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Aquatic Biology

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AB 24:151-161 (2016)  -  DOI:

Density, size, and biomass of Diadema mexicanum (Echinoidea) in Eastern Tropical Pacific coral reefs

Juan José Alvarado1,2,*, Jorge Cortés1,2, Hector Guzman3, Héctor Reyes-Bonilla

1Centro de Investigación en Ciencias del Mar y Limnología (CIMAR), Universidad de Costa Rica
2Escuela de Biología, Universidad de Costa Rica; 11501-2060, San José, Costa Rica
3Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Panama
4Departamento de Biología Marina, Universidad Autónoma de Baja California Sur, La Paz, Mexico
*Corresponding author:

ABSTRACT: Diadema is among the most abundant, widely dispersed, and ecologically important genera of sea urchin in tropical shallow waters. D. mexicanum is distributed from the Gulf of California to northern Peru, including the oceanic islands of Revillagigedo, Clipperton, Coco, Malpelo, and Galápagos, and it is one of the most important sea urchin species in Eastern Tropical Pacific (ETP) coral reefs. In the 1980s, El Niño caused high coral mortality, resulting in an increase in macroalgal cover. This resulted in higher sea urchin bioerosion activity, which weakened the reef frameworks. Considering the high vulnerability of the ETP coral reefs, the aim of this study was to determine regional differences in the density, size (test diameter), and biomass of D. mexicanum at 12 localities in 4 countries between 2009 and 2010, and to determine possible causes of these differences. The average density, size, and biomass of D. mexicanum were 0.47 ± 0.15 ind. m-2, 4.38 ± 1.50 cm, and 0.26 ± 0.33 g m-2. The test size frequency that predominated was 2 to 3 cm. Predation by macrophagous fishes seems to be one of the most important factors that explains the presence of low densities and small size of sea urchins throughout the region. The increase in D. mexicanum predators is probably a result of overfishing of top predators.

KEY WORDS: Marine protected area · Biomass · Organic matter · Overfishing · Shelter

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Cite this article as: Alvarado JJ, Cortés J, Guzman H, Reyes‑Bonilla H (2016) Density, size, and biomass of Diadema mexicanum (Echinoidea) in Eastern Tropical Pacific coral reefs. Aquat Biol 24:151-161.

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