MEPS 413:55-67 (2010)  -  DOI: https://doi.org/10.3354/meps08700

ABSTRACT: Understanding the role of predatory fish within a community is essential to predict how ecosystem structure and function may respond to loss of fish species and to ensure conservation strategies are effective. The aim of the present study was to characterize relationships between predatory fish assemblages, sea urchin abundances and ecosystem function and services. By means of diet analyses and direct observations in the field, we identified key fish species with the potential to control the herbivore Diadema aff. antillarum and hence preserve fishing resources and coastal productivity in sublittoral rocky reefs around the Canary Islands. Differences in the composition and relative importance of predatory assemblages were observed along a gradient of fishing intensities comprising highly fished, lesser fished and marine protected areas. Increased fishing activity was associated with lower fish predator richness and higher urchin density. Most measures of predatory performance (frequency of predation, ingestion time, urchin size selection) differed between predatory fish species, showing that most predators of Diadema aff. antillarum are not functionally similar. This level of functional variation highlights the relevance of predator richness in controlling sea urchin populations. Depletion in species diversity leads to a loss of functional roles and cascading effects that may constrain ecosystem processes.

KEY WORDS: Diadema aff. antillarum · Top-down control · Functional diversity · Ecosystem function · Ecosystem service · Fishing resources