FISHERY BULLETIN: VOL. 84, NO. 2 



their availability is most stable. Other objectives were 

 to investigate the possible causes of their diel 

 aggregation habits and to develop an ability to 

 distinguish widow rockfish schools from those of 

 other species on the basis of echosign 4 characteris- 

 tics and test fishing. 



Methods 



The behavior study was initiated 11-13 August 

 1980 aboard the chartered trawlers Pat San Marie 

 and Mary Lou. Concurrently, scientists aboard the 

 NOAA RV Miller Freeman conducted a conventional 

 echo integration survey in the study area and made 

 four midwater tows to identify the species composi- 

 tion of the schools sighted. The survey was repeated 

 during 10-26 April 1981 aboard the NOAA RV Chap- 

 man and included 7 d of hydroacoustic and sonar 

 observations. 6 Descriptions of the vessels, trawls, and 

 hydroacoustic equipment employed appear in Tables 

 2, 3, and 4, respectively. 



Demersal trawl stations were located around a 

 seabed rise known as Nelson Island off Newport, OR, 

 to determine if significant quantities of widow rock- 

 fish occurred on or near the bottom in an area where 

 they were known to form dense midwater aggrega- 

 tions. A 4 x 4 station grid with interstation 

 distances of 4.6 km (Fig. 2) was established between 

 the depths of 110 and 360 m with the rise at the 

 center. Two trawl hauls were attempted at each sta- 

 tion: one during daylight and one during darkness. 



When significant midwater fish schools were ob- 

 served, they were sampled with midwater trawl gear 

 for species composition. 



The contents of each trawl haul were sorted by 

 species, weighed, counted, and recorded. Otoliths 

 were removed from samples selected for age deter- 

 mination and stage of maturity was recorded for 

 some individuals. Stomach sample collections, 

 stratified by fish length, were also taken and pre- 

 served for feeding studies. 6 No meaningful descrip- 

 tion of age and length composition was possible 

 because of the small catches. 



Consultations with fishermen, observation trips 

 aboard commercial trawlers, and observations dur- 

 ing research operations provided further informa- 

 tion about school characteristics and diel behavior 

 patterns of widow rockfish and other species on and 

 around widow rockfish fishing grounds. 



Results 



Twenty-seven demersal tows were completed dur- 

 ing the August 1980 widow rockfish behavior study, 

 including 12 at night and 15 during the day. The 

 trawl was damaged during two night hauls. The wi- 

 dow rockfish catch was small, with 1 or 2 specimens 

 in six hauls and 20 specimens in one of the night 

 hauls during which the trawl was damaged (Fig. 3, 

 1980). Therefore, no conclusions about diel move- 

 ment patterns were possible from the 1980 study. 



The Miller Freeman transected the Nelson Island 

 area during the same study period and found one 



4 "Echosign" can be defined as the echo return output (paper echo- 

 grams, video chromoscope displays, etc) of an echo sounder aimed 

 at targets in the water column. 



6 Thomas, G. L., C. Rose, and D. R. Gunderson. 1981. Rockfish 

 investigations off the Oregon coast, annual report. Unpubl. 

 manuscr., 20 p. Univ. Wash., Fish. Res. Inst, FRI-UW-8119. 



6 Adams, P. B. 1984. The diet of widow rockfish (Sebastes en- 

 tomelas) in northern California. Unpubl. manuscr. Southwest 

 Fisheries Center Tiburon Laboratory, National Marine Fisheries 

 Service, NOAA, 3150 Paradise Drive, Tiburon, CA 94920. 



1 FRI = Fishery Research Institute; NWAFC = Northwest and Alaska Fisheries Center. 



290 



