World Aquaculture - December 2014

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• WORLD AQUACULTURE • DECEMBER 2014 61
Mitigating Eutrophication in Lakes
and Reservoirs
The success of cage culture in Nigerian lakes and reservoirs
depends on good water quality, which requires the reduction, control
and management of cultural eutrophication. Mitigating measures for
cultural eutrophication before the use of the lakes and reservoirs for
cage culture should involve the following strategies.
An initial environmental examination provides a baseline
assessment of the sources, quantities and concentrations of nutrients
in the lakes and reservoirs to be used for cage fish culture. This will
show the causes and potential severity of the eutrophication expected
and possible mitigation measures that could be implemented before
commencing cage culture. An environmental risk assessment from
the perspectives of fish stocks in the cage should be carried out in
association with the initial environmental examination. Lakes and
reservoirs with large watersheds should not be used for cage culture
because of the erosive tendency and high level of human activities on
such watersheds.
An environmental impact assessment should be carried after
the beginning of cage culture project. These assessments will provide
information and data on eutrophication, ecological interactions and
the impacts of watershed uses. This could then be used to guide
management and operation of the cage culture project.
There should also be regular monitoring of anthropogenic
activities in the watershed that can cause cultural eutrophication.
Geographic Information Systems (GIS) allows effective
environmental management planning. The usefulness of this
methodology for site selection in cage fish culture has been explored
and is now becoming widely established (Perez et al. 2003).
Best management practices (BMPs) in the watersheds of lakes
and reservoirs should be adopted (Mustapha 2009, 2010a, 2010b).
These include nutrient control, biomanipulation, regulations, public
awareness, environmental education and changes in social and
cultural perspectives of lakes and reservoirs. These will go a long
way to mitigate cultural eutrophication.
Conclusion
The prospects of cage fish culture in providing cheap fish
protein, sustaining livelihoods, alleviating poverty and ensuring
food security largely depends on water quality in the lakes and
reservoirs where cage culture is practiced. Good water quality
depends on effective curbing, control and management of the threat
of cultural eutrophication. An integrated and synergistic approach
among various sciences, culture, society, legislation, governmental
and non-governmental entities is necessary. Their involvement and
participation in management and control of eutrophication will help
to ensure that lakes and reservoirs have water quality that will sustain
cage fish culture and thereby making the advantages of cage culture
feasible and realizable.
Notes
MoshoodMustapha, Dept. of Zoology, University of Ilorin, Ilorin,
Nigeria
+2348035797590
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