194 



Fishery Bulletin 



1990 



day-21 the herring captured did not contain food items. 

 This may have been due to regurgitation during cap- 

 ture, or the larvae may not have been feeding imme- 

 diately prior to capture. The absence of food is likely 

 a combination of the shock of capture and preserva- 

 tion, two processes which have been shown to cause 

 significant voiding of the gut (Rosenthal 1969, Hay 

 1981). 



By day-22 the stomach had begun to differentiate, 

 and greater than 7.5% of the larvae had food items in 

 the stomach from this time forward. The frequency of 

 copepod eggs and nauplii occurrence decreased and 

 adult copepods increased; also, other items appeared 

 in the diet, primarily veligers and crab zoea. 



On day-43 cannibalism was observed in the basin. On 

 that date a school (A^ = 10) of 60-80 mm herring was 

 observed attacking schools {N = 10-60) of smaller her- 

 ring. Immediately afterward, dip net samples were at- 

 tempted and two herring, one 57 mm and the other 32 

 mm, were obtained. The 32-mm herring was found to 

 contain a 20-mm herring. 



Comparison of feeding relative to abundance, using 

 the Ivlev (1961) electivity index, shows that adult cope- 

 pods were increasingly selected as the herring grew 

 and that copepod nauplii were less utilized (Table 2). 

 Veligers and crab zoea were not utilized initially but 

 were strongly selected after the larvae had grown large 

 enough to consume these species. 



Growth 



The average length of newly hatched larvae was 7.61 

 mm (SD 0.53), average dry weight 190 /ug (SD 38.5) 

 and yolk volume 0.16 mm'* (SD 0.09) (Table 3). 

 Measurements were taken of herring hatched each day 

 and no significant differences were found between days 

 (F test, a =0.05). 



Figure 4 



(A) Number of calanoid copepods/L, (H) number of calanoid copepod 

 nauplii/L, and (C) number of hydromedusae and other plankton/L 

 in net samples in the 200O-m' basin, Fl^devigen Biological Station, 

 Norway. 



