Coral reef planktivores are important to coral reefs by concentrating and delivering nutrients and allochthonous carbon from the plankton to reef building corals. In an otherwise very oligotrophic system this function may be of major importance. Planktivorous Damselfish (Pomicentridae) were analysed for prey selectivity through enumeration of stomach contents. Simultaneous plankton tows were conducted to establish the plankton community composition of the waters they were taken from. There was a statistically significant variation between the stomach composition and that of the water column. While there was not a significant difference among Simpson’s diversity indices of the stomach contents, there was a significant difference between the mean diversity indices for the reef zones. The diversity index of the fish stomachs (.13 of back flat fishes and .15 of front flat fishes) was found to be significantly different from diversity index of the water column (.37 of the back flat and .36 of the front flat) Chesson’s index of selectivity was calculated from the average number of individuals per plankton category within each species and the difference between these calculated values were found to be statistically significant. Amphipods were heavily selected for, while Chaetognaths, Pteropods, and gelatinous organisms were completely avoided, possibly due to chemical defenses. The combined average selectivity of back flat fishes was compared to that of front flat fishes and no statistically significant difference was found. The combined averages were not significant, but the difference between the means of individual fish was found to be significant. This supports the idea that the selectivity of each species is independent of reef zone and possibly confounded by another variable, perhaps individual size (total length in mm). This led to an acceptance of the second null hypothesis (H0b) which states that there is no statistically significant difference in the selectivity between fronflat fishes and back flat fishes. Future study should be conducted to asses the size preferenceof planktivores as well as the changes in selectivity along the reef flat within one species.
Animal Sciences | Aquaculture and Fisheries | Terrestrial and Aquatic Ecology
O'Hare, James, "Prey Selectivity of Planktivorous Fish: Analysis of Stomach Contents in Four Pomacentrids at Lizard Island, Great Barrier Reef" (2008). Independent Study Project (ISP) Collection. 54.