Variation among bays in spatiotemporal aggregation of Baltic Sea pike highlights management complexity

Understanding the movement ecology of fish communities is necessary to take effective management actions that aim reverse population declines, especially in stocks containing sympatric subpopulations with local adaptations, such as Northern pike (Esox lucius) Baltic Sea. We followed and survival adult for one year by tagging 198 individuals an estuary (an anadromous subpopulation) well two neighbouring bays (individuals unknown origin) acoustic transmitters. found was vital sustaining coastal stock, mainly inhabited a area radius 3 km aggregated large numbers several months prior spawning. Management should thus prioritise identify, restore, protect estuaries from exploitation. The demonstrated distinct differences spatiotemporal aggregations no to, during, spawning bay without estuaries. habitat choice during season suggests 92% sampled adjacent belong subpopulation, while 94% subpopulation(s) resident brackish spawners. Survival tagged 84% suggest low mortality fisheries top predators, which have been proposed threats populations other areas Together, these results call high resolution highlight importance detailed data.