Spatiotemporal Patterns of Representative Groundfish Species in the California Current Large Marine Ecosystem

Conservation of coastal marine fish populations could benefit from a better understanding of the spatiotemporal patterns of the fish species involved. While management plans obviously track populations over time and within distinct ocean zones, they usually do not account for finer grained spatial patterns of the species being studied. As a result, the potential efficacy of any given management program could be increased if these spatiotemporal patterns were better understood. In this research project, we quantified the spatiotemporal patterns of 17 representative fish species that are commonly found on the continental shelf within the California Current Large Marine Ecosystem (CCLME). We used georeferenced groundfish trawl survey data from 2003 to 2009, collected by the Northwest Fisheries Science Center (National Oceanic and Atmospheric Administration). We only used data collected on the continental shelf within the CCLME. We calculated the centroid or mean center of each species for each year using biomass and abundance as weighting factors. We then measured the variance in location of the mean centers for all years and characterized latitudinal patterns in the species distributions over time. We also calculated the variance and temporal trends in the weighted mean depth of each species. We tested for significance in the latitudinal and depth trends over time by running linear regressions on the mean center locations as a function of year. There was considerable interspecific variation in the clustering of mean center locations as well as variance of those locations over time. Overall, there were not any trends across species with regard to either northerly or southerly shifts in mean centers over time. However, three species exhibited statistically significant latitudinal trends (northerly or southerly) in their mean center locations from 2003-2009. While most of the 17 species exhibited a trend towards deeper water over time, only four of the species had statistically significant shifts. Our results suggest that the representative species in this study do not have homogenous distributions over space and time, and the latitudinal and depth shifts observed in some species can be substantial. Incorporating this information in future management plans may reduce the uncertainty associated with assessing the population dynamics of the various species.