Author(s): Shelby Richins , Kare Tonning

Presentation: poster

Coral reef fish population structures vary with tidal movements. Fishes use tidal movements to guide transportation, feeding, predator avoidance, and reproduction. Utilization of tidal movements can also be considered an energy saving behavior. This study focused on the abundance of parrotfish (Scaridae) on the reef flat of Heron Island, Australia during ebb, low, flood and high tide. Seventy-three 5-min transects were preformed over two consecutive days, 22 and 23 January 2013. Total number of parrotfish, regardless of species and sex, over 20 cm were counted while snorkeling each transect. 1381 parrotfish were counted overall. A Kruskal-Wallis test found significant difference in the numbers observed at different tides (P =< 0.001). Parrotfish abundance on the reef flat peaked at ebb tide with a mean 30 parrotfish per transect. Our results support the hypothesis that parrotfish participate in tidal migrations on Heron Reef. Predator avoidance of species of Carcharhinius, reef sharks, may help to explain lower parrotfish numbers during flood and high tide than during ebb tide. Knowledge of the movement of parrotfish aids the design of future census studies. Parrotfish movements and distributions are relevant to coral reef ecology due to their role in algae consumption and overall coral health.

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