Use of fishes as sampling tools for understanding biodiversity and ecosystem functioning in the ocean

Across the globe, regulatory bodies are moving towards an ecosystem-based approach to management (EAM) of oceans. As part of this directive, criteria have been outlined for defining ecologically and biologically significant areas and marine protected areas. One of the first steps in identifying either is the development of an inventory of species' spatial distributions and the identification of habitats used by different life history stages of these species. Many of these data have been gleaned from research vessel trawl surveys that only sample a slice of the ecosystem. Here, for the first time, food habits data collected from a trawl survey were integrated with the original trawl data to improve estimates of species richness, distribution, and habitat associations with the objective of providing additional information for an EAM. The inclusion of stomach content data in creased the number and size range of species ob served: its greatest value was in describing invertebrate and small finfish species richness. We found differences in the spatial patterns and the influence of environmental factors on species richness be tween stomach and trawl samples. We conclude that the addition of stomach data can en rich the definition process for spatial management tools, adding dimensions that would otherwise be missed. This has important implications for EAM since we may not be using all of the resources at our disposal.