A Comparison of Catch Between Research and Commercial Vessels During a Trawl Survey of Hecate Strait, May 30 June 13, 1996

Transcription

1 A Comprison of Ctch Between Reserch nd Commercil Vessels During Trwl Survey of Hecte Strit, My 3 June 13, 1996 J. Frgo nd G. D. Workmn Fisheries nd Ocens Cnd Science Brnch, Pcific Region Pcific Biologicl Sttion Nnimo, British Columbi V9R 5K Cndin Mnuscript Report of Fisheries nd Aqutic Sciences 2425 Fisheries Peches 1+1 nd Ocens et Ocens

2 Cndin Mnuscript Report of Fisheries nd Aqutic Sciences Mnuscript reports contin scientific nd technicl informtion tht contributes to existing knowledge but which dels with ntionl or regionl problems. Distribution is restricted to institutions or individuls locted in prticulr regions of Cnd. However, no restriction is plced on subject mtter, nd the series reflects the brod interests nd policies of the Deprtment of Fisheries nd Ocens, nmely, fisheries nd qutic sciences. Mnuscript reports my be cited s full publictions. The correct cittion ppers bove the bstrct of ech report. Ech report is bstrcted in Aqutic Sciences nd Fisheries Abstrcts nd indexed in the Deprtment's nnul index to scientific nd technicl publictions. Numbers 1-9 in this series were issued s Mnuscript Reports (Biologicl Series) of the Biologicl Bord of Cnd, lld subsequent to 1937 when the nme of the Bord ws chnged by Act of Prliment, s Mnuscript Reports (Biologicl Series) of the Fisheries Reserch Bord of Cnd. Numbers were issued s Deprtment of Fisheries nd the Environment, Fisheries nd Mrine Service Mnuscript Reports. The current series nme ws chnged with report number Mnuscript reports re produced regionlly but re numbered ntionlly. Requests for individul reports will be filled by the issuing estblishment listed on the front cover nd title pge. Out-of-stock reports will be supplied for fee by commercil gents. Rpport mnuscrit cndien des sciences hlieutiques et qutiques Les rpports mnuscrits contiennent des renseignements scientifiques et techniques ques qui constituent une contribution ux connissnces ctuelles, mis qui tritent de problemes ntionux ou regionux. L distribution en est limitee ux orgnlsmes et ux personnes de regions prticulieres du Cnd. II n'y ucune restriction qunt u sujet; de fit. l serie reflete l vste gmme des inten~ts et des politiques du ministere des Peches et des Ocens, c'est--dire les sciences hlieutiques et qutiques. Les rpports mnuscrits peuvent etre cites comme des publictions completes. Le titre exct prit u-dessus du resume de chque rpport. Les rpports mnuscnts sont resumes dns l revue Resumes des sciences qutiques et h/ieutiques, et ils sont clsses dns I'index nnul des publictions scientifiques et techniques du Ministere. les numeros 1 9 de cette serie nt em publies titre de mnuscrits (selie biologique) de l'office de biologie du Cnd, et pres Ie chngement de l designtion de eet orgnisme pr deeret du Prtement, en 1937, ont ete clsses comme mnuscrits (serie biologique) de l'office des recherches sur les pecheries du Cnd. Les numeros ont em publies titre de rpports mnuscrits de I'Office des recherches sur les pt'lcheries du Cnd. Les numeros sont prus titre de rpports mnuscrils du Service des peches et de l mer, ministere des Peches et de I'Environnement. Le nom ctuel de l selie ete etbli lors de l prution du numero Les rpports mnuscrits sont produits I'echelon regionl, mis numeroit~s l'echelon ntionl. Les demndes de rpports seront stisfites pr I'etbfissement uteur dont Ie nom figure sur l couverture et l pge du titre. Les rpports epuises serent foumis contre retribution pr des gents commerciux.

3 Cndin Mnuscript Report of Fisheries nd Aqutic Sciences A COMPARISON OF CATCH BETWEEN RESEARCH AND COMMERCIAL VESSELS DURING A TRAWL SURVEY OF HECATE STRAIT, MAY 3 - JUNE 13,1996 by J. Frgo nd G.D. Workmn Fisheries nd Ocens Cnd Pcific Region, Science Brnch Pcific Biologicl Sttion Nnimo, British Columbi V9R5K6

4 - ii Minister of Supply nd Services Cnd 1997 Ct. No. Fs E ISSN Corred citti'1 for this publiction: Frgo, J., nd G. D. Workmn A comprision of ctch between reserch nd commercil vessels during trwl survey of Hecte Strit, My 3 - June 13, Cn. Mnuscr. Rep. Fish. Aqut. Sci. 2425: 41 p.

