Meeting Abstract
Body morphology influences swim performance in fishes and is often reflective of natural habitat. In general, fish living in high-flow habitats (e.g., river rapids) tend to have more streamlined bodies and fins designed for steady swimming, while fish from low-flow, structurally complex habitats (e.g., swamps) tend to be maneuverable with large fins that aid in unsteady swimming. Here, we quantified the relationship between morphology and swimming performance across closely related species of wild-caught elephant-nose mormyrid fishes from divergent habitats. A suite of techniques, including geometric morphometrics, were used to characterize differences in body and fin shapes among Campylomormyrus spp. from a high-flow habitat, an open-water species (Gnathonemus petersii), and a swamp-dwelling population of Marcusenius victoriae. We also determined swimming capabilities of each species at four swim speeds (0.5-2.0 body lengths s -1). While our results confirmed morphological differences among species reflect their natural habitats (e.g., high-flow fish are more streamlined than swamp fish), we found a mismatch between morphology and performance. The high-flow Campylomormyrus spp. spent significantly more time swimming unsteadily at every speed compared to G. petersii and M. victoriae. This can be explained, at least in part, by differences in head shape among species, which may influence swimming patterns more than overall body shape. Our results highlight the importance of considering head morphology when studying swimming performance. We suggest future studies in these fishes investigate performance in turbulent flows, as they may be more reflective of the flow regimes they encounter in their natural habitat.
