Nonlethal Batch Identification of Atlantic Salmon Using Coded Wire Tags

Abstract

AbstractHatchery fish are a valuable asset to and often an essential component of endangered species recovery programs. The recovery program for Atlantic Salmon Salmo salar in the Penobscot River, Maine, uses multiple life stages of hatchery fish. Correct identification of returning adults is vital to assess the contribution of each stocked life stage to overall Atlantic Salmon returns. We investigated the use of coded wire tags (CWTs) implanted into various body locations of salmon parr to determine whether the tags could be used as a nonlethal batch identifier after recapture. We tagged 200 (four groups of ~50) Atlantic Salmon parr with CWTs in four different anatomical locations (right and left dorsal and right and left adipose areas) using a Northwest Marine Technology (NMT) handheld multishot injector. We used an additional 51 nontagged parr as a control. We examined fish for CWTs using a NMT blue handheld wand and kept track of individuals using PIT tags. We monitored CWT recovery, correct identification of CWT location, growth rates for all tagged groups, and growth rates for the control group. Tag recovery was 94.7% at 28 months posttagging. Correct identification of CWT location improved with each sampling event to 88.3% at 28 months. Tag location did not affect growth rates, but we found a significant difference between tag location and tag recovery. The left dorsal and left adipose areas had the highest recovery rates. Tagging fish in different anatomical locations with CWTs can provide a minimally invasive batch mark when benign recovery is desired.Received June 16, 2015; accepted May 25, 2016 Published online August 30, 2016