UC Marine Council

The California market squid (Loligo opalescens) has been harvested since the 1860s and it has become the largest fishery in California in terms of tonnage and dollars since 1993. The fishery began in Monterey Bay and then shifted to southern California, where effort has increased steadily since 1983. The California Department of Fish and Game (CDFG) collects information on landings of squid, including tonnage,location, and date of capture. We compared landings data gathered by CDFG with sea surface temperature(SST), upwelling index (UI), the southern oscillation index (SOI), and their respective anomalies. We found that the squid fishery in Monterey Bay expends twice the effort of that in southern California. Squid landings decreased substantially following large El Niño events in 1982−83 and 1997−98, but not following the smaller El Niño events of 1987 and 1992. Spectral analysis revealed autocorrelation at annual and 4.5-year intervals (similar to the time period between El Niño cycles). But this analysis did not reveal any fortnightly or monthly spawning peaks, thus squid spawning did not correlate with tides. A paralarvae density index (PDI) for February correlated well with catch per unit of effort (CPUE) for the following November recruitment of adults to the spawning grounds. This stock– recruitment analysis was significant for 2000−03 (CPUE=8.42+0.41PDI, adjusted coefficient of determination,r2=0.978, P=0.0074). Surveys of squid paralarvae explained 97.8% of the variance for catches of adult squid nine months later. The regression of CPUE on PDI could be used to manage the fishery. Catch limits for the fishery could be set on the basis of paralarvae abundance surveyed nine months earlier.

Toxic diatom blooms of Pseudonitzschia spp. are becoming a severe threat to the California coastal ecosystem and fishery. Generally, eutrophication is considered the likely cause for the "worldwide epidemic" of increased frequency and severity of harmful algal blooms (Smayda, 1990). However, for the domoic acid producing Pseudonitzschia blooms the link is less clear. In order to mitigate these blooms and associated financial loss to fisheries environmental triggers for Pseudonitzschia blooms need to be identified. Based on current knowledge, a model has emerged that would predict a Pseudonitzschia bloom to emerge after the upwelling of a seed population from the deep ocean. The model also predicts that Pseudonitzschia survives near the bottom due to its capability of taking up organic nutrients, which would be enhanced by eutrophication. My research intends to supplement research currently funded by the Coastal Environmental Quality Initiative, to test the following hypothesis aiming at validating this model:

I. Pseudonitzschia is capable of adapting to an extreme light shift, such as associated with an upwelling event from dim light near the bottom to high light at the surface.

II. Pseudonitzschia survival and viability in the dark near the bottom is enhanced due to eutrophication.

While upwelling of seed populations is a natural phenomenon over which state agencies have no control, eutrophication via runoff and sewage outfall can and is being managed by state agencies. If my experiments support the physical/biological coupling of upwelling and sewage effluent as a mechanism driving the initiation of Pseudonitzschia blooms, monitoring programs need to expand to include sampling of the phytoplankton community near the bottom, particularly near areas of sewage and wastewater discharge. Together with results from two Coastal Environmental Quality Initiatives underway, validation of this model will improve the predictability of location and timing of such harmful blooms in the future.

The management of California's coastal resources, particularly nearshore fisheries, is increasingly recognizing the importance of protecting key habitats. The challenge that is emerging is how can we characterize marine habitats? The answer is not simple, since marine habitats include both a substrate and a water column component. Regardless of the substrate affinities of a target species, its performance and dynamics will be linked to characteristics of the surrounding water column. The pelagic component of the habitat sets many physical characteristics, determines the availability of planktonic food, and commonly plays a key role in the delivery of young. Describing habitats solely on the basely of the bottom characteristics is clearly insufficient. Yet, to date habitat descriptions and characterization of essential species habitats include at most only rudimentary characteristics of the water column such as depth.

Here I propose a new approach that applies modern statistical techniques to analyses of time series of spatially explicit oceanographic data for the coast of California (e.g., satellite remote sensing [sea surface temperature, Chl a, and sediment concentrations], CODAR measures of surface circulation, moored arrays of instruments). Unlike benthic characteristics, which are typically consistent over time, water column characteristics are quite dynamic. Therefore habitat descriptions will include both the average state and their pattern of variation over time. The analytical approach will utilize modern statistical procedures that incorporate nonlinear time series analysis and stochastic spatial modeling. The goal will be to develop a framework for defining and mapping oceanographic habitats for the coast of California.

The proposed study will provide important new insight on the spatial and temporal dynamics of marine habitats. The resulting characterizations should have broad application for a number of coastal management programs in California, including the development of nearshore fisheries management plans and the establishment of marine protected areas.