Research Document - 1999/065

Tag Loss and Reporting Rates for 1997 and 1998 Cod Tagging Experiments in 3Psc and 3KL.

By N.G. Cadigan and J. Brattey

Abstract

Estimation of fishery exploitation rates from tagging studies requires information on tag-shedding rates and tagging-induced mortality rates, as well as tag reporting rates. In this paper we present statistical analyses of tag reporting and tag loss rates for tag-return data from the 1997 and 1998 cod fisheries off the south coast of Newfoundland in Placentia Bay (3Psc) and off the northeast coast of Newfoundland (3KL). Tag loss is especially important when the time at liberty for tagged fish is relatively long, and this is the case for the data we examine. Inference about tag loss and tag reporting rates are based on the differential recaptures from simultaneous releases of cod tagged with three types of tags: low reward tags, high reward tags, and those from double tagged fish. We use robust and efficient inference methods to estimate the rate at which fish lose tags, and the regional reporting rates for the various tag types.

Our results suggest that the reporting rate for single low-reward tags in Placentia Bay is 63%, and 68% for double low-reward tags. These reporting rates appear the same in 1997 and 1998. In 3KL the reporting rates are slightly higher. Tag loss appears to be higher within the first 15 weeks following release. Approximately 80% of tags are retained after two years.

Complete document (PDF, 232 KB)

Accessibility Notice

This document is available in PDF format. If the document is not accessible to you, please contact the Secretariat to obtain another appropriate format, such as regular print, large print, Braille or audio version.