Publication Abstract

Spillover from six western Mediterranean marine protected areas: evidence from artisanal fisheries

This study investigated spillover (biomass export) around six marine protected areas (MPAs) in the western Mediterranean based on catch and effort data from artisanal fisheries. The selected MPAs were Cerbère-Banyuls and Carry-le-Rouet in France, and Medes, Cabrera, Tabarca, and Cabo de Palos in Spain. These MPAs had been functional for more than 8 years and incorporate areas of fisheries closure and restricted use where fishing is limited. We based our study on the hypotheses that in the presence of biomass export: (1) fishing effort would concentrate close to MPA boundaries, and (2) fishery production, expressed as catch per unit area (CPUA), would be highest near MPA boundaries and decrease with distance. We selected data from 14 fishing tactics using gill nets, trammel nets and bottom long lines targeting sparids, mullids, serranids, scorpaenids and palinurids. We analyzed the spatial distribution of effort, fishery production and revenues per unit area using generalized additive models (GAMs) and tested regression slopes of effort density and CPUA with distance to closure boundaries using generalized linear models (GLMs). GAMs helped recognize habitat discontinuities or ‘hot spots’ (areas of high production) in the vicinity of the MPAs and to identify the extent of potential effects of fishery closures on adjacent effort and catches in order to implement GLMs. We found evidence of effort concentration and high fishery production near fisheries closures for all fishing tactics analyzed and significant negative slopes for most. With a few exceptions revenues followed similar trends to CPUA. Significant negative slopes from GLM of effort density and CPUA with distance from fisheries closures were interpreted as indicative of biomass export where habitats across closure boundaries had some degree of continuity. Significant production gradients extended 700 to 2500 m from fisheries closure boundaries and varied from shallow slopes in the Sparid gill net and long line tactics of Tabarca to steep slopes in the trammel net tactics for Lobster in Cabo de Palos and Banyuls and for Mullus in Carry.

Reference:

R. Goñi, S. Adlerstein, D. Alvarez-Berastegui, A. Forcada, O. Reñones, G.Criquet, S. Polti, G. Cadiou, C. Valle, P. Lenfant, P. Bonhomme, A. Pérez-Ruzafa, J. Sánchez-Lizaso, J. A. García-Charton, G. Bernard, V. Stelzenmüller*, S. Planes (2008) Spillover from six western Mediterranean marine protected areas: evidence from artisanal fisheries. Marine Ecology Progress Series, 366: 159-174 (2008)