Rastrineobola Research Articles

Unravelling taboos and cultural beliefs associated with hidden hunger among pregnant and breast-feeding women in Buyende district Eastern Uganda.

Food taboos and cultural beliefs among pregnant and breast-feeding women influence their food consumption patterns and hence the health of women and unborn children. Cognizant of their neglect in programs aimed to ameliorate hidden hunger among pregnant and breast-feeding women in Buyende and other resource-poor communities in sub-Saharan Africa, we opted for a study to unravel them to inform program design. We documented food taboos and beliefs amongst pregnant and breast-feeding women from six sub-counties of Buyende district in Eastern Uganda. A mixed-methods approach was used, which was comprised of questionnaire interviews with 462 women, eight focus group discussions with 6-10 participants in each and a total of 15 key informant interviews. The present study revealed that 129 (27.9%) of the respondents practice food taboos and adhere to cultural beliefs related to their dietary habits during pregnancy and breast-feeding that are fuelling the prevalence of hidden hunger. The most tabooed foods during pregnancy were sugarcane (17.8%), fishes which included lung fish, catfish and the Lake Victoria sardine (Rastrineobola argentea) (15.2%), oranges (6.6%), pineapples (5.9%), eggs (3.3%), chicken (3.3%) and cassava, mangoes and Cleome gynandra (each at 3%). Most foods were avoided for reasons associated with pregnancy and labour complications and undesirable effects on the baby. Most women learnt of the taboos and beliefs from the elders, their own mother, grandparents or mother-in-law, but there was also knowledge transmission in social groups within the community. The taboos and cultural beliefs in the study area render pregnant and breast-feeding women prone to micronutrient deficiency since they are denied consumption of a diversity of nutritious foods. There is a need to educate such women about consumption of nutrient-rich foods like fish, eggs, fruits and vegetables in order to improve their health, that of the unborn and children being breast fed. Additionally, culturally appropriate nutrition education may be a good strategy to eliminate inappropriate food taboos and beliefs with negative impact on the health of pregnant and breast-feeding women.

Use of black soldier fly larvae and freshwater shrimp to partly substitute commercial diet for Nile tilapia cultured in smallholder fish farms – A case study in Busia County, Kenya

Fish-farming in Kenya is challenged by the availability and high cost of feed ingredients, especially protein sources. Using black soldier fly larvae (Hermetia illucens) (BSFL) directly or indirectly as a feed ingredient to feed fish is interesting as they efficiently convert organic wastes into high-quality proteins. In addition, the freshwater shrimp (Caridina nilotica) (CN), an important by-catch of the silver cyprinid (Rastrineobola argentea) fisheries in Lake Victoria, could be another alternative protein source. Therefore, this study determined whether dried BSFL or dried CN could partly substitute the commercial diet when growing Nile tilapia (Oreochromis niloticus) in a smallholder farm aggregated in an aquapark. The nutritional values and cost-effectiveness of the alternative feeding strategies were compared to commercial diet (CD) only. During an 84-day experimental period, Nile tilapia were fed one of the three feeding strategies, including the use of only the commercial diet, to be compared with diets replacing 20% of the commercial diet with BSFL or CN. The fish were fed to apparent satiation twice a day. At the end of the trial, biomass, the number of fish, growth, survival rate, total fish production, economic feed conversion rate and productivity per pond, were determined. As such, Body Weight (BW) was similar across feeding strategies (P > 0.05), measured 63.2 ± 3.9, 68.0 ± 7.4 and 68.0 ± 7.4 g for fish-fed diets with CD, BSFL and CN, respectively. Hence, nutritionally and from a production point of view, the three feeding strategies used in this study performed equally well. Notably, the use of BSFL led to a significantly higher economic return (P < 0.05) compared to the use of CN and commercial diet alone. The trials in this study demonstrate that BSFL and CN can be used to partly substitute commercial diet. In addition, the trial show that the use of BSFL to partly substitute the commercial diet can boost sustainable fish production in a smallholder farm set-up aggregated in an aquapark.

