FISHERY BULLETIN: VOL. 81, NO. 3 



TABLE 6.— Number of fish caught, amount (% BW) of food in the silver hake stomachs (x ± standard error of mean), and estimated mean amount 



of food ingested during each 3-h period. BW= body weight. 



Time 



Total 



no. of fish 



(No. of tows) 



Total food 



Fish prey 



Other prey 



Stomach contents 

 (% BW) 



Ingestion 

 (% BW) 



Stomach contents 

 (% BW) 



Ingestion 

 (% BW) 



Stomach contents 

 (% BW) 



Ingestion 

 (% BW) 



spring. 



When the daily ration was estimated using an R 

 value for fish prey derived from Equation (3) (Tables 

 (6-8), then fish prey constituted 28.1 and 4.8% of 

 the daily ration of small hake during spring and fall, 

 respectively. In large cod, fish prey constituted 38.2 

 and 55.1% of the daily ration, whereas in large silver 

 hake, fish prey constituted 64.4 and 76.0% (Tables 6- 

 8). However, if the lower estimate of the evacuation 

 rate for fish prey items is used in the calculation, the 

 importance of fish prey in the diet of all groups was 

 sharply reduced (Table 8). The effect on the total 

 estimated daily ration was small for hake <20 cm, 

 because this size class did not feed heavily upon fish 

 prey. However, since large hake and large cod feed 

 extensively upon fish prey, a change in the R value for 

 this prey type significantly affected the total 

 estimated daily ration (Table 8). 



DISCUSSION 



Application of 

 the Elliott and Persson Model 



The Elliott and Persson model was originally de- 

 scribed for field samples collected in a restricted area 

 from the same population over time. Present data 

 were obtained from extensive surveys over large 

 areas rather than intensive surveys of single pop- 

 ulations. As applied here, the model provides a broad 

 overview of ingestion by fish located over a very large 

 geographic area. Resolution of this composite pic- 

 ture to include possible differences in fish behavior in 

 different years or areas would have required ad- 

 ditional intensive field surveys and was beyond the 

 scope of the present study. 



Daily ration estimates, which are based on field 



446 