5 -iii- ABSTRACT Frgo, J., nd G.,.D. Wor1<mn A comprision of ctch between reserch nd commercil vessels during trwl survey of Hecte Strit, My 3 - June 13, Cn. Mnus-. Rep. Fish. Aqut. Sci. 2425: 41 p. We nlysed replicte hul dt from bottom trwl survey conducted in Hecte Strit. The huls mde by the reserch vessel were replicted by trwler using commercil trwl net with 6 inch mesh. The purpose of this work ws to exmine the vlidity of the reserch vessel CPUE dt for stock ssessment work nd to evlute the effect of the mesh regultion imposed by the DFO in this re in We found no significnt difference in the replicte CPUE dt between the two vessels for Pcific cod (Gdus mcrocephlus), Dover sole (Microstomus pcificus), English sole (Pleuronectes vetulus) nd Rock sole (Plueronectes bilinet). However, length composition dt did differ between the two vessels due to the different mesh sizes in the nets used. Men lengths for the four commercil species were significntly greter for the commercil vessel using 6 inch mesh thn the reserch vessel using 3.5 inch mesh. Ctch rtes for juvenile fltfish for the commercil vessel were s 1% of those for the reserch vessel. Ctch-rtes for lrger fish were times greter for the commercil vessel thn the reserch, possibly due to the greter herding effect for the commercil ger. The length-specific selectivity rtio for the Commercil vessel pproched 1 t length corresponding to the recommended minimum size limit for ll of the fltfish species. The chnge in size selectivity for commercil fltfish species due to the lrger mesh size must be ccommodted in ctch-ge nlysis used for stock ssessment of these species. The differentil ctch rtes for lrger fish between the two vessels should be evluted on the next survey.

6 - iv- RESUME Frgo, J., nd G. D. Workmn A comprision of ctch between reserch nd commercil vessels during trwl survey of Hecte Strit, My 3 - June 13, Cn. Mnuscr. Rep. Fish. Aqut. Sci. 2425: 41 p. Nous vons nlyse les donnees obtenues pr trits repetes pendnt un releve u chlut dns Ie detroit d'hecte. Les trits effectues pr Ie nvire de recherche ont ete repetes pr un chlutier nne pour Ie chlutge commercil vec un filet millge de 6 pouces. L mission vit pour objet de verifier l vlidite des donnees CPUE obtenues pr Ie btiment de recherche pour Ie trvil d'evlution des stocks, et de determiner I'effet de l reglementtion sur Ie millge imposee en 1995 pr Ie MPO dns cette region. Nous n'vons ps observe de difference significtive dns les donnees CPUE obtenues en prllele pr les deux bteux pour l morue pcifique (Gdus mcrocephlus), l limnde-sole (Microstomus pcificus), Ie crlottin nglis (Pleuronectes vetulus) et l sole pcifique (Pleuronectes bilinet). Les donnees sur l composition pr longueur differient toutefois entre les deux bteux cuse des millges employes. Les longueurs moyennes pour les qutre especes commerciles etient nettement plus grndes vec Ie chlutier commercil utilisnt un millge de 6 pouces qu'vec Ie bteu de recherche qui employit un filet it millge de 3,5 pouces. Les tux de cpture des poissons plts juveniles etient # 1 % de ceux du btiment de recherche. Les tux de cpture des poissons plus gros etient 1,5 2 fois superieurs vec Ie chlutier, ce qui peut etre do I'effet de regroupement plus efficce vec Ie greement commercil. Le rpport de selectivite specifique l longueur dns Ie filet commercil pprochit de 1 it une longueur correspondnt it l limite minimle de tille recommndee pour tous les poissons plts. Le chngement de l selectivite pr tille des especes commerciles de poissons plts doit etre pris en compte dns I'nlyse de I'ge l cpture qui sert I'evlution des stocks de ces especes. L difference entre les deux bteux dns Ie tux de cpture des poissons de grnde tille doit etre evluee lors du prochin releve.