Modelling andin situobservation of broadband acoustic scattering from the Silver cyprinid (Rastrineobola argentea)in Lake Victoria, East Africa

AbstractLake Victoria is the second-largest freshwater lake in the world, and fish from the lake are a vital food resource for millions of people living around it. The silver cyprinid (Rastrineobola argentea), a small schooling pelagic species known in Tanzania as “dagaa” contributes ca. 55% to the total annual catch (ca. 0.51 million tonnes (MT) in 2014). The acoustic target strength (TS, dB re 1 m2) of dagaa, a key factor for biomass estimation, is however not well described, and is a major source of uncertainty in biomass estimation. In this study, we developed a Kirchhoff-ray mode (KRM) model to predict the TS of dagaa at standard fisheries survey frequencies. The model was based on the morphology of the body and the dual-chambered swimbladder, as obtained from X-ray images of fish ranging in total length (TL) between 2.8 and 5.4 cm. The results suggested that the swimbladder (which comprises 2.6 to 8.2% of body volume) accounts for ca. 65 to 90% of the total backscattering at 120 kHz. The predicted TS was highly dependent on tilt angle, varying by 14.0 dB at 120 kHz across the tilt range 65–115˚ (where 0˚ is head up and 180˚ is tail up), and TS variability with tilt generally increased with increasing frequency. The tilt angle of acoustically tracked individual fish indicated a distribution of tilt angles with a mean and s.d. of 93.5 and 15.1°. Our model suggested a new tilt-averaged TS–TL relationship for dagaa [$T{S}_{120\ kHz} = 19.49\log ( {TL} ) - 70.3$], which leads to a TS 1.5 dB higher than the value in the relationship presently used to estimate stock biomass. The new relationship will lead to a substantial reduction (by ca. 30%) in estimated biomass. The discrepancies between the mean relative frequency response of the in situ measurements of backscatter from dagaa and the KRM model predictions were in the range of -2.9–3.1 dB at frequencies from 45 to 250 kHz. The KRM modelling and in situ broadband measurements of dagaa will be beneficial for acoustic identification and behavioural studies of dagaa, and will enable improved biomass assessment, thereby underpinning sustainable long-term management.

Putting small fish on the table: the underutilized potential of small indigenous fish to improve food and nutrition security in East Africa

Sub-Saharan Africa has a high prevalence of food insecurity. Small pelagic fish such as Silver cyprinid (Rastrineobola argentea) which is indigenous to Lake Victoria, can be a nutritious animal sourced food that contributes to a more nutrient dense diet. Potential sustainable catch of Silver cyprinid is estimated at 2 million tonnes yearly, which is four times the amount of the current catch. Whole sun-dried Silver cyprinid was purchased from several markets in Kenya and analysed for nutrient composition, microbial counts and metal content. The results show that utilizing the whole potential catch of Silver cyprinid would provide a significant daily source of vitamin B12, calcium, zinc and iron to the roughly 33 million people living in the Lake Victoria basin. Heavy metal concentration appears to be low, but other food safety aspects like microbial counts call for value chain improvements. We conclude that the underutilized potential of sun-dried Silver cyprinid could substantially contribute to fight malnutrition and food insecurity by providing an affordable nutrient dense animal sourced food to a large number of people. It also highlights the need to improve the value chains to increase the safety of these products.

Changes in fatty acids during storage of artisanal-processed freshwater sardines (Rastrineobola argentea).

