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Positive rheotaxis increases settlement success of walleye (Sander vitreus) larvae in western Lake Erie
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DOI：10.1093/icesjms/fsag116.png)
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Abstract
En 中文
Biophysical models commonly assume passive drift when modeling larval dispersal. Mounting evidence has demonstrated, however, that incorporating larval behavior alters dispersal outcomes. Yet the effects of positive rheotaxis, in which individuals orient and swim against oncoming flow, remain under-investigated. We applied a particle tracking model to evaluate how positive rheotaxis affects the dispersal of larval walleye (Sander vitreus) in western Lake Erie. Informed by laboratory results, three behavioral scenarios were simulated: (i) passive dispersal (case P), where larval velocity (u) equals ambient flow velocity (U) (i.e. |$u = U$|); (ii) semiactive dispersal (case S), in which larvae remain stationary (|$u = 0$|) when the oncoming flow velocity does not exceed the critical velocity (|$U \le {U_{\textit{crit}}}$|), but drift with the flow (|$u = U$|) when |$U \gt {U_{\textit{crit}}}$|; and (iii) active dispersal (case A), in which larvae remain stationary when |$U \le {U_{\textit{crit}}}$|, and swim against the flow at a velocity of |$u = U - {U_{\textit{crit}}}$| when |$U \gt {U_{\textit{crit}}}$|. Results revealed important differences among the three behavioral scenarios. Specifically, settlement density (number of settlers km−2) increased under positive rheotaxis by 24%–158% from case P to S, and by 504%–1065% from P to A. Dispersal kernels shifted toward shorter distances and became progressively steeper from passive to semiactive and active behavioral scenarios, with theoretical local retention increasing by approximately one and two orders of magnitude, respectively. The median-dispersal distance decreased by 30%–39% from P to S and by 84%–95% from P to A, while active rheotaxis greatly reduced mean larval movement velocity relative to passive dispersal. From case P to A, long-distance dispersal declined by 75%–89%, and the proportion of potential successful settlers increased by 42%–60%. By increasing settlement density and reducing large-scale spatial spread, positive rheotaxis may also create conditions favorable for post-settlement aggregation, although schooling behavior itself was not simulated in the model. The findings suggest that larval swimming behavior may be an important factor in Hjort’s aberrant drift hypothesis, with positive rheotaxis mitigating aberrant drift by reducing transport away from favorable habitats. Overall, this study demonstrates that larval swimming behavior, particularly positive rheotaxis, can influence dispersal, retention, and recruitment, thereby refining classical theories and improving predictions of population connectivity.
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