The effects of daily spawning patterns on cleaning dynamics of Thalassoma bifasciatum, bluehead wrasse

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Cleaning is a prevalent behavior on coral reefs. Many fish, including Thalassoma bifasciatum (bluehead wrasse), obtain some portion of their diet from cleaning. Another important behavior of T. bifasciatum is that they engage in group spawning each day around noon. The ratio of male to female initial phase T. bifasciatum increases dramatically with increasing population size. As a result of this sex ratio shift, initial phase spawning comprises a large portion of all T. bifasciatum spawning on reefs with large T. bifasciatum populations. These initial phase individuals are presented a choice: food or reproduction. This study investigates the choice that T. bifasciatum make between cleaning behavior and spawning behavior during their daily spawning period. To study the trade-off between cleaning and mating, T. bifasciatum cleaning stations were observed during mating and non-mating times. Data on each cleaning event and station population were recorded. There was no difference in mean initial phase T. bifasciatum populations at the cleaning stations during mating and non-mating periods (ttest, p = 0.301). There were no differences in the mean number of cleaning events (t-test, p = 0.478) and cleaning time (t-test, p = 0.189) during mating and non-mating periods. Likely explanations for this result include client choice, the opportunistic feeding strategy coupled with the daily spawning habits of T. bifasciatum, and experimental design.

This student research was retrieved from Physis: Journal of Marine Science II (Fall 2007)19: 9-14 from CIEE Bonaire.