7 INTRODUC1"ION Between My 3 nd June 13, 1996 we conducted bottom trwl survey in Hecte Strit using the reserch vessel W.E. RICKER. This ws the eighth survey in binnul series (Workmn et t 1997). Informtion from the surveys is used in stock ssessment work t the Pcific Biologicl Sttion. On the 1996 survey commercil fishing vessel ws chrtered to replicte huls mde by the reserch vessel. This ws done to compre the ctch-rte nd biologicl dt for typicl commercil vessel with tht for the reserch vessel to ssess: 1) how pproprite the reserch vessel CPUE indices re for stock ssessment work, nd 2) the length-specific selectivity of commercil groundfish species under the current minimum mesh regultion in the Strit. This report presents the results of nlyses compring ctch-rte nd biologicl dt between the reserch vessel, W.E. RICKER, nd chrtered commercil trwler, the STEADFAST. METHODS VESSELS AND GEAR Specifictions for the two vessels nd their fishing ger hve been reported by Workmn et l. (1997). Briefly, the RN W.E. RICKER (WER) is 25 hp, 57.3 m steel stem trwler which used Ynkee 36 trwl of hevy construction with 8.75 cm (3.5 in) mesh throughout nd 2.5 em codend liner. The FN STEADFAST (STD) is 38 hp, 2 m steel stem trwler tht ws chrtered to replicte sites occupied by WER during the first hlf of the survey. The net used by STD ws Sfri 5 with 15.2 em (6 in) mesh throughout. This net is typicl of the commercil fishery in Hecte Strit. The systemtic strtified design for the survey hs been described in Westrheim et l. (1984) nd Frgo et t (1984). The hul loctions re pproximtely the sme on every survey conducted. The survey covers the entire Strit nd replicte huls were done throughout the Strit on the 1996 survey. Fishing occurred during dylight hours only. Towing time ws 3 minutes, mesured from the time the wrp drums were locked to the time net retrievl begn. For replicte huls STD wited until WER hd locked its wrps nd then set off the port or strbord stem qurters, usully within 5 m of WER. CATCH DATA To fcilitte comprison between vessels we stndrdized the dt for differences in towing time, net configurtion nd net mesh size. First we corrected for differences in the size of the re swept by the two nets, using mesurements of vrious fishing components ssuming tht the effective re swept by trwl net ws

8 - 2 best represented by the door spred (Ngtegl 1986). We estimted the door spred for ech net using the method of Crrothers (198). Wingspred, sweep length nd bridle length were used for these clcultions. Wingspred for the Ynkee 36 (WER), mesured directly during the survey, rnged from 1 m to 12 m. For the Sfri net rigged with Thyboron 96 doors we used vlue of 1.75 m for the wingspred determined from flume tnk studies conducted on the Atlntic cost (Jon Johnnesson, Cntrwl Pcific Ltd., prs. comm.). We lso used two lternte methods of estimting the wingspred: 1) dividing the length of the hedline in hlf; nd 2) dividing the length of the hedline plus the footrope by 4 (Tble 1) (Hnd et l. 1995, Ymnk et I.1996). The re swept by the doors ws djusted for the curvture of the ground wrp using ctenry prmeters determined in previous work (Ymnk et l. 1996). We ssumed tht the herding effect of the sweeplines ws similr for both vessels. The finl estimte of door spred for STD ws 14% greter thn tht for WER nd we multiplied the ctches for STD by.86 to correct for this difference. We corrected for minor differences in towing time by clculting the ctch weight for one hour of towing (corrected CPUE) for ech vessel. To correct for differences in net mesh size we used the length frequency dt nd corresponding length-weight reltionship to estimte the ctch of fish greter thn 34 em (the size fltfish re grded for t se by the fishermen for the processing plnts nd pproximtely equivlent to the size fully selected for the STO net). For the few instnces where length dt were not collected we used the men weight of fish greter thn 34 em for the 48 replicte huls for given species nd vessel. We tested for differences in CPUE between the two vessels using the Fisher test nd the non-prmetric Mnn-Whitney signed rnk test. We used the Fisher rndomiztion test (Mnly 1991) to test for differences in men corrected CPUE between vessels. Both tests re pproprite for dt tht re not normlly distributed s is typicl of CPUE dt. The Fisher test re-smples the differences from the replicte CPUE dt to produce distribution of differences from which the probbility level for the men of the differences is determined. The Mnn-Whitney test gives rnk sum sttistic for the two sets of CPUE dt tht ws used to test for differences between the two sets of dt. We removed replictes where CPUE ws zero for both vessels prior to sttisticl testing. We estimted the length-specific retention rtios for S-rO compred to WER for Pcific cod (Gdus mcrocephlus), Dover sole (Microstomus pcificus), English sole (Pleuronectes vetulus) nd Rock sole (Pleuronectes bilinet) using the following proce,dure. For the fltfish species, we clculted the numbers cught per hour for 3 em length intervls nd divided these vlues for STD by those for WER. The resulting rtio then reflects the length-specific retention rtes for the fltfish species for STO compred to WER. We used the sme procedure for Pcific cod but grouped the dt by 5 em length intervls.