For ages, indigenous small fish species have been important in food and nutritional security of poor communities in low income countries. Freshwater fish, in particular fatty fish species are attracting a great attention because they are good sources of health promoting long chain omega-3 fatty acids. Docosahexaenoic acid (DHA, C22:6n-3), Docosapentaenoic acid (DPA, C22:5n-3) and eicosapentaenoic acid (EPA, C20:5n-3) are the main omega-3 PUFAs known to confer health benefits in humans if consumed in required amounts. While nutritionally valued, omega-3 PUFAs in fish are susceptible to oxidative damage during processing, transportation and subsequent storage. Lake Victoria sardines (Rastrineobola argentea), are rich source of chemically unstable omega-3 fatty acids DHA, DPA and EPA. Traditionally, sardines are preserved by sun drying, deep frying and smoking. Sardine products are transported, stored and marketed at ambient temperatures. Generally, uncontrolled and higher temperatures are known to increase vulnerability of polyunsaturated fatty acids to oxidation which in turn results into loss of nutritional and sensory qualities. This study investigated changes of fat acids in sun dried, deep fried and smoked sardines during storage. Lipolysis and the progressive hydroperoxides formation were monitored by free fatty acids (FFAs) and peroxide value (PV) respectively. None volatile secondary products of lipid oxidation were measured by thiobabituric acid reactive substances (TBARS). Fatty acids were analyzed by gas chromatography with a flameionization detector (GC-FID). Deep fried sardines maintained the lowest and apparently stable PV, TBARS and FFAs. Proportions of saturated fatty acids and polyunsaturated fatty acids decreased with time while that of monounsaturated fatty acids increased. Omega-3 fatty acids EPA, DPA and DHA decreased with increase in storage time. In 21 days of storage, DHA was oxidized beyond detectable levels in all sardine products. Gradual increase in FFAs in sun dried sardines was suggestive of lipid hydrolysis induced by enzymes.

English

Silver cyprinids (Rastrineobola argentea) are small pelagic fish endemic to Lake Victoria. High-quality dried fish are an important protein-rich human food. This study was carried out to determine if it would be practical to use renewable energy to dry silver cyprinid. Drying is presently achieved by laying fish out in the sun on the ground or on racks. In the wet seasons, however, drying is compromised and much of the catch becomes fit only for animal consumption, or spoils. Lake Victoria’s surface waters are c. 25°C year-round. Its enormous volume of tropical water offers a source of thermal energy that could be used to dry fish. As a proof of concept, we used solar-generated electricity to drive a heat pump to harvest heat energy from water in a 10,000-L rainwater tank beside Lake Victoria, used the energy to heat air, and blew the air over fish in a tent-like enclosure. Fish in the enclosure dried in about 4 h versus about 7 h outside, were free from insects, and not at risk of theft by or defecation upon by birds. The drying processes inside and outside the enclosure were modelled. The model correctly reproduced observed drying times, and enabled exploration of options to improve drying performance. Up-scaling the prototype could provide year-round sustainable fish-drying capability, reduce waste, boost food security, and add value to the catch.   Key words: Rastrineobola argentea, dagaa, mukene, omena, drying, renewable energy, food security.

Performance of diets composed ofArtemiabiomass and fish meal fed to juvenile marine Tilapia in cages

AbstractMariculture development in Kenya has previously relied on culture of fish in intertidal earthen fish ponds that are fertilized to enhance primary production and use of limited supplementary feeds. Most of the supplementary feeds used have previously been obtained from those of freshwater fish due to lack of marine fish feeds in the country. Cage culture is being introduced to utilize the open space in the sea and hence introduction of more species for farming, that require new feeding strategies that are feasible. Therefore the need to develop marine based fish feed formulations. Taking this into consideration, Kenya Marine and Fisheries Research Institute is developing a feed formula that brings ingredients from the coastal environment that are unique: i.e. seaweeds, coconut husks and Artemia for development of a marine feed. Initial assessments of the developed feed indicate that marine Tilapia grows at 1.2 g day-1, Rabbitfish at 1.9 g day-1 and Milkfish at 1.4 g day-1. The formula is being refined and validated over time before being given out for commercial use in the feed industry to enhance production from mariculture. The treatments were carried out in replicate during a culture period of 138 days. Locally formulated and prepared diets containing 30% crude protein were applied. Treatment 2, a fish meal omena (Rastrineobola argentea) based feed showed better growth outcome as compared to treatment 1 (Artemia based feed) in terms of weight gain, specific growth rate (0.93), survival rate (70%) and feed conversion ratio (2.2). Frequent data collection for both water quality and growth parameters is recommended to enable visualize better growth trends and culture conditions. Further research at different stocking densities with larger juveniles (50g weight) that can withstand the cage environment is recommended.

