Physiological Response of Grower African Catfish to Dietary Black Soldier Fly and Mealworm Meal.

A six-week experiment was carried out to test the effects of total (100%) and partial (50%) replacement of fish meal in the diet of African catfish growers with black soldier fly (B) meal, yellow mealworm (M) meal, and a 1:1 combination of both (BM) on the production and health of fish. A total of 420 fish with an average initial body weight of 200 ± 0.5 g were randomly distributed in triplicate to seven diet groups (C, B50, B100, M50, M100, BM50, and BM100, respectively). The growth performance and feed utilization of fish fed with partial or total replacement levels of FM with B were not significantly affected (p > 0.05) during the 6 weeks of feeding. In contrast, significant differences were observed between the groups fed with a diet where FM was totally replaced with M meal and the control in terms of final body weight, specific growth rate, feed conversion ratio, protein efficiency ratio, and protein productive value. Among the blood plasma biochemistry parameters, total cholesterol exhibited a significant difference (p = 0.007) between the M treatments and the control diet. The fatty acid profile of the liver was changed with respect to the long-chain polyunsaturated fatty acid content in all experimental groups. Parallel with this, the upregulation of elovl5 and fas genes in liver was found in all experimental groups compared to the control. Overall, this study shows that fish meal cannot be substituted with yellow mealworm meal in the practical diet of African catfish without compromising the growth, health and feed utilization parameters.

Antimicrobial peptides from freshwater invertebrate species: potential for future applications.

Invertebrates are a significant source of antimicrobial peptides because they lack an adaptive immune system and must rely on their innate immunity to survive in a pathogen-infested environment. Various antimicrobial peptides that represent major components of invertebrate innate immunity have been described in a number of investigations over the last few decades. In freshwater invertebrates, antimicrobial peptides have been identified in arthropods, annelids, molluscs, crustaceans, and cnidarians. Freshwater invertebrate species contain antimicrobial peptides from the families astacidin, macin, defensin, and crustin, as well as other antimicrobial peptides that do not belong to these families. They show broad spectrum activities greatly directed against bacteria and to a less extent against fungi and viruses. This review focuses on antimicrobial peptides found in freshwater invertebrates, highlighting their features, structure-activity connections, antimicrobial processes, and possible applications in the food industry, animal husbandry, aquaculture, and medicine. The methods for their synthesis, purification, and characterization, as well as the obstacles and strategies for their development and application, are also discussed.

Apparent Digestibility Coefficients of Black Soldier Fly (Hermetia illucens), Yellow Mealworm (Tenebrio molitor), and Blue Bottle Fly (Calliphora vicina) Insects for Juvenile African Catfish Hybrids (Clarias gariepinus × Heterobranchus longifilis).

A digestibility trial was conducted with African catfish hybrid juveniles in order to determine the apparent digestibility coefficients (ADCs) of different nutrients. The experimental diets contained defatted black soldier fly (BSL), yellow mealworm (MW), or fully fat blue bottle fly (BBF) meals, in a 70 : 30 ratio between the control diet and the tested insect meals. The indirect method for the digestibility study was performed using 0.1% yttrium oxide as an inert marker. Fish juveniles of 217.4 ± 9.5 g initial weight were distributed in 1 m3 tanks (75 fish/tank) of a recirculating aquaculture system (RAS), in triplicates, and fed until satiation for 18 days. The average final weight of the fish was 346 ± 35.8 g. The ADCs of the dry matter, protein, lipid, chitin, ash, phosphorus, amino acids, fatty acids, and gross energy for the test ingredients and diets were calculated. A six-month storage test was carried out to evaluate the shelf life of the experimental diets, while the peroxidation and microbiological status of the diets were also assessed. The ADC values of the test diets differed significantly (p < 0.001) compared to those of the control for most of the nutrients. Altogether, the BSL diet was significantly more digestible for protein, fat, ash, and phosphorus than the control diet but less digestible for essential amino acids. Significant differences were found between the ADCs of the different insect meals evaluated (p < 0.001) for practically all nutritional fractions analyzed. The African catfish hybrids were able to digest BSL and BBF more efficiently than MW, and the calculated ADC values agreed with those of other fish species. The lower ADCs of the tested MW meal correlated (p < 0.05) with the markedly higher acid detergent fiber (ADF) levels present in the MW meal and MW diet. Microbiological evaluation of the feeds revealed that mesophilic aerobic bacteria in the BSL feed were 2-3 orders of magnitude more abundant than those in the other diets and their numbers significantly increased during storage. Overall, BSL and BBF proved to be potential feed ingredients for African catfish juveniles and the shelf life of the produced diets with 30% inclusion of insect meal retained the required quality during a six-month period of storage.

Microplastic pollution in surface water of Lake Victoria.

Microplastic pollution of aquatic systems is a widely recognised environmental challenge. In this study, the occurrence, abundance, distribution and chemical nature of microplastics within the size range 0.3-4.9 mm, was assessed in the surface water of northern Lake Victoria. Lake surface transects in the sites were sampled using a floating manta net and analysed for microplastics. The various sites examined were grouped into three: Group A- sites in vicinity of fish landing and recreational beaches, and within urban or semi urban setting; Group B - sites in vicinity of only fish landing beaches within a rural community setting, and Group C - Sites in the vicinity of river inflows. Our results show occurrence of microplastics in all sites (range: 2834-329,167 particles/km2 or 0.02-2.19 particles/m3), with the abundance highest in group A (range: 103,333-329,167 particles/km2 or 0.69-2.19 particles/m3) and lowest in group C (range: 2834-20,840 particles/km2 or 0.02-0.14 particles/m3). All the microplastics were secondary in nature being derived from plastic materials utilised by the community. The largest proportion (36%) of microplastic counts were of the size <1 mm which poses a threat to water quality and fisheries of the lake. Analysis of the chemical composition of microplastics indicated dominance by the low density polymers: Polyethylene and Polypropylene across the microplastic types. The occurrence of microplastics derived from degradation of large plastic debris implies that proper plastic waste management measures be implemented in the communities operating on the lake and in its vicinity, in order to safeguard the ecosystem benefits derived from the lake.

