An Approach to Incorporate High Tag Loss in Jolly-Seber Open Population Models Using a Long-Term Walleye Tagging Study

Since very few tag types used on fish have reported tag retention rates of 100%, the “no tag loss” assumption is often violated in Jolly-Seber models.  A method to incorporate tag loss in Jolly-Seber models has not been well defined, thus population parameters may be seriously biased if tag retention is low.  Many tagging studies are designed with the intent of using the Jolly-Seber model where tag retention rates for a specific species in a specific location are unknown.  Subsequent tag retention studies may indicate high tag loss and managers are uncertain how to incorporate these estimates into the population model.  A 22-year walleye tagging database and double tagging study was used to develop a model that estimated the number of walleye that would have been captured if tag retention was 100%.  All linear regression models comparing corrected and uncorrected population parameter estimates (abundance, survival, catchability, and recruitment) were significantly correlated, however, abundance and recruitment estimates were overestimated by 22-25% using the uncorrected model.  The uncorrected model severely overestimated walleye abundance at high population levels (> 5,000 fish).  Model testing indicted that the corrected model population parameters were more precise.   Comparisons of the corrected and uncorrected model for three walleye populations will be described.