Traditional Considerations for Contemporary Tagging Studies: Factors Influencing Acoustic Telemetry Recaptures and Recoveries When Estimating Mortality Components

Recent advances in telemetry technology have led to its increased use for estimating the population dynamics of fish stocks.  However, telemetry studies often fail to account for factors known to bias mortality and population abundance estimates from traditional tag-recapture/recovery studies.  To address the potential for these factors to influence estimates from acoustic tagging studies, we took advantage of a large-scale telemetry study to evaluate transmitter failure, tagging mortality, and transmitter and external tag loss.  Short-term tagging mortality (i.e., 10 days post release) was low, averaging 8% across seven discrete tagging events (range 0-17%).  Of the recaptures and transmitters reported from harvested fish up to 4-years post-tagging, transmitter retention was 100% and transmitter failure was low (<1%).   External tag loss rates were variable and depended upon tag type and the tagging location. Immediate tag retention for t-bar, internal anchor, and loop tags was high (range 0.91-1.0), and chronic shedding rates for the different tag types was 0.42, 0.00, and 0.02, respectively.  Because external tags are used to alert anglers a fish has been tagged, the results of our study demonstrate the importance of accounting for biases associated with tag loss if estimating fishing mortality via contemporary tagging studies is of interest.