@article {470,
	title = {Fish predation and the structure of the sea urchin Paracentrotus lividus populations in the NW Mediterranean},
	journal = {Marine Ecology Progress Series},
	volume = {140},
	year = {1996},
	abstract = {<p>Large differences in the sea urchin Paracentrotus lividus (Lamarck)  population structure have been observed in the NW Mediterranean.  Differences have been attributed to removal of predatory fish through  human fishing activities. This study attempted to determine the effect  of predation by fishes on sea urchin population structure. Three  infralittoral areas (2 within a marine reserve with a high density of  predatory fish, and 1 within an unprotected area with a low density of  predatory fish) were studied to compare population structure differences  attributable to differing fish predation pressure. P lividus  populations were 3 to 4x denser and predation rates were -5x lower in  the unprotected site than in the protected sites. Within the reserve,  fish accounted for 100\% of the predation. P lividus individual mean size  was lower within the protected sites than in the unprotected site.  Size-frequency distributions showed a negative exponential pattern for P  llividus within the reserve, and a bimodal pattern outside the reserve.  The urchins showed a crevice-dwelling behaviour in response to the  intense predation in the marine reserve. Within the reserve, P lividus  population structure appears to be determined by predation by fish. In  contrast, in the unprotected area, where the predation rate is much  lower, P lividus population structure appears to be determined by  recruitment rate. We suggest that a recent increase in P lividus  abundance on infralittoral rocky bottoms in the NW Mediterranean, where  urchins are not harvested, is caused by human fishing activities. Since P  lividus is the major benthic herbivore in the NW Mediterranean, fishing  level may, due to cascading effects, determine the structure of benthic  infralittoral communities.</p>},
	keywords = {comparison, density, distribution, echinoderm, fish, fish assemblage, fishery impact, marine protected area, marine reserve, Medes, Mediterranean sea, Paracentrotus lividus, population, predation, protected area, recruitment, rocky shore, sea urchin, size, unprotected area, western Mediterranea},
	author = {E. Sala and M. Zabala}
}