9 - 3 BIOLOGICAL DATA We,compred the numbers cught nd the size composition dt between the two vessels for four importnt commercil species in the region: Pcific cod, rock sole, Dover sole nd English sole. Rndom sub-smples were collected from lrge ctches of individul species. All fish were smpled from smller ctches «5 kg) We extrpolted from sub-smples to totl numbers cught using the rtio of totl weight cught, the numbers sub-smpled nd the weight of the sub-smple. RESULTS CATCH DATA The two vessels completed 48 replicte huls on the survey (Figure 1). Both totl ctch nd species composition for replicte huls were similr between the two vessels (Tble 2). Ctches of fltfish nd roundfish were higher for WER while ctches of rockfish nd selchii were higher for STD (Figure 2). Rockfish nd selchii re not primry trgets of the survey. The uncorrected ctch for the four species exmined is presented by vessel in Figure 3. The uncorrected ctch for Pcific cod nd rock sole ws nerly the sme between the two vessels while tht for Dover nd English soles ws higher for WER (Tble 3, Figure 3). The corrected ctch for Pcific cod, rock sole nd Dover sole ws higher for STD while the corrected ctch for English sole ws slightly higher for WER (Tble 3, Figure 3). CPUE dt by replicte hul, species nd vessel re presented in Tble 4. Sttistics for corrected nd uncorrected CPUE by species for ech vessel re presented in Tbles 5-6. The uncorrected men CPUE for English sole nd Dover sole ws higher for WER while the uncorrected men for Pcific cod ws higher for STD (Figure 4) nd the uncorrected men for rock sole ws nerly the sme between the two vessels. Correcting for door spred reduced the species men CPUEs of STD becuse the net used by STD hd lrger swept re thn tht of WER. However, correcting for mesh size hd the most significnt effect on the finl estimtes of the ctches nd men CPUEs. This resulted in decrese in ctch nd men CPUEs clculted for WER. The men corrected CPUE for Pcific cod, rock sole nd Dover sole ws higher for STD while tht for English sole ws nerly the sme for both vessels (Figure 4). The 9% confidence intervls of the mens for ll four species overlpped between the two vessels. We used non-prmetric sttistics to test the CPUE dt for differences between the two vessels. Plots of the corrected CPUE dt (Figure 5) suggest tht there ws little difference in CPUE in replictes between the two vessels, lthough the highest CPUEs for both vessels did not necessrily occur on the sme hul. There

10 - 4 ws no significnt difference in the corrected CPUE dt mong replictes for the two vessels for ny of the species exmined (Fisher test, Mnn-Whitney test). BIOLOGICAL DATA Summry sttistics for the length dt for ech vessel re presented in Tbles 7 nd 8. The men length offish smpled for ll four species ws significntly greter for STD for ll four species (t test, p<.1). There were significnt differences in the species length distributions between the two vessels s well (Mnn Whitney test, P<.1) (Figures 6-9). Rock sole cught by WER showed modes t 21 em nd 33 em. The 21 em mode is bsent in length frequency distributions for STD. For Pcific cod, mode t 28 em is prominent in the distribution for WER but is not in the distribution for STD. Dover sole cught by WER showed strong mode t 3 cm while fish cught by STD showed modes t 33 em nd 43 em. English sole cught by WER showed mode t 26 em compred to mode t 33 em for fish cught by STD. Cumultive frequency plots of numbers-t-iength for the four species re presented by vessel in Figure 1. Approximtely fifty percent of the Pcific cod cught by both vessels were less thn 5 em. However, 29% of the Pcific cod cught by WER were less thn 4 em while only 13% cught by STD were less thn 4 cm. For rock sole 53% of the fish cught by WER were less thn 25 em while only 4% of those cught by STD were under 25 em. For English sole 47% of the fish cught by WER were less thn 25 em while only 11 % of those cught by STD were under 25 cm. For Dover sole 65% of the fish cught by WER were less thn 3 cm while only 7% of the fish cught by STD were under 3 em. The length-specific retention rtios for STD I WER re presented by species in Figure 11. The lines in the plots indicte the lowess smoothed trend to these dt. Overll STD cught fewer smller nd more lrger fish thn WER for ll four species. However, the smll smple sizes t the high end of the length rnge contributed to high vribility of the rtio in ll cses. The STD retention rtio for Pcific cod rnged from.2 for fish of 26 em to between for fish lrger thn 5 em. The retention rtio for Pcific cod pproched 1 t size of 35 em. The retention rtio for rock sole rnged from. for fish smller thn 2 em to for fish lrger thn 35 em. The retention rtio for rock sole pproched 1 t size of 33 cm. The retention rtio for Dover sole rnged from. for fish smller thn 3 cm to between for 'fish lrger thn 4 em. The retention rtio for Dover sole pproched 1 t size of bout 38 em. The retention rtio for English sole rnged from. for fish smller thn 2 em to for fish lrger thn 36 em. The retention rtio pproched 1 t size of bout 36 em.

