Nearshore assemblages of larval rockfishes and their physical environment off central California during an extended El Niño event, 1991-1993

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Yoklavich, M. M., Loeb, V. J., Nishimoto, M., & Daly, B. (1996). Nearshore assemblages of larval rockfishes and their physical environment off central California during an extended El Niño event, 1991-1993. Fishery Bulletin, 94(4), 766-782.
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TitleNearshore assemblages of larval rockfishes and their physical environment off central California during an extended El Niño event, 1991-1993
AuthorsM. Yoklavich, J. Loeb, M. Nishimoto, B. Daly
AbstractRockfish are among the most prevalent members of nearshore ichthyoplankton assemblages off central California, yet their abundance varies greatly from year to year. Warm events, like El Niño, can have pronounced effects on the success of a year class. We evaluate distribution, abundance, and species composition of rockfish larvae on small spatial and temporal scales in the upwelling center north of Monterey Bay during an extended El Niño (December 1991 through June 1993) relative to regional hydrography. Anomalously warm, low-salinity water to depths greater than 50 m during much of our study was indicative of an onshore displacement of the California Current. Upwelling was reduced and delayed relative to other years. The two years differed, however, in the intensity, duration, frequency, and direction of wind events. Larval rockfish abundance was similar in both years of the El Niño, peaking in early February, and was among the highest when compared with estimates from CalCOFI surveys off central California (1951-84). Using larval ages, we determined that median birthdates of shortbelly rockfish were in early- to mid-February both years. Growth rates of larval shortbelly rockfish did not differ among months or between years. Relative to 1993, rockfish larvae were more abundant, and sizes of larval shortbelly were significantly greater at onshore stations in 1992. This coincided with onshore advection of water during the onset of the El Niño, suggesting retention of larvae nearshore. Initiation of upwelling in March and April 1993 and fewer larvae at onshore stations are indicative of greater offshore transport during the second year. Juvenile rockfishes were extremely rare in summer of 1992; in 1993 they were twenty times more abundant and larger. Surviving juvenile shortbelly rockfish were born late during both years; upwelling occurred coincidentally during this period in 1993 but not in 1992. We suggest that substantially higher survival and recruitment of juvenile rockfishes in 1993 was due to increased offshore transport and perhaps lower predation during the larval stages.
JournalFishery Bulletin
Date1996
Volume94
Issue4
Start page766
End page782
ISSN00900656
SubjectsEl Nino, fish larva, fish larvae, fishery oceanography, nearshore assemblages, rockfish, USA, California, Sebastes
NoteCited By (since 1996):34, CODEN: FSYBA

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