Abstract
Larval dispersal is a crucial factor for fish recruitment. For fishes with relatively small-bodied larvae, drift has the potential to play a more important role than active habitat selection in determining larval dispersal; therefore, we expect small-bodied fish larvae to be poorly associated with habitat characteristics. To test this hypothesis, we used as model yellow perch (Perca flavescens), whose larvae are among the smallest among freshwater temperate fishes. Thus, we analysed the habitat association of yellow perch larvae at multiple spatial scales in a large shallow fluvial lake by explicitly modelling directional (e.g. due to water currents) and non-directional (e.g. due to aggregation) spatial patterns. This allowed us to indirectly assess the relative roles of drift (directional process) and potential habitat choice on larval dispersal. Our results give weak support to the drift hypothesis, whereas yellow perch show a strong habitat association at unexpectedly small sizes, when compared to other systems. We found consistent non-directional patterns in larvae distributions at both broad and medium spatial scales but only few significant directional components. The environmental variables alone (e.g. vegetation) generally explained a significant and biologically relevant fraction of the variation in fish larvae distribution data. These results suggest that (i) drift plays a minor role in this shallow system, (ii) larvae display spatial patterns that only partially covary with environmental variables, and (iii) larvae are associated to specific habitats. By suggesting that habitat association potentially includes an active choice component for yellow perch larvae, our results shed new light on the ecology of freshwater fish larvae and should help in building more realistic recruitment models.
Highlights
Larval dispersal is crucial to several fish species, determining, among other things, the chances of individuals to settle in optimal habitats or the level of connectivity among populations [1]
Because most larval stages of fishes have limited locomotion capabilities, processes governing their distribution in large systems should act across multiple spatial scales; passive processes should dominate at broad scales, while active habitat selection should dominate at smaller scales
The distribution of yellow perch larvae in Lake St. Pierre (LSP) revealed in several occasions both directional and non-directional patterns, depending on the spatial scale considered
Summary
Larval dispersal is crucial to several fish species, determining, among other things, the chances of individuals to settle in optimal habitats or the level of connectivity among populations [1]. A better knowledge of the ontogeny of this transition will improve our understanding of dispersal patterns and, in turn, our ability to integrate behavior into dispersal models It is recognized, at least for marine species, that even small larvae can select the habitat in which they settle [2], but there is limited knowledge on the relative roles of drift versus habitat selection in shaping the spatial distribution of fish larvae. The duration of the pelagic period may be even longer in systems driven by marinelike hydrodynamics such as the Great Lakes, with some individuals captured in the pelagic zone after 75 days [3,4] This extended pelagic phase suggests that spatially and temporally variable current patterns could be crucial for yellow perch larvae timing of settlement Whereas Perca spp. habitat shifts were typically studied in lacustrine systems with a narrow littoral zone and a welldefined pelagic habitat [6,7], we have poor knowledge about this phenomenon in systems lacking a true offshore habitat
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