Diet of Damselfishes (Pomacentridae): a multidisciplinary approach

Coral reefs are the marine ecosystem showing the greatest fish diversity. Damselfishes (Pomacentridae) represent, with more than 340 species, one of the most important families in the coral reef environment. Currently their diet is understudied. This work has 2 aims: (i) to characterize the diet of 13 pomacentrid species of the reef of Toliara (Madagascar) and (ii) to investigate if the specific diversity of this family would result from a strong trophic segregation. A multidisciplinary approach including morphological data (teeth, lower jaw-lever mechanics and intestine length), stomach contents and stable isotope analysis were used. The morphological approach and the stomach contents show that each studied species is able to capture small planktonic preys (e.g. copepods). However, the 13 species can be divided into two trophic guilds: alguivores and planktivores (respectively species where the filamentous algae and the planktonic preys count for more than 60% of their diet). Within these two principal classes, the analysis of the stomach contents and stable isotopes permit to define sub-groups : (1) the species having a food behaviour exclusively alguivore or planktivore (> 90% of their diet) (2) species showing a more varied diet by also eating other types of preys such as vagiles and/or sessiles invertebrates. The diet would contribute but could not explain all diversity in Pomacentridae. Some species show a very similar diet. Consequently other ecological factors should be responsible for the reduction of interspecific competitions and for the existence of such diversity.