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The four papers presented in this publication address major fishery issues in relation to dams as identified by the World Commission on Dams (WCD) and FAO for the purpose of WCD's global review on "Dams and Development". Characteristics of river and reservoir fisheries in various regions of the world are reviewed. As reservoirs provide significant contributions to global freshwater fisheries, production figures for reservoirs in Africa, Asia, Latin America and the Caribbean, as well as for the Commonwealth of Independent States, are mentioned. Also fish production figures for large rivers are provided, emphasizing the importance of floodplains for fish production. The extent to which fisheries can be developed, sustained or protected along riverine ecosystems modified by dams reflects basin topography, geological features, watershed hydrology, and climate, as well as engineering features of the dam itself, and operational programmes for retention and release of water from the reservoir, through the dam and into the tailwaters.

Compensation for loss in yield from river fisheries can be difficult to achieve through development of reservoir fisheries. Even if compensation is achieved from a fishery perspective, specific needs of fish species that are not included in the fishery, but are threatened or endangered, must be considered to avoid negative impacts to these fishes. The importance of free longitudinal passage of river fauna is stressed. The construction of dams can block or delay upstream fish migration and thus contribute to the decline and even the extinction of species that depend on longitudinal movements along the stream continuum during certain phases of their life cycle. Mortality resulting from downstream passage through hydraulic turbines or over spillways can be significant. Habitat loss or alteration, discharge modifications, changes in water quality and temperature, increased predation pressure, as well as delays in migration caused by dams, are discussed. Various technical solutions are suggested and critical points, that have to be considered in fishpass construction, are stresssed.

A non-exhaustive review of the current status of the use of fish facilities at dams throughout the world is presented, with the main target species considered from North America, Europe, Latin America, Africa, Australia, New Zealand, Japan and Asia. The main challenges to maintaining and enhancing reservoir fisheries, as well as associated social and economic benefits, are fish habitat and environmental degradation, inadequate fish assemblages, inefficient harvesting systems, stakeholder conflicts, and insufficient institutional and political recognition. Fishery administrators find it difficult to defend the interests of their sector; decisions over developments affecting fisheries and aquatic environments are often made with minimum or no consideration of these sectors, mainly for lack of reliable economic valuation and lack of political clout by the users. Given this lack of political power, the interests and needs of fishers and fisheries managers are often not properly represented within existing political frameworks, and thus neglected or ignored. Fishery administrators and stakeholders should seek every opportunity to communicate their needs and demonstrate the value of fisheries and the aquatic natural resources.

The multi-sectoral nature of water resources development in the context of socio-economic development must be recognized. Management policy must be country-specific and take local conditions into account as blind application of imported principles may lead to policy failures. Fisheries management capacity and information base requirements are reviewed for the six phases of the dam project cycle, i.e. dam identification, dam design, dam project appraisal, dam construction, dam operation and dam decommissioning. Effective environmental assessment and management coupled with improvements in design of civil engineering structures has made some recent dam projects more fish friendly and environmentally acceptable. The need for drafting legal instruments, which will facilitate modification of dam structures to incorporate mitigation measures and help altering dam operation rules to be more beneficial to fish biodiversity and fisheries, is emphasized.