Daily larval production of Pacific hake (Merluccius productus) off California in 1951-2006

Pacific hake (Merluccius productus) daily larval production at hatching per 10 m(2) from 1951-2006 was estimated based on data collected from California Cooperative Oceanic Fisheries Investigations (CalCOFI) surveys off the California coast from San Diego to San Francisco in January-April, the peak spawning time. CalCOFI cruises covered this area prior to 1985, and have covered it during January surveys since 2003 and other non-CalCOFI surveys. For some years between 1980 and 2003, the CalCOFI survey area reached only to just north of Morro Bay. For those years, the larval production at hatching was estimated using a conversion factor to scale to the entire area. The density of daily Pacific hake larval production fluctuated with major peaks in 1986 and 1987. Minor peaks were in 1952, 1958, 1972, and 1979. The density of daily larval production has been decreasing since 1987 and was particularly low in 2003-06. The decrease of Pacific hake larval production coincided with the increase of sea temperature since the 1980s. This fishery-independent time series should benefit assessments and provide a better understanding of the dynamics of the Pacific hake population.