ICES CM 19981M:04 Theme Session eM) Impact of Cephalopods in the Food Chain and their Interaction with the Environment

SQUID (Loligo peale i) REACTIONS TO TOWED FISHING GEARS; THE ROLE OF BEHAVIOUR IN BYCATCH REDUCTION

C.W.Glass, B. Sarno, H. O. Milliken*, G. D. Morris, H. A. Carr* Manomet, Center for Conservation Sciences

Manomet, MA, USA 02345-1770 (phone) 508 224 6521 (fax) 508 224 9220

email: glasscw@manomet.org

* Massachusetts Division of Marine Fisheries 50A Portside Road

Pocasset, MA, USA 02559

In New England waters, Atlantic Longfm squid (Loligo peale!) over-winter offshore along the edge of the continental shelf. During spring Loligo squid undertake seasonal migrations to spawn in shallow inshore waters. The resulting spawning aggregations are fished heavily by towed otter trawls. These aggregations have been targeted since the late 1800's. The stock is currently characterized as fully exploited at a medium biomass level and squid is in danger of being over-fished throughout the region. Each year a single cohort supports both the fishery and spawning stock; consequently, the potential for recruitment overfishing is substantial. Concerns about the spawning stock biomass are exacerbated by recent increases in the effort of offshore fisheries, which has been accompanied by a decrease in catch and catch per unit effort in the inshore fisheries. In addition, small-mesh fishing for squid in Nantucket and Vineyard Sounds during this seasonal fishery result in high catch and discard of undersized flounder and scup, both important commercial and recreational fishery species. This study was designed to assess the extent of bycatch and discard in the Loligo squid inshore fishery and to describe and document the behaviour patterns of squid and non-target fish. Bycatch rates vary but over 30% by weight of total catch is discarded at sea. The main bycatch and discard species comprise flatfish, scup and butterfish. Videotape recordings and behavioural analysis of squid reactions have shown that squid display classical herding behaviour and considerable swimming endurance in the forward part of the net Loligo are shown to rise when dropping back towards the codend and in some cases to tum and rise on tiring. This behaviour may be used to separate squid from the main bycatch species. Separator trawl test-trials have demonstrated that clear separation between squid and bycatch species can be achieved by simple gear modifications.

Introduction

In New England waters, Atlantic Longfin squid (Loligo pealei) overwinter offshore along the edge of the continental shelf (Serchuck & Rathjen, 1974; Summers, 1969). Loligo squid move into the shallow inshore waters off Nantucket Sound in the spring to spawn (Figure 1, NMFS Statistical reporting area 538). The resulting spawning aggregations have been fished since the late 1800's, but the advent of towed otter trawls has heavily increased the pressure on the stock (Anon., 1978; Wilbour, 1963). The Mid-Atlantic Fisheries Management Council (MAFMC) has characterized the stock as being fully exploited at a medium biomass level (Anon., 1994). Moreover, it has been recently ascertained that Loligo pealei do not live beyond one year, contrary to previous beliefs about a life history that spanned up to 3 years (Brodziak & Macy, 1994). Each year a single cohort supports both the fishery and spawning stock; consequently, the potential for recruitment overfishing may be substantial (Brodziak & Rosenberg, 1993). In addition to fears concerning spawning stock biomass, there is a negative relationship between catch and effort in the offshore fisheries and performance of the inshore fishery. Recent increases in effort in offshore areas, which has doubled since 1985, have been accompanied by a decrease in catch and catch per unit effort in the inshore fisheries (Anon., 1993; Brodziak, 1994). For this and other reasons the Massachusetts Division of Marine Fisheries (MaDMF) and the New England Fisheries Management Council (NEFMC) argue that controls are needed in the offshore fishery (conducted in Federal waters), to protect the inshore fishery (conducted in State waters). In addition to controls in Federal waters, MaDMF and NEMFC also state that refinements are required in state management of the inshore fisheries. Boats fishing in Massachusetts inshore waters (Nantucket and Vineyard Sounds) are permitted to fish with fine mesh nets (li -2 in. codend mesh). The use of such small mesh nets can result in high catches and large discard of nndersized fish. In a recent report McKiernan and Pierce (1995), recommend that, among a suite ofregulatory and management changes, effort should be directed towards design of a trawl to harvest squid but exclude flatfish and minimize bycatch. Furthermore they recommended that investigations should begin with studies of behaviour of sqnid and bycatch fish.

