Table l. — Summary of the stomach contents of juvenile groundfish from the northwestern Atlantic, expressed as a percentage of total 

 food weight, for fish collected between the years of 1953 through 1976. Subtotals are italicized and a " + " indicates present in the diet but 

 <0.1%. Dietary differences related to predator length are given in the text 



The stomach content data are summarized on a 

 weight basis as the percentage weight each prey 

 category made up of the total stomach contents 

 weight for each of the 10 predators. Empty stom- 

 achs were included in the calculation of the mean 

 weight per stomach for each species. In the text, 

 the percentage weight is included in parentheses 

 after the first mention of a particular prey to 

 quantify the importance of that prey in the diet. 

 Also included in the text, for each species offish, is 

 a two-part evaluation of the food based on fish 

 length (given only for predators for which suffi- 

 cient food data were available). This evaluation 

 was made to determine the smallest fish collected 

 of each species, which exhibited signs of feeding on 

 the bottom, and also to discern, based on the 

 available data, at what fish length the food was 

 made up predominantly of prey usually associated 

 with the bottom. 



The nomenclatural distinctions categorizing 

 prey species as either planktonic or benthic were 

 taken from Gosner (1971). Planktonic organisms 

 include the euphausiids and calanoid copepods. 

 Benthic forms are typically noted as including 

 most of the polychaetes, amphipods, and decapods. 

 The distinction of these two generalized prey 

 groupings, and what percentage they make up of 

 the diet with fish length, indicates the fish's 



degree of association with the bottom when feed- 

 ing. For the purpose of this paper it is assumed 

 that when a fish's diet changes from primarily 

 planktonic organisms to 50% or more benthic 

 organisms (occurring when the fish has grown to 

 within some specified length range), the fish can 

 appropriately be referred to as "demersal." Before 

 this change in diet occurs the fish are only loosely 

 associated with the bottom and are therefore more 

 likely to move off bottom in search of food. 



Results 



Table 1 summarizes the stomach contents of 10 

 species of juvenile groundfish collected during the 

 years from 1953 through 1976. Only small num- 

 bers of such species as fourbeard rockling and 

 spotted hake were available for stomach content 

 analyses. Since little is known about their diets 

 the data were included. 



Atlantic Cod 



Crustacea represented the largest portion of the 

 diet of juvenile Atlantic cod (81.6%). Amphipods 

 were the largest contributor to the crustacean 

 prey (22.5%) and those identified were Gammar- 

 idae (6.5%) and Caprellidae (12.9%). Euphau- 



202 



