Bolz and Burns: Age and growth of larval Clupea harengus 



393 



1991-92 



1992-93 



30 



20 



10 



W" f 



• L = 34.2036e-" 684 '' 



30 t 



20 t 



20 40 60 80 100 120 



20 40 60 80 100 120 



1988 94 



30 



20 



10 h 



L = 34.9959e ' 



74 „ e -»»»'»»» 



20 40 60 80 100 120 



20 40 60 80 100 120 



Estimated age in days 



Figure 2 (continued) 



Fish hatched in 1976 were longer by 2.8 to 7. 1 mm 

 SL than those collected during the 1980's and early 

 1990's. Since temperatures in the autumn of 1976 

 did not differ significantly from the long-term aver- 

 age (Mountain and Holzwarth, 1989), a density-de- 

 pendent function is the most likely explanation for 

 this difference. It is possible that the less dense beds 

 enhanced growth by permitting eggs to be oxygen- 

 ated better or that the diminished spawning popula- 

 tion produced eggs with greater food reserves 

 (Blaxter and Hunter, 1982). Despite their initially 

 robust appearance, larvae during the 1976-77 sea- 

 son exhibited poor growth and high mortality ( Lough 



et al., 1979). The severe storms discussed above most 

 likely dispersed the prey of larval herring and led to 

 a reduction in daily food rations. Poor feeding is re- 

 flected in the rapid lessening of mean otolith diam- 

 eter noted during 1976-77. This observation is in 

 agreement with the previous study of Cohen and 

 Lough (1983), where larvae collected during the 1976 

 season had lower prey numbers and biomass per 

 larva than those in 1974 and 1975. Similar results 

 were found by Karakiri et al. ( 1989) in their study of 

 age-0 plaice (Pleuronectes platessa L. ). They also con- 

 cluded that food limitation accounted for an observed 

 difference in growth between two years with similar 