The present study was designed to investigate these bycatch problems and address the specific management recommendations outlined above. The aim was to assess the current state of the squid fishery in relation to bycatchldiscard and describe and document the behaviour patterns of squid and non-target fish. Then, based on this information, design and test gear modifications aimed at reducing unwanted bycatch.

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Materials and methods

I) Sea sampling Sea sampling was carried out by National Marine Fisheries Service (NMFS) certified fisheries observers on commercial fishing boats conducting commercial fishing operations. Twenty trips were monitored during the 1997 fishery resulting in a total of 118 hauls sampled and a coverage of24 sea days. A wide range of information was collected during each trip, including: 1) vessel and trip information, 2) trawl gear characteristics, 3) a trawl haul log for each individual haul which included fisheries information such as: weight kept for each species, weight of discard of each species, reason for discard, length frequency for each species (whether kept or discarded) and age structure where possible. Historical records from the NMFS fisheries database were also accessed as part of the analysis of squid fishery trends over recent years. This level of sampling in the fishery represented approximately a fivefold increase in levels of sampling in previous years.

2) Behavioural observations Behavioural observations were obtained by attaching self-contained underwater video cameras to trawl gears on board commercial fishing vessels. Two cameras were used on each haul where feasible. One was attached underneath the headline looking back and down into the mouth of the net. The other was rigged in the wing-end of the net to view across the net mouth. Both cameras (Sony 8mm in an Aquasport housing and Panasonic 8mm CCD camera in an Equinox housing) were operated in nornml ambient lighting conditions only. Observations were made throughout the months of May and June 1997 on board 4 different commercial fishing vessels and over 15 hours of useable videotape were obtained.

3) Bycatch separation trials Results of the behavioural analysis (see following section and discussion) indicated that sufficient behavioural differences existed between squid and bycatch species to facilitate separation by species. Based on these observations, a separator trawl similar to that described by Galbraith and Main (1989), (of similar size to normal commercial fishing nets), was manufactured. This modified net was fished commercially during the squid fishery in 1998 in an attempt to quantify the degree of separation and potential for discard reduction. All hauls with the separator net were sampled by NMFS certified observers and each codend (upper and lower) treated as a separate haul. Underwater observations recording the behavior of fish and squid were taken as above. Additional videotape recordings were made of reactions of squid and fish to the separator panel by inserting a camera inside the net at a point just forward of the separator panel.

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Results

Fisheries data Figures 2, 3 and 4 illustrate the trend in landings of three of the major species over a 19-year time period. Squid catches (Figure 2) have declined dramatically as have the catches of two of the species of major concern, scup (Figure 3) and blackback flounder (Figure 4). Sampling in the 1997 fishery revealed that squid comprised 69% by weight of all the catch (Figure 5). Six other species made up the bulk of the remainder (31 %) ofthe catch (Figure 5) and over 80% by weight of this was discarded at sea (see Table I). Figure 6 illustrates the catch rate for each of these species per 1000 lbs of squid caught and highlights the extent of the bycatch problem in this fishery. The major discard species and their contribution to the overall discard are shown in Figure 7. Some species are discarded completely either due to regulation (e.g. striped bass) or lack of market (northern sea robin/winter skate). Others, such as scup, are a valuable bycatch species with a ready market for legal sized fish. However, fishing with small mesh nets results in substantial discard of small size classes below the legal minimum landing size of 9in (23cm) (Figure 8).

Table I summarizes some of the catch data obtained by observers at sea during the 1997 Loligo squid fishery. Notice the proportion of the catch made up by scup in each trip and the variability in catch rate, (outlined in italic (column 6)), and the average proportion of the overall catch discarded, 26%.

Behavioural observations The most obvious observation from the videotapes was that squid were often encountered in very large numbers. Rarely were individual animals or small groups observed entering the net and for long periods of time on each observed haul, no squid were encountered by the net. This suggests that squid schools are extremely patchy in their distribution. In many tows, the net was observed to capture all of the squid present in the catch either within the first or the last few minutes of the tow.

