishing season in 2H is determined by the Makkovik

plant with ice being a factor, this year the fishery took place from July 7 to August 30. The snow

crab fishery is managed by quota and Nunatsiavut Government has a communal quota

contributing 18% of the total allowable catch (TAC) for 2HJ. In 2013, the total allowable catch

(TAC) for Div. 2HJ was set at 1,765 mt, with the TAC for 2HJN being 310 mt (DFO 2013c). The

2HJ TAC was not landed in 2013, with 83% of the TAC not taken (Table 1). DFO has reported a

decreasing trend in pre‐recruit and exploitable biomass (Mullowney et al. 2012) in Div. 2HJ

likely driven by warmer water temperatures. Snow crab prefer cold conditions (Dawe et al

2012), however water temperature has been warming since the mid‐1990s (Mullowney et al

2012).

In 1989, the area north of latitude 54ʹ40ʺ was reserved exclusively for Nunatsiavut but the first

official Snow Crab communal allocation (500 mt) was given to the Labrador Inuit Association

(LIA) in 1999. From 1999 to present, Div. 2J North (in addition to Div. 2GH, which combine to

be the same area as DFO Crab Fishing Management Area 1) have been the exclusive Snow Crab

fishing area for the Nunatsiavut Government and the Torngat Fish Producers Co‐operative

Society Limited (Coombs 2010). While management is by CMA, there is no Snow Crab resource

or fishery in Div. 2G, so the fishery in CMA 1 is limited to fishing area 2HJN. In addition to

quotas, a fishing area, and a defined fishing season, the fishery is also managed by gear

restrictions which include maximum number of traps and minimum mesh size limits (135 mm).

Undersized males, females, and soft‐shelled crabs that are captured in traps are returned to the

sea. Only hard‐shelled males with a carapace width (CW) of 95mm or greater are retained

(Mullowney et al. 2012).

4

Year Quota

(MT) Landings (MT)

% Taken

Remaining (MT)

1999 600 600 100 0 2000 450 446 99 4 2001 450 478 106 -28 2002 490 478 98 12 2003 450 273 61 177 2004 270 269 100 1 2005 216 175 81 41 2006 216 324 150 -108 2007 238 312 131 -74 2008 362 354 98 8 2009 362 354 89 38 2010 362 348 96 14 2011 362 344 95 18 2012 367 181 49 186 2013 310 52.3 17 259.7

Table 1. Quota reports by year Quota reports (in metric tonnes) by year for CMA 1 (North of 54ʹ40ʺN) communal licences, as

reported by the Department of Fisheries and Oceans (1999‐2013).

The Nunatsiavut snow crab fishery is considered to be small‐scale and was prosecuted by only

5 vessels in 2013. Accordingly, the fishery and fishing grounds have not been the focus of

detailed scientific study, however the region is included in the Department of Fisheries and

Oceans (DFO) Newfoundland and Labrador Region snow crab stock assessment. While

absolute biomass and fishery‐induced mortality are not known, DFO monitors trends from

several data sources in the stock assessment to indicate the status of commercial males, females,

recruits, production, mortality, and fishery performance from year to year. The autumn multi‐

species bottom trawl survey data are compared with data from fisher logbooks (catch per unit

effort, CPUE), at‐sea observers, vessel monitoring system (VMS), dockside monitoring, and

inshore and offshore trap surveys (south of 2J North). The snow crab population is variable by

nature, however the biomass in NAFO Div. 2J experienced a sustained decline in the early 1980s

and then increased through the 1990s to a peak in 1998 (Mullowney et al. 2012). The multi‐

species trawl survey indicates that the overall exploitable biomass in the North (NAFO Div.

2HJ3K) has recently decreased due to a decline in recruitment (Mullowney et al. 2012). The

multi‐species survey had been sampling NAFO 2H every second year until 2012 but it will

henceforth be sampled every year. The fall multi‐species survey samples NAFO 2HJ first,

following the closing of the snow crab fishery. The multi‐species survey samples a broad depth

range, and provides data to predict short, mid, and long‐term recruitment prospects.

5

Snow crab prey upon a wide range of benthic organisms including, polychaetes (marine

worms), clams, shrimp, and fish (capelin Mallotus villosus, Atlantic spiny lumpsucker

Eumicrotremus spinosus, redfish Sebastes spp.) (Squires & Dawe 2003). They also prey upon

(cannibalize) small snow crab (Squires & Dawe 2003) and dead fish (e.g. discarded bait)

(Wieczorek & Hooper 1995). Their predators include Atlantic cod (Gadus morhua), thorny skate

(Amblyraja radiata) (Robichaud et al. 1991), species of wolffish (Anarhichas spp.), and seals (DFO

2011). Snow crab have a circumpolar distribution and support fisheries in the Pacific (Alaska,

Russia) and Atlantic Oceans (Greenland, Norway, Atlantic Canada) (Herrmann and Greenberg

2007). They have a complex life cycle (Fig. 1) that includes several stages in the plankton before

settling to the ocean floor where they moult their shells in the spring to grow. Males reach

commercial size of 95 mm CW after approximately 8‐9 years (DFO 2011), or longer in coldest

areas. Males and females segregate by depth with small crabs settling in shallow cold areas and

migrating to deeper warmer areas as they grow. First‐time spawning (primiparous) females and

small adult males are generally found in shallower water whereas repeat spawning

(multiparous) females and large adult males are found in deeper water (Sainte‐Marie & Hazel

1992). Snow crab are most commonly found in waters less than 5°C (Tremblay 1997) and an

upper limit of 7°C appears to exist for normal metabolic function (Foyle et al. 1989).

