A Spatially-Explicit Study Of Prey-Predator Interactions In Larval Fish: Assessing The Influence Of Food And Predator Abundance On Growth And Survival

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We apply a coupled bio-physical model of transport to reconstruct the environmental history of larval radiated shanny in Conception Bay, Newfoundland. The model is applied to data collected during a two week period during which larvae, their food (Copepod nauplii) and their predators (capelin) were monitored in three intensive surveys. Our goal is to determine whether environmentally explicit information can be used to infer the characteristics of individual larvae which are ‘most likely to survive. Backward reconstruction is used to assess the influence of variations in the feeding environment on changes in the growth rates of individual larvae. Forward projections are used to assess the impact of predators on the cumulative density distribution of growth rates on the population of larvae in different areas of the bay. An individual’s past growth has a strong influence on the pattern of growth during the course of our study. There was relatively little influence of current feeding conditions on increment widths for larvae less than 15 days old but there was some evidence of a slight positive influence of increasing prey abundance on growth beyond this age, although this was not statistically significant. Patterns of selective mortality suggest that fast growing individuals suffered higher mortality rates, suggesting they are growing into a predator’s prey field. However, the mortality rates appeared to increase with decreasing predator abundance, based on the drift reconstructions The relationship of growth and mortality with environmental conditions suggests that short-term, small scale variations in environmental history may be difficult to describe accurately in this relatively small system (1000 km2)