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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
Figure 28. Shell condition and carapace width (CW) of station 311 males measured in
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
Figure 31. Shell condition and carapace width (CW) of station 312 males measured in
the small mesh pot, N= 20. ........................................................................................................ 33
Figure 32. Shell condition and carapace width (CW) of station 313 males measured in
the large mesh pot, N=37. ......................................................................................................... 34
Figure 33. Shell condition and carapace width (CW) of station 313 females measured in
the small mesh pot, N=5. ........................................................................................................... 34
Figure 34. Shell condition and carapace width (CW) of station 313 males measured in
the small mesh pot, N=9. ........................................................................................................... 35
Figure 35. Shell condition and carapace width (CW) of station 316 males measured in
the large mesh pot, N=15. ......................................................................................................... 35
Figure 36. Shell condition and carapace width (CW) of station 319 males measured in
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
Figure 27. Shell condition and carapace width (CW) of station 309 males measured in
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
Figure 28. Shell condition and carapace width (CW) of station 311 males measured in
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.
Figure 31. Shell condition and carapace width (CW) of station 312 males measured in
the small mesh pot, N= 20.
34
Figure 32. Shell condition and carapace width (CW) of station 313 males measured in
the large mesh pot, N=37.
Figure 33. Shell condition and carapace width (CW) of station 313 females measured
in the small mesh pot, N=5.
35
Figure 34. Shell condition and carapace width (CW) of station 313 males measured in
the small mesh pot, N=9.
Figure 35. Shell condition and carapace width (CW) of station 316 males measured in
the large mesh pot, N=15.
36
Figure 36. Shell condition and carapace width (CW) of station 319 males measured in
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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