Figure 1. Life cycle of snow crab

6

Schematic diagram of the snow crabʹs lifecycle, adapted from Sainte‐Marie et al. 1995. Years and

carapace widths (CW) are approximations. Male snow crabs have three benthic stages, juvenile

(non‐reproductive), adolescent (reproductive but small clawed), and adult (reproductive,

terminally moulted, and large clawed). Females also have three stages, immature (narrow

abdomen), prepubescent (ovaries begin to develop), and adult (fully rounded abdomen and

reproductive) producing 12,000 to 160,000 eggs at a time, increasing with body size (Fig. 2, 3,

and 4). Females can also store sperm to fertilize clutches at later times (Sainte‐Marie and

Carrière 1995). Male snow crab can reach a maximum CW of 150 mm, and females 80 mm CW,

at their terminal moult to sexual maturity (females) or adulthood (males) (Conan and Comeau

1986, Chabot et al. 2008). Terminal moult in females occurs from 40 to 75 mm CW and in males

within a size range of approximately 40 to 115 mm CW (DFO 2011). Snow crabs are expected to

live 5 to 8 years after their terminal moult with a maximum lifespan of approximately 15 years

(Sainte‐Marie et al. 1995, Choi & Zisserson 2008, Fonseca et al. 2008). Females in addition to the

males that mature and terminally moult at a CW < 95mm escape commercial harvest and thus

are able to reproduce without exploitation.

7

Figure 2. Female crabs

From top to bottom, two mature females with rounded abdomens, one immature female with a

narrow abdomen, and a male with a tapered abdomen.

8

Figure 3. Immature and mature female crabs

Immature female with clean (egg‐free) pleopods (swimmerets) (top) and a mature female with

orange eggs (bottom).

9

Figure 4: Male crab

Males have two pleopods found under their abdomen and are used for the transfer of sperm. Fundamentally, a population’s abundance is governed by three processes; birth, death, and

migration (Ricker 1954). These three factors are further influenced by interactions with other

individuals, species, and the environment. With regard to fisheries, birth can be thought of as

recruitment and death as fisheries mortality. If the fished population is considered healthy, then

the underlying goal of fisheries management is to ʺbalanceʺ the new individuals growing and

entering into the fishery with those being removed (both by fisheries and natural mortality). In

essence, this requires identifying where maximum catches are reached but the population

remains stable. With the conservation of healthy stocks as a goal, and because populations

fluctuate with environmental conditions, it is important to have several strong years of

recruitment to sustain a fishable biomass and a commercial fishery if conditions become

unfavourable. The Fisheries Resource Conservation Council (FRCC) (2005) recommended that

the keys to achieving long‐term sustainability in the snow crab fishery are, good egg

production, a reasonable fishing mortality, and a biomass composed of several year classes.

Snow crabs have been tagged opportunistically on the Scotian Shelf since 2004. A total of 9,471

crabs were tagged with 611 recaptures reported and the recaptured crab travelling an average

distance of 15.6 km. Although migration is not generally thought to be a major influence on

population size, snow crab have the potential to move larger distances; a maximum distance of

10

280 km in was reported in the Scotian Shelf study (Choi et al. 2012). Another study in the

southern Gulf of St. Lawrence and eastern Nova Scotia tagged 12,755 adult male snow crabs

(between 1993 and 2003). Of the 1971 tag returns between 1994 and 2004, 1,703 had accurate

recapture positions. The average distance travelled was 16.7 km for those in the southern Gulf

of St. Lawrence (maximum 165 km) and 61.5 km for eastern Nova Scotia (maximum 368 km)

(Biron et al. 2008). Snow crab along the Newfoundland shelf are now believed to travel larger

distances than in the rest of Atlantic Canada due to the expanse of the Continental Shelf and the

stockʹs distribution (Mullowney pers. comm. and under review). Snow crab in the eastern

Bering Sea also undertake long‐range migrations, with females travelling an average of 136 km

(73.5 nautical miles) (Ernst et al. 2005). In NAFO Div. 2J, it is possible that crabs move across the

54ʹ40ʺ line. Tagging could shed some light on this aspect of the fishery as well as provide

information about exploitation by dividing the number of tag returns by the total number

tagged. An accurate estimate of exploitation would require that all recaptured tags are reported

and that tagged and untagged crab are exploited equally. For more details on this approach see

Choi et al. (2012).

Presently, DFO expresses fisheries exploitation rate in Newfoundland and Labrador as an

index, comparing commercial landings with the exploitable biomass index from the fall survey

of the previous year. Long‐term changes in this ratio over time reflect trends in the exploitation

rate of the fishery. In NAFO Div. 2J, the index declined from 2003‐2007 but has gradually

increased from 2007 to 2010 (Mullowney et al. 2012). A precautionary approach (PA) framework

(DFO 2009) has been developed by DFO and is beginning to be implemented in all fisheries. The

goal of the framework is to estimate reference points and establish baselines for managed

stocks. These reference points have yet to be estimated for the Newfoundland and Labrador

snow crab fishery, however in the Southern Gulf of St. Lawrence, the removal rate limit

reference point, i.e., the maximum removal rate for a population in the ʺhealthy zoneʺ (DFO

2009), was calculated to be F = 0.346, or 34.6% of the fishable biomass. This value is the average

exploitation rate expressed as catch in fishing year divided by the commercial sized adult male

crab biomass estimate of the previous year for the 1998 to 2009 fishing years (Hebert et al. 2012).

