THE LIFE-HISTORY OF THE SPOTTED SAND-BASS (PARALABRAX-MACULATOFASCIATUS) WITHIN THE SOUTHERN CALIFORNIA BIGHT

Spotted sand bass (Paralabrax maculatofasciatus) are under increasing angling pressure in the shallow waters off southern California. In sou thern California, spotted sand bass are largely restricted to shallow, warm-water areas such as bays, estuaries, and harbors, which appear t o serve as warm-water refuges for this basically subtropical species. Rod-and-reel sampling from June 1991 to August 1993 yielded 639 indivi duals from seven locations. Specimens ranged from 51 to 400 mm SL, wit h only 8 fish below 150 mm SL and 10 above 330 mm SL. Analysis of otol ith sections revealed that a single opaque zone was laid down each sum mer. The oldest fish was 14 years old; the vast majority of the large specimens were 6 to 10 years old. Growth rate was sharply asymptotic, with some fish reaching 200 mm SL in their first year. Because growth rates varied significantly among the four locations tested, the overal l growth model was highly variable (R(2) = 0.67). Half of the female s potted sand bass matured very early (age class 0) and at a small size (155 mm SL). Males matured later (50% maturity at 1.4 years) and at a somewhat larger size (50% at 180 mm SL). Gonosomatic indices indicated that spawning occurred from June through August in southern Californi a. S potted sand bass inhabiting the northern Gulf of California are b elieved to be protogynous hermaphrodites, and populations from San Die go Bay showed an age/sex composition pattern consistent with protogyny However, populations from the six other southern California locations had roughly equal representation of the sexes throughout the age stru cture, and many of the oldest individuals were females. This pattern i s more consistent with gonochorism or ''partial'' protogyny. Southern California spotted sand bass seem to have a complex reproductive strat egy which may include flexible rates of female sex change among popula tions and sneaking males that mimic females within spawning aggregatio ns. Back-calculation of annual recruitment success from otolith data r evealed that almost all of our fish came from two pulses during 1984-8 5 and 1989-90. These pulses occurred during post-El Nino years. Recrui tment into southern California during El Nino years (1982-83, 1986-87, and 1992-93) appears to have been extremely low to nonexistent. Howev er, summer sea-surface temperatures at the Scripps Pier peaked one to two years after these El Nino events, resulting in a highly significan t correlation (r = 0.723, df = 13, P = 0.002) between recruitment (cor rected for mortality) of spotted sand bass and mean summer sea-surface temperature off southern California over the past 15 years.