Department of Aquaculture and Fisheries Management

Permanent URI for this collectionhttp://localhost:4000/handle/20.500.12092/1915

Browse

Now showing 1 - 20 of 37

Ecology and Management of Lake Naivasha, Kenya, in Relation to Climatic Change, Alien Species' Introductions, and Agricultural Development
(Environmental Conservation; Cambridge Journals, 1990) Harper, David, M.; Muchiri, Mucai; Mavuti, Kenneth, M.
Lake Naivasha is an important freshwater resource for Kenya's foreign-currency-earning agriculture and tourism, and for water-supply. It has always experienced extensive water-level fluctuations as a consequence of irregular rainfall patterns that are affected by continental-scale climatic events, and its communities — particularly of aquatic plants — were adapted to these changes.
Organochlorine and organophosphorus pesticide concentrations in water, sediment, and selected organisms in Lake Naivasha (Kenya)
(Kluwer Academic Publishers, 2002) Muchiri, Muchai; Gitahi, S. M.; Harper, D. M.; Tole, M. P.; Ng’ang’a, R. N.
The status and future of the Lake Naivasha fishery, Kenya
(Kluwer Academic Publishers, 2002) Muchiri, Mucai; Kundu, Rodrick; Taylor, Andy; North, Rick; Harper, David M.; Bailey, Roland; Hickley, Phil
Lake Naivasha is a freshwater lake situated in the eastern rift valley of Kenya. Only five species of fish are present, all of which have been introduced. They are Oreochromis leucostictus, Tilapia zillii, Micropterus salmoides (largemouth bass), Barbus amphigramma and Poecilia reticulata (guppy). The first three of these form the basis of an important gill net fishery and bass are also taken by rod and line for sport. Barbus are occasionally caught by dip net. Actual and potential yields for the Lake Naivasha fishery are discussed and the fishery is shown to be under-performing. The feeding regimes of the commercially exploited fish were examined in the context of available food supply, in particular the benthic fauna. Small bass depend heavily on Micronecta and large bass mostly take crayfish. Detritus predominates in the diet of Oreochromis leucostictus and Tilapia zillii but the former also eats algae and the latter, Micronecta and macrophyte. Various food resources, especially the benthos, appear to be under-utilized and so it is possible that further species could be introduced to enhance the commercial fishery.
Habitat degradation and subsequent fishery collapse in Lakes Naivasha and Baringo, Kenya
(2004) Muchiri, Mucai; Hickley, Phil; Boar, Rosalind; Britton, Robert; Adams, Chris; Gichuru, Nicholas; Harper, David
Lakes Naivasha and Baringo in the eastern Rift Valley of Kenya are shallow, freshwater lakes that are subject to major fluctuations in water level and suffer from habitat degradation as a consequence of riparian activity. Lake Naivasha is approximately 160 km2, is bordered by Cyperus papyrus and its aquatic macrophytes are in a state of flux. The most significant riparian activity is the large scale production of flowers for the European market. Lake Baringo is approximately 140 km2 and lies in a semi-arid region. Its most noticeable feature is its extreme turbidity which is mainly due to excessive soil erosion resulting from deforestation and overgrazing. This turbidity has led to near extinction of submerged macrophytes and a lake bed virtually devoid of benthic fauna. Fishing pressure has added to the environmental stresses being endured by the fish populations and commercial catches have been detrimentally affected. Accordingly, periods of fishery closure are now imposed upon both lakes. Limited remedial action is feasible and some local stakeholders are attempting to introduce mitigation measures. For Lake Naivasha there is an agreed riparian owners' management plan which tackles issues such as water usage and protection of the C. papyrus margin. For Lake Baringo there is a Rehabilitation of Arid Environments initiative which promotes such activities as restoration of riparian vegetation and appropriate stock management.
Shifts in the food of Nile tilapia, Oreochromis niloticus (L.) in Lake Victoria, Kenya
(African Journal of Ecology, 2004) Muchiri, M.; Cowx, I. G.; Okeyo-Owuor, J. B.; Njiru, M.
Exotic introductions to the fishery of Lake Victoria: What are the management options?
(2005) Muchiri, M.; Knaap, M. van; Cowx, I. G.; Waithaka, E.; Njiru, M.