11 - 5 DISCUSSION Overll the species ctch composition between the two vessels did not differ pprecibly. In fct, the ctch of fltfish ws nerly identicl. The differences in the ctch of roundfish between the two vessels were due minly to smll noncommercil species tht were cught by WER nd not by STD. STD cught more rockfish thn WER, however this is to be expected. The Sfri 5 (STD) is high lift box trwl, which is better for ctching off-bottom species like rockfish while the Ynkee 36 (WER) is flt trwl with groundline composed of 152 mm (6 inch) rubber discs designed to ctch ll sizes of fltfish. There ws no mesurble difference in CPUE between the two vessels fter correcting for differences in the fishing ger used. This is despite the fct tht depth nd loction differed slightly between the two vessels for the replicte huls. However, the highest CPUEs for ll species did not occur on the sme hul. This is probbly due to the fct tht the hbitt in the Strit is very diverse nd the distributions for individul species re not homogeneous (Frgo nd Tyler 1991 ). There were significnt differences in species size composition between the two vessels due to the different mesh size in the two nets. WER cught more smll non-commercil species nd juveniles of commercil species thn STD did. STD cught greter numbers of lrge fish thn WER. To be ble to relte this to the fishing ger used we require more detiled knowledge of the ger voidnce behviour of these species. It is well known, however, tht longer sweep lines hve greter herding effect on fltfish species (Hrden Jones et l. 1977). Underwter cmer work in the Gulf of Alsk nd in Hecte Strit indictes tht fltfish swim continuously in front of pproching trwl ger until they re exhusted nd re either cptured or the groundline nd net psses over them. The lrgest individuls re the strongest swimmers. The longer sweep lines of STD my hve contributed to greter herding effect forcing the lrger individuls to swim hed of the net for longer period, mking them more susceptible to exhustion nd cpture. More work on fish voidnce behviour nd fishing ger performnce is necessry to confirm this. If we ssume tht WER cught 1% of the juvenile 1~tfish vilble then the net used by STD ws 1% selective for rock sole t 33 em, English sole t 38 em nd Dover sole t 36 em. Length t 5% mturity hs been used s guidnce for setting minimum size regultions for fltfish nd other groundfish species. This corresponds to size/ge where yield per recruit is mximized for moderte-fst growing species. Length of 5% mturity is 34.1 em for rock sole, 35.5 em for English sole nd 38.1 em for Dover sole. Thus, there is evidence from this work tht 6 inch mesh size significntly lowers the discrd rte for juvenile sole (ges 1-3) nd Pcific cod (ges 1,2). In ddition, the byctch of smll, non-commercil species such s Pcific snddb (Cithrichthys sordidus), C-O sole (P/euronichthys coenosus), curlfin sole (P/euronichthys decurrens), sblefish (Anp/opom fimbri) nd others ws lso reduced.

