FISHERY BULLETIN: VOL. 81, NO. 3 



TABLE 1 . — Total number of tows from which silver hake and Atlantic cod were sampled, 

 total number of fish sampled, mean number of fish sampled per tow, and mean tempera- 

 ture and depth of capture. Cruise dates were: (Spring) 3/3 to 15/5 1973; 12/3 to 4/5 

 1974; 4/3 to 12/5 1975; 4/3 to 8/5 1976; (Fall) 26/9 to 20/1 1 1973; 20/9 to 14/1 1 1974; 

 15/10 to 18/11 1975; 20/10 to 23/11 1976. 



TABLE 2. — Mean length and estimated wet weight of silver hake and Atlantic cod. 



considered; evaluation of such differences would re- 

 quire a separate study, with additional, more inten- 

 sive field surveys designed to investigate these 

 problems (see Pennington et al. (in press) for a dis- 

 cussion of the required sampling design). 



As stated above, for the analysis of diel changes in 

 stomach contents and the calculation of daily ration, 

 data from tows within each successive 3-h period of 

 the day were grouped together and arbitrarily 

 assigned to the midpoint of the time period. The 

 number of tows taken during each period is shown for 

 each species by season and size class in Tables 6 and 

 7. Large silver hake and large Atlantic cod were fair- 

 ly evenly sampled throughout the day. Small hake 

 were caught in larger numbers by night, however. 

 Small cod were few, and generally the sample sizes 

 for each time period were very small (<10 individ- 

 uals). 



In order to compare mean values from different sub- 



440 



sets of the data, anF-test for the equality of variances 

 was first performed. If the variances were not 

 significantly different (P <0.05), a Student's Mest 

 was applied to test for the significance of the differ- 

 ence in the mean values of the two subsets. If the 

 variances were unequal, Satterthwaite's approxima- 

 tion (Steel and Torrie 1 960) was used to compute the 

 degrees of freedom associated with the approximate 

 t value, using a computer program which is available 

 in the Statistical Analysis System (SAS 79) statisti- 

 cal package (SAS Institute, Inc.). 



RESULTS 



Stomach Contents 



In both Atlantic cod and silver hake, the food habits 

 and the mean amount of food in the stomachs 

 changed with increasing fish length (Tables 3, 4). The 





