External Review of Shortbelly Rockfish Stock Assessment

The shortbelly rockfish (Sebastes jordani) is an abundant unexploited resource with centers of abundance in southern California and the San Francisco region of the west coast. A stock assessment was reviewed during June 28-30 at the SWFSC Fisheries Ecology Division in Santa Cruz. This assessment does not currently bear on any significant fishery management decisions, but makes a significant contribution to our understanding of the natural (i.e., unfished) behavior of fish stocks as well as their role in the ecosystem as forage for fish, seabirds and mammals, and as competitors of other exploited rockfish species. The review panel consisted of Chris Francis (CIE, New Zealand), George Watters (PRD), and Bill Lenarz (FED, retired).

Lacking a historical fishery, all information for the assessment came either from fishery-independent surveys (e.g., FRD’s CalCOFI larval abundance since 1951, FED’s juvenile rockfish abundance since 1983), or from biological monitoring programs. Shortbelly rockfish otoliths recovered from sea lion scats (collected in southern California since 1981 by Mark Lowry, PRD) provided a historical record of length compositions. Juvenile rockfish from seabird foraging observed at the Farallon Islands (data collected by Point Reyes Bird Observatory since 1973) provided an annual index of recruitment strength. The assessment confirmed that an unexploited resource can experience large natural fluctuations in abundance, in this case ranging from more than 50% above the estimated long-term equilibrium in the early 1950s to 50% below equilibrium currently. Notably, like many exploited west coast stocks, this unexploited stock also saw a very sharp decline in abundance during the 1990s. (July 3, 2006)