12 - 6 The selectivity rtios determined in this study cn be used to djust the size nd ge dt for the fltfish species to ccount chnges in fishery selectivity fter the mesh size regultion imposed in This will result in more ccurte popultion estimtes from ctch-ge nlysis used for stock ssessment of these species. ACKNOWLEDGMENTS The uthors wish to thnk the Cptin Sirj Gulti nd Fishing Mster Brin West bord the W.E. RICKER nd Cptin Kelvin Mrk nd crew bord the STEADFAST. Their enthusism nd coopertion contributed gretly to the success of this study. Funding for the chrter ws provided by the Cndin Groundfish Reserch nd Conservtion Society. Smpling personnel for the FN STEADFAST were provided by Archipelgo Mrine Reserch Ltd. Ron Tnsichuk review drft of the mnuscript nd provided mny helpful suggestions. REFERENCES Crrothers, P.J.G Estimtion of trwl door spred from wingspred. J. Northw. Atl. fish. Sci. Vol 1: Frgo, J., AV. Tyler, J. Cooper, S.C. Sheilds, nd S. Stebbins ARCTIC OCEAN ssemblge survey of Hecte Strit, My 28-June 17, Cn. Dt Rep. Fish. Aqut. Sci. 491: 18 p. Frgo, J.,AV. Tyler, nd RP. Foucher Distribution of demersl fishes in Hecte Strit, British Columbi, Bsed on systemtic trwl surveys conducted from Cn. Tech. Rep. Fish. Aqut. Sci. 1745: 115 p. Frgo, J., nd AV. Tyler Distribution of demersl fishes in Hecte Strit, British Columbi, bsed on systemtic trwl surveys conducted from Cn. Tech. Rep. Fish. Aqut. Sci. 1745: 115 p. Hrden Jones" RF., AR Mrgetts, M. Greenwlker, nd G.P. Arnold The efficiency of the Grnton otter trwl determined by sector-spnning sonr nd coustic trnsponding tgs. Rpp. P-V. Reum. Cons. Int. Explor. Mer. 17: Mnly, B.F.J Rndomiztion nd Monte Crlo Methods in Biology. Chpmn nd Hll. London U.K p

13 - 7 Ngtegl. D. A., B.M. Lemn nd R.D. Stnley Ctches nd trwl loction of the RN G.B.REED nd the MN EASlWARD HO during the Pcific Ocen Perch ssessment cruise to Queen Chrlotte sound, August - September, Cn. Dt Rep., Fish. Aqut. Sci. 611: 19 p. Westrheim, S.J., A.V. Tyler, R.P. Foucher, M.W. Sunders, nd S.C. Shields G.B. REED groundfish cruise no. 84-3, My 24-June 14,1984. Cn. Dt Rep. Fish. Aqut. Sci. 488: 131 p Workmn, G.D., J. Frgo, B. Bell, nd E. Hildebrnd RN W.E. RICKER nd FN STEADFAST trwl survey of Hecte Strit, My 3-June 13,1996. Cn. Dt Rep. Fish. Aqut. Sci. (In press). Ymnk, KL., L.J. Rutherford, nd G.D. Workmn Bottom trwl survey for rockfish in Queen Chrlotte Sound, September 11-22, Cn. Mnuscr. Rep. Fish. Aqut. Sci. 2362: 116 p.

14 - 8 Tble 1. Net Dimensions nd clculted door spred (Crrothers 198). Mesured wingspred vlues were used, but two lternte methods of estimting wingspred were evluted to provide some dt for comprison. Vlues selected to stndrdize the dt re in bold. Net Hedline Sweep Bridle Wingspred Method for Doorspred length (ft) Length (ft) length (ft) (ft) estimting (ft) wingspred Ynkee HLJ2' 97 Ynkee HLFR/ Ynkee M-FS Sfri HLJ Sfri HLFR/ Sfri M-Fr HLJ2 Hedline length divided by 2 2 HLFR/4 = Hedline length plus Footrope length divided by 4 3 M-FS33 = Men net opening mesure with FS33 hedline net sounder 4 M-FT = Mesured in flume tnk, Jon Johnnesson t Cn-Trwl Pcific Pers. Comm.

15 - 9 Tble 2. Ctch by species for 48 replicte huls mde by the RN W.E. RICKER (WER) nd the FN STEADFAST (STD) on the Hecte Strit groundfish survey, My 29 - June 14,1996. Ctch (kg) % of Totl ctch Species WER STD WER STD Fltfish Arrowtooth flounder Petrle sle Rex sle Flthed sle Pcific hlibut Butter sle Rock sle Slender sle Dover sle English sle Strry flounder Curlfin sle Snd sle Pcific snddb Totl Roundfish Pcific herring Chinook slmon 3. Eulchon 48.2 Pcific cod Pcific hke 1. Pcific tomcod 98.3 Wlleye pollock Eelpouts 2. Wolfeel 1 2. Sndlnce 51.2 Sblefish Greenlings 4.

