The role of marine reserves in achieving sustainable fisheries (One contribution of 15 to a Theme Issue 'Fisheries: a Future?')

Many fishery management tools currently in use have conservation value. They are designed to maintain stocks of commercially important species above target levels. However, their limitations are evident from continuing declines in fish stocks throughout the world. We make the case that to reverse fishery declines, safeguard marine life and sustain ecosystem processes, extensive marine reserves that are off limits to fishing must become part of the management strategy. Marine reserves should be incorporated into modern fishery management because they can achieve many things that conventional tools cannot. Only complete and permanent protection from fishing can protect the most sensitive habitats and vulnerable species. Only reserves will allow the development of natural, extended age structures of target species, maintain their genetic variability and prevent deleterious evolutionary change from the effects of fishing. Species with natural age structures will sustain higher rates of reproduction and will be more resilient to environmental variability. Higher stock levels maintained by reserves will provide insurance against management failure, including risk-prone quota setting, provided the broader conservation role of reserves is firmly established and legislatively protected. Fishery management measures outside protected areas are necessary to complement the protection offered by marine reserves, but cannot substitute for it

Quantifying the potential for marine reserves or harvest reductions to buffer temporal mismatches caused by climate change

Climate change has caused shifts in seasonal timing of climatic events such as the onset of spring upwelling, which can lead to temporal mismatches between fish spawning and production of zoopklankton prey. Fishing may exacerbate mismatches through age truncation, particularly when offspring survival is dependent on maternal age, but no-take reserves or harvest reductions might buffer this effect. To quantify the potential for management to buffer synergistic interactions between fishing and climate, we developed a dynamic population model of a harvested species where larval survival depended on spring transition timing and maternal age. We applied this model to rockfishes (Sebastes spp.) after verifying empirically that spring transition timing affects their recruitment success. We found that yield and persistence changed more with maternal-agedependent larval provisioning than maternal-age-dependent spawning timing across a range of spring transition timings, especially with environmental stochasticity. Either implementing reserves or reducing fishing can mitigate impacts on larval survival, but reserves convey the added benefit of decreased sensitivity of yield and persistence to fishing. However, reserve buffering effects decreased with the inclusion of environmental stochasticity

Designing marine reserves to reflect local socioeconomic conditions: lessons from long-enduring customary management systems

Coral reef conservation strategies such as marine protected areas have met limited success in many developing countries. Some researchers attribute part of these shortcomings to inadequate attention to the social context of conserving marine resources. To gain insights into applying Western conservation theory more successfully in the socioeconomic context of developing countries, this study examines how long-enduring, customary reef closures appear to reflect local socioeconomic conditions in two Papua New Guinean communities. Attributes of the customary management (including size, shape, permanence, and gear restrictions) are examined in relation to prevailing socioeconomic conditions (including resource users’ ability to switch gears, fishing grounds, and occupations). Customary closures in the two communities appear to reflect local socioeconomic circumstances in three ways. First, in situations where people can readily switch between occupations, full closures are acceptable with periodic harvests to benefit from the closure. In comparison, communities with high dependence on the marine resources are more conducive to employing strategies that restrict certain gear types while still allowing others. Second, where there is multiple clan and family spatial ownership of resources, the communities have one closure per clan/family; one large no-take area would have disproportionate affect on those compared to the rest of the community. In contrast, communities that have joint ownership can establish one large closure as long as there are other areas available to harvest. Third, historical and trade relationships with neighboring communities can influence regulations by creating the need for occasional harvests to provide fish for feasts. This study further demonstrates the importance of understanding the socioeconomic context of factors such as community governance and levels of dependence for the conservation of marine resources