Gaya Defense Behavior in Cardinalfish project

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Cardinalfish of the family Apogonidae are small, reef-dwelling fish characterized by dark bands and dots near the base of their tail. Around two hundred and fifty species are distributed throughout the Indo-Pacific region. Several species of cardinalfish are known to inhabit the waters surrounding Pulau Gaya, including Black-striped Cardinalfish, Yellowbelly Cardinalfish, Intermediate Cardinalfish and Singapore Cardinalfish. Cardinalfish are frequently observed taking shelter in various structures throughout the day to avoid predators, however it has not been established whether cardinalfish prefer certain shelters. In the waters around Pulau Gaya, the Long-Spined Urchin is widely distributed, and aggregates in large groups during the day to avoid predation. These clusters form a unique form of protection similar to those provided by corals, and Cardinalfish are one of the few groups noted to associate with both corals and urchins. A two-day study was conducted in a single reef bed off of Padang Point in Pulau Gaya to determine the correlations between cardinalfish defense behavior, and the size of the cardinalfish school and size of the urchin conglomerations. Our hypothesis was that cardinalfish will show a preference towards sea urchin protection over coral protection when given the option. Our basic method was to survey the reef over one and a half hour periods on two separate occasions occurring during the same period of the day. We began the surveys from the same point, and traveled from east to west following the same zig-zag pattern over the reef noting the number of cardinalfish, number of urchins, presence of coral in each particular location, as well as whether they associated with either coral or urchins. Using a logistic regression model, the defensive behavior of cardinalfish relative to the size of each grouping of fish as well as to the amount of urchins present was analyzed. There was significant evidence (p=.0141) that as fish school size increases, a greater proportion of the fish schools tend to associate with coral, while smaller fish schools utilize urchins. In addition, as urchin group number decreased, fish schools were shown to choose corals (p=.0351). This indicates that cardinalfish prefer urchin protection when provided an adequate area of refuge space relative to school size. Further studies of cardinalfish protection preferences could enhance the current understanding of urchin importance in coral reef ecosystems, as well as enrich our knowledge of the relationship between cardinalfish and urchins.