Extraction and characterization of type 1 collagen from the skin and scales of Heterotis niloticus and Lates niloticus

The study is aimed to extract and characterize collagens from the skin and scale of two selected Nigerian freshwater fish species (Heterotis niloticus and Lates niloticus) using either pepsin (PSC) or acid-soluble (ASC) extraction. The collagen was extracted using 0.5M acetic acid and pepsin. The collagen yield was determined and characterized by SDS PAGE, and FTIR. Collagen extraction yields varied with the extraction process; the yield was significantly higher in the skin (5.08±0.34–33.97±1.78 %) than in the scale (1.76–8.05 %). The absorption peaks of the extracted collagen using acetic acid and pepsin show that only ASC of skin (3344.27 cm-1) and scale (3495.85 cm-1) of H. niloticus shows the peaks characteristic of Amide A, while Amide B peaks of collagen extracted from the skin and scale of H. niloticus and L. niloticus were found at 2974.46 cm-1 and 2925.7 cm-1 , representing an asymmetrical stretch of CH2. Similarly, ASC on the skin (1558.36 cm-1) and scale (1576.46 cm-1) of H. niloticus shows the absorption peak characteristics of amide II. ASC on the skin of H. niloticus (1671.05 cm-1), PSC on scale of H. niloticus (1658.55 cm-1), and on scale of H. niloticus (1678.65 cm1) shows absorption peaks in range characteristic of amide 1. There were no differences in the skin and scale collagen profiles among the two fish species when characterized by SDS-PAGE. Our data revealed that the skin and scale of Lates niloticus and Heterotis niloticus could be a good alternative source of high-quality collagen for industries.

Stock Assessment of Lates niloticus in Upper Victoria Nile and its Impact on Uganda’s Economy

This study investigated the growth, mortality, recruitment, and catch estimates of Nile perch, Lates niloticus (Linnaeus, 1758), in Upper Victoria Nile, basing on total catches and length-frequency data collected between 2008 and 2018. The asymptotic length (L∞) had a value of 93.45 cm TL, growth curvature (K) was 0.446 year-1, total mortality (Z) was 1.85year-1, natural mortality (M) was 0.79 year-1, fishing mortality (F) was 1.09 year-1, exploitation rate (E) was 0.59 and growth performance index(ᴓ) of (L∞) was 3.604. There were two peaks recruitment period, a minor one in March and a major one in August. These respectively accounted for 12.8 and 26.3 percent of the total catch. The optimum sustainable yield (E0.5), maximum sustainable yield (Emax) and, economic yield (E0.1) was 0.278, 0.421 and 0.355 respectively. The findings suggest that there is a decline in the population of Lates niloticus in Upper Victoria Nile. Therefore, strict management of the fishery by adhering to the recommended slot size of 50-85 cm TL and curtailing use of illegal gears is needed. This will be possible through enforcement of regulations, monitoring, control and surveillance in order to ensure sustainability of the Nile perch fishery and ecosystem restoration in the Upper VictoriaNile.Keywords: Lates niloticus; Catch rates; Growth parameters, Upper Victoria Nile.

A survey of fish fauna distribution and abundance in Gwaigwaye Reservoir Katsina State, Nigeria

The study on a survey of fish fauna distributions and abundance in Gwaigwaye Reservoir, Katsina State was carried out from May 2013 to April 2014 to establish physical, chemical, and biological parameters (fish) of Gwaigwaye reservoir. Four sampling stations were selected. Some physico-chemical parameters were also determine to assess the level of pollution of the reservoir using standard methods and procedures which were correlated with the different fish species to determine fish abundance and distributions. Analysis of variance indicates no significant difference in fish fauna distribution and abundance among the four stations (P>0.05). The result indicated Fish fauna percentage composition were Tilapia zilli (17.32%), Clarias gariepinus (16.17%), Oreochromis niloticus (15.27%), Lates niloticus (13.80%), Bagrus. bayad (12.91%), Momyrus senegalensis (9.90%), Labeo senegalensis (7.41%) and Synodontis clarias (7.28%).

Scanning morphology, prevalence and histopathology of some acanthocephalans infecting some River Nile fish

Acanthocephalan morphology and their adverse pathological impact on fish are of great concern. Two species of acanthocephalans were recorded from 800 samples of live freshwater fish collected randomly during 2017–2018 from Lake Nasser, Aswan, Egypt. The recovered species were identified morphologically as Acanthogyrus (Acanthosentis) tilapiae from three Tilapia spp. (Sarotherodon galilaeus, Oreochromis niloticus and Tilapia zillii) and Rhadinorhynchus niloticus from Lates niloticus. The intensity of parasitic infection and the seasonal prevalence were higher in L. niloticus than in Tilapia spp. The clinical signs and post mortem lesions of infected fish were reported. Morphological description of the detected parasites using light microscope was then confirmed by electron microscopy to amplify ambiguous details. The histopathological findings of the intestine of naturally infected fish with acanthocephalan parasites were investigated and described. The main damage caused by them is destruction of the mucosal epithelium of the villi, necrosis and degeneration of intestinal epithelial cells.

Impact of Nile perch (Lates niloticus) overfishing on fishers’ income: Evidence from Lake Victoria, Tanzania

Despite the crucial role played by Nile perch in the income of fishers around Lake Victoria, Tanzania, fishing pressure has increased in recent years and has led to overfishing and, consequently, a risk to the lake’s future sustainability and the fishers’ livelihoods. This study used data collected in 2018 from 268 randomly selected sample fishers at 10 landing sites across Lake Victoria. In conjunction with the endogenous switching regression model, the potential impact of Nile perch overfishing on the fishers’ income per fishing trip in Lake Victoria was evaluated. The results show that there is a significant difference in the socio-economic, institutional and fishing effort characteristics of Nile perch fishers who overfish and those who do not. In particular, Nile perch fishers who overfish earn significantly higher incomes per fishing trip than fishers who do not overfish. The study recommends the need for policy makers to develop policies that acknowledge the dynamics of socio-economic, institutional and fishing effort factors. In addition, more flexible fish quota restrictions and consistent fishing patrols need to be enforced to ensure compliance with fishery regulations. These measures should promote a balance between the sustainability of fishery resources and an improved income for Nile perch fishers in Lake Victoria.