Influences of land use/cover on water quality in the upper and middle reaches of River Njoro, Kenya
(Blackwell Publishing Asia Pty Ltd, 2007) Muchiri, Mucai; Shivoga, William A.; Kibichi, Samuel; Odanga, Jethro; Miller, Scott N.; Baldyga, Tracy J.; Enanga, Eric M.; Gichaba, Maina C.
Remote Sensing Applications for Sustainable Aquaculture in Africa
(IEEE, 2007) Quansah, Joseph, E.; Rochon, Gilbert, L.; Quagrainie, Kwamena, K.; Amisah, Steve; Muchiri, Mucai; Ngugi, Charles
The authors review the current state of the science with respect to remote sensing applications for aquaculture, including site location, aquaculture facility mapping, market proximity analysis and associated roadway infrastructure, epizootic mitigation, meteorological event and flood early warning, environmental pollution monitoring, and aquatic ecosystem impact, primarily for catfish (Clarias spp.) and tilapia (Tilapia spp.; Oreochromis spp.), inter alia. The potential of technology transfer from the controlled environment aquaculture research facilities at Purdue University, West Lafayette, Indiana, USA to partnering institutions in Ghana and Kenya are explored. The potential for multi-sensor remote sensing deployment to support sustainable fish production in these environments and subsequently in other African countries is evaluated.
Macroinvertebrate assemblages along a land-use gradient in the upper River Njoro watershed of Lake Nakuru drainage basin, Kenya
(Blackwell Publishing Asia Pty Ltd, 2007) Muchiri, Mucai; Miller, Scott N.; Shivoga, William A.; Kibichii, Samuel
Influences of land use/cover on water quality in the upper and middle reaches of River Njoro, Kenya
(Lakes & Reservoirs: Research and management, 2007-06) Shivoga, William, A.; Muchiri, Mucai; Kibichi, Samuel; Odanga, Jethro; Miller, Scott, N.; Baldyga, Tracy, J.; Enanga, Eric, M.; Gichaba, Maina, C.
Data from 10 sampling sites along the River Njoro are used to examine the contribution of nutrients from upstream land uses draining each of the sampling sites. The data also are used to assess whether both the proportion of land uses and the size of the subwatersheds account for the variability in water quality in the River Njoro watershed. Geographical Information System analysis was used to determine the spatial distribution of land-cover types and subwatersheds contributing run-off to the sampling sites in the River Njoro. Standard Digital Elevation Model-based routines were used to establish the watershed area contributing run-off to each sampling site. Water and sediment samples were collected for chemical analysis, and the nutrient levels were related to the upstream land-use types and the size of the subwatersheds. The mid-stream portion of the River Njoro (near Egerton University) accounts for the highest nutrient contributions. The percentage contribution is magnified by additions from industrial, human settlements and agricultural land uses around the University. There is a significant decrease in nutrient levels downstream, however, indicating natural purification as the river flows through an area of large-scale farming with intense, well-preserved riparian and in-stream vegetation. Steep slopes of the land upstream of Egerton University enhance erosion and nutrient losses from those subwatersheds. Mixed small-scale agricultural and bare lands contribute over 55% of the phosphorus load to the upper and mid-reaches of the River Njoro. The size of the subwatershed accounts for about 53% of the variability in the soluble phosphorus in the river. The land-use subwatershed proportions are important for characterizing and modelling water quality in the River Njoro watershed. Upland land uses are as important as near-stream land uses. We suggest that conservation of intact riparian corridor along the river and its tributaries contributes significantly to natural purification processes and recovery of the ecological integrity of the River Njoro ecosystem.
Changes in population characteristics and diet of Nile tilapia Oreochromis niloticus (L.) from Nyanza Gulf of Lake Victoria, Kenya: what are the management options?
(Taylor &Francis, 2007-11-26) Muchiri, Muchai; Njiru, M.; Okeyo-Owuor, J. B.; Cowx, I. G.; Knaap, M. van der
Economic Gain versus Ecological Damage from the Introduction of Non-native Freshwater Fish: Case Studies from Kenya
(2008) Muchiri, Mucai; Hickley, Phil; Britton, Robert; Boar, Rosalind
Non-native freshwater fish species that have been introduced to the inland waters of Kenya are listed and the consequences of stocking such fish are reviewed. Original species composition and lake ecosystem function can be detrimentally affected but, also, the introduction of non-native species can result in significant economic benefit. In the context of impact on recipient fish communities and the performance of exploited fisheries, the merits or otherwise of alien fish species introductions are discussed with the aid of two case histories; lungfish (Protopterus aethiopicus) in Lake Baringo and a number of species, particularly carp (Cyprinus carpio), in Lake Naivasha.
