MEPS 317:211-223 (2006)  -  doi:10.3354/meps317211

Spatial variation in structure of an intertidal fish assemblage reflects daily settlement patterns

Amy F. Ritter*, Rikke K. Preisler

Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, 1156 High Street, Santa Cruz, California 95064, USA

ABSTRACT: Patterns of population replenishment for marine organisms with dispersive larvae can be influenced by processes acting prior to, during, or subsequent to larval settlement into adult populations. We investigated the relative importance of settlement and post-settlement processes in determining the population structure of an assemblage of rocky intertidal fishes (the sculpins Clinocottus globiceps, C. recalvus and Oligocottus snyderi) in central California. We monitored the daily arrival of new settlers and the monthly density of other life history stages, comprising recruits, juveniles, and adults, during the peak of the sculpin recruitment season in 2002 and 2003 at 2 intertidal sites. We also used mark–recapture methods in 2003 to estimate differences in post-settlement mortality, and report the results of laboratory studies which indicate that these methods do not bias mortality estimates. The daily settlement and monthly abundance surveys revealed that for both years the differences in species densities between sites were largely consistent across all life history stages, even though the stages reflected different cohorts. There was also no evidence that differences in rates of post-settlement survivorship among species altered the original assemblage structure determined at settlement. Together, these results indicate that processes acting at or prior to settlement are a major determinant of the local population size and structure of intertidal fishes in the study region. This study suggests that a more complete understanding of the relative influence of settlement versus post-settlement processes requires further examination of processes influencing larval dispersal and delivery and the degree to which local populations of marine organisms are open or closed.

KEY WORDS: Settlement · Recruitment · Intertidal zone · Tidepool fishes · Population dynamics · Assemblage structure · Cottidae

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