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Distribution, Abundance, and Size Composition of Echinoids from Basin Slopes off Southern California





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Distribution, abundance, and size composition of echinoids from basin slopes off southern California by Bruce E. Thompson, Gilbert F. Jones, Jimmy D. Laughlin, and David T. Tsukada, Bull. Southern California Acad. Sci. 86 #3. Four echinoid species are commonly collected from the basin slopes off southern California, and often are the dominant (abundance and biomass) megabenthic species. Allocentrotus fragilis is collected in low densities on the upper slopes (150-480 m) of all basins studied. Brissopsis pacifica inhabits all slope areas of the region and is most abundant mid-slope (300-600 m). It increases in abundance from the northern to southern nearshore basin slopes. Brisaster latifrons is most abundant on upper slopes of the northern nearshore basins and in contrast to B. pacifica, it decreases in abundance to the south. Spatangus californicus is only a minor component of upper slope assemblages. Although all four echinoid species co-occur on the slopes, there are differences in their abundances among the basin slopes and over slope depth.