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ABSTRACT
van Zwieten, P.A.M.; Béné, C.; Kolding, J.; Brummett, R.; Valbo-Jørgensen, J., eds.
Review of tropical reservoirs and their fisheries – The cases of Lake Nasser, Lake Volta and
Indo-Gangetic Basin reservoirs.
FAO Fisheries and Aquaculture Technical Paper. No. 557. Rome, FAO. 2011. 148 pp.
Freshwaters contribute 15 percent of the world’s reported fish catch, or about
10.1 million tonnes in 2006, most of which comes from tropical systems. The true
contribution of tropical inland fisheries is likely to be higher, as less than half of the
inland capture production is actually reported. While reservoir fisheries are already
an essential component of this production, the potential of most of them may even
exceed their current catch levels. Opportunities exist to increase productivity, provided
that environmentally and socially sustainable management systems can be adopted.
To realize this untapped potential, it is necessary to improve understanding of the
processes influencing reservoir productivity in such a way as to involve both biological
principles and stakeholder participation, as each reservoir has different properties and
different research and management institutions.
Seen in isolation, catch and productivity data of individual reservoirs may be difficult
to interpret. The present technical paper attempts to address this issue by reviewing
the knowledge accumulated in reservoirs in some very different tropical river basins:
the Indus and Ganges/Brahmaputra Basin in India, the Nile River Basin in Eastern
Africa and the Volta River Basin in West Africa. In particular, it focuses on many of the
reservoirs of northern India and Pakistan in the Indus and Ganges systems, Lake Nasser
in the Nile River and Lake Volta in the Volta River.
Information collated from grey and published literature on the three basins is
synthesized and standardized with reference to wider knowledge and up-to-date
information on tropical reservoir fisheries. A considerable quantity of data and
information were collected on many aspects of the systems of the three reservoirs,
including hydrological, biophysical and limnological features, primary production, and
fish and fisheries data. This information was condensed and synthesized with the aim
of providing a baseline against which the ecological changes that have taken place since
impoundment can be described and analysed. Efforts are made to explain changes in
fish catch in relation to climatic variations, ecological succession and fishing effort. The
review shows that biological data and information are generally available.
However, as is also common elsewhere, all three cases suffer from the general
tendency to isolate and compartmentalize research into separate disciplines. Usually,
there is very limited cross-disciplinary flow of information or recognition of how
results of various disciplines can contribute to a more comprehensive understanding
of the behaviour of fish populations, human communities and ecosystems and the
productive activities that depend on them. This uniform tendency severely hampered
the identification of relevant management actions.
A more pragmatic and holistic understanding of reservoir ecosystems is needed in
order to guide the choice of indicators and the development of monitoring systems that
can inform management of changes in reservoir productivity and, hence, the potential
catch. The next step would be to devise a hierarchy of indicators describing the different
ecological and economic processes influencing fisheries catches and to organize
monitoring systems around those indicators. Only by combining information across
sectoral disciplines will it be possible to reach a better understanding of the processes
that drive fish stocks, fisheries and reservoir productivity.
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