ABSTRACT Approximately 850 bp of the mitochondrial control region was used to assess the genetic ... more ABSTRACT Approximately 850 bp of the mitochondrial control region was used to assess the genetic diversity, population structure and demographic expansion of the endangered cyprinid Barbus altianalis, a species known to be potamodramous in the Lake Victoria drainage system. The 196 samples taken from the four main rivers draining the Lake Victoria catchment (Nzoia, Yala, Nyando and Sondu–Miriu) yielded 49 mitochondrial DNA haplotypes; 83.7% thereof were private haplotypes restricted to particular rivers. The overall mean haplotype diversity was high (0.93663 ± 0.008) and ranged between 0.566 (Sondu – Miriu) and 0.944 (Nzoia). The overall mean nucleotide diversity was low (0.01322 ± 0.00141), ranging from 0.0342 (Sondu – Miriu) to 0.0267 (Nzoia). Population differentiation tests revealed strong and highly significant (P ≤ 0.001) segregation of populations in the four river basins. FST values among the four river-based populations ranged from 0.05202 to 0.44352. The samples formed two main haplotype networks based on a 95% parsimony criterion, each exhibiting a strong signature of past population expansion. The smaller network was restricted to the River Nzoia, whereas the larger network contained representatives from all four rivers; within this the central haplotypes were found in more than one river, whereas the peripheral haplotypes tended to be river-specific. The degree of population differentiation and the number of river-specific haplotypes are too high to be explained by recent anthropogenic impacts alone and suggest that the species has probably existed in the Lake Victoria catchment as two populations: the now ‘extinct’ migratory population and the extant river restricted non-migratory populations.
The African catfish Clarias gariepinus is an important species in the rapidly expanding aquacultu... more The African catfish Clarias gariepinus is an important species in the rapidly expanding aquaculture industry in East Africa. Most Kenyan catfish farmers use stocks with unknown genetic characteristics, with uncertified seeds and inter-basin exchange of brood stocks threatening the genetic distinctness of wild populations. Using 346 base pairs of D-loop sequence variation, genetic diversity and gene flow between C. gariepinus populations from Lake Victoria and its satellite, Lake Kanyaboli, were explored. A total of 17 haplotypes were identified in 52 individuals sampled, with the two populations sharing four haplotypes, and one haplotype being the most frequent (50%) in both populations. Catfish from Lake Victoria showed marginally higher genetic variation compared to those from Lake Kanyaboli, reflected in the higher number of haplotypes, singletons, polymorphic sites and haplotype and nucleotide diversities. Yet neither population showed signs of significant loss of diversity compared to other wild populations of the species. Clarias gariepinus from Lakes Victoria and Kanyaboli clustered into one clade, showing low population structuring and with a between-population FST value of 0.026, which was not indicative of significant (p ≥ 0.05) differentiation between the two lakes. Nevertheless, each population contained 60–64% of unique haplotypes. Inter-basin transfer of Clarias populations and human impact on Lake Kanyaboli should be controlled to conserve the unique Clarias genetic resources in the lake basin of Kenya.
African catfish, Clarias Gariepinus, is an important farmed food fish species in Kenya. It is als... more African catfish, Clarias Gariepinus, is an important farmed food fish species in Kenya. It is also used as live bait to catch Nile perch in Lake Victoria using longline hooks and so increases food and nutrition security, income and national development. The daily demand of 3 million live bait samples required by fishermen on the Kenyan side of Lake Victoria is largely unmet by hatchery and fish farms. This is mainly because of inadequate supply of quality seeds for use by farmers to stock their ponds (Rasowo et al., 2007) and for fishermen in Lake Victoria to use as live bait for Nile perch. Limited availability and supply of farm-raised catfish seeds are due to poor survival of catfish fry (Sulem et al., 2006), with farmers losing up to 99.8 per cent of the seed material (Hogendoorn, 1980) mainly due to use of poor quality brood stock of unknown ancestry (Barasa et al., 2014) and poor husbandry practices by farmers (Musa et al., 2012; Barasa et al., 2017). This occasions low annual...