On the Scotian Shelf, the target removal reference is 22% of the fishable biomass (F = 0.22), with

alternative indicators between 11 and 36% of fishable biomass (F = 0.11 to F = 0.36). Here F is

defined as the fishing mortality of the legal sized adult male population (Choi et al. 2012).

Objective of Post‐Season Trap Survey The objective of the TJFB‐DFO Post‐Season Trap Survey is to infer the continued health of the

Nunatsiavut snow crab resource in fishing area 2HJN (Within CMA 1) by obtaining data on the

recruitment into the fishery, as well as the mortality and abundance of the crabs within

commercially fished areas. Tagging will provide information on mortality rates and on

abundance while small meshed pots will target juvenile and adolescent males as well as females

to give an indication of recruitment prospects and larval production in the area.

11

The results will be distributed to the Torngat Joint Fisheries Board to inform decision‐making

for recommendations to the Minister of Fisheries and Oceans and to the Fisheries and Oceans

scientists for annual stock assessment.

Methods

Recommendation from past year’s survey Snow crab trapping surveys have previously been conducted within NAFO Div. 2H in 2009 and

2010 (Brothers and Coffey 2013) and within Div. 2J North in 2012 (Boudreau and Whalen 2012).

The TJFB’s snow crab survey was changed for 2013 from a mid‐season collaborative survey to a

fishery independent post‐season survey based on recommendations from the past year. The

methodology was adjusted to use a similar approach to that of the FFAW‐DFO Collaborative

Post‐Season Trap Survey (Mullowney et al 2012), but it included a tagging component. The fall

survey allows for the tagged crab to be available for the fishery of the following year and data

obtained may provide an estimate of exploitation rate.

The fishery‐independent post‐season survey would also not remove any of the catch from the

fishers in terms of tagged crab being returned and small mesh pots being put on the string

replacing commercial pots. Post‐fishery surveys for snow crab are common at NL and

elsewhere (i.e., Nova Scotia, Choi et al. 2012 and Southern Gulf of St. Lawrence, Hebert et al.

2012) and fall trapping surveys are ideal for estimating incoming recruitment to the exploitable

biomass. New recruits are identified as new‐hard‐shelled legal‐sized adults that were soft‐

shelled during the past fishery. The fall survey catch rate of new‐hard‐shelled crabs

(recruitment) plus the intermediate and old shelled adults (residual biomass) would provide a

good index of the exploitable biomass available to the yearʹs fishery. Fishery‐independent post‐

season surveys would not have to rely on fishers taking a researcher onboard while

commercially fishing and would also provide a better opportunity to sample shallower grounds

where smaller individuals (pre‐recruits) are likely found in higher concentrations and these

cohorts could be followed through time.

Application Process The advertisement requesting vessel, captain and crew to apply to conduct the survey is posted

via several avenues including the Secretariat website, newspapers and mailed copies to

previous applicants and fishers in the region. Applicants meeting mandatory safety and gear

requirements will be separated in two pools: (1) Vessel with Labrador Inuit beneficiary/ies, (2)

Vessel with Non‐Labrador Inuit beneficiary/ies. A candidate from pool one will be drawn, if

there are no candidates in the pool, then a candidate will be drawn from pool two.

12

Study Areas The study sites (stations) were established within CMA 1, and specifically in fishing area 2HJN

(Fig. 5) based on historical snow crab landings (Fig 6.). The survey design was intended to

encompass a broad depth range so as to sample the exploitable population as well as all other

components of the population (smaller crabs) at shallower depths. Small crab are typically

found in shallower areas than large crab. Lessons learned from the FFAW‐DFO Post Season

Trap Survey led us to target small crabs using small‐meshed pots only in shallow areas.

Figure 5. The survey stations in NAFO Division 2H‐J North.

Legend‐ Red‐ string of commercial sized pots, Green‐ string with one small mesh pot, Blue‐

string where all adult male crab are measured from commercial sized pots.

13

Figure 6. Fishery catch per unit effort (CPUE) in NAFO 2J

Fishery catch per unit effort (CPUE) in NAFO 2J, the solid black horizontal line marks the 54ʹ40ʺ

line dividing NAFO 2J North from South. CPUE ranges from darker blue (lowest) to brightest

red (highest). (DFO Regional Advisory Process meeting, 2012)

Gear and Survey Design A total of 10 baited commercial crab traps and 1 small mesh pot will be set at each station. There

is a total of 20 stations, of which 10 require the contents of small mesh pots to be sampled

(Stations 1, 3, 4, 5, 7, 10, 12, 13, 14, 17) and thus baited. The small mesh pot, with a mesh size of

1 inch, will be placed fourth in the string. Conical commercial traps with a diameter not greater

than 133cm (52.362 inches) are to be used with a mesh size of 5 ½ inches. Traps will be spaced at

25 fathom intervals along each string. Each trap will be baited with 3 pounds of squid on a

single skiver. No bait protection devices will be used. A standard 20‐lb weight will be affixed to

both down‐ropes of each string; with the weights located 15 fathoms from the end trap. Gear

must be soaked a minimum of 12 hours and a maximum of 24 hours. All contents in the traps

could not be retained as per DFO Experimental License. The Minilog temperature gages are to

14

be affixed to the first trap at each station to record bottom temperature every hour. It is best to

add the gage to the skiver inside the trap to prevent loss.

