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• INTERNATIONAL COUNCIL FOR THE EXPLORATION OF THE SEA ICES CM. 1994/8: 20 Ref. K

The Bigouden Nephrops trawl, and the Devismes trawl, two otter trawls efficiently catching benthic stages of Snow (), and American (Homarus americanus). • by G.Y. Conan1, M. Comeau1, G. Robichaudl, C. Gosset2, and C. Gara"icoechea2

1 Department of Fisheries and Oceans Science Branch, Gulf Region Gulf Fisheries Center P.O. Box 5030 Moneton, New Brunswick E1C 9B6

2 Institut National de la Recherche Agronomique Station d'hydrobiologie de St-Pee-sur-Nivelle B.P.3 Saint-Pee-sur-N ivelle 64310 ASCAIN France 2 •

ABSTRACT

The combined use of two otter trawls efficiently allow to sampie snow crab (Chionoecetes opilio) and lobster (Homarus americanus) from early benthic stages to commercial size. A Bay of Biscay Bigouden Nephrops trawl is used in the southern Gulf of 51. Lawrence for snow crab stock assessments and a Devismes brown () trawl is used for sampling early benthic stages of lobster and snow crab. The technical specifications of the trawls are described. • RESUME

L'utilisation combinee de deux chaluts a panneaux permet d'echantillonner efficacement les crabes des neiges (Chionoecetes opilio) et les homards (Homarus americanus) depuis les tous premiers stades benthiques jusqu'a la taille commerciale. Un chalut a langoustines Bigouden du golfe deGascogne est utilise dans le sud-ouest du golfe d~ 5aint-Laurent pour les evaluations de stock de crabes des neiges et un chalut Devismes a crevettes grises (Crangon crangon) est utilise pour echantillonner les premiers stades benthiques de homards et de crabes des neiges.. Les caracteristiques techniques des deux chaluts sont decrites. • 3

r ... !' .,". INTRODUCTION

.The value of the iobster (Homarus arrieficanus) and snow crab (Chionoecetes opilio) fisheries landings in the Gulf of SI. Lawrence ranked first ($164,440,000) arid sacond ($45,297,000) respectively in'1992.' for the marketing needs of t,he fishirig industry and for stock management purposes it is important to monitor the sarly benthlc life stages of these in order to forecast fluctuations in the catch over subsequent years.

In the Gulf of SI. Lawrence, are harVested mostly inshore at depths rariging fram 0 to 35 m, aboard day boats not exceeding 13 m in length and during daily trips. Snow crao are harvested pariiy fram the lnshora, aooard boats smalier than 35 min length, and partly from the mid-shore, aboarct boats ;-anging in lengÜl from • 13 to 21 m equipped for 3-day trips (Einer 1982; Chiasson et al. 1992). Although lotister and snow crab are harvested by single species trap fishing, the ,catch from commercial fishing does not allow to satisfactol"ily monitor abundance of early benthic stages of lobster or snow crab. Commerciai traps are designed to allow the escape of lcitister smaller than the legai minimal' sizes (ranging from 63.5 i6 70 mm carapace length (CL) dependlng öf the fishing district) arid snow crab smaller than 95 mm carapace width (CW). Furthermore, smalliobster arid snow crab da nat appear to enter commerclal 'traps. The catchabllity of larger individua.ls varies as ci functiori ofsex, stage of malting and maturity, season; geographie location and even fram individual to individual (Miiler 1975; Conan er al. 1984; Krause 1989). " • Between 1984 and 1988, we intraduced the use öf two beiithic otter trawls to quaniiiatively sampie early benthic stages of lobster and snow crab for research purposes. These trawls are adapted fram traditional gear designed for haiVesting benthic di-ustacean spedes sharing the cryptic burrowing behavior of lobster arid snow crab. Ineastern ; lobster and snow crab are not harvested comrilercially by trawling.. The area covered by the range of attracti~n 6i ci set of traps is greater than the area covered by a fishing boat irawiing over an equivalent working period. 4 •

Benthic otter trawls us~d tor coninierciai tishing in eastern Canada are designed to harvest mobile fish. These trawls are open:ited at high speed (3 to 5 knots) and have wide wings tor concentrating the tish, large doors tor stretching the wings open, a high rise front rope, a foot rope equipped wittl rollers tor avoiding grips. Such trawls are not speclfically design'ed for catc~ing lobst~r or snow crab.

