No abstract

Marine reserves have been advocated worldwide as conservation and fishery management tools. It is argued that they can protect ecosystems and also benefit fisheries via density-dependent spillover of adults and enhanced larval dispersal into fishing areas. However, while evidence has shown that marine reserves can meet conservation targets, their effects on fisheries are less understood. In particular, the basic question of if and over what temporal and spatial scales reserves can benefit fished populations via larval dispersal remains unanswered. We tested predictions of a larval transport model for a marine reserve network in the Gulf of California, Mexico, via field oceanography and repeated density counts of recently settled juvenile commercial mollusks before and after reserve establishment. We show that local retention of larvae within a reserve network can take place with enhanced, but spatially-explicit, recruitment to local fisheries. Enhancement occurred rapidly (2 yrs), with up to a three-fold increase in density of juveniles found in fished areas at the downstream edge of the reserve network, but other fishing areas within the network were unaffected. These findings were consistent with our model predictions. Our findings underscore the potential benefits of protecting larval sources and show that enhancement in recruitment can be manifested rapidly. However, benefits can be markedly variable within a local seascape. Hence, effects of marine reserve networks, positive or negative, may be overlooked when only focusing on overall responses and not considering finer spatially-explicit responses within a reserve network and its adjacent fishing grounds. Our results therefore call for future research on marine reserves that addresses this variability in order to help frame appropriate scenarios for the spatial management scales of interest.

No abstract

Community-based management and the establishment of marine reserves have been advocated worldwide as means to overcome overexploitation of fisheries. Yet, researchers and managers are divided regarding the effectiveness of these measures. The “tragedy of the commons” model is often accepted as a universal paradigm, which assumes that unless managed by the State or privatized, common-pool resources are inevitably overexploited due to conflicts between the self-interest of individuals and the goals of a group as a whole. Under this paradigm, the emergence and maintenance of effective community-based efforts that include cooperative risky decisions as the establishment of marine reserves could not occur. In this paper, we question these assumptions and show that outcomes of commons dilemmas can be complex and scale-dependent. We studied the evolution and effectiveness of a community-based management effort to establish, monitor, and enforce a marine reserve network in the Gulf of California, Mexico. Our findings build on social and ecological research before (1997–2001), during (2002) and after (2003–2004) the establishment of marine reserves, which included participant observation in >100 fishing trips and meetings, interviews, as well as fishery dependent and independent monitoring. We found that locally crafted and enforced harvesting rules led to a rapid increase in resource abundance. Nevertheless, news about this increase spread quickly at a regional scale, resulting in poaching from outsiders and a subsequent rapid cascading effect on fishing resources and locally-designed rule compliance. We show that cooperation for management of common-pool fisheries, in which marine reserves form a core component of the system, can emerge, evolve rapidly, and be effective at a local scale even in recently organized fisheries. Stakeholder participation in monitoring, where there is a rapid feedback of the systems response, can play a key role in reinforcing cooperation. However, without cross-scale linkages with higher levels of governance, increase of local fishery stocks may attract outsiders who, if not restricted, will overharvest and threaten local governance. Fishers and fishing communities require incentives to maintain their management efforts. Rewarding local effective management with formal cross-scale governance recognition and support can generate these incentives.

No abstract

Marine reserves (areas closed to fishing) have been advocated for the management of many species, including the rock scallop Spondylus calcifer in the northern Gulf of California (NGC), Mexico. We developed an explicit coupled biological-oceanographic model (CBOM) to assess connectivity among fished subpopulations of S. calcifer. We focused on the Puerto Peñasco corridor, located in the northeastern portion of the NGC. We validated CBOM's outputs through 2 different techniques: population genetics with 9 microsatellite loci and measurements of spat abundance on artificial collectors. We found strong demographic connectivity between the corridor and southern sources. Sampled localities showed low levels of genetic structure; however, we identified 2 subtly differentiated genetic clusters. On average, the spatial scale of demographic and genetic connectivity is in agreement, suggesting that connectivity decreases when the spatial scale is >100 km. We observed a gradient of higher values of both predicted particles and observed densities of settled spat for the northern and southern sites and lower values for the central sites. Larval recruitment within the corridor could be linked to a large spatial scale of larval inputs, including local sources and subpopulations further south. The absence of a strong barrier to migration suggests that the siting of marine reserves along upstream sites would likely benefit downstream subpopulations. The spatial scale of connectivity (~100 km) could be used as a reference for the strategic siting of marine reserves in the study area. CBOMs and population genetics are powerful complementary tools to assess the relative strength of connectivity among sites. KEY WORDS: Spondylus calcifer · Larval dispersal · Genetic structure · Marine reserves · Gulf of California Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 463: [159][160][161][162][163][164][165][166][167][168][169][170][171][172][173][174][175] 2012 grounds (Gell & Roberts 2003, Beukers-Stewart et al. 2005, Pelc et al. 2009).Benthic bivalve species are structured in metapopulations in which separate subpopulations of sessile juveniles and adults are connected through larval dispersal (Lipcius et al. 2005, Orensanz et al. 2006. The extent to which these subpopulations are linked by the exchange of larvae is termed connectivity and can have multiple and different patterns (Palumbi 2003, Orensanz et al. 2006. Thus, effective design and implementation of marine reserves requires knowledge about the spatial and temporal dynamics of biological connectivity between subpopulations, particularly those that are sources of larvae that can populate other habitats (Fogarty & Botsford 2007, Pelc et al. 2010.Depending on how connectivity is measured it can have different meanings and implications (e.g. for fisheries management, conservation of species and their evolutionary potential) (Lowe & Allendorf 2010). Demographic connectivity is the degree to which the subpopulation growth ...

No abstract

No abstract