Elemental composition of small pelagic fishes in three East African lakes: Implications for nutritional security

Micronutrient deficiencies and food insecurity constitute major threats to human health across Africa. With decreasing availability of large-bodied fishes (>20 cm), strategies have developed to target small pelagic fish (SPF) species (<20 cm total length) to improve the food availability; yet little is known regarding their nutritional content. Three species of SPFs - Engraulicypris bredoi (muziri), Brycinus nurse (ragoogi) and Rastrineobola argentea (mukene) - were collected from lakes Albert, Victoria, and Nabugabo in Uganda, East Africa. The content of essential elements (Ca, Fe, K, Mg, Na, P, Se, and Zn) and non-essential, potentially toxic elements (Cd and Pb) were measured and compared in fishes across landing sites within lakes Victoria (R. argentea) and Albert (B. nurse, E. bredoi) and between lakes (R. argentea). Rastrineobola argentea was the most nutritious of the fishes examined, although some variation was present in their elemental concentration among landing sites. Overall, all three species contain high levels of essential nutrients and fall within a safe range for non-essential, toxic elements based on current consumption habits. These SPFs can play an important role in addressing nutritional deficiencies in Uganda, and effort should be made to increase the availability, accessibility, and consumption of these under-utilized small fishes.

Lake Victoria’s bounty: A case for riparian countries’ blue economic investment

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 maximize the lake’s benefits through product diversification, value addition, and sustainable use of its fisheries. We show that minimizing post-harvest losses of the silver cyprinid (Rastrineobola argentea), locally known as Dagaa, will provide more high-quality fish for human consumption, while significantly increasing fishing earnings. Furthermore, by utilizing biowaste (frames, skin, and fish mouth), revenues from Nile perch could be increased up to thrice. Furthermore, if fishing could target maximum sustainable yield (MSY), landings of Nile perch and Dagaa could increase significantly in the long run. These, combined with investments in other areas such as lacustrine tourism and recreation, as well as fish cage culture, can help the Lake Victoria region’s blue economy expand.

Are the Solar and Battery-Powered Lights used for Dagaa Rastrineobola argentea Fishing a Threat to the Nile Perch Lates niloticus Fishery in Lake Victoria?

For decades, the harvesting of Dagaa (Rastrineoboala argentea) from Lake Victoria and other waters bodies relied on lanterns as the primary source of light attraction. Being one of Lake Victoria’s top four economically significant fisheries, Dagaa has a significant impact on the macro- and microeconomics of East African nations. Recent innovation for harvesting Dagaa using solar and battery-power lights, have raised conserns about the sustainability of Nile perch. The current declining Nile perch is associated with the introduction of solar and battery-powered lights. To validate the consern, TAFIRI conducted a Dagaa fishing light research. Dagaa fishing research was conducted in offshore waters around Bwiru in Nyamagana district and questionnaires administered in Ilemela district in May 2022. It was revealed that solar light caught 6 fish species and battery-powered had 5 with relatively higher catch rate dominated by Dagaa solar (60.2 kg/boat/day) and battery-powered lights (105 kg/boat/day). The widest range of species were caught in boats using no fishing light (12 species), with catch rates dominated by Haplochromines (15.1 kg/boat/day). Nile perch catch rates were relatively low in (i.e., battery-powered 18.8; solar 15.7; and no light 1.8) kg/boat/day. Finally, it was determined that catching immature fish, such as Nile perch, is more frequently associated with fishing in inshore areas and fishing illegally, rather than accusing any types of fishing light. While it was found that competition for the same fishing ground was the main source of the conflict between Nile perch and Dagaa fishermen, fish theft by Dagaa fishers and Nile perch patrol boats swindling the solar and battery-powered lamps was another instance of conflict. Strengthening law enforcement may help to eliminate all of these discrepancies, including those that result from the use of illegal fishing gear and techniques and those that restrict use of drifting gill nets in Lake Victoria.