An adequate trawl for haniesting benthic Reptantia (Le. crawling) does not require wings and large hovering doors for concentrating the catch or a high O rise front rape but, rather, sniall doors and a heavY foot rape pieughing ths sediment. It should also be hydrcidynaniically suitable to operate at iow töwing speeds. Such a trawl should be buHt with strang material and be towed smoothly over short distances us!ng thick warps since it frequentiy collects rocks and mud.. Otter trawls usually perform better than rigid beam trawls as they can conform to the irregularities of bottom sediment and ailow for a greater opening at equal weight. •

A"Bigouden" trawl traditionally used for harVesting Nephrops noivegicus in n6rthern Bay of Biscay (Conan 1978) and a "Devismes" trawl used by recreatlonal and commercial tishermen tor harVesting browri s~i"imp {Crangon crangon} in· shallow water ~ays Of ·northern France were successtully introcluced by us arid tested in Canada in the 1980's. These trawls are now gairiing popularity among .eestern Canada. tishei"ies scientists tor quantltatively sampling lobster and snow crab. +hey also efiiciently catch small pre-recruits of hake and flatfish which were reputedly difficult io catch. The trawls were originaily purchased in Francs but are now built in Canada.

This report describes the designs of the Bigöuden arid Devismes trawls arid o • comp~re thei;- catch ancl workability with ether research sanipling methods • available for assessing early berithic stages of lobster and snow crat>.

MATERIAL AND METHODS' .. Gear Design Bigouden Nephrops Trawl

The trawl is a traditioniil design from the Bigouden region of Brittany (Francs) used .by tishermen harvesting NoiWay lobster (). The tishery r------.

5

o6perates on the continentai shelf of northem Bay of Biscay at depttis ranging from 80 to 120 m. The 12 to 15 m trawlers flsh for 1 to 3 days on miJddy sediment patches among rocks and bouldars (Conan ·Ür78). The trawls are designed to capture Ncirway lobsters while they are elther inside the shailow burrows they dig , into Üie sediment or while they are foraging on the surlace of the sediment.

The mcidel presented in this paper was assembled by Captain Henri Cariou from oLoctudy harbor (i=inistere, France). The 20 m headline otter trawl (Fig. 1) has a 27.3 m footrope on which is mounted a 3.2 m 10l1g, 8 mm galvanized chain (Fig. 2). The upper and lower wing bridles (Fig. 3) are connected to ihe'doors (Fig. 4) bya 60 m ground warp (Fig. 3). A 25 m Nephrops trawl is aiso used. Asmall mesh "sock" sllghtly larger size than the trawl itself carl be mounted inside in order io .... , retain the earlY benthic stages of crab or lohster. '

• DevismeS 8rown Shrimp Trawl

The design was originaliy used for a very srriall otter trawl (0.8 to 1.2 rri headline) Üiat couid be attached °to a harriess and towed by a person walking along saridy shores in ttie shallow waters oi Baie da la Somme (Francs). Such smali trawls are still buHt commercialiy töday for recreational fishing of brown shrimp and iiatfish.

The model shown in Figure 5 was designed and buHt in 1976 by Pierre Devismes, a skipper from Le Crotoy (Somme, France) for the "Laboratoire da M~th6d6iögie des Inventaires de la Statiqn de Recherche Hydrobiolgiques de Biarritz"i Institut National de ia Recherche Agronomique (INRA) France, now reriamed ,iStation . .\ ~'... d;Hydrobiologie de Saint-pee-sur-Niveile".o The 4.88 ITI headline trawl Carl be operated by tw6 persons and towed from a small boat powere'd by ä 25 HP

• outboard engine at depths rangirlg from 0 to 30 The isometric assembiy shown 3 rri. in Figure 6 shows how the upper and lowerowing bridies are aitached directly to tne

two small stael doors (Flg. 7). Two 8 m warps run from the doors to a single warp 0 which is used for towinQ ar'ld hauling trom a small boat (Fig. 6). There is no need for steel warps or winches, asingle polypropylene or nylon rops is strong enough fortowlng. 6·

~,." ", Fjeld Sampllng

Introduced in 1984, the Bigouden Nephrops otter trawl is now routiriely used by the Department of Fishei-ies and Oceans (DFO) tor anriual sUrVeys of snow crab stocks in the Gulf of S1. Lawrence (Conan arid Comeau 1986; Conari et ai. 1988; Comeau et al. 1989, 1991; Malletet al. 1989, 1990, 1992; Chiasson et al. i 991 ; Comeau arid Conan 1992). It has been successfuiiy deployed fram the 17 in research ship "Opitlo". The Opilio was specially designed iJrider the supervision of orie of us' (Gerar~ Conan) for towing Nephrops trawis, it carries winches holding 400 rri of 15 mni 0 warp. An acoustic Scanmar system is used for continuously recording the effective opening and the time the trawl stays on the boltom in order to calculate the exact swept area. Usually short 10min. hauls 8t :2 knots iimits the risks of mud clogging tha trawl and ailow tor measurement of the whole catch . , .. without sub-sampling. The Neph;ops trawi has beeri used since 1985 for monitoring year to year recruitment in ä. population of snow crab in the Bonne Bay • fjord, NeWfoundlarid (Comeau et al. 1989, 1991; Comeau and Conan 1992) (Fig. 8). Triais were also made in ~estern Northumberland Strait (Flg. 9) at depths ranging fram 15 to 20 m on June 22 and 28, 1993 to test the efficiency of a Nephrops trawl for quantitative samplirig of lobster aburidance on soft bottoms.

