Predation and habitat depth affect coral reef fish recruitment
Reef fish have a pelagic larval stage and settle onto the reef before transitioning to their juvenile or adult morphologies. Settlement can be dangerous for new recruits and mortality is highest during the first one to two days after settlement. Experiments were conducted to determine the effects of predation and habitat depth on reef fish recruitment. Standard habitat units (SHUs) were created from pieces of Millepora skeleton. Two treatments were created using SHUs. The first contained an SHU placed on the substrate that was open to predation (NC). The second treatment contained an SHU in a wire cage to exclude predators (FC). Two replicates of each treatment were placed in two meters of water and at six meters. New recruits were surveyed twice a week for six weeks (n=11 surveys). SHUs were cleared of recruits and algal growth was removed after each census. Overall recruitment was greater in two meters than six meters of water. Recruitment was also greater in FC treatments than in NC treatments at both two and six meters. Trends in recruit density should not have been observed since recruit censuses were taken as replicates. However, recruitment increased over the course of the experiment, which coincided with the lunar cycle. Seven species of fish were observed over the course of the experiment but only two of these species, the wrasse, Halichoeres bivittatus, and the razorfish, Xyrichtys splendens, were observed at six meters. One species, the pufferfish Canthigaster rostrata, was only observed once.