Evaluation of a mark-recapture procedure to assess the catchability rate of the Tyee test fishing gill-net


Estimates of the Tyee test fishery catchability rate (i.e., the fraction of fish present which are captured during a fishing period) are combined with the number of steelhead captured to produce an estimate of total number of steelhead entering the Skeena. The accuracy of catchability estimates that have historically been used for steelhead at Tyee is unknown, resulting in much uncertainty about the true number of steelhead migrating up the Skeena each year. This report uses simulation modeling to evaluate the potential costs and benefits of different implementations of a proposed tagging program that may improve the accuracy of the Tyee catchability estimate. The report identifies the most cost-effective options and discusses tradeoffs between program cost and the levels of precision and accuracy that can be achieved.