Connecting Coastal Marshes Using Movements of Resident and Migratory Fishes

Abstract:

In the Laurentian Great Lakes, diurnal migration of fishes into and out of coastal wetlands is well documented, but movement among wetlands is more poorly understood despite important conservation implications. We assessed movements of typically resident species using mark-recapture. For seven species, only 9 (6.2 %) individuals were recaptured in a wetland different from where they were tagged. Conversely, based on radio-tracking, typically migratory Northern Pike (Esox lucius) moved among wetlands that were 1.4 km apart, although some moved as far as 3.9 km. Results suggest that while the majority of fishes remain in a single wetland throughout the year, a large top predator requires multiple wetlands over comparatively larger areas. Currently, coastal wetlands in Ontario are evaluated for protection if greater than 2 ha, but smaller proximate marshes (within 750 m) can be grouped into complexes. Our results demonstrate that while this distance likely protects fish habitat for most resident fishes, it fails to cover the observed movement patterns of Northern Pike. A modification to this grouping rule for coastal wetlands would delineate more ecologically appropriate complexes by incorporating movement among wetlands by top predators. Delineating larger wetland complexes would protect critical fish habitat and populations in the Great Lakes.