The Devismes trawl was evaluated for its ability to capture the eariy benthic' stages of lobstel' in Malpeque Bay, Prince Edward Isl~md (Fig. 10) fram August 1to 12, 1988 (Currie a~d Comeau 1989). The trawl was initially fitted with anel,ectric toot rope;' but the effect of electricity on lobster behavior was negligible and (jid not enhance the catch (M. Comeau and G; Conari, unpublished datä)., Aprellminary diving survey indicated that the study area had shallow soft bottoms pärtially covered by eel grass, small and commercial size iobsters were abundant and . • some lobsters had dug short burraws in the sediment. Teri min. tows were taken from a 11 m"Cape Islander" lobster fishing boat at depths rariging from 2 to 12 m and at a speed of 1.5 to 2 knots. The carapace length (CL) of all i6bsters were recorded. The Devismes trawl can also be towed successfully fram a 6 in boat equipped wiih a 45 Hp outb6ärd angina. No winch is required. Ahydraulic trap h~mler cari be used tor taking in the towing rape.

The Devismes trawl was also used to collect early benthic stages of snow crat> in Bonne Bay (Fig. 8) from May to September 1991. Eleven 5 min. to~s were taken I-

i 7

from the Opilio ai depths rariging from 70 to 140 m arid at speeds ranging from 1.5 to 2 knots. For iowing at these ~ep,ths. astaei, warp wa.s use8. Tha snow crab were sexad and their carapace width (CW) measursd.

We present generiil information on the charactenstics of the catch in the form of cumulated size frequency distributions in order to provide a refererice for comparisan with ether sampling methods.

.... ~ RESULTS

The effective opening of the 25 rri Nephrops trawl hauled by the Opilio in Bonne Bay. as measured by the Scanmar. varies from 6.5 io 11 mwhh an average of 10.3 m. The opening varies depending on the battom substrate (Iarger on ~oft hohom .' and srriallar on rocky bottom) arid is co~related with depth arid wlih His n~mber of floats mourited on the headline (Corian et al. 1988). The effeetive opening of the Devismes trawl estimated by divers is approximately 1.5 m.· The openirig of this trawl cannat be measured by Scanmar due te lts small size.

The size. frequency distributions of male snow crab caught by the Bigoudsn Neph~ops trawl in the southwestern Gulf cf St. Lawrence are presented in Figura 11; Tha CW rciiiged from 12 to 135 mm. For comparison. an equivaient size frequency distribution taken by comillercial traps is presented in Figura 12. The traps catch oniy tha larger snow crab (from 55 to 146 mm CW).

The size frequericy distribution of maie and temale snow crab taken by the . • Bigouden Nephröps trawl in Bonne Bay were cumulated for years 1985 t,o 1990 in Figures 13 and 14 respectively. The siie range observed in Bonne Bay is similar . to the ones from the southwestern Gulf of St. Lawrence (Fig. 11). but the modes are märe conspicuous. Bonne Bay contains a tiomogeneou~. sub-population of snaw crab. Modal sizes (aga groups or cohörts in some ~ases) äre not bluJ'Ted by geographie variations occurring ät a iarger scale such as in the southwestern Gulf.

The size frequency distributions of snow crab hikEm in Bonne Bäy by the Devismes trawl are presented in Figure 15. The sizes range from 2 ta 118 mm CW; For standardized swept areas. the Devismes trawl catches smaller siies thai1 tne 8

" Bigouden Nephr~ps tr~wl but does appear t6 be about as efficlerit as the Nephrops trawl for eatching larger sizes (>90 mm CW). The Devismes trawl covers; however, only about 5 % of the area swept by the Nephrops trawl for identieal towing times.

