Early life history studies of prey–predator interactions: quantifying the stochastic individual responses to environmental variability

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Abstract
Laboratory evidence shows that growth and survival of larval fish are strongly affected by variations in prey and predators; field evidence, in general, does not. This discrepancy may be partly due to the mismatch of scales at which manipulative and observational studies are conducted, or perhaps field studies are somehow not detecting the variable component of the larvae or their environment. I discuss potentially important variable features of fish larvae and their environment and show how mean values can be misleading. Using data from several field studies dealing with the growth and mortality of radiated shanny (Ulvaria subbifurcata) larvae, I illustrate how observational programs can miss important variation. I show evidence of how differences among individuals may lead to varying responses to fluctuations in prey availability. I also discuss issues concerning the level of variability in environmental conditions that may be described by standard survey methods used in the study of larval fish. The examples are intended to serve as illustration of the need to better describe the underlying stochastic structure of environmental conditions to understand early life dynamics. Résumé : Bien que les données de laboratoire démontrent que les variations des proies et des prédateurs affectent for- tement la croissance et la survie des larves de poissons, les données de terrain ne le font généralement pas. Cette con- tradiction peut en partie être due à un désaccord d'échelle entre les observations de terrain et les expériences de