Cryptic density dependence: the effects of spatial, ontogenetic, and individual variation in reef fish

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Ecologists have long been interested in the factors that drive spatial and temporal variability in population density and structure. In marine reef systems, attention has focused on the role of settlement-the transition of pelagic larvae to a benthic stage-and on density-dependent processes affecting recently settled juveniles. Recent data suggest that co-variance in settlement and subsequent density-dependent survival can obscure the patterns of density dependence at larger scales, a phenomenon called cryptic density dependence. This research will explore the mechanisms that underlie the spatial covariance of settlement and site quality - a process that has received little attention in the standard paradigm. These mechanistic studies of cryptic density dependence will facilitate the development of new frameworks for fish population dynamics that incorporate larval ecology, habitat quality, density dependence, life history, and the patterns and implications of spatial covariance among these factors. More generally, the work provides a specific empirical context, and a general theoretical treatment, of cryptic heterogeneity (hidden individual variation in demographic rates). Training in this project will involve undergraduate and graduate students in quantitative and experimental marine ecology. Additionally, undergraduates will be involved through supervised research courses. Students will be trained in field and lab techniques; they will also have the opportunity to work with collaborators from Australia and New Zealand. This project has broader implications for the management of marine fisheries, including harvested food fisheries (which can seldom be studied experimentally and thus probably exhibit cryptic density dependence) and marine ornamentals (fish and invertebrates harvested for the aquarium trade) which can be studied well but for which there is a significant divide between science and management and policy.