Planning programs to estimate salmon harvest with coded-wire tags

Abstract

Methods are presented for planning individual catch-sampling, tagging, and field-sampling programs to estimate salmon (Oncorhynchus spp.) harvest in recreational and commercial fisheries from several hatchery-produced and wild cohorts through recovery of coded-wire tags. We show how to determine sample sizes sufficiently large to detect harvest and link sample sizes to expenditures through linear and allometric cost functions to determine optimal tagging and catch-sampling rates. Sample sizes that will minimize bias and variance are charted for field-sampling programs designed to estimate the fraction of a cohort with tags. We describe sampling strategies that can be used to detect or to minimize bias in harvest estimates from tag loss, tag-induced mortality, tag-induced straying, and nonrandom sampling. Methods are demonstrated with data on cohorts of chinook (O. tshawytscha) and coho salmon (O. kisutch) from Alaska.