Yoklavich et al.: Larval rockfishes and their physical environment off central California 



777 



mary prey of juvenile and adult rockfishes) during 

 the 1958 El Nino. Poor condition of adult rockfishes 

 could influence larval production and reproductive 

 timing. Abundance of rockfish larvae in our study, 

 however, was not significantly different between the 

 two years of the extended El Nino event along the 

 central California coast and was much greater than 

 estimates from earlier ichthyoplankton surveys 

 coastwide. Greatest mean abundance of rockfish off 

 Oregon was 350 larvae/10 m 2 in May 1971 (Richard- 

 son and Pearcy, 1977), 199/10 m 2 in March 1972, and 

 176/10 m 2 in March 1973 (Richardson et al., 1980). 

 Peak abundance of rockfish sampled during CalCOFI 

 surveys in February 1951-81 averaged about 200 lar- 

 vae/10 m 2 off northern and central California and 90 

 larvae/10 m 2 off southern California (Moser and 

 Boehlert, 1991). Average larval rockfish abundance 

 estimated from those CalCOFI lines (i.e. 63, 67, 70) 

 and stations (i.e. 49-57) closest to our sampling sites 

 was 486 larvae/10 m 2 in February, 1960-84. We esti- 

 mated a mean abundance of 990 rockfish larvae/10 

 m 2 at the three offshore stations in February during 

 our 2-year survey. This figure demonstrates that 

 overall larval abundance was not negatively affected 

 by an El Nino event and that the area north of 

 Monterey Bay is a significant production ground for 

 larval rockfishes. This finding is substantiated by 

 the results of pelagic juvenile rockfish surveys along 

 California, which indicate a center of distribution in 

 this area (Larson et al., 1994). 



Further, the El Nino event of 1991-93 did not seem 

 to have caused a significant shift in overall timing of 

 parturition, at least for the two species that domi- 

 nated our ichthyoplankton surveys. Median hatch 

 dates of shortbelly rockfish larvae collected during late 

 winter and early spring of 1991-92 and 1993 were simi- 

 lar to each other (first and second week in February, 

 respectively), and to the primary month of parturition 

 (i.e. February) according to reproductive stages of this 

 species off central California from 1977 to 1984 (Wyllie 

 Echeverria, 1987). Release of blue rockfish larvae dur- 

 ing our study likewise was as expected (i.e. January; 

 Wyllie Echeverria, 1987). Absence of sampling in late 

 December 1992 could have masked an unlikely peak of 

 parturition earlier in the 1993 season. 



Although reproductive timing and production 

 seemingly were not influenced by the prolonged El 

 Nino event, occurrence of juvenile rockfishes in trawl 

 samples collected in late spring and summer was 

 dramatically different between years. Extremely low 

 numbers of pelagic juvenile rockfish were encoun- 

 tered during midwater trawl surveys (rc=56 trawls) 

 conducted from 4 May to 10 July 1992 north and 

 south of Monterey Bay (Loeb et al. 1 ). In contrast, 

 pelagic juvenile rockfishes collected during the same 

 time period in 1993 (rc=65 trawls) were 20 times more 

 abundant, comprised twice as many taxa, and were 

 substantially larger than juveniles collected in 1992 

 (Loeb et al. 1 ). Shortbelly, copper-complex, and kelp 

 rockfishes dominated the relatively low numbers of 