Spatial and seasonal variations in phytoplankton community structure in alkaline–saline Lake Nakuru, Kenya
(Blackwell Publishing Asia Pty Ltd, 2009) Mucai, Muchiri; Okoth, Oyoo Elijah; Shivoga, Wiliam A.; Miller, Scott N.; Rasowo, Joseph; Ngugi, Charles Chege
Difficulties of fishing at Lake Naivasha, Kenya: is community participation in management the solution?
(Blackwell Publishing Asia Pty Ltd, 2010) Muchiri, Mucai; Njiru, James Murithi; Ojuok, Jacob E.; Aura, Christopher Mulanda; Kundu, Rodrick
Difficulties of fishing at Lake Naivasha, Kenya: is community participation in management the solution?
(2010) Muchiri, Mucai; Aura, Christopher Mulanda; Kundu, Rodrick; Njiru, James Murithi; Ojuok, Jacob E.
Unlike other lakes in tropical regions, Lake Naivasha exhibits low fish species diversity. The fishery is based on introduced fish species that are not native to the lake. The lake ecosystem is very fragile, as reflected in its fluctuating fish catches. The fishery almost completely collapsed in 2001, due partly to mismanagement and ignorance about needed conservation measures. The Kenyan government, like many governments around the world, recognized the need to involve fishers and other stakeholders, in order to ensure better management of the lake fisheries resources. Also referred to as collaborative management (co-management), this management approach provides the opportunity to share responsibility for managing the fishery resources between the government and the community. A total ban on fishing was imposed in February 2001, lasting for 1 year, to allow lake fish stocks to recover. This study analyses the co-management process for Lake Naivasha, and discusses the role played by the community during the fishing ban, as well as the successes and challenges encountered, and the tribulations and perceptions of the fishers regarding the new management strategy. It also comprises the first documentation of community participation in fisheries management begun for Lake Naivasha in the year 2001.
Macroinvertebrate assemblages as biological indicators of water quality in the Moiben River, Kenya
(African Journal of Aquatic Science, 2010-01) Muchiri, Muchai; Raburu, P.O.; Masese, F. O.
Zooplankton partitioning in a tropical alkaline-saline endorheic Lake Nakuru, Kenya: Spatial and temporal trends in relation to the environment
(Lakes & Reservoirs: Research and management, 2011) Okoth, Elijah-Oyoo; Muchiri, Mucai; Ngugi, Charles, C.; Njenga, Elizabeth, W.; Ngure, Veronica; Orina, Paul, S.; Chemoiwa, Emily, C.; Wanjohi, Bernard, K.
Spatial and temporal zooplankton variations were studied for 1 year in tropical alkaline–saline Lake Nakuru to determine how they partition in the habitat, relative to environmental variables. Monthly samples were collected at 10 sampling sites, with subsurface tows, using 33.5-lm mesh plankton nets. Physicochemical parameters displayed clear seasonal variations associated with precipitation patterns. Nine species, belonging to two main zooplankton taxonomic groups (ciliates; rotifers), were identiﬁed in the samples. Brachionus dimidiatus dominated the samples, accounting for 80% of the total zooplankton abundance. Kruskall–Wallis tests indicated signiﬁcant (P < 0.05) temporal and spatial variations among all taxonomic groups. Different zooplankton species displayed a clear succession throughout the year. The total abundance of the rotifers and ciliates peaked at sampling sites near inlets during the long rainy seasons, while those in the inshore sites displayed variable succession patterns. Spatiotemporal structure of the zooplankton assemblages, and its correlation with environmental variables, indicated each species displayed distinct niche-based partitioning. The ciliates niche was associated with increasing soluble reactive phosphorus, total phosphorus and nitrite–nitrogen (NO –N) concentrations. Niche partitioning in rotifers was associated with nitrate–nitrogen (NO –N), conductivity and pH. These results indicate physical niche separation, even in a small, relatively homogenous lake among species of rotifers and ciliates, providing information from which future changes in their abundance and spatial distributions can be predicted, given continuous water quality changes.
