DURBIN ET AL.: STOMACH CONTENTS OF HAKE AND COD 



Table 7. — Number of fish caught, amount ('7< BW) of food in the Atlantic cod stomachs (x ± standard error of mean), and estimated mean 



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



Table 8. — Upper and lower estimates of R for fish prey, and the 

 effect upon the estimated daily ration, where: Rf ls ^ max — 0.0406 

 e onu ; fi fish> min = 0.00406 e onu , and« other = 0.0406 e 0111 '. Basic 

 data from Tables 6 and 7. BW = body weight 



stomach content data, require information on diges- 

 tion rate of the various prey types. Equation (3) is 

 based on maximum evacuation rates observed in the 

 laboratory for small, easily digested food items. 

 Evacuation rates determined from this equation 

 should provide an upper limit to estimates of inges- 

 tion rates (Table 8). Since there are indications that 

 fish prey may be digested more slowly, the daily ra- 

 tion was also estimated using the lowest observed 

 values of evacuation rate for fish prey (Table 8). This 

 reduced the estimate of ingestion of fish prey by a 

 factor of 10, and provided a lower limit for the prob- 

 able ingestion rates. The potential significance of this 

 10-fold range in the R value is well illustrated by the 

 case of silver hake >20 cm, where during the spring, 

 for example, fish prey constituted 66.2% of the 

 stomach contents by weight, yet the calculated inges- 

 tion offish ranged from as much as 647c to as little as 

 15'/ of the diet, depending on the R value used. 



447 