A more specific analysis of the videotapes showed that the behaviour of Loligo squid towards trawl gear is very similar to that adopted by many fish species. That is, they react to the approaching ground-gear of the net by turning and swimming at the same speed as the net in the direction of the tow. This is likely to be an optomotor response to the moving pattern of netting similar to that shown by most fish species. While being herded in the mouth of the net, squid tend to move to the edges ofthe net close to the wing-ends and side panels and gradually rise up to a position close to the top of the net (Figure 9). One particular school was seen holding station in the mouth of the net by a combination of mantle squirt swimming and wing undulation swimming. We estimated the school to include many hundreds of individuals and the group as a whole maintained a very coordinated school structure. The squid held this position for nearly 3 minutes at a towing

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speed of 2.9 kn. (over the ground), before gradually being overtaken by the net. Mantle length of the squid was around 25cm. On tiring, Loligo seems to rise upwards and turn so that the mantle faces directly towards the codend of the net. The squid ceases to swim and allows the net to overtake it (Figure 10). The overall effect of these behaviour patterns results in squid being distributed in the upper and upper-lateral parts of the net during herding and falling back through the main body of the net (Figure II). None of the major bycatch and discard species showed this rising behaviour but seemed to remain in the lower portion of the net as they passed into the belly of the net. This obvious difference in behaviour suggested that a separation panel in the net (see Figure 12) may be effective in separating squid from all other non-target species. Further analyses of these and other behaviour patterns continue and a more complete analysis and description of the behaviour of Loligo squid in fishing gears is currently in preparation (Glass et ai, in prep).

Bycatch separation trials Analysis of the fisheries data collected during these trials is still in progress. However, preliminary analysis on data collected in one 3-day trip covering 22 hauls, shows that a remarkable degree of separation occurs. Figure 13 shows the distribution of squid, scup and all flatfish between upper and lower codends. An index in the range -I to + I was calculated for each species in each haul, where a value of +1 represents all individuals of that species being present in the upper codend and -I represents all individuals being caught in the bottom codend. Squid were almost all caught in the upper codend while flatfish and, to a lesser extent scup, were predominantly caught in the bottom codend. Ongoing analysis also reveals; I) the weight of squid caught by the top codend is significantly higher than that caught in

the bottom codend (Wilcoxon test,p<O.OOI); 2) the weight of scup caught by the top codend is significantly lower than that caught in

the bottom codend (Wilcoxon test,p<O.OOI); 3) the weight of black back flounder and fluke caught by the top codend is significantly

lower than that caught in the bottom codend (Wilcoxon test, Pwt<O.O I; Psw<O.05); 4) the length frequency distributions of squid in the top and bottom codend were not

significantly different (Kolmogorov-Smirnoff test, p~O. 09).

Discussion

The significance of the occurrence of large schooling groups of squid and the observed patchiness of scup (as bycatch) may suggest that more directed fishing may lead to cleaner catches. Squid can be difficult to detect on sonar, particularly in the shallow waters «25m) encountered in Nantucket Sound. However, the large groups, which comprise many thousands of squid and which seem to be the most commonly encountered schooling groups, are detectable, and therefore could be targeted directly. A

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simple change of fishing practice may therefore help to reduce catch of non-target species.

As shown in Table I, the proportion of the catch discarded in the observed fishery is variable from haul to haul but, overall, over 26% of total catch is discarded. This value is consistent with data from previous years. However, the proportion of scup in the overall catch, although varying with each trip in 1997 (Table I), was found to be much lower than in previous years leading to the suggestion that scup bycatch is not a significant problem. There are several factors that might contribute to the observed reduction in scup catch. 1) The 20-trip coverage generated by this project was almost three times the previous years' coverage and may therefore be a more realistic representation of scup stocks and their distribution. 2) The patchy nature of scup distribution may lead to wide variability in capture rates from year to year. 3) It may simply reflect an obvious decline in biomass of scup in Nantucket Sound. Analysis on these and other historical data continues.

