There are many interactions between fisheries, including aquaculture and capture fisheries as well as their intermediate forms in freshwater and marine environments, and other uses of the aquatic systems such as agriculture, flood control, power generation, tourism, mining, transportation, land development (e.g. housing), and urban and industrial effluent disposal.
Synergistic interactions between fisheries and agriculture are primarily derived from the recycling of livestock or farming wastes and nutrients and optimal use of scarce land and water resources. In aquaculture, the active search for synergies has led to a number of development and management concepts such as Integrated Agriculture-Aquaculture (IAA), Integrated Irrigation-Aquaculture (IIA), as well as to livestock-fish or rice- fish production systems. These synergies have been enhanced by improving the use of water and reducing agricultural impacts on aquatic systems, e.g. through the Integrated Pest Management concept (IPM). These improvements have been beneficial in improving water and fish quality and productivity. Unexpected synergies have also been detected in marine fisheries where the nutrients of continental origin (e.g. phosphates, nitrates), often a source of eutrophication and red tides, are believed to have increased productivity (e.g. in the Mediterranean and the North Sea).The development of reservoirs and other small-water bodies for agricultural and other purposes offers additional opportunities for both aquaculture, culture-based fisheries through stocking, and capture fisheries.
Antagonistic interactions between agriculture and fisheries occur where these two sectors compete for the same kinds of resources, especially land and water, where rising productivity in one production system leads to reducing productivity in the other. For example, bad farming practices and deforestation impact on aquatic habitats and water resources - and therefore on fishery resources productivity and quality - through erosion, siltation, pollution and eutrophication (and red tides) resulting from excessive use of pesticides and fertilisers. Similarly, extensive saltwater or brackish water culture on coastal land areas affects the quality of soils (salinization, water logging) and the quality and level of the water table. Dams established for the purpose of irrigation, flood control or energy production impair fish migration and reproduction routes and change the qualitative nature of the habit which in turn influences the aquatic communities, e.g. changing species composition from riverine to lacustrine species. Efficiency in the use of water, primarily fresh water, and land resources is becoming of central importance to sustain increases in fisheries so as to provide for rural village communities and supply urban areas with the needed quantity, quality and variety of food. In many areas where human activities have rapidly expanded during the last decade, there is increasing pressure on limited land and water resources.
There are also interactions between capture fisheries and aquaculture. Development of aquaculture may adversely impact capture fisheries through habitat change associated with farming systems or impacts of introduced species. There is competition for space between the production systems; for habitat and resources between wild and farmed species; for the market between respective harvests and products; for wild seeds. Pollution from aquaculture may also be a problem. On the other hand, aquaculture may provide alternative employment in overexploited areas or additional resources for fishing through enhancement, and may be an important alternative source of fish for rural communities thus reducing the fishing pressure and helping in the rehabilitation of wild fish stocks.
The negative sides of these numerous interactions is progressively being recognised by Governments and industry and integrated management of natural resources is the strategy of choice to improve efficiency despite obvious implementation difficulties. The integrated management of watersheds, river basins and coastal areas (and of productive ecosystems in general) aims at managing sectoral components as parts of a functional whole. The overall objective of better integration between fisheries and other sectors in policy development and management is to maximize synergistic interactions and minimize antagonistic ones.
Awareness of inter-sectoral dependencies, through the environment and the global economy, is rapidly rising, stimulated inter alia by growing media coverage of ecological catastrophes, advances in data processing and information technology, development of ecological economics, increased mobilisation of social forces through NGOs communications. The abilities of local communities to participate in information gathering, analysis, decision-making and enforcement is better recognised together with the need to involve them directly in decisions regarding common property resource use. All of this has created favourable conditions to fully realize the benefits of better integration between fisheries and agriculture as well as of these sectors with the rest of the economy.
Numerous difficulties remain on the way towards better integration. Among these:
- the technical difficulty of integrated development planning;
- the political and economic difficulty of an equitable allocation of resources;
- the organisation of a balanced leadership of the interaction between sectors;
- the decentralisation of rights and responsibilities;
- the development of the human resources necessary for effective decentralisation;
- the cost of better understanding of the ecosystems functioning and resilience;
- the application of the precautionary approach when information is lacking;
- the development of integrated indicators of sustainability.