Fisheries management on Lake Victoria at a crossroads: Assessing fishers’ perceptions on future management options in Uganda

AbstractFishers’ perceptions on the state of fisheries and the applicable fisheries management system in Lake Victoria (LV), Uganda, were assessed. Fisheries management in the lake is currently at a crossroads. The government abolished a co‐management system in November 2015 and installed the military to temporary enforce management. The objective of this study was to explore how fishers envisage future management options by assessing past management regimes and analysing perceptions of alternative regimes. A total of 273 semi‐structured interviews at six selected landing sites on LV in Uganda were conducted. Fishers targeted two dominant species, Nile perch, Lates niloticus (L.), mainly on motorised vessels representing the commercial fishers and dagaa, Rastrineobola argentea (Pellegrin), using both motorised and paddled vessels. The dominance of motorised fishing vessels depicted a consequence of the army operations and represents government priority to protect rather than regulate commercial fishing operations. Fishers mainly perceived regulations they knew about as effective, strongly opposed local governments as a management entity and assigned management to fisher groups as expected. The results support a management regime of key resource users organised by common interest groups to participate in decision‐making and combined government structures to regulate and enforce sustainable fisheries measures.

Trends in an emerging artisanal fishery of the African cyprinid Rastrineobola argentea in Lake Nabugabo, Uganda

AbstractFishing pressure can have strong impacts on fish populations, driving declines in abundance and, occasionally, changing life history traits. However, much of our current understanding of these phenomena derives from studies conducted decades or even centuries after the onset of fishing. Newly established fisheries provide an excellent opportunity to understand this critical early phase. Temporal trends in catch data and life history traits of the cyprinid fish Rastrineobola argentea (Pellegrin), now the target of a burgeoning artisanal fishery in Lake Nabugabo, Uganda, were analysed. Results showed that the R. argentea fishery intensified and became more selective during the first decade since its establishment (2008–2019), while catch‐per‐unit‐effort of R. argentea (fisheries‐independent abundance) at repeatedly sampled sites in the lake decreased over this same time period. Size‐adjusted egg volume and ovary mass increased significantly over the time period, which may reflect a density‐dependent response to a fisheries‐induced population decline.

Comparison of calcium concentration in scales and vertebral column of a cyprinid from calcium-limited environments in the Lake Victoria Basin, Uganda

Despite dramatic differences in calcium concentrations within aquatic systems, very few studies have explored the relationships between ambient calcium concentration and the calcium concentration of resident fish under natural conditions. This study compares calcium concentration in the water to that of the scales and vertebral column of the African cyprinid, Rastrineobola argentea from lakes Nabugabo and Victoria, East Africa. The concentration of calcium in Lake Nabugabo, which averaged 1.50 mg l−1, was much lower than the average of literature-derived values for the Ugandan portion of Lake Victoria (6.96 mg l−1). Rastrineobola argentea from Lake Victoria were characterised by higher levels of calcium in the scales than that of conspecifics from Lake Nabugabo, whereas there was no difference in vertebral column calcium concentration between the two populations. Within Lake Nabugabo, calcium concentration was lower in the scales than in the vertebral column of R. argentea, whereas no difference was detected between the scalar and vertebral calcium concentrations of conspecifics from Lake Victoria. These results suggest that ambient calcium concentration may affects tissue levels and that fish in Lake Nabugabo may remobilise calcium from their scales to maintain skeletal growth and development.

