MEPS 289:273-283 (2005)  -  doi:10.3354/meps289273

Effects of small-scale isolation and predation on fish diversity on experimental reefs

Jonathan Belmaker1,2,*, Nadav Shashar2,3, Yaron Ziv1

1The Departments of Life-Sciences, Ben-Gurion University of the Negev, PO Box 653, Beer-Sheva 84105, Israel
2The H. Steinitz Marine Biology Laboratory, The Interuniversity Institute for Marine Sciences, PO Box 469, Eilat 88103, Israel
3The Department of Evolution Systematics and Ecology, The Hebrew University of Jerusalem, Givat Ram,Jerusalem 91904, Israel

ABSTRACT: A positive correlation is often found between fish species diversity on coral reefs and their degree of isolation. We examined whether isolation creates differences in fish assemblages among reefs through changes in predation pressure. First, small artificial reefs were placed at increasing distances from a naturally continuous reef, over a sloping bottom. Species richness and density of each species increased with isolation. Next, artificial reefs were relocated, together with all their fish inhabitants, closer to the natural reef. Following relocation, resident fishes of the artificial reefs exhibited a sharp decline in numbers, while predatory fish density increased. Both video observations of the relocated artificial reefs and the correlation between piscivore aggregation and decline of the resident fishes revealed that the cause of decline was the strong predation around the artificial reefs. The decline was density-dependent, such that the per-capita rate of decline was higher on artificial reefs with higher fish density. This study shows that the impact of piscivores on resident fish is modified by small-scale isolation. The results suggest that the high density of fish on small, isolated reefs is enabled by low predation.

KEY WORDS: Reef fish · Artificial reef · Piscivores · Red Sea

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