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, model-averaged instantaneous rates (annual) ranged from 0.07 to 0.28. Jaw tag reporting rates, estimated via releases of high-reward tags in 1990 and 2000, varied among tagging years, tagging basins, and commercial and recreational fisheries. In general, tag reporting rates were higher for the recreational fishery (range, 33–55%) than for the commercial fishery (10–17%), and the reporting rates for both fisheries and tagging basins were found to have declined between 1990 and 2000. Uncertainty in the tag reporting rates was greater for the recreational fishery than for the commercial fishery. Our findings will benefit management of the economically important Lake Erie walleye fisheries by providing managers with robust tag shedding and reporting rate estimates, providing more reliable estimates of important dynamic rates (e.g., fishing and natural mortality) by correcting the long-term jaw tagging data set for these previously unaccounted for biases.

Received September 13, 2011; accepted November 30, 2011

ACKNOWLEDGMENTS

This publication is manuscript 2012-02 of the Quantitative Fisheries Center at Michigan State University. Funding for the tagging studies was provided by the Michigan Department of Natural Resources, New York State Department of Environmental Conservation, Ohio Department of Natural Resources, and the Ontario Ministry of Natural Resources. Partial funding for the tag shedding study was provided by the Great Lakes Fish and Wildlife Restoration Act. Monetary rewards for the high-reward tagging studies conducted in 1990 and 2000 were distributed by the Great Lakes Fishery Commission, Ann Arbor, Michigan. Special thanks are extended to P. Kocovsky, M. Bur, M. Porta, B. Edwards, J. Baughman, T. Hartman, J. Tyson, E. Weimer, K. Knight, J. Deller, A. Gorman, T. Bader, R. Zimmer, D. Zeller, B. Beckwith, and D. Fielder for field assistance. We also thank N. Cadigan for his willingness to share SAS code and provide insight for the estimation of tag reporting rates. The authors would like to express our deep gratitude to Robert Haas of the Michigan Department of Natural Resources (retired) for his long-time commitment to understanding the biology of Lake Erie walleyes. Under his direction, walleye tagging studies in the Michigan waters of Lake Erie were initiated in the early 1970s. These early tagging efforts clearly illustrated the migratory nature of Lake Erie walleyes and the need for interagency management strategies and tagging studies. The tagging study was adopted by the Lake Erie Committee walleye task group as a critical component of the walleye management process and became an interagency cooperative effort in the mid-1980s. He successfully lobbied for conducting the high-reward tag studies (1990 and 2000), which further enhanced the value of the tagging data set for estimating exploitation, survival, and natural mortality of walleyes in Lake Erie.