Abstract . - The diets of pelagic 

 juveniles of widow rockfish Sebastes 

 entom.elas, yellowtail rockfish S.. /la - 

 iridus, chilipepper S. goodei, short- 

 belly rockfish S. jordani, and bocac- 

 cio S. paucispinis were compared 

 using samples collected during 1984- 

 87. All five species co-occur as pelag- 

 ic juveniles off central California. 

 Frequency of occurrence, percent by 

 number, and a ranking index of prey 

 items were determined from 1088 

 stomachs. Major prey of pelagic juve- 

 nile rockfish were the various life 

 stages of calanoid copepods and sub- 

 adult euphausiids (including eggs). 



For each year, dietary overlap was 

 quantified between interspecific 

 pairs using the Colwell and Futuyma 

 (1971) index. Amount of overlap 

 varied from year to year. Long-term 

 intraspecific dietary overlap, based 

 on the 4 years of data, was general- 

 ly less than interspecific overlap 

 within years. Year-to-year variation 

 in the diets of these species was gen- 

 erally greater than within-year varia- 

 tion among them, suggesting that, as 

 a group, pelagic juvenile rockfishes 

 are opportunistic feeders. Also, if in- 

 terannual variation in the distribu- 

 tion and abundance of foods has a 

 major impact on recruitment, the 

 high dietary overlaps of these co-oc- 

 curring species would suggest paral- 

 lel survival and year-class success. 



Multivariate analysis of variance 

 was used to examine the effects of 

 latitude, depth, and fish size on food 

 consumption. Alterations in diet 

 were related to latitude, depth, and 

 a latitude-depth interaction for three 

 species in 1987 and, also, for short- 

 belly rockfish in 1984-86. Diet was 

 apparently unrelated to fish size. 



Interannual variation and overlap 

 in tlie diets of pelagic juvenile 

 rockfish (Genus: Sebastes) 

 off central California 



Carol A. Reilly 



Tiburon Laboratory, Southwest Fisheries Science Center 



National Marine Fisheries Service, NOAA, 3 1 50 Paradise Drive. Tiburon, California 94920 



Tina Wyllie Echeverria 



Tiburon Laboratory, Southwest Fisheries Science Center 



National Marine Fisheries Service, NOAA, 3 1 50 Paradise Drive, Tiburon, California 94920 

 Present address: School of Fisheries and Ocean Sciences 

 University of Alaska, Fairbanks, Alaska 99775-1080 



Stephen Ralston 



Tiburon Laboratory, Southwest Fisheries Science Center 



National Marine Fisheries Service, NOAA, 3 1 50 Paradise Drive, Tiburon. California 94920 



Manuscript accepted 20 May 1992. 

 Fishery Bulletin, U.S. 90:505-515 (1992). 



Rockfishes of the genus Sebastes are 

 a major component of the west coast 

 groundfish fishery (Gunderson and 

 Sample 1980), yet little is known of 

 their early life history. Kendall and 

 Lenarz (1987) noted a particular lack 

 of information on the biology of the 

 pelagic juvenile life-stage. To date 

 most work on pelagic juveniles has 

 addressed problems in identification 

 (e.g., Moser et al. 1977, Laroche and 

 Richardson 1980 and 1981, Matarese 

 et al. 1989), growth (Boehlert 1981a, 

 Boehlert and Yoklavich 1983, Penney 

 and Evans 1985, Laidig et al. 1991, 

 Woodbury and Ralston 1991), and 

 vertical distribution (Boehlert 1977 

 and 1981b, Moser and Alhstrom 

 1978, Moser and Boehlert 1991, 

 Lenarz et al. 1991). 



Female rockfishes undergo inter- 

 nal fertilization and the eggs develop 

 within the ovary for a 40-50 day pe- 

 riod (Kendall and Lenarz 1987). Lar- 

 vae hatch internally, are extruded 

 approximately 1 week later, and be- 

 gin feeding. Larvae grow and trans- 

 form into juveniles, a developmental 

 stage characterized by the attain- 

 ment of full meristic characters. 

 Many rockfishes have a pelagic juve- 



nile stage. Pelagic juveniles ranging 

 in size from 15-100 mm SL are abun- 

 dant off central California from April 

 to June, although distributional pat- 

 terns vary markedly among species 

 and years (Wyllie Echeverria et al. 

 1990). The pelagic juvenile stage ends 

 with settlement into demersal or 

 nearshore habitats. 



Evidence strongly indicates that 

 the recruitment of marine fishes is 

 heavily influenced by events that oc- 

 cur early in the life history (Blaxter 

 1974). A frequently proposed expla- 

 nation is that the availability and 

 abundance of foods appropriate for 

 first-feeding larval and later juvenile 

 stages are critical to adequate sur- 

 vival and growth. A reduction in the 

 fine-scale density of suitable prey 

 items, whether due to an absolute 

 decrease in prey abundance (Hjort 

 1914) or to a randomized dispersion 

 of what formerly was a patchy prey 

 resource (Lasker 1975), can have a 

 negative impact on survival. Reduced 

 prey densities can affect survivorship 

 directly through starvation, or in- 

 directly by reducing growth rates 

 and thereby prolonging exposure to 

 other size-specific mortality factors 



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