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Section 3 to fishery management would seek to reduce existing stressors to marine and freshwater ecosystems and fish stocks: these will not be able to “solve” all the problems for marine ecosystems emerging from climate change but can provide a higher chance of maintaining fish stocks. In a broad review undertaken for WWF, Roberts and Hawkins (2000), identify a range of benefits of fully protected reserves for marine fish: • Enhancing the production of offspring which can restock fishing grounds: researchers conclude that fish density is generally higher inside marine protected areas (MPAs), particularly when surrounding areas are heavily fished338. A recent review of 112 independent studies in 80 different MPAs found that all biological measures were strikingly higher inside the reserve than in surrounding areas (or in the same area before an MPA was established). Relative to reference sites, population densities were 91 per cent higher, biomass was 192 per cent higher, and average organism size and diversity were 20–30 per cent higher in MPAs, usually after as little as 1-3 years; furthermore these increases were found even in small MPAs339. • Allowing spill-over of adults and juveniles into fishing grounds: as population size and the size of individual fish increases within MPAs, they will start to spill-over into surrounding waters, providing additional catch for fishing operations and helping build up wider populations. Six factors affect spill-over: the success of protection; the length of time that the MPA has been established;
intensity of fishing outside the MPA; the mobility of species; the boundary length of the reserve (with greater edge to area ration increased spill-over); and boundary porosity, with out-migration encouraged if there is continuous habitat type340. Table 6 on the previous page summarises some recent research. • Providing a refuge for vulnerable species: that react to even minor disturbance or fishing pressure. • Preventing habitat damage: all forms of fishing create some associated damage: trawling and use of dynamite are the most serious but even line fishing results in some disturbance and litter that can damage bottom-living communities. • Promoting development of natural biological communities (which may be different from communities found in fishing grounds): for example in Chile establishment of an MPA led to a replacement of mussel beds with barnacles, due to recovery of a predatory snail Concholepas concholepas, which controlled the former but was over-exploited elsewhere341. • Facilitating recovery from catastrophic human disturbance: healthy ecosystems, with a full complement of species and effective ecosystem functioning, are more likely to recover from sudden major disruptions than ecosystems that are already weakened by overexploitation342. This benefit will become increasingly important under conditions of climate change.
Case Study A new marine protected area network in Papua New Guinea is being specifically designed to maintain marine resources and biodiversity in the face of climate change Climate change will add to the existing pressures on both coral reefs and marine resources; with rising sea temperatures leading to coral bleaching and death, and sea-level rise threatening critical coastal habitats such as mangroves and turtle nesting areas. The Nature Conservancy has been working with the provincial and local governments of West New Britain province in Papua New Guinea and with many of the communities in the biologically richest areas of Kimbe Bay to develop a marine protected area (MPA) network that is designed specifically for resilience to climate change366. The network aims to ensure representation of each habitat type, maintain connectivity for larval dispersal and protect areas more likely to survive the effects of climate change, for example areas that have proven more resilient to past coral bleaching events. These efforts seek to ensure that coral reefs can survive the effects of rising sea temperatures and allow coral larvae from healthy reefs to replenish those affected by bleaching. Socioeconomic studies were
also carried out during the planning of the network to ensure communities’ marine resource needs were also addressed. While these efforts may not address the impacts on coral reefs of ocean acidification, they will have the effect of reducing other stressors on the area’s ecosystems, which is expected to play a critical part in enhancing their resilience. The approach is necessarily participatory, because local communities are ultimately the decision-making powers in the region367. The locally-managed marine areas are being established under local government legal frameworks, and plans are being developed for a Bay-wide designation to encompass the whole MPA network. Preliminary research in the area suggests that even quite small MPAs could be effective in replenishing some fish stocks368, and thus providing for long-term food security. Four large locally-managed marine areas have already been established and a further six are in development369. Source: TNC