Damselfish Territoriality: Influence on Diadema Distribution and Implications for Coral Community Structure

Abstract

Experiments were performed in Discovery Bay (Jamaica, W I.) to determine the relationship between behavior of threespot damselfish Eupornacentrus planifrons Cuvier, and distribution of the common shallow-water echinoid Diaderna antillarum Philippi. E planifrons actively excludes Diadema from its algal lawn, causing a distinct alteration in local distribution of Diaderna on the reef. Physical attacks on the urchin were usually sustained for 2 5 min. The damselfish's agonistic behavior occurred only dunng the day. Diadema densities were higher withln algal lawns at night than during the day but were always significantly lower than the mean density outside. The size of the damselfish's algal lawn was positively correlated with damselfish density, implying that damselfish which occur in aggregations are able to defend larger territories together than they would when occurring alone. The impact of interactions between fishes, urchins and sessile epibenthos are predictable from experimental data derived from a concurrent study. E. planifrons territories are probably sites of locally high mortality in coral spat, particularly in Agaricia and Porites spp. This would result from competition for space with algae and encrusting epifauna. The algal lawns, however, may also represent refuges for other corals such as Favia fragum which are well-adapted to survive competition with other sessile epifauna as well as with algae. Thus, the algal lawns could represent dlscrete patches In the environment within which mortality of dominant species is high and that of rarer species is relatively low, causing an increase in the latter's representation in the benthic community. The net effect of this would be a n overall increase in coral diversity within the community. This interpretation is consistent with hypotheses concerning the role of patch-formation in determining con~munity structure.

Algal cover and sea urchin spatial distribution at Madeira Island (NE Atlantic)

“…Sammarco, 1980;Sammarco and Williams, 1982). It is generally accepted that human activities are responsible for high sea urchin densities because of the removal of predators through over-fishing (e.g.…”

“…(1) Sea urchin densities were measured from July to August, while the water turbulence scale is an annual average, which may account for some of the variation in this dependent variable. (2) Although previous studies have suggested some factors that might explain the distribution of D. antillarum, there are other factors that might have equal importance, such as the aggressive behaviour of territorial pomacentrid fishes (Sammarco and Williams, 1982), and the density of other invertebrate species (Casañas et al, 1998). (3) Neither recruits nor juveniles (test diameter <10 mm) were found during the sampling months, and the inclusion of both recruits and juveniles in addition to adults should be considered in future studies since this may increase the adjusted R 2 value.…”

“…Sammarco et al, 1974;Sammarco, 1980Sammarco, , 1982aCarpenter, 1981Carpenter, , 1984Liddel andOhlhorst, 1986, 1992;Lessios, 1988aLessios, , b, 1995. Several studies have found that the spatial distribution of D. antillarum correlates with a number of other factors, such as the substratum type (Valdez and Villalobos, 1978), structural morphology of the reef, food availability, predation pressure (Weil et al, 1984), aggressive territorial behaviour of fishes (Sammarco and Williams, 1982), and water turbulence (Casañas et al, 1998). However, an integrated analysis of the major factors has not previously been undertaken.…”

A survey of cellular reactions to environmental stress and disease in Caribbean scleractinian corals

“…Normally, tissue may regenerate to cover small lesions very quickly (Bak & Steward-van Es, 1980). Sammarco & Williams (1982) found that damselfish increased the numbers of rarer corals such as Favia because this species is more resistant to algae. From his studies of Pacific damselfish, Potts (1977) concluded that the algal mat caused corals to expend energy to keep surfaces clean, and death followed the exhaustion of metabolic reserves during periods of minimum nutrient availability, Fish and other organisms which prey on corals (Robertson, 1970;Ott & Lewis, 1972;Antonius, 1973;Glynn, 1973;Endean, 1976;Brawley & Adey, 1982) may be responsible for the spread of some of the diseases and microparasites.…”

Damselfish territories: zones of high productivity on coral reefs

“…We have demonstrated that herbivorous damselfish territories, by the nature of their high productivity and extensive cover of the reef substratum, must exert a strong influence on this production. Sammarco & Williams (1982) found that over 50 % of the reef flat on Jamaican back reefs was covered with territories of Eupomacentrus planifrons. The 4 species of damselfish examined by us each occupied territories covering a similarly high proportion of the reef flat (approximately 40 % for Stegastes apicalis) and in which the area1 primary productivity was significantly enhanced (2 to 4 times) over that of the surrounding substratum.…”