Partitioning among grazers of food resources within damselfish territories on a coral reef

Abstract

The net production of the turf-rich algal communities within the territories (mean planar area = 1.43 m 2) of the herbivorous damselfish Stegastes apicalis (De Vis) on Davies Reef, Great Barrier Reef, ranged between 3.116 and 3.732g C·territory −1 ·day −1 and this was partitioned almost entirely among grazers. The most important grazers of this production were the resident damselfish (25 and 38% of net production in winter and summer, respectively), mobile cryptofauna, such as amphipods, copepods, and polychaetes (31% of production in summer), and “invading” fishes, especially scarids (14% of production in winter). Grazing rates of damselfish (mean size 63 g wet wt) increased from 773 mg C · fish −1· day −1 in winter to 1433 mg C · fish −1· day −1 in summer. This damselfish selected mainly fragile filamentous red, e.g., Centroceras clavulatum, Ceramium spp., and Coelothrix irregularis, and blue green algae, Lyngbya sp. Other grazers, e.g., blennies and macroinvertebrates ( Turboand Trochus spp.), were insignificant as consumers of territory food resources because of their low biomass density. The view that damselfish territories are important in reef trophodynamic and nutrient regeneration processes is supported since their cover of the reef flat is extensive, turnover of their productive algal community by grazers is high, and grazer waste products are subsequently released locally.