Stanley et al,: Diel vertical migration by Sebastes flavidus 



325 



targets would probably have been yellowtail rock- 

 fish. Commercial fishery records fi-om these fishing 

 grounds consistently indicate a predominance of yel- 

 lowtail rockfish in midwater and bottom trawl tows. 

 The daytime tows support the assumption that the 

 aggregation over the cliff was that of yellowtail rock- 

 fish, and the nocturnal dispersion of these aggrega- 

 tions is obvious from the night transects. These ag- 

 gregations appear almost as dense as the bottom on 

 our daytime echograms. The cliffs can be identified 



only in the echogram during the night (Figs. 3 and 4). 

 We are not, however, suggesting that all fish in the 

 transect were yellowtail rockfish, nor are we suggest- 

 ing that the diurnal aggregations at the cliff repre- 

 sented all the yellowtail rockfish that were present 

 in the transects. The nocturnal "cloud" may have 

 included fish that were close to the bottom but not 

 adjacent to the cliffs. 



Figure B6-N indicates that there was some move- 

 ment from off the edge onto the long and short ver- 



