605 



Abstract — Longfin inshore iLollgo 

 pealeii) and northern shortfin Ullex 

 illecebrosus) squids are considered 

 important prey species in the North- 

 west Atlantic shelf ecosystem. The 

 diets of four major squid predators, 

 bluefish [PomatomuH saltatrix), goose- 

 fish {Lophius americanus), silver hake 

 (Merluccius bilinearis), and summer 

 flounder (Paralichthys dentatus), were 

 examined for seasonal and size-based 

 changes in feeding habits. Summer 

 and winter, two time periods largely 

 absent from previous evaluations, 

 were found to be the most impor- 

 tant seasons for predation on squid, 

 and are also the periods when the 

 majority of squid are landed by the 

 regional fishery. Bluefish >450 mm, 

 silver hake >300 mm, and summer 

 flounder >400 mm were all found 

 to be significant predators of squid. 

 These same size fish correspond to 

 age classes currently targeted for 

 biomass expansion by management 

 committees. This study highlights 

 the importance of understanding how 

 squid and predator interactions vary 

 temporally and with changes in com- 

 munity structure and stresses the 

 need for multispecies management 

 in the Northwest Atlantic. 



Seasonal and size-based predation on 

 two species of squid by four fish predators 

 on the Northwest Atlantic continental shelf 



Michelle D. Staudlnger 



Department of Natural Resources Conservation 

 160 Holdsworth Way 

 University of Massachusetts, Amherst 

 Amherst, IVlassachusetts 01003 9285 

 Email address mstaudimg'nreumassedu 



Manuscript submitted 7 November 2005 

 to the Scientific Editor's Office 



Manuscript approved for publication 

 9 March 2006 by the Scientific Editor. 



Fish. Bull. 104:605-615 (2006). 



Global depletion of marine predators 

 has had dramatic effects on ecosys- 

 tem structure and function (May et 

 al., 1979; Jackson et al., 2001; Pauly 

 et al., 20021. In many systems, the 

 ramifications of such changes may not 

 be fully realized. Groundfish declines 

 have been linked to simultaneous 

 increases in cephalopod landings 

 in fifteen key Food and Agriculture 

 Organization of the United Nations 

 (FAO) areas (Caddy and Rodhouse, 

 1998). It is uncertain whether cepha- 

 lopod populations are experiencing 

 increased growth due to a release 

 from predation (Piatkowski et al., 

 2001), or whether increased harvests 

 are representative of the trend toward 

 fishing species at lower trophic levels 

 (Pauly et al., 1998). In the Northwest 

 Atlantic, while gadids, flatfish, and 

 other demersal species have been 

 reduced because of overfishing (Link 

 and Garrison, 2002), squid have risen 

 in status from a mere bait fishery to 

 one of the most economically impor- 

 tant stocks in the region (Cadrin and 

 Hatfieldi). 



Cephalopods have been documented 

 as principal prey for numerous species 

 of finfish, elasmobranchs, and marine 

 mammals (Smale, 1996); however, in 

 comparison to the ecological relation- 

 ships between fish and their preda- 

 tors, less is known about the ecological 

 interactions between squid and their 

 predators. In a comprehensive evalu- 

 ation of the Northwest Atlantic food 

 web, bluefish (Pomatomus saltatrix), 

 goosefish {Lophius americanus), sil- 

 ver hake (Merluccius bilinearis), and 

 summer flounder (Paralichthys den- 

 tatus) were ranked among the most 



significant predators of squid (Bow- 

 man et al., 2000). Squid represented 

 between 17% and 95% of the total 

 mass consumed by these four finfish 

 regionally. Dramatic changes in stock 

 abundance and population structure 

 have occurred since specimens for 

 Bowman et al.'s study were collect- 

 ed 25-45 years ago. Exploitation of 

 squid has risen substantially, and the 

 four noted predators have experienced 

 severe depletions; stock biomass lev- 

 els have fallen as low as 20-50% of 

 their respective maximum sustain- 

 able yield (B,;^.,) limits (NOAA-). 

 Additionally, the size structure of 

 predator populations within the com- 

 munity has become skewed because of 

 age-truncation. Recent evaluations of 

 bluefish (Buckel et al., 1999a), goose- 

 fish (Armstrong et al., 1996), silver 

 hake (Bowman, 1984), and summer 

 flounder (Link et al., 2002) foraging 

 habits have been conducted; however, 

 sampling has been restricted to one 

 or two seasons, primarily spring and 

 fall. Analyses that base their results 

 on feeding habits collected during a 

 single season (Buckel et al., 1999b), 

 or where results are based on data 

 that have been pooled under the as- 



' Cadrin. S. X., and E. M. C. Hatfield. 1999. 

 Stock assessment of inshore longfin 

 squid Loligo pealeii. Northeast Fish. 

 Sci. Cent. Ref Doc. 99-12, 107 p. 



- NOAA ( National Oceanic and Atmospheric 

 Administration). 2001. Northeast 

 Fisheries Science Center (NEFSC). 

 Status of fishery resources off the north- 

 eastern United States. Website: http:// 

 www.nefse.noaa.gov/sos/spsyn/species. 

 html (accessed on 8 March 2006]. 



