Fish out of water

Inland fisheries are coming under increasing pressure, with many other demands being made on finite water resources. While statistics abound to quantify how much water is needed for various purposes (drinking water needs are 2-5 litres per person per day, household needs are 100-500 litres per person per day, to produce 1 kg of grain takes 300-3000 litres and to produce 1 kg of beef 7000-10,000 litres), no good estimates exist for the water required to produce a kilogram of fish. For wild capture fisheries no water needs to be diverted or removed from the river system, while for aquaculture and other managed systems the water cost of production is generally regarded to be the costs of evaporation and the water requirements of any feed ingredients. While these figures still need to be calculated, it is clear that many fisheries require no, or little, consumptive water use and fish can therefore contribute to improving water productivity in river basins. There is growing consensus that more attention therefore needs to be paid to managing water for fish.

Freshwater fisheries are often far from the public gaze and are therefore overlooked. Yet the current annual production of inland fisheries is at least 8 million tonnes, with a first sale value of US$6 billion. The lower Mekong alone yields 2 million tonnes valued at $2 billion, while from many smaller rivers yields, though lower, are of great local, national and even regional significance. For example the Rufiji River floodplain and delta in Tanzania generates $7 million annually, whilst the Inner Delta of the Niger in Mali can yield up to 135,000 tons of fish that are traded regionally and are worth over $40 million. In total over 50 million people in the developing world derive income, food and livelihoods from inland fisheries, including those involved in processing and marketing. Yet despite their importance, national policies often fail to acknowledge inland fisheries and they are at risk from large-scale water abstraction and pollution.

The challenge of providing answers to how water resources for fisheries might be managed most efficiently is complicated because it is not just the quantity of water available over the course of a year that is important, but the timing of peak and minimum flows, and also water quality. Fish breeding and feeding depend on flows, and flow velocity can also be crucial to survival. Collecting and quantifying such data is difficult and techniques are only now being developed to provide answers to management questions. A crucial question posed during World Water Week in Stockholm by Patrick Dugan, Deputy Director General of the WorldFish Center, is how much water can be abstracted from a river, and with what pattern of removal, without damaging the fisheries benefits and livelihoods that the river sustains.

How much is too much?
As another speaker observed at Stockholm, the definition of water scarcity differs from place to place. In agreement, Dugan pointed out, "River fish communities are complex and different species have different flow needs. Equally, flows need to sustain the varied nature of the riverine environment, with its diversity of habitats that sustain different fish populations, and the connectivity between the channel and its floodplain that accounts for the high productivity of many river fisheries." The Comprehensive Assessment of Water Management in Agriculture(CAWMA), which is being coordinated by the International Water Management Institute (IWMI), has reviewed the methodologies that are now available for assessment of environmental flows and recommended an integrated approach to developing environmental flow assessment for fish. This will involve combining the DRIFT (Downstream Response to Instream Flow Transformation) methodology that has been developed in South Africa and Australia, but for relatively small rivers, and adapting it to larger rivers, while integrating other tools for modelling fisheries production and developing scenarios for future fish production.

Dugan is optimistic that there is growing awareness of the value of aquatic ecosystems and in particular of the economic importance of river fisheries. He stressed that there is growing consensus among policy makers, fisheries scientists and aquatic scientists that three key conditions need to be met if there is to be better water management for fisheries.

1. Governance arrangements need to allow for effective participation of fishing communities and other poor stakeholders in decisions concerning allocation of water at different scales within the river basin.
2. Information on the value of river resources needs to be available and communicated effectively within these governance systems.
3. The quantity and quality of water (and other management parameters) required to sustain these resources needs to be understood and communicated effectively within these governance processes.

The stark example of the drying of the Yellow River in China (see China's water problems) demonstrates the worst-case scenario for river basins and the ecosystems and people who depend on them. There was agreement at World Water Week that any future use of water resources must be within limits that ensure the environment is conserved. To achieve this these limits need to be defined and this information used to improve water management. If that can be achieved there is hope that freshwater fisheries will survive and continue to contribute substantial food and economic benefits to fishers and consumers.

For further information see WorldFish Center or CAWMA