M. Njiru

University of Eldoret · Fisheries and Aquatic Sciences

of their riparian nations, providing, fisheries and aquaculture products, drinking water, microclimatic buffering, relatively cheap transport means, tourism, biodiversity, employment, and sources of energy (hydropower and oil). Economic growth comes with a cost in the form of pollution (municipal waste, industrial waste, sedimentation, agricultural...

People residing in Lake Victoria’s basin and riparian countries benefit from ecosystem services provided by the lake. However, the lake’s resources, particularly fish, are under threat from pressures caused by humans such as overfishing, alien species invasion, rising eutrophication, and climate change. In this assessment, we look at how to maximiz...

Nile perch were secretly introduced into Lake Victoria in the 1950s, and officially in the 1960s, amid unresolved controversy. Proponents were of the view that the introduction would improve fisheries production and sport fishing. Although the former objective was achieved, the side effects were dire, including extinction of many native species, es...

In the wake of climate change events, spatio-temporal integrated ecosystem models and indices are useful decision support tools for ecosystem management. We developed a preliminary spatio-temporal macroinvertebrate multi-index of biotic integrity (MMiBI) in a major tropical river basin in Kenya. Separation power of Mann–Whitney U test (p < 0.05) qu...

The present study investigated on Length-weight relationship, Condition factor, Sex ratio, Gonadal Somatic Index (GSI) and Size at Maturity of Omena Rastrineobola argentea. Samples (2240 fish) were collected monthly between August 2014 and March 2015 in the Kenyan waters of Lake Victoria. Results for length-weight relationship revealed that R. arge...

Studies on the diet of Rastrineobola argentea were conducted between August 2014 and March 2015 in the Kenyan waters of Lake Victoria. Stomach contents of 1154 specimens collected from commercial fishers and experimental seining were analyzed. Juveniles of R. argentea under 30 mm SL fed almost exclusively on zooplanktons, while adult fish larger th...

Land‐use changes in the upper reaches of the Mara River Basin have modified their biophysical and hydrological processes, resulting in water quality degradation in streams. This study was conducted to investigate the effects of human activities on water quality and macroinvertebrates along the Nyangores River, one of the main tributaries of the Mar...

A study was done on feeding ecology of re-introduced Oreochromis niloticus (L.) in Lake Naivasha, Kenya between November 2013 and February 2014. The main focus of the study was on fish size, diet, habitat, and diel feeding regime. 434 fish samples were collected every two weeks from five stations covering the entire lake by use of gill nets (50 mm...

Fish samples (541) were collected every two weeks from different parts of Lake Naivasha using gill nets (50 mm to 150 mm mesh size) and beach seines (< 10 mm) between November 2013 and February 2014.The main focus of the study was on sex ratio, length-weight relationship and body condition of Nile tilapia. Results revealed that there were more male...

Lake Victoria, East Africa, supports a fishery that yields about one million tonnes per annum consisting predominantly of three species, Nile Perch (Lates niloticus), Nile Tilapia (Oreochromis niloticus) and a native sardine-like cyprinid called Dagaa (Rastrineobola argentea). The non-native Nile Perch is the most valuable of these species and supp...

The spatial and seasonal structures of fish assemblages in a tropical mangrove tidal creek, Tudor, Kenya, were analysed from monthly survey data, extending from October 2007 to July 2008, and covering the north-east (NEM; October–March) and south-east (SEM; April–July) monsoon seasons. A total of 2 118 individuals, representing 84 species belonging...

Oreochromis variabilis (Boulenger), a fish species endemic to Lake Victoria, was abundant, forming an important component of the indigenous fisheries stocks before and up to the late‐1950s. Catches declined drastically thereafter, and only sporadic catches are currently found in Lake Victoria. Remnants population of the species, however, are found...

The decline in fish species in Lake Victoria is one of the largest documented losses of biodiversity in an ecosystem. The reduction in species in the lake was attributed to overexploitation through increased fishing capacity, use of illegal fishing gears and poor enforcement of regulations. Introduction of the predatory Nile perch is blamed for the...

A study on some biological parameters of the mountain catfish, Amphilius uranoscopus Pfeffer 1889 (Silurifomes: Amphiliidae), was carried out in the Thego stream on the slopes of Mount Kenya from February to December 2002. Physical and chemical profiles of the Thego show that the water quality parameters is typical of high altitude streams with tem...

