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

Since 1990, Lake Erie walleyes Sander vitreus have been tagged annually with jaw tags to better understand population dynamics and ecological characteristics of individual spawning populations.  Although the data collected from this tagging have been used for a variety of purposes (e.g., estimating migration patterns, stock intermixing, and mortality rates), there has been only cursory examination of shedding and reporting rates associated with the long-term tagging 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 tagging method and tagging agency contributed to observed variability in both immediate (within 21 days 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 year, tagging basin, and commercial and recreational fishery.  In general, tag reporting rates were higher for the recreational fishery (range 33-55%) than for the commercial fishery (range 10-17%); 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.  The results of this study will be beneficial for the management of the economically important Lake Erie walleye fishery by providing managers with robust tag shedding and reporting rate estimates.  These estimates provided for more reliable estimates of important dynamic rates such as fishing and natural mortality because recoveries from the long-term jaw tagging dataset could be corrected for these previously unaccounted for biases.