Abstract

The usefulness of fish community metrics as indicators for Ecosystem-Based Fisheries Management (EBFM) has been mostly investigated in temperate systems. Here, we use 415 coral reef-surveys spanning the Caribbean to assess and compare the potential of four simple fish community metrics, i.e. fish biomass, fish density, mean fish weight and species richness, to separate fishing effects from natural variation at both local (10s of kms) and broad (100 - 1000s of kms) spatial scales. We found that these metrics differed considerably in redundancy, environmental correlates and the spatial scales underlying metric-environment associations. Mean fish weight and fish biomass were largely redundant and sensitive to fishing at both spatial scales, although mean fish weight was better at specifically detecting fishing effects than fish biomass. Fish density and species richness were also largely redundant but sensitive to temperature over broad scales and to macro-algae and relief height over local ones. This redundancy was likely driven by environmental effects on species richness, ultimately affecting fish density. In contrast, mean fish weight and fish density exhibited little redundancy, indicating that they were driven by fundamentally different processes. All four metrics were negatively correlated with macro-algae over broad scales, supporting the value of macro-algae as an indicator of the integrity of entire reef ecosystems. Finally, most of the metric-fishing covariance operated over broad scales, highlighting the need for a Caribbean-wide view of resource status to prevent shifting baselines. Our study clarifies the utility of simple fish community metrics as indicators for EBFM in the Caribbean.

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