Uncertainty of Exploitation Estimates Made from Tag Returns

Authors

L.E. Miranda, U.S. Geological Survey, Biological Resources Division, Mississippi Cooperative Fish and Wildlife Research Unit
R.E. Brock, U.S. Geological Survey, Biological Resources Division, Mississippi Cooperative Fish and Wildlife Research Unit
B.S. Dorr, U.S. Geological Survey, Biological Resources Division, Mississippi Cooperative Fish and Wildlife Research UnitFollow

Document Type

Article

Date of this Version

4-30-2002

Comments

Published in North American Journal of Fisheries Management 22:1358–1363, 2002.

Abstract

Over 6,000 crappies Pomoxis spp. were tagged in five water bodies to estimate exploitation rates by anglers. Exploitation rates were computed as the percentage of tags returned after adjustment for three sources of uncertainty: post-release mortality due to the tagging process, tag loss, and the reporting rate of tagged fish. Confidence intervals around exploitation rates were estimated by re-sampling from the probability distributions of tagging mortality, tag loss, and reporting rate. Estimates of exploitation rates ranged from 17% to 54% among the five study systems. Uncertainty around estimates of tagging mortality, tag loss, and reporting resulted in 90% confidence intervals around the median exploitation rate as narrow as 15 percentage points and as broad as 46 percentage points. The greatest source of estimation error was uncertainty about tag reporting. Because the large investments required by tagging and reward operations produce imprecise estimates of the exploitation rate, it may be worth considering other approaches to estimating it or simply circumventing the exploitation question altogether.