Size frequeney distributions of lobsters eaught tiy the Nephrops trawl in western Northumberland Stralt and by the Devismes trawl in Maipeque Bay are presented in Figures 16 arid 18 ,respectively. The size frequency distribution öf Ic:;tisters eaught by eommercial traps in the vicinity of Cap-Pele and Malpeque BaI' are presented in Figures 17 and 19, respectively. Both trawls efficiently eapture iotisters müch smailer than the smallest sizes eaught in commereial traps. The sizes of lobsters eaught in "the Nephrops trawl ranged from 24 to 118 mm cL and from 17 to 74 mm CL in the Devismes tra~1. The lobsters caught in traps ranged in sizes from 50 t6 116 mm CL in Cap-Pele and fram 47 to 102 mm CL in Malpeque. The modes are eonspicuous iri the trawl catch but not in the traps. The Nephrops • trawl eapture~ the widest range of 16bsters. "

'. ,"'", , .. DISCUSSION

The ratio of effective opening/width of the foot rape of the trawls used in the present study is eonsiderably less than for a fish trawl but is cidequate for eatching semi­ buried erustaceans. The variation in the opening width al"low the trawl to stay on ttle bottom. The variations. are not a souree of impreeision in the ealeulations of the swept area which isconstantly monitored and integrated by the Sdinmar system.

The Nepl1rops trawl is rugged arid can be haulsd over most bottoms inhabited by snow erab and some sott lobster batiorn. The De'vismes trawl is designed for shallow water work arid should preferably be used on soft bottoms. H~rvesting small lotisters and snew crab from racky bottoms may be dons With a seallop dredge mounted with small meshing (M. Coineau, pers. obs.). Ttle Devismes trawl is now eurrently. used for sampJlng fish pre-reeruits by the Marine and Anadramous Fish Division. Gulf Fisherles Center. Moneten.

, I I" Underwater video obserVations taken tram a sied iowed by the Opilio showed that beyond the first benthie stage, snow erab da not eseape by rUnning sideways from the trawl (G. Conan, unpublished observatioris). . 9·

The Devismes trawl a~"d the Neph~ops trawl aliow the sampling cf snow crab in their first and third recruitment year, respectiveiy. The modes observed from Üie frequency distributions of lobste'rs and sn~w 'crab c'apture by these trawls are conspicuous and caii be followed throughout the year for growth ä~alysis. .Coriimerci~lI gear is totally ineffective for sampllng early age classes as shown in .Figures 12, 17 and 1~. It is not possible to evaluate tne selectivity öf the trawls for the smaller size classes as there are no reference sampies taken from any more efficient iess selectlve gear. Coulombe et al. (1985), Breih~s et al. (1987) and Robichaud et al. (1989) have Lised beam trawls to collect snow crab.. Couiombs and Mauger (1990) have proposed a new sampllng device, based on a modified beam trawl, for snow'crab population ässessments. The catch reported by these authars were not sampled over the same lapse of time and ovar the same löcation as ours and are therefore not amenable for camparison due to the fast groWth of during ih~ir early benthic stages arid tneif' wide fluc::tuations in abundance . • fram year to year and locatiort to iocation. Attempts to eatch early bsnthic stages of lobster in colleetors desigried to attract the settling larvae h~lVe been made (C. Hudon, pers. obs. Environment Canada, Montreal, H2Y 3E7). Thls methöd lS Iimited to verY early se~ling benthic stages and c5nly ailows for very small spaiial . coveragii It doas not allow to sampIe the complete size distribution of a population at a given time. SCUBA diving (Fig. 20) eventually assisted by an air11ft pump can also tie used. This method is labor intensive, costly, it covers only a Iirrilted area, it is destruetive of the habitat ~md earl bei involuntärily biased by the diver.

Cryptic behavior is commori in early tienthic stages eH mari~e invertebrates. The relative abundance of the early benthic stages in a size frequency distribution ·maY bei underestimated, even when a very small mesh net is used to prevent any escape. Strang year to year fiuetuaii6ns in the early benthic stages recruitment öf snow cräb, as weil as lobsters, dci not ailow the estimätion of relative vulnerabiiity . of stages from the inspection of their relative atJundance l~ a same size frequency sampie. The analysis of the evolution of the size frequency distiibutions over a long series öf SlJccessive years is required tor groWth analysis.·

Böth types of trawls are pramising toois f~r monitoring abundanc::e of eariy benthlc stages of lobster or snow crab over multi-anmÜ11 time series. The data sets will , "r: "".' .' ,':, .,,' allow to analyze long term changes in growth and annual recruitment to benthic aricf commercial stages. 10

