Fisheries independent assessment of a returning fishery: Abundance of juvenile white seabass (Atractoscion nobilis) in the shallow nearshore waters of the Southern California Bight, 1995-200

摘要

Nearshore, coastal and embayment areas off southern California were sampled to determine the spatial and temporal patterns abundance and size distributions of young white seabass in the shallow (5-14m) waters from Santa Barbara south to Imperial Beach off San Diego. A total of 19 stations, 13 in nearshore coastal waters and 6 in embayments, dispersed along the Southern California Bight were surveyed in each sampling month using 45.7m variable mesh, monofilament gill nets. In the 11-year period of sampling (April 1995-June 2005), a total of 8075 juvenile white seabass was captured in 42 sampling months. The mean catch-per-unit-effort (CPUE: 2.0fishet+/-0.2) for juvenile white seabass varied significantly among stations during the 10-year period (1996-2005) of the full station sampling. Stations located near large rocky headlands, such as Palos Verdes, Santa Barbara, Newport, and La Jolla yielded the highest catches. Although CPUE peaked in August 1999 as a result of strong year classes in 1996-1998, overall, catches tripled over the 11-year sampling period at seven coastal sites increasing significantly at a rate equivalent to 0.22fish /(netyear). These relatively high catches of wild, juvenile fish over the last decade, along with significant increases in commercial CPUE and increased recreational catches overall, indicate that the natural population of white seabass is in the process of recovery. Commercial catches are again comparable to levels attained prior to the fishery collapse in the 1970s and 1980s. Therefore, we propose that the white seabass now represents one of the first documented cases of a recovering, demersal species of commercial importance. The ban of nearshore commercial gill net fishing by Proposition 132 probably contributed greatly to the increase in the population size that led to this recovery. In addition, the succession of warm water years that occurred from 1983 to the strong El Nino event of 1997-1998 also played an important role in the successful recruitment of white seabass.