The last snapshot of the natural fish communities in Lake Turkana
Ann Arbor, MI — In a recent study on the world’s largest desert lake -- Lake Turkana, Kenya -- Czech and Kenyan scientists explored patterns of fish in the community.
In the past, Lake Turkana stood away from scientific interests. The lake, situated in hostile desert territory, represents a unique ecosystem. It has only one major inlet, the River Omo, and no outlet. As the only permanent water body in the vicinity, the lake also provides the last chance for local people to make a living during frequent droughts.
This study provides a detailed picture of fish distribution. During the day, most fish were concentrated within a thin layer in the dark depths near the bottom. At night, fish ascend and occupy the surface layers. This up and down migration is probably motivated by fear of predators during day and feeding in zooplankton-rich surface layer under cover of dark. Bigger fish showed clear preference to the shallower areas and the richest fish aggregations were near the western shore. This surprising selection is influenced by currents which bring food particles to this part of the lake.
When compared with previous studies made in 1980’s, the new results show that the fish communities have declined to less than one-third previous abundance. The worst affected were the small prey fish, which are essential in every freshwater food web. This change was probably caused by high fluctuations in the amount of water carried by the River Omo. In coming years, this inflow will be further reduced by building the second largest dam in Africa upstream on the Omo River. This will likely cause salinity to increase and lake level to drop.
These estimates of fish distribution and biomass are important both for determination of the appropriate fisheries management strategy and as the last report describing the natural conditions of Lake Turkana prior to the dam project.
Original Publication Information
Results of this study, "The last snapshot of natural pelagic fish assemblage in Lake Turkana, Kenya: A hydroacoustic study," are reported by Milan Muška, Mojmír Vašek, David Modrý, Miloslav Jirku, William O. Ojwang, John O. Malala and Jan Kubecka in Volume 38, No. 1, of the Journal of Great Lakes Research, published by Elsevier, 2012.
Contacts
For more information about the study, contact Milan Muška, Institute of Hydrobiology, Biology Centre Academy of Sciences of the Czech Republic, Na Sádkách 7, Ceské Budejovice 370 05, Czech Republic, scribne3@msu.edu; (517)353-3288 or Casey Huckins, Michigan Technological University, Houghton MI, muskamilan@seznam.cz; Phone: +420 387 775 848, Fax: +420 385 310 248.
For information about the Journal of Great Lakes Research, contact Marlene Evans, Editor, National Water Research Institute, Environment Canada, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada; jglr@ec.gc.ca; (306) 975-5310.
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