16 - 1 Tble 2 - Con't. Ctch by species for 48 replicte huls mde by the RN W.E. RICKER (WER) nd the FN STEADFAST (STD) on the Hecte Strit groundfish survey, My 29 - June 14, Ctch (kg) % of Totl ctch Species WER STD WER STD Roundfish (Cont'd) Lingcod Sculpins 6 7 Pochers 3 Totl Rockfish Redbnded rockfish Silvergry rockfish Yellowtil rockfish QlJillbck rockfish Bocccio Cnry rockfish Redstripe rockfish 1.. Yelloweye rockfish Pygmy rockfish 5.. Totl Selchii Spiny dogfish Sktes Spotted rffish Totl Grnd Totl

17 - 11 Tble 3. Actul (uncorrected) ctch (kg) nd ctch corrected for differences in fishing ger used by the FN Stedfst nd the RN WE Ricker. Stedfst Percent WE Ricker Percent uncorrected corrected Chnge uncorrected corrected Chnge Pcific cod Rock sole Dover sole English sole

18 - 12 Tble 4. Uncorrected nd corrected CPUE for four commercil species cught on the 1996 Hecte Strit survey by vessel, species nd replicte. Uncorrected CPUE (kglh) Correctted CPUE (kh/h) Replicte Species STD WER STD WER 1 Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod

19 - 13 Tble 4 - Con't. Uncorrected nd corrected CPUE for four commercil species cught on the 1996 Hecte Strit survey by vessel, species nd replicte. Uncorrected CPUE (kglh) Corrected CPUE (kh/h) Replicte Species STD WER STD WER 37 Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Pcific Cod Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole

20 - 14 Tble 4 - Con't. Uncorrected nd corrected CPUE for four commercil species cught on the 1996 Hecte Strit survey by vessel, species nd replicte. Uncorrected CPUE (kglh) Corrected CPUE (kh/h) Replicte Species STD WER STD WER 25 Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Rock sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole

21 - 15 Tble 4 - Con't. Uncorrected nd corrected CPUE for four commercil species cught on the 1996 Hecte Strit survey by vessel, species nd replicte. Uncorrected CPUE (kglh) Corrected CPUE (khlh) Replicte Species STD WER STD WER 13 Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole Dover sole

22 - 16 Tble 4 - Con't. Uncorrected nd corrected CPUE for four commercil species cught on the 1996 Hecte Strit survey by vessel, species nd replicte. Uncorrected CPUE (kg/h) Corrected CPUE (khlh) Replicte Species STD WER STD WER 1 English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole

23 - 17 Tble 4 - Con't. Uncorrected nd corrected CPUE for four commercil species cught on the 1996 Hecte Strit survey by vessel, species nd replicte. Uncorrected CPUE (kg/h) Corrected CPUE (khlh) Replicte Species STD WER STD WER 37 English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole English sole

24 - 18 Tble 5. Summry sttistics for uncorrected CPUE (kglh) by species nd vessel. 1 n Men Medin Stndrd 9% confidence intervl devition Species WER STD WER STD WER STD WER. STD Pcific Cod Rock Sle English Sle Dover Sle Number of huls where the ctch of both vessels ws zero. Tble 6. Summry sttistics for corrected CPUE (kglh) by species nd vessel. 1 n Men Medin Stndrd 9% confidence devition intervl Species WER STD WER STD WER STD WER. STD Pcific Cod Rock Sle English Sle Dover Sle Number of huls where the ctch of both vessels ws zero

25 - 19 Tble 7. Summry sttistics for length dt (em) collected during the RN W.E. RICKER ssemblge survey, Hecte Strit, My 29 - June 14,1996. Species Men Stndrd Medin Mode n Devition Pcific Cod ,47, Rock Sole , Dover sole English sole Tble 8. Summry sttistics for length dt (em) collected on the FN STEADFAST, for the 1996 Hecte Strit survey, June 1-6, Species Men Stndrd Medin Mode n Devition Pcific Cod , Rock Sole Dover sole , English sole

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27 - 21 o o. o Fig. 1. Loction of replicte huls mde by the w. E. RICKER AND STEADFAST during the 1996 Hecte Strit survey.

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29 18 I I ~ W.E. RICKER o STEADFAST - ~ ~ 1 ~ (J.$ 8 N W {: o ' Fltfish Roundfish Rockfish Selchii Species group Fig. 2. Ctch composition (weight) by species group by vessel.

