Substrate characteristics determine the distribution and abundance of reef and reef-associated fish: A comprehensive study in protected and non-protected coral ecosystems of Sri Lanka.

Abstract

Coral reefs are one of the most productive marine ecosystems that support reefs and reef-associated fish and invertebrates. The abundance and distribution of reef and reef-associated fish species concerning substrate characteristics were empirically ascertained, evaluating protected (Bonavista) and non-protected (Trincomalee) coral reef ecosystems in Sri Lanka. Line Intercept Transect (LIT) and Underwater visual belt transect methods were employed to estimate fish and substrate diversity, distribution, and abundance during the non-monsoonal period. Shannon–Weiner index was employed to compute substrate and fish diversity, while the Similarity Index was computed to compare the similarity of the reef ecosystems. Data were analyzed using CPCe, SPSS, and MS Excel software, wherever applicable. Physicochemical parameters of seawater in the coral reef environs located on the east and southern coasts were indistinguishable (P > 0.05). Eighteen and 34 hard coral species were encountered, all of which accounted for 22.37 ± 1.27% and 68.40 ± 2.93% of the total substrate in the Bonavista and Trincomalee reefs, respectively. Merulinidae and Acroporidae were the dominant coral families and the two families of fish, Labridae and Pomacentridae accounted for the highest number of species and individuals in Bonavista and Trincomalee reefs, respectively. A total of 127 and 109 reef and reef-associated fish species were encountered at Bonavista and Trincomalee reefs, respectively. The number of fish families, species, and individuals was comparatively higher in Bonavista, albeit species diversity and evenness were higher in Trincomalee. The number of species and individuals in Bonavista and Trincomalee reef ecosystems showed a significant positive relationship (P < 0.05) with coral cover and the number of microhabitats. Species diversity at two reef ecosystems showed a positive relationship (P < 0.05) with coral cover and a negative relationship with rubble cover. Species of family Labridae showed a significant positive relationship (P < 0.05) with coral cover and the number of microhabitats, while family Pomacentridae showed strong relationships (P < 0.05) with rock cover. The present study elucidates that relationships between fish species and habitat characteristics are conspicuous and common to both reef ecosystems. And findings help authorities make policy decisions and manage species and reef environs for the long run.