FISHERY BULLETIN: VOL. 82, NO. 2 



north of our study area which extends from off 

 northern California to off Vancouver Island, Brit- 

 ish Columbia. 



This study represents the first attempt to exam- 

 ine broad geographical and seasonal patterns in 

 food utilization and overlap by several commer- 

 cially important species of rockfish on the outer 

 continental shelf. The species considered include 

 the yellowtail rockfish, Sebastes flavidus; canary 

 rockfish, S. pinniger; Pacific ocean perch, S. 

 alutus; splitnose rockfish, S. diploproa; and the 

 darkblotched rockfish, S. crameri, all important 

 members of the demersal shelf rockfish complex 

 (Gabriel and Tyler 1980). In addition, variability 

 in the diet of two of these species, S. flavidus 

 and S. pinniger, was examined for the purpose 

 of determining the effects of factors such as sea- 

 son, geographic area, time of capture, and pred- 

 ator size. 



MATERIALS AND METHODS 



Sampling Methods 



The food utilization patterns of the five rockfish 

 species were determined by examining stomach 

 contents. Fishes were obtained by two different 

 survey methods (hereafter referred to as the 

 summer and seasonal surveys). As the collection 

 methods differ, they will be discussed separately 

 The laboratory methods are similar and will be 

 presented together. 



Summer Survey Methods 



Collections for the summer survey were made 

 during the National Marine Fisheries Service 

 (NMFS) 1980 West Coast Survey which took place 

 from 12 July to 28 September 1980. The purpose of 

 this survey was to assess the distribution and 

 abundance of commercially important rockfishes. 

 The area encompassed by the survey included 

 much of the continental shelf and inner slope 

 (ranging in depth from 55 to 366 m) between 

 Monterey, Calif., (lat. 36°48'N) and the northern 

 end of Vancouver Island, British Columbia (lat. 

 50° 00' N). Two commercial stern trawlers, the FV 

 Mary Lou and the FV Pat San Marie, were 

 utilized for the survey. A Nor'Eastern 3 high- 

 opening bottom trawl with an estimated 13.4 m 

 horizontal and an 8.8 m vertical mouth opening 



was used on both vessels. The main body was 

 constructed of 127 mm stretched mesh with 89 mm 

 mesh in the cod end. The cod end also contained 

 a 32 mm mesh liner. Half-hour tows were made 

 at random depth-stratified stations chosen by 

 a method described in Gunderson and Sample 

 (1980). 



The majority of the stomach samples used in 

 this study were collected in August and Septem- 

 ber from north of lat. 43° N (Table 1, Fig. 1). 

 Complete station data are given in Brodeur (1983). 



Stomachs were removed at sea from a random 

 subsample of the catch of the five target species 

 (Table 1). Sebastes pinniger and S. flavidus were 

 the primary target species, and stomachs of these 

 species were collected first and the other species 

 sampled as time allowed. Altogether, 480 stom- 

 achs were collected during the survey, all from 

 adult fish ( > 200 mm FL). Fork length (measured 

 to the nearest millimeter) and sex were recorded 

 for all fish sampled, and stomachs were then 

 removed, individually wrapped and labeled, and 

 preserved in a 10% Formalin-seawater mixture. 

 The intestinal tracts of many of the fish were 

 examined at sea but few contained any recogniz- 

 able food and none were retained. Total elapsed 

 time between bringing the fish on board and 

 preserving the stomachs was < 1 h. The oral 

 cavities of all fish were examined for signs of 

 stomach eversion and regurgitation; any fish 

 showing such signs were discarded. Individual 

 fish weights were not recorded at sea but were 

 later calculated using the length-weight relation- 

 ships of Phillips (1964). 



TABLE 1. — Number of rockfish stomachs 

 analyzed from the 1980 National Marine 

 Fisheries Service summer survey. The 

 approximate latitudinal ranges covered 

 by each leg were I, lat. 37°-42°N; II, lat. 

 43°-46°N; III, lat. 46°-50°N. 



Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



270 



