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dc.contributor.authorSchmidt, Laura
dc.date.accessioned2021-05-06T16:19:51Z
dc.date.available2021-05-06T16:19:51Z
dc.date.issued2014-08
dc.identifier.urihttp://digital.library.wisc.edu/1793/81762
dc.description.abstractHistorically, lake trout in Lake Superior supported a large fishery, but stocks collapsed in the lake in the 1950s primarily due to overexploitation and predation by the invasive sea lamprey. Stocking, sea lamprey control, and harvest control were implemented to facilitate stock recovery. Following recovery of lake trout stocks in Lake Superior, agencies developed statistical-catch-at-age (SCAA) models to set harvest quotas for limiting fishing mortality. Stock assessment models were developed for individual lake trout management units and movement among units is assumed negligible. Recent studies have shown that lake trout move among management units. Therefore, I developed a simulation metapopulation model which coupled previously estimated abundance, mortality, and recruitment from SCAA models and movement rates to evaluate future sustainability of lake trout stocks. I simulated two movement scenarios (with and without movement) under varying total instantaneous fishing mortality rates in Apostle Islands region of Lake Superior, to estimate the response of lake trout abundance. I found that movement of lake trout among stocks increased abundance and sustainability of lake trout within Wisconsin waters of Lake Superior. Median abundance of age-4, age-4-and-older, and age-8-and-older lake trout was higher with movement than without movement within eastern Wisconsin waters (WI-2). Abundance in WI-2 steeply declined as fishing mortality increased in the absence of movement, but not with movement, which suggests the WI-2 management zone is functioning as a sink for lake trout in Lake Superior. Other management units in Michigan and Minnesota (MN1-WI1, MI-2, and MI-7) also functioned as sinks for age-4, age-4-and-older, and age-8-and-older lake trout. Abundance in MI-5 was higher with movement than without movement for age-4-and-older and age-8-and-older fish, but not for age-4 fish, so this management unit functioned as a sink for the first two age groups of lake trout but was neither a source nor a sink for age-4 lake trout. Similarly, MN-2 functioned as a sink only for age-8-and-older lake trout, whereas, for age-4 and age-4-and-older lake trout, abundance did not differ with or without movement. Median abundance of age-4, age-4-and-older, and age-8-and-older lake trout was higher without movement than with movement for MN-3, so this management unit functioned as a source for all age classes of lake trout. MI-3 and MI-6 functioned as sources for age-4 and age-4-and-older lake trout, but were not sources or sinks for age-8-and-older lake trout. Median abundance for age-4, age-4-and-older, and age-8-and-older lake trout was not different with or without movement for MN-2 and MI-4. In conclusion, with movement, the lake trout population in eastern Wisconsin was protected from extinction even at high levels of fishing mortality. Without movement, the lake trout population in eastern Wisconsin declined to extinction in less than 100 years. Metapopulation dynamics prevented lake trout stocks from declining in most areas, and functioned differently for younger and older lake trout in some areas. Therefore, accounting for movement in stock assessment models is recommended to better estimate dynamics of lake trout in Lake Superior.en_US
dc.description.sponsorshipThis project was funded by the University of Wisconsin Sea Grant Institute under grants from the National Sea Grant College Program, National Oceanic and Atmospheric Administration (Project Number R/FI-2) and the State of Wisconsin.en_US
dc.language.isoen_USen_US
dc.publisherUniversity of Wisconsin-Stevens Point, College of Natural Resourcesen_US
dc.titleEffect of Movement on Lake-Wide Sustainability of Lake Trout Stocks in Lake Superioren_US
dc.typeThesisen_US


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