DURBIN ET AL.: STOMACH CONTENTS OF HAKE AND COD 



Fic.i'RE 1. — Five geographic areas of the northwest Atlantic com- 

 posing the sampling area for fish food studies. 



tion by the preservative. With the larger fish the 

 length, sex, and maturity were determined at sea, and 

 the stomach was then removed, individually labeled, 

 and preserved in 107o Formalin for later analysis. 

 Fish showing signs of regurgitation (everted 

 stomach, food present in mouth or esophagus) were 

 not included in the samples. In the laboratory the 

 stomach contents were identified to the lowest pos- 

 sible taxon and weighed (wet weight). For the present 

 study, the weight of sand and gravel were subtracted 

 from the total stomach content weight, and stomachs 

 that contained recognizable food in amounts too 

 small to be weighed (<0.01 g) were considered 

 empty. 



The weight of each fish was calculated from its total 

 length and length-weight relationships (Wilk et al. 

 1978) where 



Wet wt (g) = 0.3555 X 10~ 5 length (mm) 3 - 1109 

 (silver hake) 



Wet wt (g) = 0.6031 X 10" 5 length (mm) 30979 

 (Atlantic cod). 



Combining all cruises, 1,159 silver hake were collect- 

 ed during the spring, and 1,555 during the fall; the 

 number offish sampled per tow averaged 8.0 and 8.6, 

 respectively (Table 1). Silver hake were collected 

 almost exclusively in the southern three geographic 

 regions (Middle Atlantic, Southern New England, 

 and Georges Bank), where a total of 2,625 fish were 

 taken in 304 tows. Mean temperatures during spring 

 cruises were several degrees colder than during the 

 fall; however, the mean depth at which the fish were 

 collected was not greatly different during the two 

 seasons (Table 1). 



In all cruises combined, 775 Atlantic cod were sam- 

 pled during spring, and 922 during fall; the average 

 number offish sampled per tow (5.0 and 4.5, respec- 

 tively) was lower than for silver hake. Atlantic cod 

 were collected mainly from the northern three 

 geographic regions (Georges Bank, Gulf of Maine, 

 and Western Nova Scotia), where a total of 1,661 fish 

 were sampled from 351 tows. The temperatures at 

 which cod were collected in the spring were colder 

 than those at which they were taken in the fall. 

 Because of the more northerly distribution of the 

 cod, they were taken from colder water temperatures 

 than the silver hake (Table 1). The depths at which 

 hake and cod were taken during the spring were 

 similar (Table 1). However, during fall, the cod were 

 found at somewhat greater depths than hake. 



Because of the considerable size range of each 

 species (Fig. 2), and changes in food habits which oc- 

 curred with increasing size (discussed below), the 

 silver hake and Atlantic cod were divided into two 

 size-classes for further analysis: <20 cm (small) and 

 >20 cm (large) for hake, and <30 cm (small) and 

 >30cm (large) for cod. Mean lengths and weights of 

 each size class during spring and fall are presented in 

 Table 2. 



For the present study, the data from the four spring 

 cruises were combined to provide a composite pic- 

 ture of diel changes in stomach contents of each 

 species over the entire study area. Data from the four 

 fall cruises were similarly combined. Possible dif- 

 ferences in diel feeding patterns or feeding rate that 

 may have existed in different regions or years are not 



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