Abstract The fishery of Lake Victoria became a major commercial fishery with the introduction of Nile perch in 1950s and 1960s. Biological and population characteristics point to a fishery under intense fishing pressure attributed to increased capacity and use of illegal fishing gears. Studies conducted between 1998 to 2000 suggested capture of fis...

This study reports on the population parameters, catch distribution and feeding ecology of Nile tilapia (Oreochromis niloticus) from bottom trawls and commercial catches obtained in the Kenyan portion of Lake Victoria during 1997–2006. The population parameters were analysed using the FAO-ICLARM stock assessment tool (FISAT). The fish biomass and t...

Nile tilapia, Oreochromis niloticus and Nile perch, Lates niloticus were introduced into Lake Victoria in the 1950s and 1960s. The former was to boost the then declining tilapiine fishery, while the latter was to convert the abundant bony haplochromines to fish flesh. Fish samples were collected by bottom trawling from 1998 to 2000 and in 2004 to 2...

Lake Victoria is African's most important source of inland fishery production, exhibiting an annual catch of ≈500 000 mt. The lake moderates local climate, serves as a means of transport, and a source of human food and raw material for the fishmeal industry. The introduction of Nile perch transformed the fisheries from a locally based artisanal fis...

IntroductionMaterials and methodsResultsDiscussionAcknowledgements

Studies were conducted on reproductive characteristics of Oreochromis niloticus from 1998 to 2000. The results were combined with published work on growth parameters of O. niloticus from 1985 to 1999 in order to establish the current survival strategies exhibited by O. niloticus in the Nyanza Gulf of Lake Victoria. The study revealed that size at m...

Length frequency data collected from 1998 to 2001 from commercial landings was used to estimate asymptotic length (L∞), growth coefficient (K), mortality (Z, F, M), growth performance index (φ ′) and exploitation rate (E) of Oreochromis niloticus from the Nyanza Gulf of Lake Victoria, Kenya. Studies on the diet of O. niloticus collected by demersal...

Abstract Population characteristics from samples collected during bottom trawl surveys of 1998–2000 and 2004–2005 were compared to evaluate the success of the management strategies put in place for Nile perch, Lates niloticus and Nile tilapia, Oreochromis niloticus fisheries in Lake Victoria. Data were analysed using FAO-ICLARM stock assessment too...

The life history characteristics of introduced Nile tilapia (Oreochromis niloticus L.) in Lake Victoria, including, sex ratio, fecundity, reproduction, weight-length relationship and body condition were studied and compared with those of other populations. Samples were collected by trawling and seining in the Kenyan sector of Lake Victoria between...

Abstract Lake Victoria is one of the African Great Lakes, and an important source of affordable protein food in the form of fish. It provides employment, income, and export earnings to the riparian communities. Despite this importance there are major concerns about the status and exploitation of the fisheries. This study assesses if current extract...

Lake Victoria is Africa's most important source of inland fishery production, exhibiting annual catches of ≈ 400 000 mt. The predatory Nile perch, Lates niloticus, and the herbivorous tilapiines, Oreochromis niloticus, Oreochromis leucostictus, Tilapia zillii and Tilapia rendalii, were introduced in Lake Victoria in the 1950s and 1960s. Nile perch...

Studies of the food of introduced Nile tilapia, Oreochromis niloticus (L.) with respect to size, habitat and season were conducted between November 1998 and October 2000 in Kenyan waters of Lake Victoria. Stomach contents of 1980 specimens collected by demersal trawl and seining were analysed. Nile tilapia originally known to be herbivorous, feedin...

To verify that increments observed in the otoliths of R. mgentea were deposited daily, fish were immersed in tetracycline hydrochloride (TC) of 100-600 mg L.1 between 2-24 hours. TC was found to be incorporated within 12 hours after immersion in 600 mg L-1. Otoliths were marked with a band that fluoresced in ultraviolet (UV) light. Daily rings corr...

Length-frequency data collected from fish landings on Lake Naivasha were used to estimate the growth parameters: total mortality (Z), growth performance index (O’), exploitation rate and recruitment pattern in Oreochromis leucostictus. The asymptotic length (L∞) was 38 cm and K 0.48 yr -1 Z was estimated as 3.5 yr -1, M was 0.19 yr -1, F was 2.6 yr...