Effect of an artificial reef in Posidonia meadows on fish assemblage and diet of Diplodus annularis

Along the western Mediterranean Sea coast, many artificial reefs have been deployed as an anti-trawling device to protect seagrass (Posidonia oceanica) meadows. These reefs may have important effects on the structure of the associated fish assemblages. We examined changes in fish assemblages and diets of Diplodus annularis related to the presence of reef blocks in Posidonia meadows using non-metric multidimensional scaling. Visual censuses were carried out at monthly intervals during 3 years (19921995). Comparison of the fish assemblages 2 years after deployment indicated differences associated with reef and control habitats. D. annularis, D. vulgaris, Chromis chromis, and Apogon imberbis were the species most responsible for assemblage differences. Gut contents of individual D. annularis collected from the two habitats indicated a different diet, especially for larger fish. Although similar prey were eaten, relative abundance of the different items varied. Apparently, habitat differences contributed to differences in dietary patterns and to the diversity and abundance of fish assemblages. (C) 2002 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights reserved.