The study was conducted at Kegati Aquaculture Center (KMFRI) for 12 weeks to evaluate the effect of water quality parameters on the growth and survival rates of Oreochromis jipe and Oreochromis niloticus. The fingerlings (n = 270), were stocked in triplicates in 9m2 raised ponds arranged in double series and fed on a 30% CP ration twice a day at 10% total bodyweight. Water quality parameters were measured daily using the YSI multi-parameter meter. Fish total length and bodyweight was determined biweekly using a measuring board and a digital weighing balance, respectively, and survivals were determined from the initial and final counts of fingerlings. Data were analyzed with an unpaired sample t-test using R-software and statistical significance was considered at p < 0.05. Temperature, total dissolved solids (TDS), and salinity showed no significant differences, whereas the pH and dissolved oxygen (DO) levels were significantly different (p < 0.05) between the O. jipe and O. niloticus. Furthermore, O. jipe attained a lower final mean weight (12.16 ± 0.34 g) compared to O. niloticus (29.79 ± 0.91 g). The study recommends a further study be conducted in a controlled culture environment to establish optimal conditions for O. jipe culture.

Length-weight relationships (LWRs) and condition factors are important for effective management of riverine fisheries. This study investigated the LWRs and condition factors of the dominant fish species from Nyangweta tributary of River Kuja, in Lake Victoria Catchment, Kenya. A total of 615 fish of seven dominant species were analyzed: Enteromius altianalis, Enteromius neumeyeri, Clarias theodorae, Labeo victorianus, Labeobarbus altianialis, Chiloglanis species and Amphilias jacksonii. The fish were sampled from five locations from October 2020 to March 2021. The length and weight measurements were taken using a measuring board and an electronic balance respectively and used to determine Fulton's (KF) and allometric (Ka) condition factors. The largest species was E. altianalis (70.74 ± 8.72g), followed by L. altianialis and L. victorianus with mean body weights of 62.14 ± 3.48g and 56.43 ± 11.26g respectively. With exception of E. altianalis and C. theodorae, the Fulton's condition factors (KF) of all the species were greater than (1) and not significantly different (p = 0.43) among the species. Majority (four) of the species exhibited positive allometry (Ka > 3), while only one species exhibited isometric (Ka = 3) growth, due to different body profiles which may not allow uniform growth of all individuals of the same species, a large percentage of females in adult fish populations and high nutrient influxes. The LWRs were significant and showed strong linear relationships between total and standard lengths and body weight (p < 0.05, R2 > 0.5). These findings suggest that conservation measures need to be taken to improve the fish health and physiological condition in upstream areas of the Nyangweta tributary.

Partial least squares (PLS) is a multivariate dimension reduction technique which is not based on ordinary regression assumptions. The use of PLS regression in life sciences is still a novel concept despite many scientific applications. This paper analyses the influence of physicochemical in the two fish species, Oreochromis jipe and Oreochromis niloticus to determine the cause for their growth difference in the same culture environment. The graphical display of the multi-parameter analysis was performed using a suite of open access R-software packages. The modeling hypothesis was assessed using experimental data collected for the period of 84 days. The findings revealed that significant linear relationship exists between water quality and mean weight of both O. jipe and O.niloticus fish species. Being a crucial study meant to provide baseline information to asses the aquaculture potential O. jipe, we recommend a further study to be conducted on several other predictor variables that can be measured under controlled aquaculture conditions.

Species introductions have impacted the fishery potential, ecology and native fisheries populations of Lakes Victoria and Jipe. Oreochromis esculentus and Oreochromis niloticus have been widely introduced outside their native range establishing feral populations. However, the impacts of invasive species on management of native species biodiversity has not been documented. The establishment of exotic O. niloticus species populations in Lake Victoria has been accompanied by declining native populations of the O. esculentus and Oreochromis variabilis. These declines have been accelerated by the introduction of Nile perch, Lates niloticus, which preys upon the native O. esculentus, and overfishing of native fisheries which have slow growth rates and low fecundities. Moreover, nutrient pollution and eutrophication have impacted negatively the the food resources for native Singida tilapia O. esculentus. Native Jipe tilapia, Oreochromis jipe is limited in distribution to a small native range in the Pangani system comprising of Lake Jipe, the Pangani River tributaries and the downstream Nyumba ya Mungu Reseivoir. In Lake Jipe, two non-native species O. niloticus and O. esculentus have been introduced. Although the impact of O. niloticus on native O. jipe populations has not been documented, O. jipe has witnessed dwindling catches since the introduction of O. esculentus from the downstream reservoir. The decline can also be attributed to overfishing and the changing ecology of the lake after proliferation of emergent macrophytes such as Typha domingensis. There is need to formulate management policies to monitor and control fishing effort, pollution and protecting the lake and its catchment from degradation caused by human activities.

The study was conducted at Kenya Marine Fisheries Research Institute (KMFRI), Sangoro Station, Kenya to compare the growth perfomance of Oreochromis niloticusfry under different protein levels in a biofloc system using weight-length regression models and Fulton`s condition factor (K). Fry of initial mean weight 0.07 ± 0.03 g and length 1.30 ± 0.24 cm were randomly stocked in 18 aquarium tanks with capacity of 50 litres at stocking density of one fish Litre-1. The experiment was set in a greenhouse under controlled temperature and dissolved oxygen conditions using aerators and thermostat heaters. The biofloc used glucose and molasses as carbon sources which were assigned at 22%, 27% and 35% crude protein levels randomly to the aquaria. The fish were fed on their daily ration twice a day at 5% body weight for 14 weeks. Physicochemical parameters were recorded daily using a multiparameter meter and water samples collected before fish sampling for nutrient analysis. A sample of 30 fish per tank were used for taking body weight and total length measurements using an electronic balance and a measuring board respectively. Fry in all treatments exhibited allometric growth with b coefficient varying between 2.54 and 2.66. Average Fultons condition factor ranged between 1.77-1.84 with no significant difference (P>0.05)among the protein levels and the bioflocs. The condition factor showed both carbon sources were suitable for use in the biofloc system and hence replacement of higher protein level (35%) with lower protein level (22%) to reduce the production cost is a feasible application of the biofloc system in fish farming.