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The second group are those predators which ate prima- 

 rily planktonic organisms (e.g., chaetognaths, copepods, 

 pelagic amphipods, mysids, euphausiids, and/or salps). 

 Most of the herrings, Atlantic argentine, northern sand lance, 

 Atlantic mackerel, Acadian redfish, and butterfish are among 

 the fishes included in this group. 



The third group of fishes preyed almost totally on some 

 combination of small benthic crustaceans (mostly amphi- 

 pods), echinoderms, cnidarians, and polychaetes. Species 

 such as haddock, Gulf Stream flounder, witch flounder, 

 American plaice, yellowtail flounder, and winter flounder 

 are among the predators in this group. 



PREY ACCORDING TO GEOGRAPHIC AREA 



A qualitative and quantitative understanding of preda- 

 tion on fish by fish (i.e., natural mortality, in part) is criti- 

 cally important for development of multispecies fishery 

 models. The percentage offish in the diet of all piscivores 

 sampled from at least two geographic areas, in sufficient 

 numbers for analysis (about 20 fish per area), during bot- 

 tom trawl surveys from 1 977 to 1 980 are presented in Table 

 2. Excluding apex predators, the listed species represent 

 the majority of the demersal fish and squid biomass within 

 the entire study area. 



Spotted hake, which is not listed in Table 2, is a domi- 

 nant piscivore in the Middle Atlantic, but too few were 

 sampled during the 1977-80 period to warrant inclusion. 

 However, during the 1973-76 period in the Middle Atlantic, 

 15.9% and 36.9% of their food was fish and squid, respec- 

 tively (Bowman and Michaels 1 984). 



Many large apex predators which fed primarily on fish 

 and/or squid (e.g., blue shark, thresher shark, and sword- 

 fish) are migratory. They occur in the survey area only 

 during certain periods of the year. Their predatory impact 

 on fish and squid populations during these periods should 

 not be overlooked. 



Information on how functional prey groups such as 

 fish, squid, polychaetes, decapods, other crustaceans, and 

 other organisms are partitioned by predators within the 

 study area is given in Tables 2-7. (See also Appendix B.) 

 For each functional prey group, the principal predators 

 which utilize that group as food are discussed, by area, in 

 the following sections. 



Fish 



Overall, northern sand lance was the primary fish prey 

 in almost all geographic areas during the study period. (See 

 Table 2 and the detailed prey listings in Appendix B.) In the 

 Middle Atlantic, northern sand lance was an important food 

 (>10% of all food by weight) of little skate, silver hake, red 



hake, summer flounder, and windowpane. Other notable 

 fish prey in the Middle Atlantic were silver hake (consumed 

 by silver hake, fourspot flounder, and windowpane), her- 

 rings (eaten by spiny dogfish, summer flounder, and blue- 

 fish), and scup (prey of smooth dogfish and black sea bass). 



Southern New England piscivores which ate northern 

 sand lance include, in part, smooth dogfish, winter skate, 

 silver hake, Atlantic cod, summer flounder, windowpane, 

 and yellowtail flounder. In this area, silver hake were prey 

 of fourspot flounder, silver hake, and goosefish. Atlantic 

 cod were identified as prey of Atlantic cod and fourspot 

 flounder. Unidentified gadids were found in the stomachs 

 of spiny dogfish, white hake, red hake, and Gulf Stream 

 flounder. Herrings were the prey of spiny dogfish and sum- 

 mer flounder. One of the few instances of predation on 

 spiny dogfish (i.e., by Atlantic cod) was observed in this 

 area. 



Georges Bank predators fed on a wide assortment of 

 fish prey. Major fish prey were northern sand lance (eaten 

 by winter skate, thorny skate, Atlantic cod, pollock, red 

 hake, summer flounder, winter flounder, windowpane, blue- 

 fish, and longhorn sculpin), herrings (consumed by spiny 

 dogfish, thorny skate, silver hake, and bluefish), various 

 gadids (found in the stomachs of spiny dogfish, white hake, 

 red hake, Atlantic halibut, bluefish, sea raven, and 

 goosefish, with Atlantic cod and haddock specifically be- 

 ing identified as food of Atlantic halibut and goosefish, 

 respectively), and longhorn sculpin (prey of little skate, 

 Atlantic halibut, bluefish, and goosefish). 



Gulf of Maine predators ate primarily northern sand lance 

 (food of spiny dogfish, winter skate, silver hake, haddock, 

 red hake, and Atlantic halibut), silver hake (prey of silver 

 hake, Atlantic cod, white hake, red hake, Atlantic halibut, 

 Acadian redfish, sea raven, and goosefish), and herrings 

 (found in the stomachs of thorny skate, silver hake, Atlan- 

 tic cod, Atlantic halibut, and goosefish). Haddock was 

 preyed on by goosefish. 



Scotian Shelf fishes ate northern sand lance (prey of 

 red hake), mackerel (eaten by spiny dogfish and silver hake), 

 herrings (food of silver hake), silver hake (preyed upon by 

 silver hake, white hake, and red hake), haddock (identified 

 in the stomachs of red hake and goosefish), unidentified 

 gadids (a portion of the diet of Atlantic halibut and 

 goosefish), and longhorn sculpin (found in the stomachs 

 of goosefish). 



Inshore north of Cape Hatteras (i.e., Cape Hatteras to 

 Nova Scotia), fish prey were northern sand lance (>10% of 

 the food of winter skate, silver hake, Atlantic cod, pollock, 

 summer flounder, black sea bass, and scup), herrings (con- 

 sumed by Atlantic sharpnose shark, spiny dogfish, thorny 

 skate, Atlantic cod, Atlantic halibut, summer flounder, blue- 

 fish, weakfish, and goosefish), mackerel (eaten by dusky 

 shark), silver hake (a food of silver hake, red hake, Atlantic 

 halibut, and windowpane), butterfish (prey of smooth dog- 



