Efficacy of passive integrated transponder tags to determine spawning-site visitations by a tropical fish

Abstract

Individual identification of organisms is a crucial part of assessing the processes that influence small-scale distribution patterns and the maintenance of social organizations. This study evaluates the use of passive integrated transponder (PIT) tags to quantify small-scale space use in a marine damselfish, Pomacentrus amboinensis (Pomacentridae). Implanting small PIT tags in the body cavity of fish down to 5.2 g with a hypodermic needle had no adverse effect on mortality or growth over a 47-day tank study. A 63-day field study also showed that tags had no influence on body condition as measured by Fulton’s condition factor (K), gonadosomatic indices, or plasma cortisol levels (a physiological indicator of stress). The utility of PIT-tag technology is illustrated by preliminary information from a study on the diel periodicity of visitations to male nest sites by female P. amboinensis. Information suggests that there is a strong periodicity in visitations. Females first entered the nest site at 03:20 h, with 88% of the total of 4 h 45 min that females spent within a single nest occurring prior to dawn. Despite this, 81% of the total visitations to the nest occurred after dawn, with most being very brief, averaging 17 s. No one female monopolized access to the nest, with nine females accounting for 90% of the time that females spent within the nest site. This methodology will be particularly useful in the study of activity rhythms, patch dynamics, and social interactions in a wide range of marine organisms.