The decline and recovery of four predatory fishes from the Southern California Bight

Abstract

What to do about Wsheries collapse and the decline of large Wshes in marine ecosystems is a critical debate on a global scale. To address one aspect of this debate, a major Wsheries management action, the removal of gill nets in 1994 from the nearshore arena in the Southern California Bight (34°2630N, 120°2709W to 33°3203N, 117°0728W) was analyzed. First, the impe- tus for the gill net ban was the crash of the commercial Wsh- ery for white seabass (Atractoscion nobilis; Sciaenidae) in the early 1980s. From 1982 to 1997 catch remained at a his- torically low level (47.8 § 3.0 mt) when compared to land- ings from 1936-1981, but increased signiWcantly from 1995-2004 (r = 0.89, P < 0.01) to within the 95% conW- dence limit of the historic California landings. After the white seabass Wshery crashed in the early 1980s, landings of soupWn (Galeorhinus galeus; Triakidae) and leopard shark (Triakis semifasciata; Triakidae) also signiWcantly declined (r =0 .95, P < 0.01 and r =0 .91, P < 0.01, respec- tively) until the gill net closure. After the closure both soupWn and leopard shark signiWcantly increased in CPUE (r =0 .72, P = 0.02 and r =0 .87, P < 0.01, respectively). Finally, giant sea bass (Stereolepis gigas; Polyprionidae) the apex predatory Wsh in this ecosystem, which was pro- tected from commercial and recreational Wshing in 1981, were not observed in a quarterly scientiWc SCUBA moni- toring program from 1974 to 2001 but reappeared in 2002- 2004. In addition, CPUE of giant seabass increased signiW- cantly from 1995 to 2004 (r = 0.82, P < 0.01) in the gill net monitoring program. The trends in abundance of these Wshes return were not correlated with sea surface tempera- ture (SST), the PaciWc Decadal Oscillation (PDO) or the El Nino/Southern Oscillation (ENSO). All four species increased signiWcantly in either commercial catch, CPUE, or in the SCUBA monitoring program after the 1994 gill net closure, whereas they had declined signiWcantly, crashed, or were absent prior to this action. This suggests that removing gill nets from coastal ecosystems has a posi- tive impact on large marine Wshes.