With an estimated global value of US$15.6 billion, farmed salmonids represent a precious food res... more With an estimated global value of US$15.6 billion, farmed salmonids represent a precious food resource, which is also the fastest increasing food producing industry with annual growth of 7% in production. A total average of 3,594,000 metric tonnes was produced in 2020, behind Chinese and Indian carps, tilapias and catfishes. Lead producers of farmed salmonids are Norway, Chile, Faroe, Canada and Scotland, stimulated by increasing global demand and market. However, over the last 2 years, production has been declining, occasioned by effects of diseases as well as rising feed costs. Over the last year, production has declined sharply due to effects of covid-19. This chapter reviews the species in culture, systems of culture, environmental footprints of salmon culture, and market trends in salmon culture. Burden of diseases, especially Infectious pancreatic Necrosis, Infectious salmon anemia and furunculosis, as well as high cost of feed formulation, key challenges curtailing growth of ...
African catfish, Clarias gariepinus, is an important species in aquaculture and fisheries in Keny... more African catfish, Clarias gariepinus, is an important species in aquaculture and fisheries in Kenya. Mitochondrial D-loop control region was used to determine genetic variation and population structure in samples of C. gariepinus from 10 sites including five natural populations (Lakes Victoria (LVG), Kanyaboli (LKG), Turkana (LTA), Baringo (LBA) and Jipe (LJP), and five farms (Sangoro Aquaculture Center (SAN), Sagana Aquaculture Centre (SAG), University of Eldoret Fish Farm (UoE), Kibos Fish Farm (KIB), and Wakhungu Fish Farm (WKU)) in Kenya. Similarly, samples from eight localities (four natural populations: LVG/LKG, LTA, LBA, and four farmed: SAN, SAG, KIB, UoE) were genotyped using six microsatellite DNA loci. For the D-loop control region, samples from natural sites exhibited higher numbers of haplotypes and haplotype diversities compared to farmed samples, and 88.2% of haplotypes were private. All except LJP and LTA shared haplotypes, and the highest number of shared haplotypes ...
ABSTRACT Approximately 850 bp of the mitochondrial control region was used to assess the genetic ... more ABSTRACT Approximately 850 bp of the mitochondrial control region was used to assess the genetic diversity, population structure and demographic expansion of the endangered cyprinid Barbus altianalis, a species known to be potamodramous in the Lake Victoria drainage system. The 196 samples taken from the four main rivers draining the Lake Victoria catchment (Nzoia, Yala, Nyando and Sondu–Miriu) yielded 49 mitochondrial DNA haplotypes; 83.7% thereof were private haplotypes restricted to particular rivers. The overall mean haplotype diversity was high (0.93663 ± 0.008) and ranged between 0.566 (Sondu – Miriu) and 0.944 (Nzoia). The overall mean nucleotide diversity was low (0.01322 ± 0.00141), ranging from 0.0342 (Sondu – Miriu) to 0.0267 (Nzoia). Population differentiation tests revealed strong and highly significant (P ≤ 0.001) segregation of populations in the four river basins. FST values among the four river-based populations ranged from 0.05202 to 0.44352. The samples formed two main haplotype networks based on a 95% parsimony criterion, each exhibiting a strong signature of past population expansion. The smaller network was restricted to the River Nzoia, whereas the larger network contained representatives from all four rivers; within this the central haplotypes were found in more than one river, whereas the peripheral haplotypes tended to be river-specific. The degree of population differentiation and the number of river-specific haplotypes are too high to be explained by recent anthropogenic impacts alone and suggest that the species has probably existed in the Lake Victoria catchment as two populations: the now ‘extinct’ migratory population and the extant river restricted non-migratory populations.
