Effects of habitat on spillover from marine protected areas to artisanal fisheries

Abstract

Marine protected areas (MPAs) potentially enhance the long-term sustainability of coastal fish resources that have been overexploited. The types and quality of habitats, both inside and outside the MPAs, may determine the likelihood of migration by fish to surrounding unprotected areas where spillover to fisheries occurs. We assessed whether MPAs enhanced catches of artisanal fisheries, using an experimental fishing study with the same fishing gear as that used by local fishers. This approach allowed us to test the hypothesis of increased catches along the borders of MPAs in comparison with those in other fishing grounds located at medium and far distances from 3 Mediterranean MPAs: Tabarca Marine Reserve, Carry-le-Rouet Marine Reserve and Cerbère-Banyuls Marine Reserve. Surveys were done over 2 homogeneous habitats (Posidonia oceanica meadow and sand), in 3 different seasons. Catches were significantly higher for some species near the borders of the MPAs when fishing on P. oceanica meadows, but not when fishing on sandy bottoms. The spillover effect appears to be limited by a lack of continuous suitable habitat through the boundaries of the MPA. Some of the species that showed a significant response to protection and concurrent higher catches near the MPA borders, such as Dentex dentex, Mullus surmuletus, Phycis phycis, Sciaena umbra and Scorpaena porcus, are target species of artisanal fisheries. Although we found that the spatial scale of the spillover-induced density gradient was localized, it was sufficient to provide local benefits to artisanal fisheries. We conclude that spillover effects are not a universal consequence of siting MPAs in temperate waters and that they are related to the distribution of habitats inside and around MPAs.

A small-scale fishery near a rocky littoral marine reserve in the northwestern Mediterranean (Medes Islands) after two decades of fishing prohibition

“…Spill-over from marine reserves of the characteristics of the Medes Islands (small, rocky, coastal reserve), evidenced by a local concentration of fishing effort around the borders, has been demonstrated to occur within a few hundreds of metres around the protected areas and to be related to the distribution of habitats inside and around the protected area (Stelzenmüller et al 2007, 2008, Harmelin-Vivien et al 2008, Forcada et al 2009). Halpern and Warner (2003) argue that a single general design of a network of reserves of moderate size and variable spacing can meet the needs and goals of most stakeholders interested in marine resources, but if biomass export from marine reserves takes place at small spatial scales, Mediterranean reserves may be too far apart to act as a network at regional scale (Claudet et al 2008).…”

Spillover from marine reserves and the replenishment of fished stocks

“…Finally, spillover estimates may be spurious if underlying habitat heterogeneity instead drives abundance patterns. However, there is no evidence that reserves are sited in better habitat Lester et al 2009), although there is evidence that spillover is facilitated by habitat continuity across reserve boundaries (Forcada et al 2009). Furthermore, habitat protection provided by a reserve could actually decrease the potential for spillover if habitat quality drives abundance patterns and therefore fish preferentially remain inside the reserve (Rodwell et al 2003;Forcada et al 2008).…”

Simulation of the combined effects of artisanal and recreational fisheries on a Mediterranean MPA ecosystem using a trophic model

“…Our model cannot take spillover into account, an essential process by which MPAs sustain fishing activity in their neighboring areas (Pérez-Ruzafa et al 2008, Forcada et al 2009). However, all fishing activities tend to concentrate in the vicinity of no-take areas, which may lessen the spillover effect at a regional scale (Goni et al 2008, Stelzenmüller et al 2008.…”

“…These restriction levels are often a result of a compromise between conservationists and extractive user groups (professional and recreational). However, positive reserve effects such as the spillover of biomass to professional fisheries (Forcada et al 2009) have not reversed a decline in some Mediterranean artisanal fisheries (Gómez et al 2006). Thus, the sustainability of artisanal fisheries on Mediterranean coasts is becoming ever more challenging, and there is increasing pressure from recreational fisheries which may further weaken such traditional socio-economic activities.…”