Factors Affecting Prestocking Coded Wire Tag Loss in Lake Trout Tagged by an Automated System

Abstract

Tag loss is an important consideration in tagging studies. We used two approaches to describe prestocking coded wire tag (CWT) loss in Lake Trout Salvelinus namaycush tagged by an automated tagging system and released in the Laurentian Great Lakes. First, four strains of Lake Trout tagged by an automated system through the Great Lakes Mass Marking Program were observed for up to 254 d to describe how tag loss and adipose fin clip success relates to time posttagging. Second, we also evaluated final tag loss and fin clip success from 197 tag lots from 2011 to 2013 that were tagged with an automated system to explore the factors affecting tag loss and fin clip success, and to compare tag loss and fin clip success rates with those from 1,080 tag lots from 1985 to 2003 that were manually tagged. Coded wire tag losses from experimental lots of four strains of Lake Trout were low and ranged from 2.8% to 5.7%. Coded wire tag losses stabilized 150 d posttagging, when fish had a mean length of 131 mm, which is far longer than that reported for other salmonines (30 d). We developed a descriptive model to correct for time effects on tag loss; tag loss could be estimated with high confidence after 100 d posttagging. Coded wire tag losses varied by genetic strain, possibly due to differences in body size and shape. Fish that lost a CWT were significantly smaller than fish retaining a CWT. In our comparison of the automated system with manual tagging, CWT loss across 197 automated tag lots was highly variable (0.0–14.0%), but it was <5.5% in 86% of samples and less than the loss rates from manually tagged fish (<5.5% in 72% of samples). Our results provide important details for CWT studies on Lake Trout and other species.

Received July 28, 2015; accepted February 7, 2016 Published online June 1, 2016

Acknowledgments

Funding for this work was provided by the Great Lakes Restoration Initiative. John Beckman, Sandy Lind, Sandy Petersen, Nick Berndt, Martha Adams, Mary Rejo, Debra Frostman, and Kyle Krajniak collected data for the time series experiment. We thank Dale Bast (Iron River National Hatchery manager, retired) and his staff for assisting with the time series study, and personnel at the Pendills Creek, Jordan River, and Allegheny River National Fish hatcheries who collected tag and clip loss data prior to stocking. We also appreciate the constructive suggestions of Rachel Van Dam and two anonymous reviewers on earlier drafts of this manuscript. Reference to trade names does not imply endorsement by the U.S. Government. The findings and conclusions in this article are those of the authors and do not necessarily represent the views of the U.S. Fish and Wildlife Service.