Effect of Packaging on the Stability of Stored Dry Silver Cyprinid (Rastrineobola argentea)

Dried silver cyprinid (Rastrineobola argentea) has the potential to provide an affordable and accessible food-based strategy to fight malnutrition among Ugandans and enrich diets of the vulnerable persons. However, there is inadequate information on changes in the nutritional content and safety of stored dry silver cyprinid along the local handling chain. This study evaluated the effect of conventionally used packaging on microbial safety and nutrient quality of dry silver cyprinid during storage. Freshly dried silver cyprinid was obtained from stores at four landing sites on Lake Victoria and stored in open and closed gunny bags for 8 weeks. Samples were collected at 0, 1, 2, 4, 6 and 8 weeks of storage and assessed for nutritional and microbial quality. The type of packaging used (open or closed gunny bags) had no significant effect on most nutrient content and microbial safety parameters (p &gt;0.05) except iron content, aflatoxin content, and TVBN content. Open gunny bags had higher aflatoxin content, greater iron degradation and greater variation in TVBN as compared to closed gunny bags throughout the storage duration. The observed difference in some of the quality parameters can be attributed to increased permeability to oxygen and moisture in open gunny bags as compared to closed gunny bags.

Potential Utilization of Dagaa (Rastrineobola argentea) Protein Hydolysate in Formulation of Media to Support Microbial Growth and Production of Bacterial Secondary Metabolites

ABSTRACT Dagaa fish hydrolysate (DFH) and dagaa protein hydrolysate (DPH) were prepared from dagaa using Alcalase enzyme. Proximate, mineral analysis, and potential use of DFH and DPH in microbial media were evaluated. Dagaa media formulations were used to culture bacteria commonly used for amylase production (Bacillus subtilis and Rhodobacter capsulatus) and that used as a bio-pesticide (Metarhizium anisopliae). Whole dagaa had the highest protein (5.2 ± 0.1 mg/ml), ash (13.5 ± 0.4%) and fat (2.36 ± 0.2%) content, while DPH had the least protein (2.6 ± 0.0 mg/ml) content. Mineral content was significantly different (p < 0.05) between dagaa and its hydrolysates. Dagaa and LB had the highest Sodium (22.7 ± 1.1 mg/ml) and calcium (0.3 ± 0.0 mg/ml), content respectively. Sustenance of amylase production in DPH-starch and standard media by both microorganisms was significantly different (p < 0.05). Sporulation rate of M. anisopliae in experimental media was not significant (p ˃ 0.05).

Socio-Economic Drivers of Fish Species Consumption Preferences in Kenya’s Urban Informal Food System

In an effort to contribute to resilient food and nutritional security in urban slums, a food system approach was applied to understand the key socio-economic factors driving fish species consumption in Kibera, the largest informal settlement in Africa located in Nairobi, Kenya. Data were collected from 385 randomly selected households using a structured questionnaire. A multivariate probit model was applied to estimate the relationship between the variables in order to determine the socio-economic drivers of preferences for different fish species. The results indicated that Lake Victoria sardine (Rastrineobola argentea) had the highest preference (73%) among the respondents, followed by Nile tilapia (Oreochromis niloticus) (70%) and Nile perch (Lates niloticus) (23%), respectively, with other fish species at 12%, including African catfish, marbled lungfish, common carp, fulu and tuna (Clarias gariepinus, Protopterus aethiopicus, Cyprinus carpio, Haplochromine cichlids and Thunnus sp., respectively). Large household size showed an increase in preference for the Lake Victoria sardine, while higher income influenced preference for Nile tilapia and Nile perch positively, implying that when more income is available, Nile tilapia is the preferred fish over other fish species. Increased fish prices positively influenced preference for Nile tilapia, which is explained by the willingness to pay extra for quality and origin, for instance, to avoid the cheaply cultivated Chinese fish. In the case of the Lake Victoria sardine, lower prices positively affected the preferences. Religious and cultural practices and beliefs influenced preference for species and consumption of fish. Residents who migrated from western Kenya had a higher preference for the Lake Victoria sardine, while residents born and raised in Kibera had a higher preference for Nile tilapia. Neighbourhood effects reduced the preference for consuming Nile perch. These findings provide insights into future market opportunities for specific target groups. For instance, given that small-sized fish like the Lake Victoria sardine is highly demanded, in order to increase resiliency in food and nutrition security, small-sized cheap Nile tilapia will have a large potential in the future, with ever higher demand specifically from the residents born and raised in Kibera.