" ,- , ... - ';.. "',. .l'''·'~'~· ~ ACKNOWlEDGMENTS

The authörs wish to thank Aaron Jones, Donald Ma}mard arid Fernand Savoie, for their assistance in the fjeld; Dr Themas W; Sephton, Mr. Yvon Chiasson; D6nald Maynard and Fransesc Maynou, tor their comments on t~a manuscript; Pierre Mallet; for his technical advice arid the c~ptairi and crew of the research "essei Opilio. The trawls were originaliy buiit'at "Coopel'ative Maritime de . Loctudy" (Loctudy 29125, FRANCE) and "Eeöle d'Apprentissage Maritime Quartier MarineIla" (Ciboure 64500, Saint-Jeari-de-Luz, FRANCE).· 'i;Ecole da Peches du Nouveäu-Bruriswickö of Caraquet (P.O. Box 178; Caraquet, N.-B., EOB 1KO; CANADA) and;'Aqua Equipement;; (CP 29, Bas-Cäraquet, No-B.; EOB 1EO, CANADA), provided a Canadian adaptation for these trawis, and prepared technlcal sketches recording the design 6f these träditional trawls. " . • ,..... REFERENCES

Br~thes, J.-C."F., F. Coulombs, P.-E. Lafleur, and R. Bouchard. 1987; Habitat and . spatial distribution of early" benthic stages of the snow crab '. Chionoecetes opilio (C>. Fabricius) off the north shore of the Guif of St. Lawrence. i Crust. Biol. 7: 667-681.

Chiasson, Y. J., M. Hebert, M. Monyasu, A. Böurgoin; arid D. Nosl. 1992. A retrospective look cit the development and expansion of the " southw~stern Gulf of St. Lciwrence snow crab, Chionoecetes opi/io, fishery. ean. Tec~. Rep. Fish. Aquat. Sci. H347: 23 p.

Chiasson, Y., M. Hebert, E. Wade, C. Galiant, P. Degräce, P. Mallet, arid M. Moriyasu. 1991. La peche au crabe des neiges (Chionoecetes r;"pilio) . dans le sUd-öuest du golfe du Saint-Laurent en 1990: Etat da la ressource et j'estimation de la" biomasse. ean. Atl. Fis~. Sci. Adv. Comm. Res. Ooc. 91/27: 22 p.

Comeau, M.; and G. Y; Corian. 1992. MorphometrY arid gonad matur"ity of male snow crat>, Chionoecetes opilio.· Can. J. Fish. Aquat. Sci. 49: 2460-

i ".\" 2468. 11

Comeau, M., G. Y. Conan, and A. D. Jones. 1989. Fluctuations in mating; reproduction and iecruitment of the snow crab population in Bonne Bay: impiications to fisheries management. Can. Atl. Fish. Sci. Adv. Comm. Res. Doe. 89fi9: 38 p.

Comeau, M., G. Y. Conan; G. Robichaud, and A. Jones. 1991. Life history patterns arid population fluctuations of snow crab (Chionoecetes opilio) in the fjord of Bonne Bay on the west eoast of Newfoundland, Canada - tram 1983 to 1990. Can. Tech. Rep. Fish. Aquat. Sei. 1817: 73 p.

Conan, G. Y; 1978. Life history, groWth, praduction and biomass modelling' of Emerita analoga, Nephrops norvegicus and Homarus vulgaris (Crustacea, ). Ph.D. thesis, University of California, San • Diego; USA. 349 p.

Conan, G. Y., and M. Comeau. 1986' Functional maturity and terminal molt of male snow erab, Chionoecetes opilio. Cän. J. Fish. Aquat. Sei. 43: 1710­ 1719.

Conan, G. Y., D. R. Mayriard, A. Merrien, and Y. Guemiegan. 1984. Monitoring the feraging activity,of lobsters and assoeiäted species by underwater television. Int. Coun. Explor. Sea, CM1984/K:45: 13 p.

Cenan, G. Y., M. Moriyasu, E. Wade, and M. Comeau~ 1988. Assessment and spatial distribution surveys of snow erab stocks by geostatisties. Int. • Coun. Explor. Sea, CM 1988/K:1 0: 21 p. Coulombe, F., and A. Mauger. 1990. Descriptiori d'un nouvel echantillonneur pour iieval.uati.on des populations de crab des neiges (Chionoecetes . opilio). Cahier (j'information, Ministere de I'a.griculture, des pecheries et de I'alimentation du Qu~bec. 124: 27 p.

. Coulombe, F., J.-C. F. Brethes, R. Bouchard, and G. Desroslers. 1985. Segregation edaphique et bathymetrique chez le crabe des neiges, Chionoecetes 12'

opilio (0. Fabricius), dans le sud-ouest du golfe du Saint-Laurent. , ' Can. J. Fish. Aquat. Sci. 42: 169-180.

Currie, L., arid M. Comeau. 1989. Overview of lobster (Homarus americanus) research coriducted in Malpeque Bay, P.E.t.: Research recommendations for 1989/90. Can. AU. Flsh. Sci. Adv. comm. Res. Ooc. 89/71 : 9 p.