The African catfish Clarias gariepinus is an important species in the rapidly expanding aquacultu... more The African catfish Clarias gariepinus is an important species in the rapidly expanding aquaculture industry in East Africa. Most Kenyan catfish farmers use stocks with unknown genetic characteristics, with uncertified seeds and inter-basin exchange of brood stocks threatening the genetic distinctness of wild populations. Using 346 base pairs of D-loop sequence variation, genetic diversity and gene flow between C. gariepinus populations from Lake Victoria and its satellite, Lake Kanyaboli, were explored. A total of 17 haplotypes were identified in 52 individuals sampled, with the two populations sharing four haplotypes, and one haplotype being the most frequent (50%) in both populations. Catfish from Lake Victoria showed marginally higher genetic variation compared to those from Lake Kanyaboli, reflected in the higher number of haplotypes, singletons, polymorphic sites and haplotype and nucleotide diversities. Yet neither population showed signs of significant loss of diversity compared to other wild populations of the species. Clarias gariepinus from Lakes Victoria and Kanyaboli clustered into one clade, showing low population structuring and with a between-population FST value of 0.026, which was not indicative of significant (p ≥ 0.05) differentiation between the two lakes. Nevertheless, each population contained 60–64% of unique haplotypes. Inter-basin transfer of Clarias populations and human impact on Lake Kanyaboli should be controlled to conserve the unique Clarias genetic resources in the lake basin of Kenya.
African catfish, Clarias Gariepinus, is an important farmed food fish species in Kenya. It is als... more African catfish, Clarias Gariepinus, is an important farmed food fish species in Kenya. It is also used as live bait to catch Nile perch in Lake Victoria using longline hooks and so increases food and nutrition security, income and national development. The daily demand of 3 million live bait samples required by fishermen on the Kenyan side of Lake Victoria is largely unmet by hatchery and fish farms. This is mainly because of inadequate supply of quality seeds for use by farmers to stock their ponds (Rasowo et al., 2007) and for fishermen in Lake Victoria to use as live bait for Nile perch. Limited availability and supply of farm-raised catfish seeds are due to poor survival of catfish fry (Sulem et al., 2006), with farmers losing up to 99.8 per cent of the seed material (Hogendoorn, 1980) mainly due to use of poor quality brood stock of unknown ancestry (Barasa et al., 2014) and poor husbandry practices by farmers (Musa et al., 2012; Barasa et al., 2017). This occasions low annual...
With an estimated global value of US$15.6 billion, farmed salmonids represent a precious food res... more With an estimated global value of US$15.6 billion, farmed salmonids represent a precious food resource, which is also the fastest increasing food producing industry with annual growth of 7% in production. A total average of 3,594,000 metric tonnes was produced in 2020, behind Chinese and Indian carps, tilapias and catfishes. Lead producers of farmed salmonids are Norway, Chile, Faroe, Canada and Scotland, stimulated by increasing global demand and market. However, over the last 2 years, production has been declining, occasioned by effects of diseases as well as rising feed costs. Over the last year, production has declined sharply due to effects of covid-19. This chapter reviews the species in culture, systems of culture, environmental footprints of salmon culture, and market trends in salmon culture. Burden of diseases, especially Infectious pancreatic Necrosis, Infectious salmon anemia and furunculosis, as well as high cost of feed formulation, key challenges curtailing growth of ...
African catfish, Clarias gariepinus, is an important species in aquaculture and fisheries in Keny... more African catfish, Clarias gariepinus, is an important species in aquaculture and fisheries in Kenya. Mitochondrial D-loop control region was used to determine genetic variation and population structure in samples of C. gariepinus from 10 sites including five natural populations (Lakes Victoria (LVG), Kanyaboli (LKG), Turkana (LTA), Baringo (LBA) and Jipe (LJP), and five farms (Sangoro Aquaculture Center (SAN), Sagana Aquaculture Centre (SAG), University of Eldoret Fish Farm (UoE), Kibos Fish Farm (KIB), and Wakhungu Fish Farm (WKU)) in Kenya. Similarly, samples from eight localities (four natural populations: LVG/LKG, LTA, LBA, and four farmed: SAN, SAG, KIB, UoE) were genotyped using six microsatellite DNA loci. For the D-loop control region, samples from natural sites exhibited higher numbers of haplotypes and haplotype diversities compared to farmed samples, and 88.2% of haplotypes were private. All except LJP and LTA shared haplotypes, and the highest number of shared haplotypes ...
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