Isolation and Identification of Bacteriocin-Producing &lt;i&gt;Bacillus &lt;/i&gt;spp from &lt;i&gt;Rastrineobola&lt;/i&gt; &lt;i&gt;argentea &lt;/i&gt;(Omena) with Activity against Bovine Mastitis Bacterial Pathogens

Rampant use of antibiotics has increased resistance of pathogenic bacteria in both animals and humans. This has triggered the investigation of novel antimicrobial agents produced by a bacterial strain of low virulence with antimicrobial activity with a wide range of clinical significance. This study sought to extract bacteriocins from Bacillus spp that were isolated and identified from Omena (Rastrineobola argentea) and to evaluate the in vitro antimicrobial effect of the obtained bacteriocin against bovine mastitis pathogens. Samples were collected from Lake Victoria using a completely randomized design method followed by isolation of the bacteriocin producing Bacillus spp. Characterization and identification of isolates was done by Gram staining, morphology and Biochemical tests which included catalase, nitrate reduction, methyl Red,-Voges-Proskauer, indole, motility and hydrogen sulphide, growth on Simmons citrate agar, triple sugar iron agar and starch hydrolysis. Antimicrobial activity was done using disc diffusion methods on the nutrient agar and zone of the inhibition measured after 24hours. An analytical profile index system (API 50CH BE, Biomerieux, Inc, France), was also used for identification. Molecular characterization was done by extracting genomic DNA using Qiagen DNA isolation Kit (Qiagen Germany) using the manufacturer's instructions. The gene encoding the 16S rRNA was amplified by PCR using universal bacterial primers pair combination of forwarding primer 27F forward (5′-AGA GTT TGA TCC TGG CTC AG-3′) and 1492R reverse, (5′-GGT TAC CTT GTT ACG ACT T-3′) about Escherichia coli gene sequence. A total of 60 pure isolates were obtained from Omena samples from Lake. Victoria. Morphological characteristics showed varied colour, form, shape and elevation of the pure colonies. About 54 isolates (90%) were gram-positive with spores, while 6 (10%) were gram-negative. Biochemical tests showed varied results among the bacterial isolates. 28 isolates showed antimicrobial activity on E. coli and S. aureus with inhibition measuring between 17-30mm. Analytical profile index system also showed that 20 isolates (71%) were identified as Bacillus subtilis, three isolates (11%) identified as Bacillus pumilus and five isolates (18%) Bacillus mycoides. The Blast analysis of the partial sequences showed100% of the strains of genus Bacillus within the Firmicutes in the domain bacteria. Twenty (20) isolates belong to Bacillus subtilis, Bacillus mycoides represent 18% (5 isolates) while Bacillus pumilus constituted 11% (3 isolates). This study contributes to understanding the use of bacteriocin in the control of diseases in dairy animal farming in Kenya.

Occurrence and Exposure Assessment of Aflatoxin B1 in Omena (Rastrineobola argentea) from Kenya

