Retention Rates of Passive Integrated Transponder Tags, Visible Implant Elastomer Tags, and Maxillary Marks in Wild Trout

Abstract

AbstractTagging or marking is a common method to identify individuals or groups of fish, but these tools are compromised if tags or marks are shed or deteriorate over time. We evaluated retention rates of passive integrated transponder (PIT) tags, visible implant elastomer (VIE) tags, and maxillary clips in stream‐dwelling Yellowstone Cutthroat Trout Oncorhynchus clarkii bouvieri and Rainbow Trout O. mykiss of spawning size. We tagged 2,891 fish ≥150 mm TL with PIT tags in the body cavity, muscle tissue posterior to the cleithrum, or muscle tissue ventral to the dorsal fin. Retention of PIT tags in the body cavity of fish at large for 1 year (72.1%) was lower than those implanted in the dorsal musculature (94.1%) or cleithrum (83.5%) locations. For PIT tags implanted in the body cavity, retention was lower for females (59.4%) than males (89.7%), suggesting that PIT tags implanted in the body cavity were expelled with eggs during spawning events. Retention of PIT tags implanted in the cleithrum and dorsal musculature were unaffected by sex, but retention rates decreased as body size increased for the body cavity tagging location. Annual growth rates were not affected by any PIT tag location. We observed a PIT tag failure rate of 1.7%. The likelihood of a PIT tag being retained in muscle tissue after filleting the fish was highest for the dorsal musculature location (65.1%), followed by the cleithrum (64.9%) and body cavity (4.0%) locations. One‐year retention rates were 95.4% for VIE tags and 93.0% for maxillary clips. While our results demonstrate higher PIT tag retention in the musculature than the body cavity, human consumption concerns may prohibit the use of musculature implantation where angler harvest is possible.Received January 28, 2016; accepted May 11, 2016 Published online August 31, 2016