Donald W. Einhouse

Movement of Walleyes in Lakes Erie and St. Clair Inferred from Tag Return and Fisheries Data

Abstract Lake Erie walleyes Sander vitreus support important fisheries and have been managed as one stock, although preliminary tag return and genetic analyses suggest the presence of multiple stocks that migrate among basins within Lake Erie and into other portions of the Great Lakes. We examined temporal and spatial movement and abundance patterns of walleye stocks in the three basins of Lake Erie and in Lake St. Clair with the use of tag return and sport and commercial catch-per-unit effort (CPUE) data from 1990 to 2001. Based on summer tag returns, western basin walleyes migrated to the central and eastern basins of Lake Erie and to Lake St. Clair and southern Lake Huron, while fish in the central and eastern basins of Lake Erie and in Lake St. Clair were primarily caught within the basins where they were tagged. Seasonal changes in sport and commercial effort and CPUE in Lake Erie confirmed the walleye movements suggested by tag return data. Walleyes tagged in the western basin but recaptured in the ...

Retention of Bythotrephes Spines in the Stomachs of Eastern Lake Erie Rainbow Smelt

Abstract The exotic cladoceran Bythotrephes longimanus is an important food resource for eastern Lake Erie rainbow smelt Osmerus mordax. Bythotrephes possesses a long, chitinous caudal spine that is generally used to quantify its presence in fish diet studies despite concerns that it may be retained within fish stomachs longer than other prey items. We investigated spine retention in rainbow smelt collected in the eastern basin of Lake Erie in June (day and night), July (night), and October (night) of 1998 and 1999. To assess differential retention of Bythotrephes spines in rainbow smelt stomachs, we compared counts of Bythotrephes caudal spines to direct counts of Bythotrephes bodies or mandible pairs. Retention of caudal spines was evident in yearling and older (age-1+) rainbow smelt caught during the day in June as well as in age-1+ fish caught at night in July and October and in young-of-year fish captured at night in October. Smelt stomach fullness decreased with time after sunset, indicating lower n...

Estimation of Tag Shedding and Reporting Rates for Lake Erie Jaw-Tagged Walleyes

Abstract Since 1990, walleyes Sander vitreus in Lake Erie have been tagged annually with jaw tags to better understand the population dynamics and ecological characteristics of individual spawning populations. Although the data collected from this tagging program have been used for a variety of management purposes (e.g., estimating migration patterns, stock intermixing, and mortality rates), there has been only cursory examination of the shedding and reporting rates associated with the program. We used double tagging and high-reward tagging experiments to estimate tag shedding and reporting rates for jaw-tagged walleyes in Lake Erie. Double tagging of walleyes with jaw and passive integrated transponder (PIT) tags suggested that the tagging method and tagging agency contributed to the observed variability in both immediate (within 21 d of tagging) retention and chronic jaw tag shedding rates. Agency-specific model-averaged estimates of immediate tag retention ranged from 95% to 99%. For chronic shedding, ...

Resolving Some of the Complexity of a Mixed-Origin Walleye Population in the East Basin of Lake Erie Using a Mark–Recapture Study

Abstract At least two genetically distinct populations of walleye Sander vitreus reproduce in Lake Erie: one west-basin-origin population and one east-basin-origin population. Each year, some west-basin-origin walleyes migrate to the east basin and create a mixed-origin walleye population. Uncertainties associated with this migratory behavior make it difficult to describe the dynamics of the east-basin-origin population. We used mark–recapture analysis to estimate the dynamics of the east-basin-origin walleye population and to measure the contribution of west-basin-origin walleyes to the total walleye harvest in the east basin. Compared with the west-basin-origin walleyes, the east-basin-origin walleyes experienced lower fishing pressure, lower natural mortality, and a higher survival rate. On average, the west-basin-origin walleye migrants comprised about 90% of the annual harvest in the east basin. The number of the west-basin-origin walleyes migrating to the east basin was linearly related to their abu...