Swimming performance of marine fish larvae: review of a universal trait under ecological and environmental pressure

The larval phase of marine teleost fishes is characterized by important morphological and physiological modifications. Many of these modifications improve the larvae’s ability to swim, which satisfies a suite of crucial biological and ecological functions. Indeed, larval fish swimming performance has been considered a good proxy for overall condition, a predictor for growth and survival, and particularly helpful in assessing effects of natural and anthropogenic stress. Several methodologies have been developed to test larval fish swimming performance; however, measured swimming capabilities can strongly depend on the methodology utilised and developmental stage investigated. The aims of this review were, therefore, to link the ontogenetic development of swimming performance in early life stages of marine fishes, particularly the anatomical and physiological processes around the fins, muscles, and gills, with both the experimental methodologies used and the environmental stressors tested. We conducted a literature search and found 156 research papers relevant to swimming performance of marine teleost fish larvae. We found swimming performance to be highly variable among species and driven by temperature. In a meta-analysis focusing on the impacts of environmental stress on larval swimming performance, we found that prey reduction had the greatest impact on swimming. Methods used to evaluate swimming should keep the ontogenetic stage a focus, as forced swimming experiments are unfit for larvae prior to flexion of the notochord. Overall, while the data are deficient in some areas, we are able to highlight where the field of larval fish swimming could be directed and provide insight into which methods are best used under certain ecological scenarios, environmental stressors, and developmental stages.