*3.1. Relationship of Reef Fish Assemblages to Habitat Structure*

The results of the multiple linear regressions supported the interpretation that at Serranilla overall fish abundance, biomass, and diversity were related to habitat structure (Table 1). Up to 66% of the variation in measures of reef fish assemblage structure was significantly explained, except for variation in biomass and evenness. Among all the measured explanatory variables, rugosity, and coral cover of branching and brain corals were most often significant. Of the diversity indices, species richness (0D) was the measure with the greatest percentage of variation described (59%), in that case by only one variable (rugosity). In contrast, 66% of variation in the abundance of small parrotfish species was explained by the combination of all six measures of habitat structure (Table 1).


**Table 1.** Habitat structure drivers of reef fish diversity and abundance at Serranilla; regressions of fish assemblage measures against reef habitat measures. The results shown within each pair of lines are for (upper line) linear models using all potential explanatory variables and (lower line) for the best fit model selected using AICc criteria. *p*-values are shown for the adjusted R2 estimates as well as for the entire model.

Abbreviations. Rugo: rugosity; Bran: branching coral; Subm: submassive coral; Sphe: spherical coral; Brain: brain coral.
