Larval Predation by Barnacles: Effects on Patch Colonization in a Shallow Subtidal Community

Laboratory studies and gut—content analysis suggest that barnacles should be important predators on invertebrate larvae. To determine if predation on larvae limits settlement, we recorded recruitment in artificially produced patches of clear substratum surrounded by monocultures of either living or dead barnacles. Living barnacles inhibited recruitment of colonial ascidians and bryozoans, but had no detectable effect on recruitment of barnacles, serpulid polychaetes, or solitary ascidians. Patch size did not influence the recruitment of any species. The presence of dead barnacle shells influenced spatial pattern of settlement in ascidians and serpulids. Comparison of blank control plates with barnacle—covered plates indicates that these spatial patterns are better explained by larval behavior than by small—scale hydrodynamic effects. Ascidians, which are dominant competitors in this community, settle primarily on shells of dead barnacles rather than on clear primary substratum. Although predation on larvae by barnacles appears to inhibit recruitment of some species, its effects are variable and easily confounded with other determinants of settlement distribution.