Behavioural differences in microhabitat use by damselfishes (Pomacentridae): implications for reef fish biodiveristy

There is considerable overlap in use of some resources among species within guilds of coral reef fish. Here, however, we describe two studies indicating behavioural differences in microhabitat use between species of damselfish (Pomacentridae). Differential association with different microhabitats during normal foraging was investigated on fringing reefs in the Egyptian Red Sea. Species present in reef quadrats were tested for an association with features such as substrate cover, coral growth forms and extent of vertical faces. For 9 damselfish species discriminant functions were derived predicting their presence or absence with success rates of 77 to 100%, implying marked association between each fish species and a particular combination of substrates. The number of damselfish species present was found to be highly correlated with various reef characteristics, especially the number of coral growth forms present. Differences in reef zone and substrate use for spawning and nesting by 12 non-territorial damselfish species were investigated in the Maldives. Overlap indices between each species pair for zone and for substrate both showed a predominance of zero values. A combined overlap index was also calculated; 83% had values lower than 0.5, confirming a high degree of resource partitioning between species. These observations support the suggestion that behavioural differences in habitat use between species may be significant in sustaining diversity among coral reef fish.