Spatially-Varying Population Demographics and Fishery Characteristics of Lake Erie Walleye (Sander Vitreus) Inferred from a Long-Term Tag-Recovery Study

Using a spatial tag-recovery model, we estimated region- and age-specific mortalities and regional movement probabilities using recoveries from a jaw-tagging study initiated in 1990 for Lake Erie Walleye.  The best performing model based on QAIC comparison had age-group-specific movement probabilities, age- and region-specific natural mortalities, and age-group- and region-specific annual fishing mortalities.  Commercial fishing mortalities varied considerably during the study, while recreational fishing mortalities were more static.  Natural mortalities of age-5 and older Walleyes were lower than those of younger fish in all regions, with natural mortalities ranging from 0.30 to 0.40 for age-4 and younger fish and 0.13 to 0.27 for age-5 and older fish.  In Lake Erie’s western basin, age-4 natural mortality was lower than that of age-3 fish.  Sensitivity analyses indicated that some natural mortality estimates were sensitive to prior probability distributions assigned to mortality components and assumed movement probabilities in regions where no tagging was conducted. Movement probabilities in the western basin were greater than those in the central/eastern basin.  The mortalities and movement probabilities estimated in this study should assist in the parameterization and scaling of a spatially-explicit Lake Erie Walleye assessment model, the development of which has been recommended for lake’s quota-management system.