Haematological Response of Rastrineobola argentea Exposed To Subchronic Doses of Inorganic Cadmium (Cd), Methylmercury and Polychlorinated Biphenyl (PCB) via Dietary Exposure Pathway
(International Journal of Science and Research (IJSR), 2012) Chemoiwa, Emily Jepyegon; Oyoo-Okoth, Elijah
Haematological indices provide information on various aspects of fish health when exposed to environmental contaminants. We evaluated the effects of cadmium, methyl mercury (MeHg), and Polychlorinated Biphenyl (PCB) on the haematological parameters of a tropical fish. One hundred and eighty (180) mature individuals of the freshwater fish Rastrienobola argentea were exposed to dietary subchronic doses of Cd (4 µg g g1 CaCl2), MeHg (0.1 CH3HgCl µg g1 ) and PCBs (0.2 µg g1). After 45 days, blood was sampled from exposed and control groups to evaluate haematological effects of contaminants on erythrocytes, total leukocytes and differential leukocytes counts, haematocrit, heemoglobin concentration, red blood cell indices, mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), and mean corpuscular haemoglobin concentration (MCHC). Results showed that red blood cells counts, haemoglobin concentration, haematocrit, leukocytes, neutrophils, and mononuclear cells counts, significantly (P < 0.05) decrease between control groups compared with the Cd, MeHg and PCB tested groups. The MCV, MCH and MHC showed significant (P > 0.05) increase between control groups with the Cd, MeHg and PCB tested groups. The present study shows that changes in haematological parameters were detectable at sub-chronic exposure to contaminants, but their application in field biomonitoring using R. argentea will need more detailed studies.
Dynamic of Stress Response in Victoria Labeo (Labeo victorianus) during transfer from the Hatchery to cages and Ponds under Differential Caged Stocking Densities
(International Journal of Science and Research (IJSR), 2012) Kuria, Gladys, M.; Ngugi, Charles, C.; Oyoo-Okoth, Elijah
Variation in fish stocking densities translate to difference in growth performance, yields and economic benefits in fish culture. Transferring fish directly from hatcheries to the cages or ponds may induce stress. We evaluated the stress response of Labeo Victoria (Labeo victorianus) in an integrated cage-cum-pond culture during transfer of fish from the hatchery to the cages and ponds at different cage stocking densities. Cages were stocked at varying densities of 10, 30, 60, 90, 120, 150 and 180 fish/m3 and suspended in a static pond of 200 m2 . The L. victorianus fingerlings of a mean weight 23.6 ± 1.8 g were stocked in the cages and the pond respectively. 20 fish were sampled during the transfer period from the hatchery to ponds and cages for analysis of primary and secondary parameters of stress response. Primary stress response occurred when fish were directly transferred to cages and ponds at stocking density ≥ 60 fish/m3 and 90 fish/m3 respectively. Parameters of secondary stress response occurred in fish transferred to the cages at stocking density ≥ 120 fish/m3 and in ponds at density ≥ 150 fish/m3 . Transfer of fish directly from the hatchery to the ponds induce primary and secondary stress.
Recent changes in fish communities of the equatorial Lake Naivasha, Kenya
(International Journal of Fisheries and Aquaculture, 2013-04) Aloo, P.A.; Oyugi, D.O.; Morara, G.N.; Owuor, M.A.
Changes in fish species composition and abundance in Lake Naivasha were investigated monthly for a period of 12 months. Data were obtained both from experimental surveys as well as commercial fish landings. The structure metrics considered included species abundance and composition, length frequency and physico-chemical attributes. Results of the study showed that the fishery is currently dominated by the recently introduced common carp, Cyprinus carpio accounting for over 95% of the total fish landings, with the naturalized fish populations performing dismally both in terms of abundance as well as health conditions. The entry of the common carp into Lake Naivasha may have completely transformed the lake’s ecosystem integrity, driving the initially abundant tilapiine species to near local extinction. The study also confirms a restricted distribution of Micropterus salmoides to rocky-bottomed habitats of Hippo Point and Crescent Lake. Conversely, the long-fin barb, Barbus paludinosus, initially confined to the north swamp and the mouth of River Malewa, currently exhibits a lake-wide distribution. The changing climatic conditions as manifested in the lake level recessions may be a real threat to the fish stocks in the lake. Human activities in the catchment areas may also have contributed to the recent ecological changes witnessed in Lake Naivasha. This study proposes a number of recommendations with a view to ensuring ecosystem integrity and consequent sustainable fisheries of Lake Naivasha.