Internal and External Tags

Identification of fish stocks is necessary for allocation of catch among competing fisheries (nationally or internationally), management of highly migratory stocks, recognition and protection of nursery and spawning areas, and development of optimal harvest and monitoring strategies. Tagging is one of several techniques that have been used to analyze stock composition, separation, and identity in time and space, providing the basis for subsequent regulation and management. External and internal tags have been used for centuries as markers on marine and freshwater fishes for the purpose of identification and information retrieval. This chapter focuses on the use of conventional tagging methods (i.e., conventional tags and deliberately applied marks) and their applications for identifying stocks, excluding electronic tags and natural marks. When referring to a mark-recapture study or marking/tagging in general, it is assumed that either a mark, a tag, or both have been applied to the fish. Further, the review is limited to finfish. The aim of this chapter is to provide a summary and critique of conventional tagging methods and applications in stock identification.