Abstract.- Shortbelly rockfish 

 Sebastes jordani is an abundant spe- 

 cies that could support a large com- 

 mercial fishery off central California. 

 Prior studies of shortbelly rockfish 

 growth were based on age data ob- 

 tained from scales or whole otoliths. 

 We show that broken and burnt oto- 

 liths provide reliable ages that are 

 substantially different than those 

 derived from previous methods. This 

 new information was used to update 

 estimates of the von Bertalanffy 

 growth curve parameters, the nat- 

 ural mortality rate, and potential 

 yield. We found that shortbelly rock- 

 fish live for up to 22 years. Males 

 grew more slowly and reached a 

 smaller maximum size than females. 

 Estimates of natural mortality from 

 three predictive models ranged from 

 0.212 to 0.378 for males and 0.203 

 to 0.437 for females. Assuming M is 

 0.20-0.35 and using biomass esti- 

 mates from hydroacoustic surveys, 

 we estimated that potential yield in 

 the Ascension Canyon-Farallon 

 Islands area ranges from 13,400 to 

 23,500 metric tons. 



Age, Growth, and 

 Potential Yield for Shortbelly 

 Rockfish Sebastes jordani 



Donald E. Pearson 

 Joseph E. Hightower 



Tiburon Laboratory, Southwest Fisheries Science Center 

 National Marine Fisheries Service, NOAA 

 3150 Paradise Drive, Tiburon, California 94920 



Jacqueline T\H. Chan 



Tiburon Laboratory, Southwest Fisheries Science Center 



National Marine Fisheries Service, NOAA 



3 1 50 Paradise Drive. Tiburon, California 94920 



Current address: 200 Ewing Terrace Drive, San Francisco, California 941 18 



Manuscript accepted 25 February 1991. 

 Fishery Bulletin. U.S. 89:403-409 (1991). 



Shortbelly rockfish Sebastes jordani 

 is an abundant species in California 

 waters. In midwater trawl surveys of 

 juvenile rockfish conducted off cen- 

 tral California, shortbelly rockfish 

 were far more abundant than any 

 other rockfish species (Wyllie Eche- 

 verria et al. 1990). The biomass of 

 shortbelly rockfish in the Ascension 

 Canyon-Farallon Islands area was 

 estimated from hydroacoustic studies 

 (E. Nunnely, NMFS Alaska Fish. Sci. 

 Cent., Seattle, WA 98115-0070, pers. 

 commun., Jan. 1989) to be 295,000 

 metric tons (t) in 1977 and 152, 700 1 

 in 1980. These estimates are one to 

 two times the estimated coastwide 

 virgin biomass for widow rockfish 

 S. entomelas (Lenarz and Hightower 

 1988), a species that supports a sig- 

 nificant commercial fishery. Current- 

 ly, there is no commercial or sport 

 fishery for shortbelly rockfish, but in- 

 terest in surimi production or a new 

 method of bone softening of whole 

 fish (Okada et al. 1988), combined 

 with their high abundance, could lead 

 to the development of a substantial 

 commercial fishery. If a commercial 

 fishery does develop, it will be impor- 

 tant to have accurate life-history in- 

 formation for management purposes. 

 Previous studies of shortbelly rock- 

 fish life-history characteristics have 



been based on age data from scales 

 (maximum age 10 years, Phillips 

 1964) or whole otoliths (maximum 

 age 12 years, Lenarz 1980). How- 

 ever, studies of other rockfish species 

 (Six and Horton 1977, Beamish 1979, 

 Kimura et al. 1979, Chilton and 

 Beamish 1982, Boehlert and Yokla- 

 vich 1984, Stanley 1986, Leaman and 

 Nagtegaal 1987) have shown that 

 ages obtained from those structures 

 tend to be underestimates, and that 

 broken and burnt or sectioned oto- 

 liths are a more reliable method for 

 determining fish age. W. Lenarz 

 (Tiburon Lab., NMFS Southwest 

 Fish. Sci. Cent., Tiburon, CA 94920, 

 pers. commun., Jan. 1989) indicated 

 that surface ageing of shortbelly 

 rockfish otoliths was difficult and felt 

 that the ages could have been greater 

 than reported. For that reason, the 

 objective of this study was to update 

 the estimates of age, growth, and 

 potential yield of shortbelly rockfish, 

 based on examination of broken and 

 burnt otoliths. 



Materials and methods 



Adult shortbelly rockfish were cap- 

 tured occasionally in 1983-88 mid- 

 water trawl surveys designed to 

 monitor the abundance of juvenile 



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