Factors influencing the abundance patterns of reef fish functional guilds in two coastal bays, Philippines

Abstract

Reef fish occupy numerous functional groups and play integral roles in maintaining the health of coral reef ecosystems. However, the management and conservation of these fish groups, and thus coral reefs, are hindered by a paucity of information regarding their spatial distribution patterns and the environmental drivers behind these patterns in the Philippines. Therefore, this study quantified the spatial abundance patterns of selected functional fish groups around two coastal bays in the Philippines, and determined which factors influenced these patterns on both small, localised and larger regional scales. A modified Reef Check methodology was utilised to determine the abundance of fish groups and the substrate composition for 15 coral reefs situated in five delineated regions. The abundance of herbivorous, coralivorous, and top predatory fishes were highly variable, both within and between reefs. Significant differences in fish group abundance were found at the reef, but not at the regional level. Commercially important fish groups (Scaridae, Lutjanidae, and Epinephelinae) were dominated by small size classes (less than 20 cm total length). Sites were also found to be variable in their substrate composition and subsistence fishing effort. Generalised Linear Mixed Models highlighted that localised influences of fishing and hard coral cover, rather than larger-scale regional influences, were the most influential on the abundance patterns of herbivorous, coralivorous and top predatory fish groups. This may suggest that the current management approach of localised small-scale marine protected areas (MPAs) may benefit some of these fish communities. However, top predatory fish likely display far-reaching movement patterns that are not encompassed by these small MPAs, and further management efforts are recommended.