Three station types were addressed in Figure 5. The nine red stations are strings of commercial

sized pots. All species are counted and a biological sampling taken of all males and female

snow crabs in pot #3. The ten green stations are strings of commercial sized pots plus an

additional small meshed pot. All species are counted and biological sampling is conducted for

all males and females in pot #3 (commercial mesh size of 5 ½ inches) and the small meshed pot

in pot #7. The one blue station was a string of commercial sized pots. All commercial sized

males from the string were biologically sampled and tagged with spaghetti tags.

Sampling Procedure Vessel set data are recorded, including: date, time, coordinates of the gear set and hauled, soak

time, depth and Minilog identification number. Catch data are also recorded, in which all

species are identified and counted.

To collect data that might provide an index of future fishery recruitment, small mesh traps with

one inch mesh must be deployed in select stations to target juvenile and female crab. A size

frequency sampling protocol is conducted for all of the snow crab specimens in the trap.

All species are counted and recorded from the third commercial trap for every station. A size

(width) frequency is done for all of the male crabs in the trap.

A pilot small‐scale tag‐recapture experiment was conducted to investigate the potential use of

this method for providing data on exploitation rate. Terminally‐moulted legal‐sized male crabs

are tagged from commercial crab traps at station 20. A size frequency distribution is generated

for all commercial‐sized male crab in the string. As terminally moulted crabs have stopped

moulting, the tags should be retained on their carapace. The crabs are tagged with a plastic

spaghetti (Floy) tag by a square knot with the tag wrapped around the carapace through the

first and second pair of walking legs (Fig. 7, Taylor et al. 1989, Taylor 1992, Sainte‐Marie &

Turcotte 2003, Gravel et al. 2006). When the tagged crab is recaptured, fishers will return the tag

with a form stating the date and location to receive a cash reward at the end of the fishery.

Return of yellow tags will receive a reward of $10 and blue tags will receive a reward of $80.

Every tenth crab received a blue tag.

15

Figure 7. Tagged crabs

Tagged crab, blue tag with a reward of $80 on top, yellow with a $10 reward on the bottom

panel.

Biological Sampling

Sampling of individual crabs included the following variables: carapace width (CW) to the

nearest millimeter (Fig 8), shell condition (soft, new‐hard, and old‐hard, Fig. 9),

presence/absence of Bitter Crab Disease (BCD), carapace damage (old and/or new), missing legs

(number, old and/or new).

16

Figure 8: Measuring carapace width (CW)

Measuring carapace width of a snow crab with calipers. Carapace width (CW) measured in

millimetres (mm) measured straight across the widest part of the carapace.

(a note that this photo was taken in Alaska and the brown spots on the crab are sea leach egg

cases from the North Pacific).

17

Figure 9. Shell ages

Shell ages. Left panels are females; a new shelled and old shelled female on top and a very old

individual on bottom. Right panels are males; the top individual is a soft‐shelled on top of a

new hard‐shelled crab, on the bottom is an old‐shelled male. General guidelines to assessing

shell condition are: Soft (1) the claw gives in to pressure, the shell is typically white underneath

and clean on the top, full (or mostly) of water, and legs have sharp points; New‐Hard (2) shell is

still brightly colored, may have a few epibionts or barnacles, claw not easily bent by thumb

pressure, legs may have sharp points or becoming less pointed; Old (3) shell is fouled, yellow to

brown underneath, full of meat, with potentially a few black spots and barnacles are common,

and points on legs will be dull.

Some additional biological measurements were required based on the sex of the snow crab. The

claw (chela) height of the right claw was measured for male crab (Fig 10). Claw (or chela) height

is measured to validate if the crab was terminally moulted. Males develop enlarged claws when

they undergo their terminal molt (Fig. 10), which can happen after they reach 40 mm CW. A

statistical model which separates two groups of claw heights relative to carapace width was

developed (Dawe et al. 1997) to classify each individual as either adult (large‐clawed) versus

adolescent or juvenile (small‐clawed). This model is defined as: CH = 0.0806CW1.1999). The model

results in a line that divides the two groups (large‐clawed vs. small‐clawed). If the measured

CH is greater than that predicted by the dividing line, for the measured CW, then the crab is

considered to be terminally moulted.

18

Figure 10: Claw sizes

A large‐clawed (terminally‐moulted, adult) male crab on top and a small‐clawed adolescent

male on the bottom. Photo source DFO.

Biological sampling of females includes determination of maturity and egg stage. Maturity has

four categories: mature with eggs, mature no eggs, mature forming eggs, and immature. Egg

stage can be subdivided into no eggs, full clutch and partial clutch. It can be further categorized

into stages such as newly formed eggs (bright orange), becoming eyed, dead or liberating.

Results

Survey summary

The post‐season trap survey took place from August 26th to 28th, 2013 (Table 2). The Labrador

Venture was the vessel used for the survey, crewed by 4 people and the fisheries researcher.

The 20 predetermined stations were successfully sampled (Fig 11). All traps were baited with 6

squid as an estimate for 3 pounds. A total of 2092 crabs was caught (1878 males and 214

females) of which 437 were measured (289 males and 148 females). Seventy‐six of the measured

males from Station 320 were tagged and released (Figure 37, Table 4). No crabs (or very few)

were caught at the northern stations (301 to 306) and also some at the southern stations (310, 315

and 317) (See Table 2, Figures 12, 13 and 14). The highest number of crabs were captured at

19

station 320. One small mesh pot was sampled at stations 301, 303, 304, 306, 307, 310, 312, 313,

314, and 317. The presence of BCD was not observed.

Figure 11. Sampled stations in 2013.

20

Table 2. Summarized data from each sampled string presented by each station.

