Subtidal spawning of the cottid fish Enophrys bison occurs in southern British Columbia, where in the field a smaller subtidal cottid, Asemichthys taylori, exclusively utilizes E. bison nests by overlaying its own eggs on top of the E. bison eggs. In the laboratory, spawning of A. taylori in the absence of E. bison nests was observed to occur adjacent to eggs of another sculpin, Icelinus borealis, but no spawning of A. taylori was observed in the field in association with nests of any fish other than E. bison. The E. bison male guards the composite cluster of egg masses, and the A. taylori eggs hatch faster than the earlier laid E. bison eggs. Enophrys bison embryonic development appears retarded by overlying A. taylori eggs so the spawning by A. taylori on E. bison egg masses is a form of nesting parasitism, a behavior previously unknown among marine fishes. This study is the first report
of interspecific nesting for marine fishes.