Omena (Rastrineobola argentea) is the most consumed fish species in Kenya. In this study, we assessed the occurrence of aflatoxin B1 (AFB1) in Omena and the potential health risk of AFB1 to Kenyan consumers of this fish. A total of 74 samples comprising Omena intended for human consumption and fish feed production were analyzed in this study. Aflatoxin levels in Omena were determined using the enzyme-linked immunosorbent assay (ELISA). Omena intended for fish feed production was most contaminated with a mean concentration of 46.93 μg·kg−1 (2.24–115.23 μg·kg−1) compared with Omena intended for human consumption (mean = 19.42 μg·kg−1, range = 2.01–49.30 μg·kg−1). Thirty-five positive samples (83.3%) exceeded the maximum level permitted (5 μg·kg−1) by the East Africa Community standard for food used for human consumption. The exposure dose of AFB1 from consuming Omena was estimated to be 1.34 ng·kg−1 BW day−1, and margin of exposure (MoE) value for AFB1 was found to be 126.3, which indicates health risk to Omena consumers. The results suggest that the current situation of aflatoxin contamination in Omena has an adverse effect on the health of the consumers as well as the animals. Therefore, more surveys are needed to understand the scope and extent of aflatoxin contamination in Omena.

English

Silver fish (Rastrineobola argentea) also locally known in Uganda as Mukene contributes significantly to Ugandan national economy and its value was estimated at $13 million US dollars in 2015. The fish is traditionally dried under direct sunshine on bare ground in unhygienic conditions, which expose it to dust and microbiological contamination. In this study, the microbial load of indicator and pathogenic organisms was determined in Mukene sold at selected landing sites of Lake Victoria and Kampala markets, Uganda. A total of 46 samples were collected randomly from landing sites and markets. The total aerobic counts, total coliforms, Escherichia coli, Salmonella and Staphylococcus aureus were enumerated using standard microbiological methods. The findings showed that Mukene was of low microbial quality for total plate counts, total coliforms, E. coli and S. aureus counts with values ranging from 2.48-8.61 log cfu/g, 0.36-3.09 log MPN/g, 0.36-3.04 log MPN/g and 0.10-6.66 log cfu/g, respectively. Of all samples analyzed, 63% were positive for Salmonella species. As salmonellae and staphylococci are often implicated in incidences of food poisoning, this study suggests that consumption of sun dried Mukene sold at landing sites of Lake Victoria, Uganda, poses a public health concern. There is the need to improve on hygiene during processing, storage and distribution of Mukene in Uganda. Key words: Silver fish, food safety, contamination.

A century of drastic change: Human-induced changes of Lake Victoria fisheries and ecology

Lake Victoria biophysical and geochemical status has changed dramatically within an unprecedentedly short time scale driven by human actions. These actions can be broadly classified as escalated fisheries exploitation, biomanipulation (characterized by species introduction) and catchment processes. A chronology of these activities since 1901 to present times is described and, where possible, related to changes in the ecology. The impacts of fishing are investigated using catch and effort data that have been consistently recorded for the past two decades. It is evident that water transparency in the offshore decreased from close to 8 m in late 1920s to less than 2 m in the 1990s before improving to about 4 m in the 2010s, a reflection of change in ecosystem functioning. The native tilapias that constituted the commercial fishery initially have since been replaced by introduced species and dagaa (Rastrineobola argentea) following biomanipulation events. Analysis of unified fishing effort index (E) reveals that in the last two decades fishing capacity has increased close to 8-fold in Kenya and Uganda and about three times in Tanzania. Illegal/prohibited gear have increased by 4.7 ± 1.9 folds whereas legal gear increased by 2.6 ± 0.8 times in the whole lake during since the year 2000. The catch per unit effort (CPUE) for Nile perch, tilapia and “others” declines with increasing effort while that for dagaa exhibits no clear trend. Haplorochromines catches and catch rates are increasing probably due to predatory release by the Nile perch. Tilapia and other fish catches and catch rates have declined with increasing harvesting capacity clearly indicating that they are over-fished. Catch and effort dynamics indicate that dagaa is still abundant in Lake Victoria. Overall, catches in Lake Victoria increase with increasing fishing effort but catch composition has shifted to one dominated by small pelagic species. It has been clearly shown that events leading to biomanipulation and processes in the catchment can fundamentally change a fishery in a different way as compared to fishing and hence the need for Ecosystem Approach to Fisheries Management (EAFM) in Lake Victoria.