Knowledge of spawning phenology may enhance selective barrier passage for wetland obligate fishes

Abstract

Abstract Within the Laurentian Great Lakes, many native fishes use wetlands for spawning; however, these areas are also used by non-native common carp (Cyprinus carpio) that may impart negative ecological impacts. There is interest to manage common carp using barriers to decrease passage to specific habitats (e.g., their spawning sites), but these barriers could also exclude native wetland obligate spawners such as largemouth bass (Micropterus salmoides) and northern pike (Esox lucius). Our objective was to determine if differences in phenologies, specifically, spawning movements could be exploited in shallow areas to operate seasonal barriers that are opened and closed to promote selective fragmentation. Using a long-term dataset from the Cootes Paradise Marsh fishway (Hamilton, Ontario), we generated predictive models based on cumulative growing degree day (CGDD) for all three fishes. These models successfully predicted earlier arrival by all species in a warmer year and delayed spawning movements during a cold year, supporting the role of temperature as a driver of interannual variation in spawning movements. We then compared the fishway model predictions to movement timing to spawning habitat within nearby Toronto Harbour; movement data was derived from acoustic telemetry information. We found that the models performed well and predictions were correlated with movements of all three species, but performance was weakest for northern pike. It is our hope that managers could use these predictive models to assist in the operation of seasonal barriers to optimize control of non-native common carp, while minimizing negative impacts for native species that require access to coastal wetlands.