Perspectives on Design, Use, and Misuse of Fish Tags

Abstract

We examined the capabilities and limitations of coded wire and external fish tags and attempted to develop an improved identification system. Coded wire tags are small implants with relatively low levels of biological effect, but as commonly used they do not facilitate individual identification, information recovery from live fish, or visible recovery. Typical external tags have these features, but are larger and have greater biological effects. We halted efforts to develop external tags with reduced negative effects when we became aware of problems resulting from permanent penetration of skin layers. Alternate approaches led to the development of a tag that is implanted in transparent tissue, and that is externally visible with a discernable code, thus combining useful features of coded wire and external tags. The process of investigating tag performance disclosed inconsistencies and deficiencies in common practices. The perceived need for individual identification appears to be exaggerated. The ability to retrieve information from live fish is important in relatively few studies. The use of large, conspicuous tags to assure recovery is also questionable. Further, in most studies crucial information about tag effectiveness is often absent and infrequently sought. There is need for more testing under specific conditions of use and for conservative assumptions when such testing is absent.