Resource use and impact of three herbivorous damselfishes on coral reef communities

Abstract

Territorial damselfish are considered to be functionally important herbivores on coral reefs, promoting the abundance of preferred algae and depleting corals through a variety of 'farming' activities. However, the composition of algal and coral communities inside territories and patterns of feeding selectivity are known for only a few species. Here we compare substrata inside and next to territories of Plectroglyphidodon lacrymatus, P. dickii and Stegastes nigricans, 3 common damselfish in Papua New Guinea, and interpret patterns in relation to diets and patterns of feeding selectivity. The coral assemblages inside territories differed among fish species and also between defended and non-defended areas. Live corals dominated P. dickii territories, while those of P. lacrymatus and S. nigricans were primarily associated with algal substrata. Territories of P. lacrymatus were similar in coral composition to adjacent areas, while those of P. dickii and S. nigricans were associated with particular coral taxa. Territories of the 3 damselfish were similar in algal composition, with mixed turf algae (primarily blue-green algae Polysiphonia spp. and other filamentous red algae) more prominent inside territories and crustose coralline algae more prominent outside. Diets for the 3 species were also similar, as each species was primarily herbivorous and diets consisted of diatoms, blue-green algae, Polysiphonia spp. and other filamentous red algae. An experimental removal of P. lacrymatus showed that they promoted epiphyte loads without influencing macro-algal or coral cover. Our results suggest that while these 3 species of damselfish vary in their interactions with coral reef habitat, they selectively cultivate a similar range of epiphytic food algae on different substrata.

Farming behaviour of reef fishes increases the prevalence of coral disease associated microbes and black band disease

“…It is likely that S. nigricans has a less diverse assemblage of turf algae because they cultivate a thick mat of Polysiphonia sp. (figure 1), a highly filamentous turf that readily retains detritus and is one of the main food sources of Stegastes [64][65][66][67][68]. When cultivated to reach high densities, such as inside S. nigricans's territories, Polysiphonia sp.…”

Food habits of the farmer damselfishStegastes nigricansinferred by stomach content, stable isotope, and fatty acid composition analyses

“…Although the stomach contents of S. nigricans contain large amounts of filamentous algae, they also include amorphous organic matter (Sano et al 1984;Kuo and Shao 1991;Wilson and Bellwood 1997;Jones et al 2006). Stomach content analyses show directly what is ingested, but there are uncertainties in the method; not all ingested material is assimilated, some food items are dissolved in the stomach much more quickly than others, and the method reflects only the feeding during short periods just before capture (Menzel 1959;Feller et al 1979;Michener and Schell 1994).…”

“…nigricans (Jones et al 2006) and >50% of the intestine contents (Wilson and Bellwood 1997). Therefore, in addition to stomach content analysis, biomarkers providing timeintegrated information can be useful tools to determine the origins of these amorphous materials and to define dietary relationships with potential food items of this territorial damselfish in Okinawa.…”

“…This behavior is called "farming" or "gardening" and is well known in fishes and limpets (Branch et al 1992). Territorial damselfishes defend their territories against intruding herbivores and manage farms of filamentous algae as their exclusive feeding sites (Ceccarelli et al 2001;Jones et al 2006). In farms, territorial damselfishes browse mainly on the upright axes of filamentous algae (Hiatt and Strasburg 1960;Hata and Kato 2002), and lyse the cell membranes of these algae through refractory cell walls in highly acidic stomachs for subsequent digestion of cell contents by fish enzymes (Zemke-White et al 1999;2000), and absorb them in the long intestines (Horn 1989;Cleveland and Montgomery 2003).…”

Effects of Multiple Ecological Drivers on Recruitment and Succession of Coral Reef Macroalgal Communities

“…Damselfish (Pomacentridae) belong to the intermediate sized herbivore group as they have limited territories and remove small amounts of algal biomass. However, they are unique since their distinctive territorial behavior affects consumption rates of other grazers (Jones et al, 2006). Because of their foraging habits and different effects on algal communities as compared to other herbivores, they are often referred to as farmers (Ceccarelli et al 2005).…”