Morphological predictors of swimming speed performance in river and reservoir populations of Australian smelt Retropinna semoni

Abstract

Dam construction is a major driver of ecological change in freshwater ecosystems. Fish populations have been shown to diverge in response to different flow velocity habitats, yet adaptations of fish populations to river and reservoir habitats created by dams remains poorly understood. We aimed to evaluate divergence of morphological traits and prolonged swimming speed performance between lotic and lentic populations of Australian smelt Retropinna semoni and quantify the relationship between prolonged swimming speed performance and morphology. Prolonged swimming speed performance was assessed for 15 individuals from each of three river and two reservoir populations of R. semoni using the critical swimming speed test (U crit ). Body shape was characterized using geometric morphometrics, which was combined with fin aspect ratios and standard length to assess morphological divergence among the five populations. Best subsets model‐selection was used to identify the morphological traits that best explain U crit variation among individuals. Our results indicate R. semoni from river populations had significantly higher prolonged swimming speed performance (U crit = 46.61 ± 0.98 cm s −1 ) than reservoir conspecifics (U crit = 35.57 ± 0.83 cm s −1 ; F 1,74 = 58.624, Z = 35.938, P R. semoni sampled from river populations had significantly higher fin aspect ratios (AR caudal = 1.71 ± 0.04 and 1.29 ± 0.02 respectively; F (1,74) = 56.247, Z = 40.107, P pectoral = 1.85 ± 0.03 and 1.33 ± 0.02 respectively; F (1,74) = 7.156, Z = 4.055, P crit was most strongly correlated with pectoral and caudal fin aspect ratios (R 2 adj = 0.973, AIC c = 41.54). Body shape, however, was subject to a three‐way interaction among population, habitat and sex effects (F 3,74 = 1.038. Z = 1.982; P

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