Einer, R. W. 1982. Overview of the snow crab Chionoecetes opilio fishery in AUantic Caria.da. Frac. Int. Symp. Chionoecetes, Alaska, Sea Grant Rep. 82-10: 3-19.

Krause; J. S. 1989. Performance and seleetivity of trap fisheries for cnjstaceans, p. • 307-325. In: J.F. Cciefdy [ed.]. Marine inver1ebl'ate fisheries: their assessment and management. John Wiley and Sons, New York, NY~

Mallet, P., M. Hebert, C. Gallant, and M. Moriyasu. 1992. Evaluation de I'etat du stock de crabe d~s neiges (Chionoecetes opilio) dans le sud-ouest du golfe du Saint-Laurerit en 1991. Can. AU. Fish. Sei. Adv. Comm. Res. Doe. 92119: 21 p.

Mallet, P., E. Wade, M. Moriyasu, and G. Y; Conan. 1990. La peche au crabe des neiges (Chionoecetes opilio) dans le sud-oue~t du golfe du Saint­ Laurent en 1989: Etat da la ressource et I'estimation de la biomasse. ! .

I Can. AU. Fish. Sci. Adv. Comm. Res. Ooc. 90/93: 35 p.. I Mallet, P., E. Wade, Y. Chiassen;' P. Oegräce, G. Y. Conan, and M. Moriyasü. 1989. • Ui peche du crabe des neiges (Chionoecetes opilio) dans le sud­ ouest du golfe Saint-Laurant en 1988: L'analyse des prises, deo I'affort de peche et I'estimation de la biomasse. ~an. AU. Fish. Sci. Adv. Comm. Res. ooc. 89/25: 59 p.'

Miller, R.J. 1975. Density cif commercial spider crab, Chionoecetes opilio and calibration of effeCtive area fisl1ed per trap using bottem ph6tography. J. Fisti. Res. Board Can. 32: 761-768. 13

Robichaud, D. A., R. F. J. Bailey, and R. W. Einer. 1989. Growth and distribution 01 snow crab, Chionoecetes opilio, in the southeastern Gul1 01 St. Lawrence. J. Shellfish Res. 8: 13-23.

•

• 14

Nephrops Trawl. .. . - Trawl Plan of Netting and Frame Lines

IQf BOTTOM 30 .30 190 mm (6) Oanlsh Seine Floals HEADLINE 20 m 30

E Il'l N J}- .c E (/) (I,) CO 50 E 49 E E E 0 CO ~-

0 CO I • E '" , 2.5mm0 E C') ! Braided Nylon ." ." !J-- 230 meshes 272 meshes ,....0 J 2.5mm0 E 2.5mm0, E Braided Nylon C') ! Braided Nylon .c ~ ~ (/) - Q) 193 meshes E ~ 25.4" mm Hercule rope 0 I 182 meshes E (0 '" E 2.5mm0 E E ~ Braided Nylon 0 N (0 lil 115 meshes ~- ~ '" E E E ! .... ~ cf}- !J--

0 11 cn '" .c E ! ,. 3.5mm0 E 3.5 mm0 E (/) ." Braided Nylon Braided Nylon Q) N g E E 72 meshes 72 meshes • E 72 meshes 72 meshes 0 0 It) CO J 3.5 mm " ' 3.5 mm 0 E ! Braided Nylon E· Braided Nylon E N g 72 meshes .72 meshes

Figure 1. Plan of netting and frame Iines of a 20 m headline Nephrops otter trawl used in northern Bay of Biscay by lobster fishermeri (modified from Conan, 1978). e e

40 cm Wire rope 15 mm 0 als 6 x 19 with 9 cm 0 Rubber Disc Nephrops Trawl • Footrope 5 '\'\ (1\ 3 (2) aIs 6 '" '\9 {O~e 5 (1\~ubbe{ 'J'J\{e '\ o\SC 15 mm Swivel 30 cm 'lJ\\'r\ 6 {1'\(1\ Wire rope 15 mm 0 als 6 x 19 with 9 c~er Disc

~L--.~~~ 15 mm Swivel >< 0 CD .­(I) (1)0 ...... "- ...... OG) .0 01 ol'S).o NE::J EEa: ....-.- 8 mm Galvanized Chain . l'S) C')~E G)O e.s::.a.CD ~~[)Ii~ 15mmSwivei 30cm Lower Wing Bridle Wire rope 15 mm 0 als 6 x 19 Wir. rope 15 mm f2) oIs 6 x with 9 cm 0 Rubber Disc r

Figure 2. Detail plan of the footrope attached to the fishing line of the 20 m headline Nephrops otter trawl. ------