The date that the string was set, the average soak time (hours), the average depth fathoms),

average temperature (oC) and standard error (SE), the number of males and females counted

(totalled), the number of traps in the set, and the number of crab caught per trap (measure of

catch rate).

Station Date set Soak (hr) Depth (fm) Temp (C) Temp SE Males Females Total Traps Crab/trap

301 Aug‐28 28 285 3.94 0.01 0 0 0 11 0.0

302 Aug‐28 25 151 1.35 0.03 0 0 0 11 0.0

303 Aug‐28 24 69 ‐1.19 0.01 0 0 0 11 0.0

304 Aug‐28 26 340 3.71 0.01 0 0 0 11 0.0

305 Aug‐28 25 219 3.18 0.01 3 0 3 10 0.3

306 Aug‐28 24 60 ‐1.27 0.00 1 0 1 11 0.1

307 Aug‐27 20 137 0.91 0.05 12 1 13 11 1.2

308 Aug‐27 21 152 1.72 0.03 321 3 324 10 32.4

309 Aug‐27 25 152 1.70 0.01 226 2 228 10 22.8

310 Aug‐27 29 80 ‐1.22 0.00 0 0 0 11 0.0

311 Aug‐26 25 146 NA NA 197 0 197 10 19.7

312 Aug‐26 16.5 100 ‐0.49 0.00 90 200 290 11 26.4

313 Aug‐26 24 142 0.71 0.04 191 5 196 10* 19.6

314 Aug‐26 23 141 0.82 0.12 19 2 21 11 1.9

315 Aug‐26 22 195 2.76 0.05 0 0 0 10 0.0

316 Aug‐26 13 227 NA NA 150 0 150 10 15.0

317 Aug‐26 24 23 ‐0.18 0.03 0 0 0 11 0.0

318 Aug‐26 24 123 ‐0.44 0.04 2 0 2 10 0.2

319 Aug‐26 14 335 3.75 0.02 300 0 300 10 30.0

320** Aug‐26 13.5 250 3.64 0.09 366 1 367 10 36.7

*lost one pot (11 were set, 10 retrieved), ** 289 of the males were unmeasured juveniles

21

Figure 12. The number of males and females caught at each station.

Figure 13. The number of crab per trap at each station.

22

Figure 14. Map of the proportional catch rate of male and female crab.

23

Temperature

Average temperature ranged from ‐1.27 to 3.94 oC (Table 2, Figure 15). Stations 312 to 320 do not

have temperature records that cover the entire soak time as they activated at 1700 hrs on

August 26 rather than 0500 hrs. Temperatures were typically colder at the shallower stations

and gradually warmed with depth (Figure 16). The majority of the females were caught at ‐0.49 oC (Figure 17) at station 312. Males were scattered throughout the temperature range (Figure 17

and 19).

Figure 15. Average temperature (oC) at each station.

There are no records from stations 311 and 316 because the temperature gage was lost at sea.

24

Figure 16: The average temperature (oC) at each corresponding average depth

(fathoms).

Figure 17. Number of crab captured at each average temperature. There are no temperature records for two stations where crab were recorded (NAʹs at the far

right).

25

Figure 18: The number of crab per trap (effort) at each average temperature (oC), from

coldest to warmest.

Figure 20. The total catch and male/female proportion with average temperature.

The temperature probability layer was produced using kriging to extrapolate average

temperatures based on the Minilog average temperature recorded at each station.

26

Depth

Station depths ranged from 23 to 340 fathoms. Most of the crabs were captured at stations at

depths between 100 fathoms and deeper (Figure 20, 21, and 22). There were 4 depths which

were shallower than 100 fm (Table 2), 23 fm (station 316), 60 fm (station 306), 69 fm (station 303),

and 80 fm (station 310). The majority of the females captured in the survey was in a small mesh

pot (station 312) at 100 fm. This depth is also where the survey began to capture males.

Figure 20. The number of males and females recorded at each depth (fathoms), from

shallow to deep.

Figure 21. Number of crab per trap by depth, shallowest to deepest.

27

Figure 22. Map of the total catch and male/female proportion with average depth.

The depth probability layer was produced using kriging to extrapolate average depths based on

the average depth recorded at each station.

Soak time Soak times ranged from 13.5 to 29 hours (Table 2, Figure 23). Most of the crabs were captured in

stations with soak times less than 24 hours (Figure 23 and 24).

Figure 23. The number of crab captured with each soak time, shortest to longest.

28

Figure 24. Number of crab per trap by soak time, shortest to longest.

29

Sampled pots There were no crabs measured at stations 301 to 306 (northern stations, Figure 14), 310, 315, 317,

and 318 (southern stations) (Table 3). There were crabs measured from the three ʺmiddle rangeʺ

stations, 307, 308 and 309. Station 307 (not displayed) captured one soft‐shelled male crab

measuring 85 mm CW in a large mesh pot. There was a small mesh pot at this station as well

with one soft‐shelled female measuring 57 mm CW, and 5 small males (Figure 25). Station 308

had a large mesh pot with 17 males (Figure 26) and two females, one new shelled measuring 56

mm CW, and the second was old shelled and 56 mm CW. Station 309 had 12 male crab

measuring < 95 mm CW and 15 of legal size in the large mesh pot (Figure 27).

Table 3. Summary of pots sampled for length measurements.

One large mesh pot (pot 3 of the string) was sampled at all stations while a small mesh pot (pot

7 of the string) was only included at stations 301, 303, 304, 306, 307, 310, 312, 313, 314, and 317.