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31 mw.e. RICKER [] STEADFAST ~ ụ. ~ 25 III Pcific cod Rock sole Dover sole Species English sole rw.e. RICKER []STEADFAST 1 Di ~ ~ 8 u 'Iii Pcific cod Rock sole Dover sole English sole Species Fig. 3. Uncorrected (top pnel) nd corrected (bottom pnel) ctch for four commercil species by vessel.

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33 - 27 o C\l - ~... ~ w ::> 11. u I (f) «LL o «w I (f) o o... - o -... /~"."H ole / /~Jsole Englis~ sole I I I I I I o o....' o - ex>.' ~... Pcifi cod / ~ w ::> 11. U o <D I Englis h.$dle (f).' «LL o «w I (f) o C\l ~~:.// ROC~.S6r~,.. ".'....'.'... o.'.' o W.E. RICKER CPUE(kg/h) Fig. 4. Uncorrected (top pnel) nd corrected (bottom pnel) men CPUE by species nd vessel. The crosses represent the 9% confidence intervls nd the dotted line is the line of 1:1 correspondence.

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35 - 29 co co 1 :2 :2 C) C) ~ ~ ur ur v =>.... => v (,) (,) I en C') I- en «u. «u. Cl Cl ««w w C\I I I- C\I en en Rock sle BOO W.E. RICKER CPUE(kg/h) W.E. RICKER CPUE(kg/h) C\I v Dover sle English sle -- ~ 1 :2 C) C) ~ ~ C') ur =>.... => (,) (,) I I- ««C\I u. u. Cl Cl en... en «w «w I I en en 1 ur W.E. RICKER CPUE(kg/h) W.E. RICKER CPUE(kg/h) Fig. 5. Corrected CPUE by species nd vessel. The digonl line in the plots indictes 1:1 correspondence.

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37 - 31 Pcific cod LO C! v ci W.E. RICKER c::: C') ci :e c.. ~ C\l 11. ci... C! ci Length (cm) LO ~ STEADFAST C') c::: C! o :e o c.. ~ 11. ~ ci... o ci o ci Fig. 6. Length (cm) Length frequency histogrms for Pcific cod by vessel.

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39 - 33 Rock sole C\J c co t ( ;to C! W.E. RICKER C\J _JIIII Length (em) C\J STEADFAST c co t (. C! ;to C! ~ C\J Fig Length (em) Length frequency histogrms for Rock sole by vessel.

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42 - 35 Dover sole co C! o W.E. RICKER ( C! c: t C! """..... N _ Length (em) co C! o ( STEADFAST c: t """ C!..... N C! o Fig. 8. Length (em) Length frequency histogrms for Dover sole by vessel.

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44 - 37 English sole co C! o CD W.E. RICKER c :e "<t. C! ' (L ('J C! ci JI.I.I Length (em) 4 5 co C! o STEADFAST CD C! c :e "<t C!. e (L ('J o o Fig. 9. Length (em) Length frequency histogrms for English sole by vessel.

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46 q ~ q... C 1: CXl Ul e c- GI ~.!'!l '<t :::l E :::l () Pcific cod...//.. C\l W.E.RICKER... STEADFAST --,... I \ l"1 I q q CXl CXl Dover sle I.. I C c 'E 1: c- Ul c- Ul e e o c c- C 'E c- e c- GI,~ CXl Ul!i '<t :::l E :::l () C\l GI GI ~,~ I'll '<t iu '<t "'5 "3 E E :::l :::l () () C\l d W.E. RICKER I STEADFAST ---_... _ d -,, I I I ,I C\l Rock sle ~....,.' W.E.RICKER STEADFAST English sle ,'././... W.E RICKER STEADFAST Fig. 1. Length (cm) species cumultive length frequency by vessel. Length (cm)

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48 - 41 Pcific cod.q iii... C') s= iii :: w C\l :E I- en.q ~ s= U1 iii :: w :E I- en U1 C\l Rock sle C? C\l C? It) Length (em) ~ Length (em) C'! co Dover sle C? English sle. ~ _._ ).Q... (l) iii s= ~ :: W ~ :E I- en.q ~ co s= iii (l) :: w :E ~ I- en C\l C\l Length (em) Length (em) Fig. 11. Selectivity rtios by species length ctegory for the STEADFAST in comprison with the W. E. RICKER. The line in ech plot represents the lowess smoothed fit.