Occurrence, distribution and size relationships of plastic debris along shores and sediment of northern Lake Victoria.

Plastic pollution has been reported in sediment, surface water and biota of freshwater systems especially in Europe, North and South America, and Asia with limited studies focussing on African great lakes. This study therefore investigated the occurrence, abundance and distribution of micro-, meso- and macro-plastic debris along shores and sediment of northern Lake Victoria. The abundance of micro-, meso- and macro-plastics measured as particles/kg dry sediment were in range of 0-1102, 0-218 and 0-100 respectively in shoreline sediment and 0-108, 0-33 and 0-77 respectively in lake sediment. The mean abundance of micro-, meso- and macro-plastic debris at fish landing beaches (75.2 ±â€¯50.0, 16.7 ±â€¯8.1 and 18.1 ±â€¯4.6 respectively) were higher than what was recorded at recreational beaches (1.5 ±â€¯0.6, 3.1 ±â€¯3.1 and 3.8 ±â€¯3.8 respectively). Similarly, mean abundance of micro-, meso- and macro-plastic debris in lake sediment were higher in areas of fish landing beaches (9.5 ±â€¯2.6, 2.1 ±â€¯1.5 and 7.7 ±â€¯4.5 respectively) than what was recorded in areas of recreational beaches (0.7 ±â€¯0.7, 0.2 ±â€¯0.1, and 0 ±â€¯0 respectively). Films, filaments, fragments, foam and pellets were the plastic types, with the shoreline sediment dominated by films (>54%) while lake sediment was dominated by filaments (>55%), across size groups (micro-, meso- and macro-plastics). Spearman's rank correlation indicated strong and significant correlation between abundance of micro- and meso-plastics for total plastic, film plastic and fragment plastic in shoreline sediment. Significant correlation between macroplastics in shoreline sediment and microplastics in lake sediment for total plastics was observed. The FTIR analysis revealed that polyethylene, polypropylene, Polyethylene Terephthalate, Polyamide (nylon), and polyvinyl chloride were the major polymers. These results demonstrated that fish landing beaches along Lake Victoria are hotspot areas for plastic pollution of the lake and should therefore be targeted for management of plastic pollution of Lake Victoria.

The Socioeconomic and Sexual Health Status of Young People Living in Urban Slum Areas of Kampala, Uganda.

Slum dweller youth in Kampala, Uganda, face social economic exclusion and a plethora of health risks, and their needs are poorly understood. The aim of the current study was to analyze their needs and to suggest contextual evidence-based solutions to improve their well-being sustainably. We conducted a qualitative study involving 10 focus group discussions (FGDs; N = 113) and 20 key informant (KII) interviews. Emerging themes and sub-themes were identified, defined, reviewed, and organized and narrated following the structuration theoretical framework, which enabled the examination of the inherent capacity of slum dweller youth to make choices independently and the recurrent rules and resources that influence or limit the choices and opportunities available to them. The findings suggest that the slum dweller youth's ability to reach and fulfil their potential remains constrained by a confluence of individual and societal-level factors. The individual factors were poor quality of and dissatisfaction with life, and poor sexual and reproductive health practices. The societal-level factors were poor sexual and reproductive health services, and an extremely weak labor market. The needs of slum dweller youth in Kampala, Uganda, remain unaddressed, and leaving such a large population economically unproductive and dissatisfied with life is a recipe for political instability and insecurity. Interventions to address their needs need to adopt a whole-community approach in order to engage and empower all parts of the slum community and strengthen community structures that improve livelihoods and harness the opportunities that engender income fortification and socio-civic transformation for the youth.

Benthic macroinvertebrate community structure in Napoleon Gulf, Lake Victoria: effects of cage aquaculture in eutrophic lake.

An investigation was conducted on the macro-benthic fauna of the Napoleon Gulf in the northern part of Lake Victoria from March 2011 to December 2016 at the cage fish farm. The aim was to examine the likely impact of cage aquaculture on macro-benthic invertebrates. Cage aquaculture is now a common practice on Lake Victoria yet little is known about its long-term effect on macro-benthic faunal assemblages. Temporal variation indicated a general decline in annual faunal density at the farm area with corresponding stability at upstream (control) and downstream sites. Arthropods remained numerically dominant at the control and downstream sites. The percentage abundance of EPT (Ephemeroptera, Plecoptera, and Trichoptera) and Malacostraca was highest at the upstream and lowest at the farm area. The farm area which initially was dominated by molluscs became dominated by arthropods after 3 years. The decrease in density of molluscs at the farm area was attributed to the general decrease in density of two species: Bellamya unicolor (Gastropoda) and Corbicula africana (Bivalvia). These two species were initially abundant but showed decline within the farm area with corresponding stability at the upstream and downstream areas. Oligochaete annelids were more abundant within the farm area than at the upstream and downstream sites. These findings suggested that molluscs offered better prediction of the impact of cages on the environment than arthropods. Besides that, in a community dominated by pollution-tolerant organisms, the impact of aquaculture may not be immediate especially when organic loading from aquaculture is moderate.