As reported above, squid enter the net well above the footrope and swim along with the net for some time, positioned near the top and the sides of the net (Figure 11), rising as they tum. Some of the main bycatch-species in this fishery, such as fluke and blackback flounder, appear to stay low at the front of the net. Observations on scup are less frequent than observations of squid, but scup and other fish were rarely observed entering the net at the higher levels shown by squid. However, one remarkable piece of videotape produced by a commercial fisherman (Capt. Frank Avila, Flv Playtime) shows squid and scup entering the net at the same time but clearly separated in the water column; squid entering the top part of the net and the scup entering much lower down. These behavioral observations suggested that it might be possible to separate squid from other species during the capture process isolating the upper portion of the net (by some means) from the lower part. The prototype separator trawl gear tested in the fishery in 1998 was designed to test the degree of separation that could be achieved and to estimate the height at which separation may occur. Clearly, the net was very successful in utilising these natural behaviour patterns with the result that almost complete separation of squid from all other species was possible. The fact that almost all squid entered the top codend and . flatfish, scup and other bycatch in the bottom codend provides considerable scope for reducing unwanted bycatch in this fishery. Two obvious and simple approaches could include either manipulation of lower codend mesh size or incorporation of a raised footrope design similar to that reported by McKiernan et al (1998).

Further work is needed to determine the most effective means of incorporating this information into gear designs which effectively reduce discard in the squid fishery while maintaining all marketable catch. However, the results illustrate the importance of direct observation and of the need to understand the natural behaviour of each of the species of concern. Information of this nature is often difficult to gather but can also help lead

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towards innovative, simple and cost effective solutions to apparently complex bycatch and discard problems in fisheries.

Acknowledgements

We thank all the staff and observers ofthe Marine Division, Manomet, fortheir assistance with work at sea. Thanks also to Devon Keeney at MaDMF for data entry. We thank Prof. Roger Hanlon, of the Marine Resources Center, MBL, Woods Hole and the skipper and crew ofFV Gemma for generous use oftheir boat and facilities and Dr Steve Murawski for his support and libral)' facilities at the Marine Fisheries Center, Woods Hole. Funding for this project was provided by The Surdna Foundation, Pew Charitable Trusts, National Fish and Wildlife Foundation, Davis Conservation Foundation, Island Foundation, the Orchard Foundation and NOAA Saltonstall-Kennedy. Finally we thank the skippers and crew of each of the commercial fishing boats who assisted throughout the study.

References

Anon., 1978. Environmental Impact StatementlPreliminary Fishery Management Plan for short finned squid (lllex illecebrosus) and longfinned squid (Loligo pealei). United States Department of Commerce.

Anon., 1993. Status of Fishery Resources of the Northeastern United States for 1993. United States Department of Commerce, NOAA Technical Memorandum NMFS-FINEC-101.

Anon., 1994. Optimum yield, domestic annual harvest, domestic annual processing, joint venture processing, and total allowable level of foreign fishing for Atlantic mackerel, Loligo, Illex, and butterfish for 1995. Mid-Atlantic Fishery Management Council, 49pp.

Brodziak,l.K.T. 1994. Stock assessment for long-finned squid, Loligo pealei, in the northwest Atlantic during 1992. NEFSC Reference Document 94-03. National Marine Fisheries Service, Northeast Fisheries Science Center. Woods Hole, MA.

Brodziak, 1.K.T. and W.K. Macy, III. 1994. Revised estimates of growth of the long­finned squid, Loligo pealei in the Northwest Atlantic based on statolith ageing:implications for stock assessment and fishery management. ICES C.M. 94!K: 13 30pp.

Brodziak, 1.K.T. and A.A. Rosenberg. 1993. A method to assess squid fisheries in the northwest Atlantic. ICES 1. Mar. Sci. 50:187-194.

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Galbraith, R.D. and J. Main, 1989. Separator panels for dual purpose fish/prawn trawls. Scottish Fisheries Information Pamphlet. Number 16.1989.

Glass, C. W., B. Sarno, H. O. Milliken, G. D. Morris, H. A. Carr, Bycatch reduction in Massachusetts squid (Lo/igo peale/) fisheries. (in prep).

McKiernan, D. J., W. Hoffman, R. Johnstone, H. A. Carr, H. O. Milliken. 1998. Southern Gulf of Maine Raised footrope trawl (1997) experimental whiting fishery. Massachusetts Division of Marine Fisheries, Internal Publication.

McKiernan, D. J. and D. E. Pierce 1995. Loligo squid fishery in Nantucket and Vinyard Sowlds. Massachusetts Division of Marine Fisheries, Internal Publication.

