A Comparison of Elastomer Marks and Fin Clips as Marking Techniques for Walleye

Abstract

Two marking techniques, fin removal and visible implant elastomer, were evaluated in walleye Sander vitreus. Although fin-clipping is widely practiced, research results have been ambiguous as to whether the technique is harmful to fish over the long term. We attempted to determine over a 7-year period whether elastomer marking might have significant benefits to growth and survival of walleye when compared with fish given a single fin clip. We also evaluated the long-term detection rates of elastomer marks as well as their cost-effectiveness. Each year for 5 years we marked and stocked an average of 8,000 extended-growth walleye fingerlings in the lower Milwaukee River, Wisconsin, as part of a project to reintroduce walleyes to the Milwaukee River estuary. One-half were given a single fin clip and one-half were given an elastomer mark. Fin clips and elastomer colors were changed each year. Fish were recaptured the following year by means of electrofishing gear. We found no significant differences in survival or growth rates between the differentially marked fish. We also found that tag detection in recaptured fish over the long term was 82.5% for fish originally marked with elastomer. The cost associated with elastomer marking was US$0.40 per mark while the cost of fin clipping was $0.03 per mark. We concluded that a single fin clip was the more desirable technique for marking walleyes.