FISHERY BULLETIN: VOL. 84, NO. 1 



fall and the larvae become larger, they would drop 

 out of the water column to the bottom. Length fre- 

 quencies of N. bairdii (Fig. 11) suggested that 



Nezumia bairdii 



6, 



5  



3- 



< o 



t- 



<n 



>- 

 C 



•- 7-1 



< 

 2 



6H 



I rh i 

 Irhl 





-EEZB- 



H=£3 — I 

 ■*=fc=H 



-EE& 



— i 1 1 1 1 1 1 



O 10 20 30 40 50 60 70 



HEADLENGTH 



Figure 10.— The gonadal maturity stages plotted against head 

 length for Nezumia bairdii. 



recruitment of young occurred between the months 

 of November and January. No small N. bairdii were 

 captured benthically between the proposed deep- 

 water spawning time and the shallower January 

 recruitment spike. 



The larger N. bairdii occurred deeper than the 

 small ones (Figs. 9, 12) demonstrating the "larger- 

 deeper" phenomenon. 



The age and growth analysis of N. bairdii 

 presented many problems. Due to the thickness of 

 the sacculus otolith a thin cross section had to be 

 removed from each. After examination of the thin 

 sections, two problems became apparent. First, all 

 of the smaller specimens had two hyaline zones. 

 Because the specimens were obtained on the winter 

 (January; 76-01) cruise, all had hyaline zones around 

 the perimeter as expected. There was, in addition, 

 a well-defined hyaline zone in the interior of all the 

 otoliths obtained from the smallest fishes available 

 (<27 mm HL). Subsequently two hypotheses were 

 proposed: 1) a period of hyaline zone formation (slow 

 growth) occurred between June-July (spawning) and 

 January, and 2) young N. bairdii were not available 

 to our trawl until the second winter hyaline zone was 

 forming (age about 1.5 yr). 



The first hypothesis was discarded because a 

 period of slow growth within the first 6 mo would 

 have no apparent selective advantage It should be 

 noted, however, that since the larvae of N. bairdii 

 were probably pelagic, a change from planktonic 

 feeding to benthic feeding would have occurred dur- 

 ing that time. Such an ontogenetic change occurs in 

 related gadid fishes. Musick (1969) described the 



70-1 



60 



50- 



40 



30 



20- 



10- 



Nezumia bairdii 



J ^ 



H.L. (mm) 



Figure 11— Head length frequency distribution for Nezumia bairdii by cruise The number above 

 each cruise indicates the number of specimens. 



46 



