Inland water fishing is an important source of food and income in many developing countries, particularly in rural areas with few job opportunities. But taking too many fish threatens both poor people’s livelihoods as well as the biodiversity of the aquatic ecosystem.

The problem of overfishing in inland waters is poorly understood. There are no global estimates of the number of people who practice inland fishing, but many inland fish stocks are in decline. A report from a coalition of organisations, led by the University of Michigan, USA, examines trends, the state of knowledge and possible responses of the development community and individual countries, regions and villages to the threat of overfishing.

There are two main types of overfishing of inland lakes and rivers. In the first, intensive fishing of a particular species leads to large declines in both numbers and sizes of fish caught. This has happened historically with a number of species, including the Murray cod of Australia, and it is happening today in Southeast Asia with the overfishing of the Mekong giant catfish. In the second type of overfishing, known as ‘assemblage’ overfishing, all types of fish are caught but larger species are selectively eliminated from the catches. This is more common in tropical regions, where fish diversity and the reliance of local people on fish harvests are both high, and a diversity of fishing methods ensures the capture of fish of many types and sizes.

The environmental impacts of overfishing in inland waters are potentially widespread and numerous. Although there are some unknown impacts, the report identifies:

• Overfishing may not always be the single or main threat to water systems, but it can have serious effects when combined with other environmental problems.
• The decline of fish species will affect the long-term nutrient, habitat and ecosystem dynamics of inland waters.
• Overfishing in freshwater systems is likely to be as serious as in marine ecosystems, but has received much less attention.
• Research into the effects of overfishing on diseases of inland water ecosystems, such as schistosomiasis and cholera, is only just beginning. However, it is predicted that overfishing could seriously impact the health of human populations in developing countries.

Four principles should guide the management of inland fisheries for the long-term benefit of local communities and the environment. These principles are: the sustainability of yields; the maintenance of biodiversity; protection from other human impacts (such as pollution), and; the provision of livelihood benefits to all consumers of inland fish. To support these principles, the research recommends:

• Governments must develop institutions and legal frameworks that increase the participation of all the communities involved in inland water management.
• Local people must become more involved in decision-making processes for managing inland waters.
• River basin management must consider the impact of upstream environmental threats on downstream freshwater systems.
• Fishery management organisations should set cautious targets to protect species from overfishing.
• Fishery management organisations should also assess the effects of fishing on how communities and ecosystems interact.
• Biodiversity conservation and fisheries should be managed together.

Source(s):
‘Overfishing of Inland Waters’, BioScience, Vol. 55, No. 12, by J. David Allan, Robin Abell, Zeb Hogan, Carmen Revenga, Brad W. Taylor, Robin L. Welcomme and Kirk Winemiller, December 2005 (PDF file) Full document.

Funded by: The Nature Conservancy and authors’ organisations

id21 Research Highlight: 2 June 2006

Further Information:
J. David Allan
School of Natural Resources and Environment
University of Michigan
Dana Building, 440 Church Street
Ann Arbor, MI 48109
United States

Tel: +1 734 764 6553
Fax: +1 734 936 2195
Contact the contributor: dallan@umich.edu

University of Michigan, USA

Other related links:
'Tackling illegal fishing practices in Africa’s protected waters'

'Shrimp farming at the cross roads'

See id21's links for fisheries

Sustainable Fisheries Livelihoods Programme