Comparing two types of internal tags in juvenile blue crabs

Although methods to tag fish and other vertebrates have been well described, tagging crustaceans, which molt, poses a greater challenge. Tagging very small juveniles, often necessary in population recruitment or stock enhancement studies, presents an ever greater challenge. We compared the success of two tagging techniques in very small (<25 mm carapace, width) juvenile blue crabs (Callinectes sapidus): (1) microwire (also known as coded wire tags) and (2) elastomer (also known as visual implant flourescent elastomer (VIFE) tags). Although growth and long-term mortality did not differ between tagging methods. each method had certain advantages. Crabs tagged with elastomer had lower immediate mortality as a result of the tagging process. Tag retention, short- and long-term and as well as field and laboratory, was higher for microwire than elastomer. Moreover, the micowire tagging process is about 70% faster. As a result of the higher tag retention and faster rate of microwire tagging, this method is recommended for very small juvenile blue crabs and other crustaceans. However, success is likely size-dependent, as better sites of elastomer application are accessible in larger blue crabs and probably other crustaceans as well. Due to its survivorship advantages and relative inexpense, elastomer tagging should not yet be ruled out for larger crustaceans or short-term studies of juveniles. (C) 2004 Elsevier B.V. All rights reserved.