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The market squid, Loligo opalescens, has been the basis of an important commercial fishery in California since the 1850's. The fishery takes place in northern California and southern California at different times of the year. The northern fishery season (mainly in Monterey Bay) traditionally occurs from April through November (Fig. 1), while the southern fishery (mostly in the Channel Islands vicinity) begins in October and generally lasts through March (Fig. 2). Most squid are caught using lights to attract aggregations to the surface where they are netted with brails, lamparas and purse seines. The method of capture differs significantly from other loliginid fisheries worldwide, since fishing activity occurs directly on spawning sites. Market squid spawn at night and deposit eggs on soft bottom at depths of 10-40 fathoms. Click squid movies to view a number of videos taken with our ROV during nighttime observations of spawning squid in La Jolla Canyon.
In the last decade, increases in catch and price have combined to make market squid the most valuable fishery in the state. Landings peaked in the 1996/97 season (April 1 through March 30, Fig. 3) totaling over 113,000 metric tons (mt) valued at approximately 41 million dollars. As a result of elevated sea surface temperatures attributable to the 1997-98 El Nino event, landings declined dramatically during the 1997/98 season to below 10,000 mt. In the first quarter of 1998, less than 40 mt of squid were landed, compared with over 60,000 mt landed for the same time period in 1997.
Many aspects of the life history of market squid remain unknown. The California Department of Fish and Gameand the National Marine Fisheries Service, recognizing the need for better scientific information on squid, have conducted cooperative research on market squid since 1997. Age and growth of squid has been a top priority since knowledge of growth and longevity is crucial to management of the species. Research at the SWFSC has shown that market squid have a short life span. Market squid live for only 6-8 months after hatching (Fig. 4). This short life span helps to explain the high productivity of the species and how the population recovers from environmental changes such as El Nino .
Because the squid fishery takes place above the spawning grounds where the females lay their eggs, escapement of eggs before capture is key to theproduction of the next generation. From research sampling, female squid have a fixed number of oocytes in their ovaries and die before all oocytes develop and spawn. The realized lifetime fecundity is the potential fecundity (number of oocytes in the ovary just before first spawning) less the residual fecundity (number of oocytes in the ovary after last spawning). Variables that effect the number of oocytes in the ovary are maturity, if spawning has begun, dorsal mantle length, mantle condition index, and the smallest oocyte diameter (Fig. 5). Various models were developed. Using the simplest model for potential fecundity, the realized lifetime fecundity of an 129 mm female was 3010 eggs spawned. Fishery caught squid are routinely sampled. Analyzing the amount of spawning that has taken place prior to capture by the fishery is critical to viability of the population and a possible management tool for the fishery. During sampling from November 1998 to December 1999, we estimated that the average female spawned a sufficient fraction (0.42) of her realized lifetime eggs before capture (Table 1).
To better understand the dynamics of the fishery, the SWFSC has conducted research with NOAA's National Geophysical Data Center to quantify effort in the fishery by surveying lights used by the fishers to attract squid using satellites. Data from 1992-2000 provide fishery independent measures of effort during the recent expansion of the fishery.