USE OF IMPLANT MICROTAGS FOR STUDIES ON POPULATIONS OF SMALL REEF FISH

Ecological studies on small reef fish could often be improved by distinguishing among individuals or cohorts within populations, but this has not been possible with conventional tagging methods. Historically, tagging of recently settled juveniles has proven to be particularly necessary and difficult. What is needed is a method for individually recognising small individuals. Here, use of 2 types of implant microtag are verified for this purpose, visible implant fluorescent tags (VIF) and coded wire tags (CWT). Retention rates of these tags were determined when injected into 2 size classes of a coral-reef damselfish, Pomacentrus moluccensis (10 to 20 mm juveniles, 25 to 40 mm adults). The influence of tagging on growth and survivorship was also measured. Microtag retention rates were high: 100% for new settlers and between 80 and 100% for adults. In addition survivorship and growth of juveniles and adults were not significantly different for fish with or without microtags. These microtags should provide the means to understand the importance of processes occurring within a few weeks of settlement and throughout the reef-associated phase of small fishes.