Community recruitment: Settlement and juvenile survival of seven co-occurring species of sessile marine invertebrates

Recruitment of a group of co-occurring sessile invertebrates (a serpulid polychaete, an oyster, a bryozoan, and several colonial and one solitary ascidian) that encrust floating docks in Pearl Harbor, Hawaii, was studied in August 1985. Daily photographs were taken of acrylic settling plates over a 14 d period, and daily settlement and juvenile mortality were measured. Settlement rates were compared between species and days, while juvenile mortalities were compared between species, days, juvenile ages and densities of juveniles on the plates. Species differed in abundance of both settlers and juveniles, and in rate and pattern of juvenile mortality. Settlement intensity varied between days for some species. Significant juvenile mortality occurred during the 14 d for most species; it appeared to be caused by fish predation. For two species, mortality varied with juvenile age, with older individuals suffering higher mortality. Mortality was density-dependent for some species, increasing with numbers of juveniles on the plates. Mortality patterns varied even within the colonial species. Assessing larval settlement and juvenile mortality for a single species or type of organism in a community thus may not indicate that similar patterns exist for co-occurring species.