FISHERY BULLETIN: VOL. 84, NO. 2 



44° 50' N 



- 44° 40' 



44° 30' 



124° 50' W 



124° 40' 



Figure 4.— Hydroacoustic transects (dashed lines) and midwater trawl hauls (solid ar- 

 rows) conducted by the RV Miller Freeman during the 1980 behavior study. Only haul 

 43 contained widow rockfish (1,247 kg). 



Pacific whiting, Merluccius productus, (Fig. 8) or less 

 dense layers of zooplankton. 



The formation and dispersal of widow rockfish ag- 

 gregations was observed during the research cruises. 

 During a typical night, small schools would appear 

 in late evening (from 2000 to 2400) either near bot- 

 tom or high in the water column. As the night pro- 

 gressed, these schools tended to grow and those high 

 in the water would settle toward the bottom. Peak 

 school size and density usually occurred between 

 0200 and dawn. Shortly after daybreak, most schools 

 would separate into smaller schools and rise off the 

 bottom. The schools would sometimes move over 

 deeper water while maintaining their nighttime 

 configuration. 



Departures from the typical behavior patterns 

 have been reported. For example, while observing 

 widow rockfish schools over the continental shelf (not 



aggregating around a seamount), Gunderson et al. 7 

 noted a progressive offshore shift in the location of 

 the schools during one night. By sunrise most of the 

 schools were located near the edge of the shelf. Most 

 of these schools dispersed after dawn, but some re- 

 mained on the bottom in the area (in one case as late 

 as 1037 when observations were terminated). This 

 apparent shift may have been related to diurnal ver- 

 tical migration behavior (Pereyra et al. 1969). 



METHODOLOGY DEVELOPMENT 



(1980-81) 



The methodology development was conducted by 



7 Gunderson, D. R., G. L. Thomas, P. Cullenberg, and R. E. 

 Thome 1981. Rockfish investigations off the coast of Washing- 

 ton and Oregon. Final report. Unpubl. manuscr., 45 p. Univ. 

 Wash., Fish. Res. Inst, FRI-UW-8125. 



294 