Nephrops Trawl - Isometrie Assembly

Nephrops Trawl ~ see Figure 1 ~ ~ ;Y'"\\ '" Swivel

~ Hea~ Foot Rope

Iit:""'" Lower Wing Bridle (15 mm 0 0/5 6 x19)

Ground lAI rvarp (15 Trawl Warp Upper Wing Bridle (15 mm 0 o/s 6 x19) mmo ols 6 X19) (to the Vessel) '" ~

Figure 3. Top view of the 20 m headline Nephrops otter trawl. Isometrie assembly showing the lower and upper bridles, ground warps, doors and trawl warps. The wings of the trawl are spread flat to show the lower and upper wing bridles.

• NephropsTrawl: • Trawl DoorJ Weight: 82 kg;

Trawl Warp Attachment:Two triangles are attaehed to the door and jointed at the top by a ring. The attaehment shown here is for a door used on the . left side of the trawl. .The trawl warps are attaehed to the ring by shaekle.

10mm0Bo~ 3.5em - Side View of the Triangle and Ring ~ _. . 6 em E .... :.';':'.::::.:'. (,) ...... : Attaehments (D H' ht) LO EJ!Ioll _,- oor elg ....cO gem ...... 3 12.5cm I\) ~©li J-~ 50.6em'

Ground Warp Attachment: Two 12.5 cm 0 rings are attaehed to a meta! plate on the opposite side of the door Two pieees of ehain (5 m in length) are 1\1\'att.aehed to these rings. The ground warp is attaehed to the chains. I . . 60cm I 4 • ~'1~2an~ 35 an ~ . g, 4 • 5~4 5~ .:.~7 mm (Height) ,

2.5cm-! . 2.8cm

Figure4: Wooden trawl door used with the 20 m headline Nephrops otter trawl. ------

Devismes Trawl • Trawl Plan of Netting and Frame Lines 29cm BonOM 28 meshes

FOOTROPE 7 m 24

1 m 14 1 m 14 112 meshes 112 meshes

Figure 5. Plan of netting and frame Iines of the Devismes otter trawl. •• •

Devismes Trawl • Isometrie Assembly Devismes Trawl\. see Figura 8 "

I~ .- - -t--_.... Footrope I 18 mm 0 Nylon II T,awl Warp Single Trawl Warp 4-- Headline < Il. (to Vessel) ...... <0

.Figure 6. Top view of the Devismes otter trawl. Isometrie assembly showing the lower and upper bridles, doors and trawl warps. The bridles are represented side by side in order to show their length and attaehments to the doors. Devismes Trawl -Trawl Door 440 Reinforcement rod 0 6 (welded) Weight ; 5.8 kg

Sheet Meta' ; 3 mm' 30 I ..-.I

G~ /07 ------~ Warpto ("'-r~ 310 ~etrawl \;;--->, L_--~:.:.:-=t=:=2 ....CA) f:~ p===,=~~ U1 " ~Bo1t08 (~-_, I\) .l:l Corner.lne 40 o ~f:'"'--, 20x20

---, --- ..... ------___ ...... --- -- ~n--

'"U1

Bolt06

All measurements in mm Detail of the ground warp attachement

Figure 7. Left metal trawl door used with the Devismes otter trawl. • • 21

Gulf of St. Lawrence

•N 5Km

58°00'00.

Figure 8. Map of the fjord of Bonne Bay, Newfoundland, with 100 m depth contour and indicating the trawling sites (X). • "20m ',> ". "':' N

.....i -.

.•..•.

"" ....

10m

". l\) '.. ····· .. 64°10'W l\)

. "......

" ... / ..•...... '. ", ...... ' '. " ',; .. .. / . . ' ,' ,,, ' . . . '. •...... -': ...... ;. 10m·.....

,,' ", " .:."::." 5km ~ ...~.. '. .

Figure 9. Map of the western Northumberland Strait with the 10 and 20 m depth contours and indicating the trawling sites (X). • • ,

23 •N

Malpeque Bay •

Prince Edward Island Summerside , 63°48'00" 5km

Figure 10. Map of Malpeque Bay, Prince Edward Island, indicating the trawling .' site (hatched). ' 24

'., 16 1991 o total 14 n - 8601 • juvenile 12 '5<-79.1 10 . SO -18.0 8 6 4 2 0 16 1990 14 n - 12815 , ~, 12 'X -71.1 ~ 10 . SO-18.2 -o. 8 -cn 6 Q) 4 '(3 2 • C 0 Q) 16 ::J 1989 0- 14 n - 9529 Q) 12 '5<-66.2 .~ lJ.;; 10 so -19.6 8 6 4 2 0 "" .....'···· ..' .. '".,J;l~_ '." '.• '~ 16 ' ",.," 14 1988 n .. 9139 12 'X - 53.4 10 so .. 18.1 8 6 . 4 2 0 • 12 21 30 39 48 57 66 75 84 93 102 111 120 129 Cärapace WiCJth (mm)

