The Dynamics of Selected Limnological Data Along a Land Use Gradient in River Molo, Kenya
Abstract
Rivers provide a suite of ecosystem goods and services to fisheries, as well as water that benefit the domestic and industrial use of the riparian communities. The increasing intensification of human activities along River Molo in the Rift Valley, Kenya continues to affect the diversity of aquatic life including fish. Whereas, information on the status and changes in fish population and ecological attributes along the river is fundamental, knowledge is currently lacking. The study evaluated the status of R. Molo fisheries and the environmental conditions longitudinally along the river. All the physicochemical water quality parameters demonstrated significant (P < 0.05) spatial variations in the sampled stations of R. Molo. There were 54 different species of algae identified in this study and the average algal density fluctuated between 2 to 16 cells ml-1. There were also, significant differences in the occurrence of macroinvertebrate among sites (Chi-square; 2 = 20.1121, df = 3, P = 0.0031). There was a significant difference in the fish catch data based on the sampling location and fish species (P < 0.05). The minimum sizes at which the species mature differed with species. Of all the species sampled, only Labeo cylindricus exhibited a positive allometric growth (b < 3). Variations in limnology attributes of R. Molo were associated with longitudinal anthropogenic activities. Consequently, the need for R. Molo watershed management plan with a single economic vision of the resource use based on an ecosystem approach cannot be overstated. The plan should capture among other components, the hydrological regime, and species life history traits, fishing impacts and stakeholders socioeconomic requirements as key elements for sustainability.
References
APHA (2005). Standard Methods for the Examination of Water and Wastewater. American Public Health Association, Washington, DC.
Arthington, A.H., Bunn, S.E., Poff, N.L. and Naiman, R.J. (2006). The challenge of providing environmental flow rules to sustain river ecosystems. Ecological Applications. 16: 1311‒1318.
Béné, C., Arthur, R., Norbury, H., Allison, E.H., Beveridge, M., Bush, S., Campling, L., Leschen, W., Little, D., Squires, D. and Thilsted, S.H. (2016). Contribution of fisheries and aquaculture to food security and poverty reduction: assessing the current evidence. World Development. 79: 177‒196.
Boerema, L.K. and Gulland, J.A. (1973). Stock assessment of the Peruvian anchovy (Engraulis ringens) and management of the fishery. Journal of the Fisheries Board of Canada. 30: 2226‒2235.
Cadwalladr, D.A. (1965). The decline in the Labeo victorianus Blgr.(Pisces: Cyprinidae) fishery of Lake Victoria and an associated deterioration in some indigenous fishing methods in the Nzoia River, Kenya. East African Agricultural and Forestry Journal. 30: 249‒256.
Hering, D., Carvalho, L., Argillier, C., Beklioglu, M., Borja, A., Cardoso, A.C., Duel, H., Ferreira, T., Globevnik, L., Hanganu, J. and Hellsten, S. (2016). Managing aquatic ecosystems and water resources under multiple stress—An introduction to the MARS project. Science of the total environment. 503: 10‒21.
Ochumba, P.B.O. and Ala, J. (1992). Distribution of fishes along the Sondu‐Miriu River of Lake Victoria, Kenya with special reference to upstream migration, biology and yield. Aquaculture Research. 23: 701‒719.
Oeding, S., Taffs, K.H., Cox, B., Reichelt-Brushett, A. and Sullivan, C. (2018). The influence of land use in a highly modified catchment: Investigating the importance of scale in riverine health assessment. Journal of Environmental Management. 206: 1007‒1019.
Rad, S.D., Allègre, C.J. and Louvat, P. (2007). Hidden erosion on volcanic islands. Earth and Planetary Science Letters. 262: 109‒124.
Tonkin, J.D., Merritt, D.M., Olden, J.D., Reynolds, L.V. and Lytle, D.A. (2018). Flow regime alteration degrades ecological networks in riparian ecosystems. Nature Ecology & Evolution. 2: 86.
Welcomme, R.L. (1985). River fisheries [Pesca fluvial]. FAO fisheries technical paper, 262, p. 330.
Whitehead, P.J.P. (1959). The River Fisheries of Kenya I—Nyanza Province. The East African Agricultural Journal. 24: 274‒278.