MIDDLETON and MUSICK: ABUNDANCE AND DISTRIBUTION OF MACROURIDAE 



ontogenetic transition for Urophycis chuss and sug- 

 gested that the transition from pelagic to demersal 

 adaptations in morphology and behavior occurred 

 within a period of 12-24 h. This short time span 

 would be unlikely to be reflected in macroscopic 

 hyaline band formation. Therefore, the second hy- 

 pothesis appeared more likely, and led to the con- 

 clusion that the juvenile N. bairdii remained pelagic 

 until the second winter and then descended from the 

 water column to the bottom where they were 

 captured. 



Nezumia bairdii 



The second problem was that in the older fish (>4 

 yr) the outer bands were very difficult to define with 

 any degree of confidence The percentage of 

 unreadable otoliths increased from about 5% in fish 

 <4 yr to about 50% in fish >4 yr. The mean head 

 length of N. bairdii with four bands was 42.7 mm, 

 the size at the onset of sexual maturity. Growth may 

 have slowed down to compensate for the energy 

 needed for reproduction, and produced spatially 

 close and obscure hyaline zones. Therefore spawn- 

 ing checks may have had considerable influence on 



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DEPTH (m) 



Figure 12— The distribution of log transformed (log (x + 1)) abundance and weight of Nezumia bairdii at each station plotted against depth. 



47 