Figure 11. ,Size frequency distributions of male sriow crab (C.. opllio) ., sampled by the Nephrops,.trawl in the southwestern Gulf of 81. Lawrence during arinual surveys tram 1988 ta 1991 (adapted tram Mallet et al. 1992). 25

3.5

-cft. 3 -Cf) 2.5 Q) 'u 2 c Q) ::::J 1.5 C'" ~ u. 1 .5

O.,j...---,----...------r--o.4W-ULLI 20 40 60 80 100 120 140 Carapace Width (mm)

Figure 12. Size frequeney distribution of male snow erab (C. opilio) measured during sea sampling aboard eommereial boat in the southwestern Gulf of St. Lawrenee in the spring of 1992 (N = 14745; unpublished data from Yvon Chiasson, DFO Moneton). e. 26

5

0 -C4 (J) .-Q) () 3 c Q) ~2 Q) '- u.. f

0 0 . 20 40 60 80 100 120 140 Carapace Width (mm) e Figure 13. Size frequency distribution of male snow crab (C. opilio) sampled by the Nephrops trawl in Bonne Bay, Newfoundland in 1985, 1988, 1989 and 1990 (N = 4502; adapted fram Comeau et al. 1991).

5 -~4 -(J) . •Q) 3 () c ~2 0­ Q) U: 1 •• o 0 10 20 30 40 50 60 70 80 90 100 Carapace Width (mm)

Figure 14. Size frequency distributionof female snow crab (C. opilio) sampled by the Nephrops trawl in Bonne Bay, Newfoundland in 1985, 1988, 1989 and 1990 (N =5583; adapted from Comeau et al. 1991). • 27

40 -~o 35 -CI) 30 Q) '0 25 c: Q) 20 • :::J 0-15Q) L- U. 10 5 o o 20 40 60 80 100 120 140 Carapace Width (mm)

Figure 15. Size frequency distribution of snow crab (C. opilio) sampled by the Devismes trawl in Bonne Bay Newfoundland between May and September, 1991 (N =183). Males and females are combined because sex is difficult to identify below 10 mm CW. • 28 •

7 ;g. 6 o -5 Cl) Q) ·u 4 c: Q) 3 ::J g- 2 u.."- 1

20 40 60 80 100 120 Carapace Length (mm)

Figure 16. Size frequeney distribution of lobster (H. americanus) • sampled by Nephrops trawl in western Northumberland Strait, Gulf of St. Lawrenee, on June 22 and 28, 1993 (N =250).

10 9 -~o 8 -Cl) 7 Q) u 6 c: 5 CD ::J 4 C­ CD 3 u.."- 2 • 1 0 0 20 40 60 80 100 120 Carapace Length (mm)

Figure 17. Size frequeney distribution of lobster (H. americanus) eaught by eommereial traps in, or in the vicinity of Cap-Pele, New Brunswiek between August and Getober, 1992 (N = 1392; unpublished data fram Mare Lanteigne, DFO Moneton). ,. 29

5,

-~4o -cn Q) 3 u c:: ~ 2 C­ a> U: 1

o-I- -.I.L o 20 40 60 80 100 120 Carapace Length (mm) • Figure 18. Size frequency distribution of lobster (H. americanus) sampled , by the Devismes trawl in Malpeque Bay, Prince Edward Island, between August 1 '- 12, 1988 (N = 450). . ' .' , .

8 7 -~o -cn 6 ,Q) "u 5' c:: Q) 4 ::l C­ 3 Q) ~ 2 • LL 1

O-l---"""T"""-_~-o4LLLl o 20 40 60 80 100 120 Carapace Length (mm)

Figure 19. Size frequency distribution of lobster (H. americanus) by caught commercial traps in, or in the vicinity of Malpeque Bay, Prince Edward Island between May and June, 1989 (N = 10159; unpublished data from Mare Lanteigne, DFO Moneton). . 30 11

9 8 ~ -o 7 -(/) a> 6 () 5 c:: a> 4 ~ • C­ 3 a> u..~ 2 1 o +-_-...._-,...II.I.I.IIL.L o 20 40 60 80 100 120 Carapace Length (mm)

Figure 20. Size frequency distribution of lobster (H. americanus) early benthic stages caught by diving in 1989 in Val Comeau, New Brunswick (N = 264; unpublished data from Michel Comeau). •