Note
Abundance data from a marine sand flat in the Pacific Northwest reveal a strong negative correlation between abundances of the spionids Pygospio elegans and Pseudopolydora kempi, and hence suggest that competition is occurring between these two deposit-feeding polychaetes. The data also suggest that the specific winner of a competitive encounter is determined by the initial densities of the two species. A density-dependence experiment was performed in the field to test this hypothesis, in which the density of each species was independently varied over four densities in experimental containers.