381 



Opportunistic feeding of longhorn sculpin 

 {Myoxocephalus octodecemspinosus) : 

 Are scallop fishery discards an important 

 food subsidy for scavengers on Georges Bank? 



Jason S. Link 



Frank P. Almeida 



National Marine Fisheries Service 

 Northeast Fisheries Science Center 

 166 Water St 



Woods Hole, Massachusetts 02543 

 E mail address Jason LinkiQ'noaa gov 



There has been much recent interest 

 in the effects of fishing on habitat 

 and non-target species, as well as in 

 protecting certain areas of the seabed 

 from these effects (e.g. Jennings and 

 Kaiser, 1998; Benaka, 1999; Langton 

 and Auster, 1999; Kaiser and de Groot, 

 2000). As part of an effort to deter- 

 mine the effectiveness of marine closed 

 areas in promoting recovery of com- 

 mercial species (e.g. haddock, Mela- 

 nogrammus aegelfinus; sea scallops, 

 Placopecten inagellanicus; yellowtail 

 flounder, Limanda ferruginea\ cod, 

 Gadus morhiia ). nontarget species, and 

 habitat, a multidisciplinary research 

 cruise was conducted by the Northeast 

 Fisheries Science Center (NEFSC), 

 National Marine Fisheries Sei'vice. The 

 cruise was conducted in closed area 

 II (CA-II) of the eastern portion of 

 Georges Bank during 19-29 June 2000 

 (Fig. 1). The area has historically pro- 

 duced high landings of scallops but was 

 closed in 1994 principally for ground- 

 fish recovery (Fogarty and Murawski, 

 1998). The southern portion of the area 

 was reopened to scallop fishing from 

 15 June to 12 November 1999, and 

 again from 15 June to 15 August 2000. 

 While conducting our planned sam- 

 pling, we observed scallop viscera (the 

 noncalcareous remains from scallops 

 that have been shucked by commercial 

 fishermen at sea) in the stomachs of 

 several fish species at some of these 

 locations, namely little skate (Raja eri- 

 nacea ), winter skate (R. ocellata ), red 

 hake iUrophycis chuss), and longhorn 

 sculpin [Myoxocephalus octodecemspi- 

 nosus). We examined the stomach 



contents of a known scavenger, the 

 longhorn sculpin, to evaluate and doc- 

 ument the e.xtent of this phenomenon. 

 Fishery discards provide food subsi- 

 dies that help maintain fish popula- 

 tions, but to what extent is unclear. 

 There is some evidence that fishery 

 discards allow fish populations to be 

 more abundant than they would be 

 with just ambient resources (e.g. Polls 

 and Strong, 1996). Others would coun- 

 ter that these discards may maintain 

 a population but not necessarily lead 

 to population growth (Fonds and Groe- 

 newold, 2000). As an extension of our 

 opportunistic field obsei"vations from 

 the closed area (CA)-II 2000 cruise, 

 we examined NEFSC historical bottom 

 trawl survey and food-habits databas- 

 es to ascertain the role of fishery dis- 

 cards in the Georges Bank ecosystem, 

 with particular respect to the longhorn 

 sculpin population. 



Materials and methods 



Our sampling was conducted concur- 

 rently with the scallop fishery, there- 

 fore it was necessary to continuously 

 monitor vessel activity in the area 

 opened to fishing prior to our arrival 

 and during our sampling. Prior to 

 sampling, we collected biweekly sum- 

 maries of scallop fishing vessel activ- 

 ity during the 1999 open season, and 

 day by day summaries of the 2000 

 season were obtained from the north- 

 east region vessel monitoring system 

 (VMS), National Marine Fisheries Ser- 

 vice. With this system, individual vessel 



location.s are transmitted to NMFS 

 every 30 minutes (McSherryM. The 

 location of each fishing vessel was plot- 

 ted (with Surfer 7.0; GSI, 1999) on a 

 map overlaid with the sampling sites 

 occupied during the 1999 study (June 

 1999). Stations from the 1999 study 

 were chosen on the basis of fleet activ- 

 ity during the 1999 open season and 

 our sampling goals. Each day while 

 the RW Albatross /Vwas in CA-II, cur- 

 rent individual scallop-vessel activity 

 data were transmitted to us by email, 

 plotted, and sampling stations were 

 selected after an examination of the 

 data. 



As part of our sampling protocol, a 

 15-minute otter trawl haul was made 

 at each station, towed at a speed of 6.5 

 km/li. A standardized NEFSC no. 36 

 Yankee otter trawl rigged with a rub- 

 ber-disc-covered chain sweep, 11 floats, 

 5-m ground cables, and 450-kg poly- 

 valent trawl doors (commonly referred 

 to as a "flatfish net") was used. Once 

 the trawl was on deck, we sorted fish 

 and macro-invertebrates by species, 

 weighed each species (0.1 kg), mea- 

 sured lengths of all fish (cm), examined 

 subsamples of the fish to determine 

 sex, maturity, and stomach contents, 

 and collected structures to determine 

 ages. For further details of the survey 

 and food habits methods used in our 

 study see Azarovitz (1981) and Link 

 and Almeida ( 2000 ), respectively. 



After initial observations of scallop 

 viscera in fish stomachs at several pre- 

 vious locations, we developed an ad hoc 

 study that deliberately selected two 

 stations located in areas of high scallop 

 fishing effort and two stations in areas 

 of little or no scallop fishing effort. On 

 21-22 June 2000 we sampled stations 

 8B, 7D, 7E, and 8E in the northeast 

 portion of the region open to the scal- 

 lop fleet (Fig. 1). At stations 8B and 7E, 

 we observed a high frequency of seal- 



' McSherry, M. 1998. NMFS Northeast 

 vessel monitoring system — operations logic 

 and geographical display interface. NMFS 

 NE Law Enforcement Office Internal Docu- 

 ment, 20 p. [Available from NMFS, NEFSC, 

 166 Water St., Woods Hole, MA 02543.] 



Manuscript accepted 18 September 2001. 

 Fish. Bull. 100:381-385 (2002). 