Serchuck, F.M. and W.F. Rathjen. 1974. Aspects of the distribution and abundance of the long-finned squid, Loligo pealei, between Cape Hatteras and Georges Bank. Mar. Fish. Rev. 36:10-17.

Summers, W.C. 1969. Winter population of Loligo pealei in the mid-Atlantic Bight. Biological Bulletin. 137:202-216.

Wilbom, F.e. 1963. A report of marine fisheries relating to restricting the use of an otter trawl in certain waters of the Commonwealth. A study of the otter trawl fishery in Nantucket and Vineyard Sound. Chapter 78 of the resolves of 1962, Appendix A.

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Figure 5

striped bass 1%

fluke 1%

blueback herring

7%

butterfish 5%

northern sea robin 2%

other 5%

squid 69%

1997 catch data for the inshore squid fishery. Only species that comprise greater than I % by weight ofthe overall catch are included. The category classed as miscellaneous is made up of assorted crustaceans and molluscs while the category classified as other, represents all fish species which make up less than I % by weight of the overall catch.

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Figure 6 Catch rates (lbs) ofthe major bycatch species per 1000 lbs of squid caught.

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winter skate 3%

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striped bass 5%

little skate 3%

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The major discard species and their contribution to the overall discard in the fishery.

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Length frequency of Scup bycatch in the overall fishery showing proportion retained (light bars) and proportion discarded at sea (dark bars).

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Figure 9 Sequence taken from videotape showing the position of 1 squid in 5 consecutive frames showing reaction behaviour on first reaction to the footrope of the approaching net. The squid tum to swim ahead of the net and gradually rise upwards into the upper part of the mouth ofthe net.

Figure 10 Sequence taken from videotape showing the position of2 squid in 5 consecutive frames. On tiring, the squid stop swimming, tum and rise upwards allowing the net to overtake them.

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Figure II Diagrammatic cross section through forward part of the net illustrating the distribution of squid during herding and falling back.

Figure 12 General view of the net mouth of the experimental separator trawl showing positioning of the horizontal separating panel. (After Galbraith and Main, 1989).

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Figure 13 Box and whisker plots showing the distribution of squid, scup and all flatfish between upper and lower codends ofthe separator trawl. An index of + I represents all individuals being caught in the top codend while a value of -I represents all being caught in the lower codend.

Table I. Summary calch data from 19 trips(118 hauls) slimpled during 1997 Massachusetts inshore squid fishery.

Trip hauls tot kepi tot discard tot Ibs scuplcatch squid/catch kept/catch discard/catch A2S603 5 2745 91 2836 0% 97% 97% 3% A2S032 3 1106 267 1373 1% 80% 81% 19% A25606 6 680 380 1060 2% 62% 64% 36% D03600 4 1362 275.4 1637.4 38% 49% 83% 17% A03035 7 3271.1 126 3397.1 0% 93% 96% 4% A25031 7 798 2337 3135 1% 24% 25% 75%

A25033 3 833 747 15BO 0% 52% 53% 47% A25604 4 820 59 879 4% 93% 93% 7% A25034 5 1263 762 2025 0% 59% 62% 38% A03034 11 3391.1 620 4011.1 2% 65% 85% 15% A25601 6 11057 2992 14048.5 D% 78% 79% 21% A25602 17 21555 11303 32858 8% 59% 66% 34% A25605 7 1015 212 1227 7% 83% 63% 17% 806001 7 1190 149.1 1339.1 1% 82% 69% 11% A03036 7 4234.6 69.6 4304.2 0% 96% 98% 2% A03038 5 1126.5 221.5 1348 1% 79% 84% 16% A03039 4 1015 105.5 1120.5 0% 84% 91% 9% A25036 5 1876 615 2491 35% 42% 75% 25%

A03040 5 1437 224 1661 0% 83% 87% 13% Total, ill 60775.3 21556.1 82330.9 6% 68% 74% 26% avg%

Trip'" trip lD haul = number of hauls tot kept = tolal weight of catch retained. tot discard'" total weiglit of catch discarded lot Ibs = total weight of catch (retained + discarded) scupkatch = proportion of scup in the total catch squid/calch = proportion of squid in the total catdl kept/calch = proportion of retained catch discard/calch = proportion of discarded catch

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