Influence of predatory reef fishes on spatial distribution of Munida gregaria (=M. subrugosa) (Crustacea; Galatheidae) in shallow Patagonian soft bottoms

GALVAN, D; A. PARMA; O. IRIBARNE

JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY

Elsevier

Lugar: New York; Año: 2008 vol. 354 p. 93 - 100

0022-0981

Predation by reef fishes may play an important role in structuring nearby soft-bottom communities. Here we evaluate the hypothesis that the abundance and spatial distribution of an epibenthic mobile organism, the squat lobster Munida gregaria Munida gregaria (=M. subrugosa), is influenced by predation by fishes that shelter in temperate rocky reefs of northern Patagonia. The density of  squat lobsters on sandy bottoms around three reefs, one natural and two artificial, was estimated at increasing distances (0, 5, 15 and 45 m) from the reefs. In one of the artificial reefs a sample was first collected four months after the reef was created, before it was colonized by fish, and again nine months later when a population of reef-dwelling fish had been established. An area between 5 and 19 m wide free of squat lobsters surrounded all colonized reefs, and no effect was evident at a distance of 45 m from the reefs. In contrast, the density of squat lobsters did not vary with distance from the reef in the new, uncolonized, artificial reef. A predation exclusion experiment conducted around both artificial reefs resulted in a larger presence of squat lobsters within exclusion cages than in partial and open cages. The caging experiment provides strong evidence for attributing the halo around the reefs to predation by fishes, and to confirm that off-reef foraging behaviour depletes prey abundance in nearby soft bottoms.