Reference | Mattson, M. T., B. R. Friedman, D. J. Dunning, and Q. E. Ross. 1990. Magnetic tag detection efficiency for Hudson River striped bass. American Fisheries Society Symposium 7:267-271. |
Abstract | The objective of this study was to quantify tag detection efficiency in recovery efforts for striped bass Morone saxatilis from the Hudson River Hatchery. Two types of detection errors were observed, type I or failure to detect a tag when one was present (false negative); and type II or detection of a tag when none was present (false positive). Since 1983, more than 1.3 million hatchery-reared fingerlings striped bass have been released in the Hudson River. Each of these fish was tagged with an internal magnetic coded wire tag. More than 64,000 striped bass have been caught in four annual winter-spring trawling periods since 1984. During trawling, all fish were examined for magnetic tags with a metal detector. All fish registering a positive response on the detector were taken to the laboratory for removal and reading of the magnetic tags. As a test for type-I-errors, a random sample of 3,805 striped bass was first passed through the detector used in the field and then through a tube-shaped detector with 100% efficiency for confirmation. Two out of 26 tagged fish (7.7%) escaped detection with the detector used in the field. In tests of type-II-errors, this detector falsely indicated that magnetic tags were present in 12 (3.4%) of the 348 fish that gave a positive response. Fishhooks (1.7%), metal particles (0.3%), other agency tags (0.3%), and false signals due to boat motion (1.1%) were four sources of false positive results identified in this study. Removal and reading of magnetic tags in the laboratory was, therefore, an important part of this program, because it permitted verification of the tag origin and the hatchery cohort, as well as recognition of sources of error due to false positive results. |
Tag | Coded Wire Tag (CWT) |
Objective | Evaluate tags |