Nezumia a equal is 



FISHERY BULLETIN: VOL. 84, NO. 1 



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DEPTH ( m ) 



Figure 8— The distribution of log transformed (log (x + 1)) abundance and weight of Nezumia aequalis at each station, plotted against depth. 



junction with Marshall's hypothesis, the advantages 

 of the type of seasonal migration suggested by our 

 data are twofold. First, the migration concentrates 

 the reproductively mature fish in a limited area 

 thereby increasing the probability of a sexual en- 

 counter. Second, it allows additional time for develop- 

 ment of eggs on their rise to the upper layers, and 

 concurrently lessens the chance that the egg will 



travel through the thermocline and be removed from 

 the area by the more aqtive surface currents 

 (although egg density could be such that neutral 

 buoyancy occurs at the thermocline). If these sug- 

 gestions hold true, it would be expected that the lar- 

 vae would benefit from the high productivity and 

 warmer temperatures of the surface waters and have 

 enhanced growth. As productivity declines in the late 



44 



