The Ecosystem Approach to Aquaculture (EAA) emphasises inter-sectoral complementarity by taking account of interactions between the activities within ecologically meaningful boundaries and multiple services of ecosystems.
The main objective of this review is to understand the status of aquaculture-fisheries interactions associated with the biological, technological, social, economic, environmental, policy, legal and other aspects of aquaculture development. It goes on to analyse how the interactions are or could be addressed under the EAA. It cover aspects of scoping, prioritising, management tools and plans (minimising negative effects and optimising positive ones) within the context of the elements of ecosystem resilience, social and economic issues and the integration of aquaculture with other sectors. Relevant spatial scales are also considered, particularly the watershed and related marine waterbody scale and potential transboundary issues.
Aquaculture and fisheries are subsectoral activities that often depend on the same resources and share the same ecosystem boundaries. Effective implementation of the Ecosystem Approach to Fisheries/Aquaculture will require a good understanding of their interactions and mutual impacts. The interactions reviewed here are the most commonly known and are often referred to as issues.
Aquaculture or culture-based fisheries (stock enhancement) has positive impacts including: establishment of new/additional fish resources for capture and recreational fisheries, provision of livelihoods, and conservation and improvement of certain fisheries through enhancement of over-fished stocks. Potential negative impacts include: pressure on natural fishery resources due to competition for food/habitat, predation and potential alteration of genetic diversity of natural stocks. However, well-managed culture-based fisheries can provide required biomass while minimising environmental effects, since no external feeding is needed. Aquaculture escapees could have positive and negative impacts similar to those described for stock enhancement, although as an unplanned event they are more likely to have negative effects on fisheries. An additional concern is the transmission of diseases to wild populations, with possible impacts on fisheries.
Within capture-based aquaculture, positive effects can include provision of livelihood for fishers as provider of seed, broodstock and feed; better priced products and greater income derived from final grow-out products. Potential negative effects include impacts on wild populations and fisheries through the capture of target larvae/juveniles and by-catch impacts on other fisheries.
The use of fisheries as feed to aquaculture in the form of direct feed (e.g. trash fish/ low-value fish) and feed ingredients (fishmeal and fish oil) could negatively affect the resource for direct fishery intended for consumption. On the other hand, positive impacts include the provision of livelihoods for fishers and of jobs and income (fishmeal fisheries).
Aquaculture systems and processes could disturb natural habitats and breeding areas, affecting fisheries (e.g. cutting of mangroves for shrimp culture, affecting sea grasses, reproductive habitats and causing fish mortality due to eutrophication from nutrient overload). Positive effects include increased fishery productivity through additional nutrients, especially in more oligotrophic areas.
The social impacts from aquaculture on fisheries communities include livelihood options for local traditional fishers and families through direct engagement or providing inputs (seed and feed). Negative effects include reduction in capture fisheries and limited access to the fishery due to aquaculture activities. There are also post-harvest and market impacts, including positive effects such as improved market access and improved trade and safety aspects for fishery products due to aquaculture outputs. There are also negative effects such as market competition and price decrease due to increased product availability. Obviously, the most important positive impacts of fisheries on aquaculture are related to seeds and feeds, while the availability of fishery processing wastes and markets can be considered as facilitating factors for aquaculture.
In order to ensure close integration between aquaculture and fisheries and the optimal management of multiple use of the same aquatic resources, the full set of ecosystem interactions needs to be considered. This includes ecological functions and the services they provide, as well as clear understanding of the economic, social and cultural values that people attach to these services. One such example is stock enhancement, which has been successfully used to mitigate nutrient overloading from aquaculture practices, thereby reducing fish kills (e.g. cultured stocks in cages) and in the same vein, increasing the output from capture fisheries in the open waters, thereby increasing fisher incomes and foodfish production, and resulting in an overall reduction in eutrophication and nutrient levels in the waterbodies, returning them to an almost original ecological status.
Within the EAA, the identification of aquaculture/fisheries interactions as relevant issues is a first step. This must be done with the relevant stakeholders, including aquaculture and fisheries players. The root of the issues must be recognised and operational objectives must be agreed upon within the existing policy frameworks. Often, however, it is necessary to review such policies and also the current regulations, this being necessary to identify the proper management measures (often affecting both sectors in a coordinated way) that must be recognised and agreed upon by the relevant fisheries and aquaculture stakeholders (including civil society and government). Concepts and indicators of environmental carrying capacity within ecosystem boundaries and a broader social and economic appraisal for both aquaculture and fisheries are required. Regular monitoring is required to assess the impacts and provide feed back into management and control. Management measures should also look for improved complementarity between the sectors, considering the need for balancing positive and negative effects and also inter-generational impacts (i.e. what is left for future generations). Often, institutional changes are required to address the issues of both fisheries and aquaculture, perhaps more often effectively implemented through a co-management strategy.
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