The number and sex of crab measured from each trap type are presented below.

Station Large

mesh Males

Large mesh Females

Small mesh Males

Small mesh Females

301 0 0 0 0

302 0 0 NA NA

303 0 0 0 0

304 0 0 0 0

305 0 0 NA NA

306 0 0 0 0

307 1 0 5 1

308 17 2 NA NA

309 27 0 NA NA

310 0 0 0 0

311 41 0 NA NA

312 6 0 20 138

313 37 0 9 5

314 3 0 0 2

315 0 0 NA NA

316 15 0 NA NA

317 0 0 0 0

318 0 0 NA NA

319 32 0 NA NA

320 76 0 NA NA

Total 255 2 34 146

30

Figure 25. Shell condition and carapace width (CW) of station 307 measured males in

small mesh pot, N=5.

Figure 26. Shell condition and carapace width (CW) of station 308 measured males

from a large mesh pot, N=17.

31


the large mesh pot, N=27.

Crab were measured at most of the southern stations (310 to 320, near the Cartwright Channel,

Figure 14) beginning with a large mesh pot at station 311 (Figure 28) where 13 small males and

28 commercial‐sized males were measured. Station 312 had both a large and small mesh pot

(Table 3). The large mesh pot had 6 male small crab (Figure 29), and the small mesh pot was full

of female crab, 138 females were measured (subsampled from 189) (Figure 30). There was also

20 male crab, one of which was of commercial size (Figure 31). At station 313, a large and small

mesh pot were sampled. There were 19 crab < 95 mm CW and 18 that were of commercial size,

additionally this pot had a big incidence soft‐shelled crab (31 of the 37) (Figure 32). In the small

mesh pot, there were 5 old‐shelled females (Figure 33) and 9 males, one of which was legal size

(Figure 34). Station 314 (not displayed) had both a small mesh pot and a large mesh pot

sampled. Three new shelled male crab were measured in the large mesh pot measuring 84, 86,

and 108 mm CW. Two small new shelled female crab were captured in the small mesh pot

measuring 50 and 53 mm CW. The 15 measured crab in station 316ʹs large mesh pot were legal

sized males (Figure 35). Station 319 had 32 commercial sized males (Figure 36).

32


large mesh pot, N=41.

Figure 29. Shell condition and carapace width (CW) of station 312 measured male

crab in large mesh pot, N=6.

33

Figure 30. Shell condition and carapace width (CW) of station 312 females measured

in the small mesh pot. Measured females were subsampled, N=138 of 189.


the small mesh pot, N= 20.

34



Figure 33. Shell condition and carapace width (CW) of station 313 females measured

in the small mesh pot, N=5.

35


the small mesh pot, N=9.



36


the large mesh pot, N= 32.

37

Station 320 (Tagged crab) A total of 76 crabs were tagged from Station 320, 15 of the 76 crab were small clawed, while 61

were terminally moulted with a large claw (Table 4). Their shell conditions were either new or

soft, with 28 being soft shelled and 48 were new hard shelled (Table 4, Figure 37). All tagged

crab were of commercial size (>95 mm CW) however 298 juvenile male crab (<95 mm CW) were

counted at this station but not measured or tagged.

Figure 37. Frequency distribution of tagged crab carapace widths (CW) and their shell

condition, N=76.

38

Table 4. Tagged crab details from station 320 including the tag number.

The carapace width (CW) in mm, shell age (1=soft, 2=new hard), claw height (CH) in mm, the

model estimator of claw size (f), and if the claw was large or small according to f (15 of 76 crabs

were small clawed).

Crab # CW (mm)

Shell condition

CH (mm) f Tag #

1 104 2 28.36 3 366

2 112 2 29.47 3 928

3 114 2 28.78 3 378

4 110 1 27.1 3 481

5 110 1 31.03 3 398

6 98 1 19.09 2 384

7 115 2 28.28 3 380

8 102 1 19.54 2 344

9 103 1 18.83 2 382

10 119 2 33.17 3 429

11 110 1 29.36 3 443

12 116 1 30.5 3 425

13 110 2 27.36 3 387

14 109 2 27.11 3 930‐B

15 114 2 26.83 3 467

16 111 2 28.39 3 347

17 109 2 27.53 3 473

18 97 1 19.42 2 392

19 97 2 20.54 3 351

20 118 2 32.51 3 367

21 108 1 28.51 3 376

22 109 2 28.63 3 353

23 118 1 19.32 2 357

24 100 1 20.54 3 355

25 96 2 19.51 3 952

26 103 1 28.79 3 404

27 111 2 28.18 3 445

28 109 2 26.07 3 312

29 104 2 25.98 3 325

30 111 2 28.25 3 317

31 100 1 20.17 2 991‐ B

32 103 2 26.03 3 262

33 126 1 35.3 3 424

34 107 2 29.4 3 475

35 111 2 27.07 3 333

36 102 1 18.3 2 343

37 102 1 20.85 3 437

39

Crab # CW (mm)

