Tagging Juvenile Blue Crabs, Callinectes sapidus, with Microwire Tags: Retention, Survival, and Growth through Multiple Molts

During an 80-day laboratory experiment we analyzed the retention of coded microwire tags implanted into 56 juvenile blue crabs, Callinectes sapidus, and compared their growth and mortality rates with those of an equal number of untagged crabs. The initial size of the crabs ranged from 29-67-mm carapace width as measured to the base of the lateral spines; 83% of the crabs molted at least twice and more than one-third molted 3 times. Though some confounding cannibalism occurred, we concluded that 96-98% of the tagged crabs retained the tag through the first molt, with no known losses through subsequent molts. No differences were evident in mortality between tagged and untagged crabs. Growth, expressed as increase in carapace width, and the intermolt period, were not different between the 2 groups. Microwire tags provide an effective long-term marking system for juvenile and adult blue crabs because (1) retention rate is high, (2) tags have no effect on growth or survival, and (3) large numbers of crabs can be batch-marked efficiently under field conditions.