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Identifying migration patterns and spatial ecology of a reef spawning stock of walleye in the western basin of Lake Erie
*Principal Investigator. 1Michigan State University, Center for Systems Integration and Sustainability, 115 Manly Miles Building, East Lansing, MI 48823, USA. 2Ohio Department of Natural Resources, Division of Wildlife, Sandusky Fisheries Research Station, 305 East Shoreline Drive, Sandusky, OH 44870, USA. 3U.S. Geological Survey, Lake Erie Biological Station, Great Lakes Science Center, 6100 Columbus Avenue, Sandusky, OH 44870, USA.
Previous tagging studies conducted with Lake Erie walleye suggests this population consists of multiple discrete spawning aggregations; however, a comprehensive understanding of stock-specific movement patterns, spawning ecology/ phenology, bioenergetics, thermal ecology and vertical distribution is lacking. Walleye from open-lake reef and tributary spawning aggregations were tagged with acoustic transmitters and their movements monitored for up to four years to understand spatial and temporal habitat use, spawning site fidelity, spawning repetitiveness (i.e., do they spawn annually or exhibited “skipped spawning” behavior) and post-spawning movement patterns. Overall, open-water reef walleye (i.e., both sexes) exhibited higher spawning site fidelity than fish tagged in the Maumee River. Male and female walleye exhibited a similar probability (0.10 – 0.15) of skipping a spawning event regardless of spawning local (i.e., open water reef and tributary). Male walleye arrived earlier, departed later and spent more time on the spawning grounds (i.e., tributaries and open-water reefs) than females. Walleye spawning on the open-water reef complex moved out of the western basin earlier than fish spawning in the Maumee River. Movement out of the western basin following the spawning period seemed to be influenced, at least partially, by fish sex and size. Female walleye vacated the western basin earlier than males, and larger (and presumably older) female walleye moved out of the western basin sooner than smaller females; however, a size-dependent pattern for males was not evident. Outmigration of walleye from the Maumee River was approximately two weeks later than fish spawning on the open-water reef complex. Although the majority of fish tagged from western basin spawning populations migrated toward the central and eastern basins following the spawning period, a contingent of the population (4-8%) from the Maumee River migrate annually north toward Lake Huron via the Huron-Erie corridor. Using surgically implanted thermal loggers (i.e., in combination with acoustic transmitters), thermal occupancy was compared between walleye in lakes Erie and Huron. Lake Erie walleye experienced higher temperatures during spring and summer months compared to Lake Huron resulting in Lake Erie walleye growing at nearly double the rate of Lake Huron walleye. Ultimately, these sex-specific differences in growth were attributed to higher forage availability in Lake Erie compared to Lake Huron. The stock-specific movement, spawning ecology and population dynamics information observed during this study provides Lake Erie scientists with a new conceptual model of how this ecologically and economically important fish stock functions within the Great Lakes ecosystem. Consequently, this information has provided Lake Erie managers with a more in-depth understanding of walleye behavior in Lake Erie and can be used to establish sustainable harvest regulations via stock assessment population modeling.