Shell condition

CH (mm) f Tag #

38 112 1 27.74 3 329

39 104 2 27.16 3 427

40 102 2 25.61 3 359

41 114 1 29.86 3 332

42 111 2 29.88 3 968

43 111 1 20.36 2 455

44 111 2 26.75 3 319

45 100 1 18.62 2 339

46 112 2 29.94 3 341

47 102 2 24.27 3 327

48 102 2 19.79 2 278

49 111 2 28.56 3 323

50 99 2 28.69 3 321

51 121 2 32.57 3 282

52 112 2 25.15 3 270

53 115 1 35.47 3 302

54 112 2 31.02 3 335

55 109 2 30.65 3 308

56 103 2 24.23 3 299

57 106 2 26.46 3 330

58 101 1 26.27 3 316

59 119 2 29.11 3 300

60 104 2 24.86 3 304

61 102 1 29.49 3 906‐B

62 104 1 18.31 2 295

63 122 1 33.17 3 306

64 121 1 28.94 3 288

65 111 1 29.39 3 291

66 108 1 26.27 3 285

67 104 2 25.39 3 290

68 106 2 19.86 2 297

69 110 2 20.05 2 275

70 102 2 18.43 2 280

71 104 2 21.51 3 272

72 123 2 30.24 3 286

73 99 2 20.21 3 268

74 102 2 19.41 2 996‐B

75 101 2 23.08 3 310

76 103 2 26.24 3 314

40

Shell Condition

With respect to the shell condition of the measured crab at all stations combined, 56% of the

male crabs were new hard‐shelled (161 of 289), 108 (37%) were soft‐shelled, and 20 (7%) were

old‐shelled (Figure 38, 39, 40). Eighty‐nine crabs were pre‐recruits and 200 were commercial

size (Figure 38). The majority, 72% (106 of 148) of the females (Figure 41) were new‐shelled, 1

(1%) was soft shelled, and 41 (28%) were old‐shelled.

Figure 38. Frequency distribution of all measured male crab from large mesh pot 3 of

all stations to examine the proportion of shell conditions present, N=180 (there was

only 1 crab present and measured in pot 3 of station 20).

41

Figure 39. Frequency distribution of all measured male crab from small mesh pots

(pot 7) of all small mesh pot stations (crab were caught at stations 307, 312, and 313) to

examine the proportion of shell conditions present, N=34.

Figure 40. Map of proportion of male crab by shell condition from large mesh pot 3.

42

Figure 41. Frequency distribution of all measured female crab from all stations to

examine the proportion of shell conditions present, N=148. We note that two of the

female crab included here, a 56 mm CW new‐shelled and a 59 mm CW old‐shelled, were

measured from the large mesh pot sampled at station 308 (no small mesh pot at this station).

The remainder of the females were from small mesh pots.

43

Bycatch

Bycatch was recorded from each pot from the entire station. There were 23 different entries

(fish, invertebrates, and including rocks) recorded as bycatch (Table 5, Figure 42 and 43).

Important fish species such as the spotted and Northern wolfish (Figure 43) and turbot were

captured occasionally while toad crab were captured most often (Figure 42), however most of

the toad crab were recorded from only one station, station 10 (Table 5).

Figure 42. The total bycatch in number by species recorded from the survey.

44

Table 5. Bycatch species, listed alphabetically, broken down by each station. Station

1 2 3 4 5 6 7 8 9 10 11 13 14 15 16 17 18 19 20 21Species

Atlantic wolffish

3

Basketstar

1 1 1 1 11 3

7

Brittle star 1

Silver Rockling

1

H. araneus

6

10 3

1 1

1

5 1

H. coarctatus

14

25

1 203

12 1 1

41 9

Hermit crab

1

Horsestar 2 5 1 1

Kelp 1

Northern Wolffish

1

4

1 3

Northern Stone Crab

2

Rocks 1 1

Sea star 2

Sea urchin

9

1

Shrimp 1

Skate case 1

Soft coral

2

Sponge 2 1

Spotted Wolffish

2

1

Starfish P. 1

Sun star 2 1

Turbot 4 1 4 1 1

Whelk 3 1

45

Figure 43. Map of proportion of different bycatch types.

This map shows proportion of by‐catch for each station based on the size of symbology.

Figure 44. Map shows proportion of Wolffish species caught by station.

46

Summary and Discussion

The 2013 Post‐Season Survey sampled 20 stations where all crabs and bycatch were counted. In

2013, crabs were measured from 19 large mesh pots across 10 stations and 10 small mesh pots.

Ten large mesh pots were sampled at station 320 where 76 commercial sized male crabs were

successfully tagged. No crabs (or very few) were caught at the northern stations (301 to 306) and

some more southern stations (310, 315 and 317) (Figure 14). Overall most crabs sampled were

recently molted (soft‐ and new‐hard‐shelled). The largest proportion of soft shelled crab was

found at station 313 (Figure 38 and 39). Soak times ranged from 13.5 to 29 hours (Table 2, Figure

23) with the majority of the crabs captured in stations with soak times less than 24 hours (Figure

23 and 24). In general, females were caught at shallow cold areas and the largest males in deep

warm areas, and the majority of crabs are found around the Cartwright Channel.

This year the average bottom temperatures ranged from ‐1.27 to 3.94 oC. In 2012, the average

bottom temperatures ranged between ‐0.87 and 1.72 oC, with more crabs being caught in pots

with temperatures between 0.5 and 1oC, and commercial crabs and temperature trending

together. A similar trend is not as evident this year, however crab were not caught at

temperatures colder than ‐0.49 oC. The majority of the females were found at ‐0.49 oC and males

were found up to 3.75 oC. Temperature was highest at the shallowest depth, dropped sharply to

below 0oC, and then gradually warmed as the stations became deeper (Table 2, Figure 16). The

range where snow crab would be expected is between – 0.5 and 5°C (Tremblay 1997). Water

temperature also influences the catchability of crustaceans; they typically become more

catchable as temperature increases (Miller 1990). Catchability and water temperature could be

an important factor in this fishery as it takes place as soon as the ice clears in the spring (season

opens June 15). Commercial catch per unit effort in NAFO 2J has been inversely related to

bottom temperature at 6 to 8 year time lags, meaning catches are greater when the water was

cold during early benthic life, implying that cold conditions are ideal for early life stages and

subsequent recruitment (Dawe et al. 2011). A warm oceanographic regime has persisted for

more than a decade suggesting relatively poor long‐term recruitment (DFO 2011).

