Retention of T-Bar anchor tags for channel catfish in the Red River of the north

Tagging fish for mark–recapture studies is a common practice in fisheries science that is used to estimate population parameters. However, biased estimates may result from an incomplete understanding of tag retention. The objective of this study was to assess tag retention for a large-river population of Channel Catfish Ictalurus punctatus over a 2,196-d period by using both discrete and instantaneous tag-retention models. A total of 3,827 Channel Catfish were double tagged with T-bar anchor tags in the Red River of the North from 2013 to 2016. The number of tagged Channel Catfish that were recaptured from 2013 to 2019 was 227, with 177 individuals retaining both tags and 50 individuals retaining one tag. Tag retention was estimated at 88% over the study interval by using a discrete tag-retention estimator. An instantaneous tag-retention model suggested that initial tag retention was high, while instantaneous tag shedding was 0.00028 (95% CI = 0.00021 to 0.00038). Based on the instantaneous model, tag retention was predicted as 90% (95% CI = 87% to 93%) at the end of the first year and 54% (95% CI = 44% to 64%) at the end of the study interval. When instantaneous estimates of tag retention are obtained, T-bar anchor tags may be appropriate for studies that evaluate population parameters for Channel Catfish over extended periods.