Long-Term PIT and T-Bar Anchor Tag Retention Rates in Adult Muskellunge

Mark-recapture studies require knowledge of tag retention rates specific to the tag types, fish species and size, and study duration. We determined the probability of tag loss for passive integrated transponder (PIT) tags implanted into dorsal musculature, T-bar anchor tags attached to dorsal pterygiophores, and both tags in relation to years posttagging for double-marked adult muskellunge Esox masquinongy over a 10-year period. We also used PIT tags as a benchmark to assess the interactive effects of fish length at tagging, sex, and years posttagging on T-bar anchor tag loss rates. Only five instances of PIT tag loss were identified; the calculated probability of a fish's losing its PIT tag was consistently less than 1.0% for up to 10 years posttagging. The probability of T-bar anchor tag loss by muskellunge was related to both the number of years posttagging and the total length (TL) of the fish at tagging. The T-bar anchor tag loss rate 1 year after tagging was 6.5%. Individuals of less than 750 mm TL at tagging had anchor tag loss rates less than 10% for up to 6 years after tagging. However, the proportion of fish losing T-bar anchor tags steadily increased with increasing years posttagging (similar to 30% after 6 years) for larger muskellunge. Fish gender did not influence the probability of T-bar anchor tag loss. Our results indicate that T-bar anchor tags are best suited for short-term applications (<= 1 year) involving adult muskellunge. We recommend use of PIT tags for longer-term tagging studies, particularly for muskellunge larger than 750 mm TL.