A range of depths were sampled this year, from 23 fm (42.1 metres) at station 317 to 340 fm

(621.8 metres) at station 304. There were five stations with a small mesh pot which were

shallower than 100 fm with the goal to target pre‐recruit (small) crab (Table 2, Figure 20 and 21).

These stations did not capture crab of any size. Four small mesh pots at stations with mid‐range

depths, stations 307 (137 fm), 312 (100 fm), 313 (142 fm), and 314 (141 fm) did capture small

crabs (Figure 25, 30, 31, 33, and 34). Station 304 was the deepest station (340 fm) and also had a

small mesh pot, but no crabs were captured (Table 3, Figure 20).

The smallest male crab measured was 60 mm CW, which indicates the crab sampled were

approximately 6 years of post‐settlement age and older, with crabs being recruited to the fishery

at an age of about 9 years (Sainte‐Marie et al. 1995). A range of shell conditions and ages were

sampled including females with soft, new, and old shells. Bycatch organisms in small mesh pots

were mostly echinoderms (brittle stars, basket starfish sea urchins etc...) and decapods (toad

47

crab) (Fig 42). Trends in bycatch with depth and temperature can be examined in the future as

more data is collected. It is worth noting that the sets without crab also contribute important

information because as the survey moves forward, it can begin to discover where or under

which circumstances small, commercial, and female crab are found in the area.

In 2012, 95 mature male crabs were tagged however no tags were returned during the 2013

season. With the 76 crabs tagged in 2013, there could be a maximum of 171 tagged crabs at large

for next year. As 15 of the crabs tagged in 2013 were small‐clawed (Table 4) and not terminally‐

moulted, it is possible that they may moult the tag off along with their carapace. Tagging

studies can be employed to address many different questions such as, movement (Taylor 1992),

life history characteristics (Taylor et al. 1989), mortality (Siddeek et al. 2002), and catchability

(Sainte‐Marie and Turcotte 2003) of terminally moulted crabs, or other life stages if they are

expected to be recaptured quickly. In one study of snow crab movement in Bonavista Bay, NL,

10,118 legal‐sized male snow crabs were tagged between 1979 and 1982 (inclusive) with 4,255

recaptured. The distance traveled ranged from 0.6 to 74.1 km (average, 10.7 km; median, 8.5 km)

(Taylor 1992). Another study used tagging to determine how long it takes for soft shelled snow

crabs to harden. They tagged 1,591 soft shelled commercial‐sized crab in Bonavista Bay, NL in

August 1984. Between September and December 1984, 68% of those animals released were

recaptured. Of the recaptures, hard‐shelled crabs made up 32.8% of crabs recaptured 31 to 60

days after released, 96% of crabs recaptured 76 to 90 days, and 100% of crabs recaptured after

>90 days (Taylor et al. 1989). In Alaska, 277 snow crabs were fitted with archival tags to record

depth and temperature, to learn if males migrate from deep waters to where the females are

expected to be in the shallower water. To date, 23 snow crabs were recaptured in the

commercial fishery after more than 9 months post‐release release. Preliminary data of tag depth

records shows that some but not all the crabs made an inshore migration and returned offshore

(Nichols and Somerton 2012). The movement of these large commercial‐sized males,

particularly if they were tagged from deep water, should be interpreted with caution. These

crabs have likely undertaken their ʺadultʺ migration to deep zones and are no longer likely to

move large distances (Mullowney pers. comm.).

Recommendations

1. Stations 304 and 317 should be brought east to a depth of 50‐60 fathom. As a goal of the

survey is to detect a signal of recruitment in the future, the northernmost stations should

be kept.

2. If current low catch trends continue, consider measuring all crab caught at the stations

or until 100 crabs have been measured.

3. As suggested by participants at the 2013 Nunatsiavut Snow Crab Workshop, an

additional unbaited four pots will be added to each end of the string to prevent

movements and ameliorate catches in high current areas.

48

4. It is recommended that the survey continue for a minimum of 3 years, so that trends

crab catch rates, male size composition, shell condition, maturity of females and males,

depth and temperature, as well as bycatch may be examined.

5. If tagging is to be continued, then it should be expanded to tag and release commercial‐

sized terminally‐molted adults (of all shell conditions) at all survey stations.

Conclusions

The TJFB‐DFO Collaborative Post‐Season Trap Survey successfully deployed 20 strings in pre‐

established sampling areas. The small mesh pots successfully captured the targeted small males

(pre‐recruits) and female crab and provided an opportunity to record a range of bycatch species

and record bottom temperature. A total of 61 terminally moulted crabs were tagged and

returned to sea. Refinement of stations 304 and 317 is recommended to achieve the key objective

of short and long‐term predictions in recruitment.

Acknowledgements

This survey would not be possible without the logistical support from Fisheries and Oceans

Canada, coordination with Seismic Industry, Labrador Venture Captain and Crew, Torngat Fish

Producers Cooperative, Torngat Secretariat staff and summer student Tobey Andersen. A big

thanks to Paul Higdon for preparing Julie Whalen for the field, and Meghan Marriott & Bryn

Wood for her mapping skills in this report.

49

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