Impoundments, barriers and abstractions: impact on fishes and fisheries, mitigation and future directions

Kemp, Paul S. (2015) Impoundments, barriers and abstractions: impact on fishes and fisheries, mitigation and future directions. In, Craig, John F. (ed.) Freshwater Fisheries Ecology. Chichester, GB. Wiley, pp. 717-769. (doi:10.1002/9781118394380.ch52).

Abstract

Globally, rivers directly support a large proportion of the human population and provide ecosystem services essential for quality of life, including the provision of protein through maintenance of fisheries. Many systems have been extensively engineered to support agricultural production, urbanization and industrialization, activities that can negatively affect ecosystem processes, with some of the most profound impacts due to impoundment and flow depletion. Environmental impacts include disruption of flow and sediment regimes; degradation and fragmentation of physical habitat; alteration of water chemistry, temperature and dissolved gases; disconnection of energy and nutrient transfer in longitudinal, lateral, vertical and temporal dimensions and associated reductions in productivity; direct and indirect mortality of aquatic biota as a result of interactions with river infrastructure. Despite often well-developed and long-term recognition that impoundment and abstraction negatively impact ecology, the complexity of the mechanisms that drive these responses often remains poorly understood and requires further investigation. Similarly, despite considerable efforts to develop environmental impact mitigation strategies (e.g. methods to assign appropriate environmental flows) and technology (e.g. fish passes and screens), partial solutions frequently fail to fully compensate for negative effects experienced and in some cases are themselves damaging. This chapter reviews the impacts of impoundments and water offtakes on freshwater fish populations and discusses the mitigation options currently available. Biases and gaps in understanding are identified, and recommendations for the future made. In the face of unprecedented future demand, it is argued that mitigation alone will be insufficient to sustain important populations of fish and that there is a need for society to discuss the need to better manage demand on resources based on more realistic valuation of existing ecosystem services.

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Contributors

Author: Paul S. Kemp

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