KMFRI Library Search for 'au:"Opiyo, M.A."'

PCBs in fish and their cestode parasites in Lake Victoria

2016 , Polychlorinated biphenyls (PCBs) are classified as persistent organic pollutants (POPs) regulated by the Stockholm Convention (2001). Although their production and use was stopped almost three decades ago, PCBs are environmental persistent, toxic, and bioaccumulate in biota. We assessed the levels of 7 PCB congeners (IUPAC nos. 28, 52, 101, 118, 138, 153, and 180) in sediment and fish (Oreochromis niloticus, Lates niloticus, and Rastrineobola argentea) and evaluated the potential of cestode fish endoparasite (Monobothrioides sp., Proteocephalaus sp., and Ligula intestinalis) as biomonitors of PCBs in Lake Victoria, Kenya. The median concentration of Σ7PCBs in sediments and fish were 2.2-96.3 μg/kg dw and 300-3,000 μg/kg lw, respectively. At all the sampling sites, CB138, CB153, and CB180 were the dominant PCB congeners in sediment and fish samples. Compared to the muscle of the piscine host, Proteocephalaus sp. (infecting L. niloticus) biomagnified PCBs ×6-14 while Monobothrioides sp. (infecting O. niloticus) biomagnified PCBs ×4-8. Meanwhile, L. intestinalis (infecting R. argentea) biomagnified PCBs ×8-16 compared to the muscle of unparasitized fish. We demonstrate the occurrence of moderate to high levels of PCB in sediments and fish in Lake Victoria. We also provide evidence that fish parasites bioaccumulate higher levels of PCBs than their piscine hosts and therefore provide a promising biomonitor of PCBs. We urge further a long-term study to validate the use of the above cestode fish parasites as biomonitoring tools for PCBs.

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Cost-Benefit Analysis and Growth Effects of Pelleted and Unpelleted On-Farm Feed on African Catfish (Claries Gariepinus Burchell 1822) in Earthen Ponds.

2013 , Fish feed constitutes 40-60% of the total operational costs of a fish farm. Commercial feeds are often too expensive for rural fish farmers. Consequently, farmers use non-conventional and locally available fish feed ingredients including agro-industrial by-products. These feeds have not led to increased pond productivity due to poor processing, higher fibre content, and anti-nutritional factors that limit nutrient bio-availability. Farmers have not embraced processing of fish feeds because the cost-effectiveness of processing has not been clearly demonstrated. The African catfish (Clarias gariepinus) is an important farmed fish in sub-Saharan Africa hence the need for research on its nutrition and growth performance. The growth performance and cost-benefit of using pelleted diets formulated from locally available feed ingredients on C. gariepinus were evaluated in a rural African setting. The experiment included diets that differed in the ingredients and form used (pelleted and un-pelleted). Four isocaloric and isonitrogenous diets were formulated from freshwater shrimp (Caridina nilotica), rice bran (Oryza sativa) and wheat bran (Triticum aestivum). The diets were C. nilotica and wheat bran pelleted (CWBp), C. nilotica and wheat bran un-pelleted (CWBup), C. nilotica and rice bran pelleted (CRBp), and C. nilotica and rice bran un-pelleted (CRBup). The diets were fed to C. gariepinus fingerlings (mean initial weight 1.75±0.03g), in triplicates for 5 months. The pelleted diets showed significantly better performance (P<0.05) compared to the un-pelleted diets. Fish grew to a weight of 266.77±6.21g on CWBp, 224.9±3.91g on CRBp, 211.38±4.46g on CWBup and 190.87±4.47g on CRBup. Cost benefit analysis of the pelleted and un-pelleted diets indicated positive net returns of US$ 180.1 for CWBp, US$142.5 for CRBp, US$ 126.8 for CWBup and US$ 115.5 for CRBup. The CWBp had significantly higher net returns than the other diets. This paper demonstrates that although on-farm pelleting of diets adds extra cost of labour, pelleted diets are cost-effective and should be incorporated as an essential part of on-farm feed production.

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Anaesthetic Effects of Sodium Bicarbonate at Different Concentrations on African Catfish (Clarias gariepinus) Juveniles.

2016 , In the present study, anaesthetic effects of different sizes (5, 10, 15, 20, 25, 30, 35 and 40g) of African catfish (Clarias gariepinus ) juveniles was investigated at different concentrations (0/control, 10, 15, 20, 25, 30, 35, 40, 45, 50 g/L) of sodium bicarbonate. Juveniles were bath immersed in each of the different concentrations of sodium bicarbonate solution for 5 minutes and recovery times in clean aerated water was established. Juveniles took between 0.67 to 5.44 minutes to reach full anaesthesia and 0.66 to 4.25 minutes to recover fully from anaesthesia. An inverse exponential relationship was observed between sodium bicarbonate concentrations and induction time, whereas exponential relationship was observed between sodium bicar-bonate concentrations and recovery time. Size of C.gariepinus juveniles significantly affected the induction time (P < 0.05) with smaller juveniles getting to full anaesthesia faster than bigger juveniles at the same concentration of sodium bicarbonate. In addition, recovery time was size dependent where smaller C. gariepinus juveniles took significantly longer time (P < 0.05) to recover from anaesthesia than bigger juve-niles. All juveniles reached anaesthesia and recovered in less than 5 minutes except for 30 g juveniles at 15g/L of sodium bicarbonate which was anaesthetized at 5.44 minutes. 2149-0236

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Good Aquaculture Practices for Seed production in Kenya Volume 1: Tilapia and Catfish

49. 978-9966-100-07-8

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Effects of Probiotics on Growth, Flesh Quality and Hematoimmunological Status of Cultured Nile Tilapia (Oreochromis niloticus) in Kirinyaga County, Kenya

Niarobi Kenyatta University 2020 , A Thesis Submitted in Fulfillment of the Requirements for the Award of the Degree of Doctor of Philosophy (Fisheries Science) in the School of Pure and Applied Sciences of Kenyatta University August, 2020 120. I84/27364/2014

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