Length-weight relationship, condition factor and sex ratio of two chrysichthys species (pisces: claroteidae) of socio-economic importance from Kpong reservoir in Ghana

A total of 392 combined samples of Chrysichthys auratus and Chrysichthys nigrodigitatus was obtained from experimental and artisanal fishing from inshore and offshore areas of Kpong Reservoir. C. auratus and C. nigrodigitatus exhibited hyperallometric (b = 3.17–3.23) and hypoallometric (b = 2.79 - 2.91) growth patterns, respectively. Fluctuating monthly condition factor for males, females and combined sexes observed for the two species based on standard length and total length could be attributed to changes in feeding activity and, or degree of nourishment, food availability, gonadal activity, and season. However, based on total length, October and June were periods of the best physiological condition for C. auratus, while for C. nigrodigitatus, December was the least physiological period. There were significantly more females than males while differences in sex ratio were significant at 95 percent confidence interval (P = 1.354), indicating departure from the expected sex ratio of 1:1 for the two species. Regular assessment of biological, ecological and environmental characteristics of the species is recommended to provide the requisite information for sustainable management of the species for reservoir fishery development and food security

Potential fish yield and Physico-chemical characteristics of Weija reservoir in Ghana

The Weija Reservoir is an important resource for the production and supply of potable water, fish and irrigation services in Ghana. The study was undertaken to estimate the potential fish yield of Weija Reservoir to provide information for planning and management and to address the challenges of paucity of information on the potential fish yield of reservoirs in Ghana. Fish and water samples were collected monthly between March and December 2011 at Intake, Machigeni and Galilea sampling stations in the Weija Reservoir. Based on the physico-chemical parameters evaluated, the Weija Reservoir is adequate for fish survival, growth and production despite indications of low levels of organic contamination. Estimates of mean fish yield and potential fish yield for the three (3) stations based on morpho-edaphic index indicate that Machigeni has the highest yields followed by Intake and Galilea due to differences in anthropogenic activities, contamination and species richness. Monthly variations in potential fish yield and physico-chemical parameters follow similar pattern at all three sites with Machigeni recording the highest values and Intake the lowest. For the section of the reservoir sampled, the mean potential fish yield was 68.27 kg ha-1 while the mean fish yield was 229.45 t yr-1 giving indication of declining fish yield compared to the earlier life of the reservoir which is attributable to physico-chemical, environmental, biological and anthropogenic changes. For successful fisheries management, regular monitoring of the fish species as well as control of fish habitat and environmental degradation are recommended

Aspects of the fecundity of the black-chinned tilapia Sarotherodon melanotheron in the Fosu lagoon, Ghana

The black-chinned tilapia, Sarotherodon melanotheron (Pisces: Cichlidae), which dominated the Fosu Lagoon fishery, was exposed to pollution, siltation, fishing pressure, destructive fishing methods, and climate change. Samples of black-chinned tilapia were obtained with cast net, drag net and gill net, out of which 441 gravid specimen were randomly selected and dissected to remove eggs which were then counted. The absolute fecundity varied from 20 eggs to 370 eggs with a mean of 78 ± 33 eggs. Fish that had fecundity below and above the reported minimum of 200 eggs constituted 98.86 percent and 1.14 percent of the total sample, respectively, indicating that fecundity is below the minimum number of eggs the species is reportedly capable of producing. Positive, linear, weak and significant relationships were found between absolute fecundity and body parameters indicating that absolute fecundity is independent of body parameters, and could be influenced by biological, environmental, or anthropogenic factors. Condition factor ranged between 2.26 SL and 10.63 SL. Length at first maturity was 4.8 cm SL and 6.4 cm TL, respectively, confirming the precocious reproductive habit of the species. The size structure of the S. melanotheron population is dominated by small-sized fish of SL 7.0 – 7.9 cm (44.90 %) and 6.0 – 6.9 cm SL (32.65 %) ranges, which together accounted for 77.55 percent of the total sample. It is recommended that the fecundity and other reproductive parameters of the species be investigated during the dry and wet seasons in order to determine the reproductive potential and strategies for survival of the species

Water Quality of the Weija Reservoir after 28 Years of Impoundment

The water quality of the Weija Reservoir was assessed and the various sources of contaminants were identified in order to provide scientific basis for finding appropriate remedies to the contamination problems that may confront the Reservoir. Monthly water samples were taken from three sampling stations in the Weija Reservoir and analysed for physico-chemical parameters in the laboratory. The mean pH values of the sampling sites were within the recommended range of 6.5–8.5 for potability and sustenance of aquatic life. The ionic dominance pattern observed was Na > Ca > Mg > K and HCO3 > Cl > SO4, indicating partial cationic characteristics of sea water and anionic characteristics intermediate between fresh water and sea water. Dissolved oxygen (DO) levels were 102.5%, 81.5% and 82.7% saturation for Weija Intake, Machigani and Galilea, respectively. Thus, the oxygen conditions in the Weija Reservoir were sufficient to support fish and other aquatic life. Maximum BOD level was 8.1 mg/l at Weija Intake. Compared with previous studies on the Weija Reservoir, results of the study show a slight increase in nitrate, ammonia, sulphate and phosphate levels. Generally, the levels of nitrate, sulphate, phosphate, trace elements (e.g. manganese and iron) and BOD were moderately high. Anthropogenic activities, such as stone quarrying, dumping of domestic wastes, as well as run-offs from agricultural activities and the occurrence of algae, are some of the sources of contamination identified in the study. Tougher legislation, stricter enforcement of existing regulations, matching of non-technical and technosocial remedial measures and education are among the recommendations made for the protection of the Weija Reservoir.West African Journal of Applied Ecology Vol. 13 2008: pp. 125-13

Fisheries and limnology of two reservoirs in Northern Ghana

The fisheries and limnology of Bontanga and Libga reservoirs in northern Ghana were studied with the objective of generating information to support the development, management and sustainable use of their fisheries to enhance the socio-economic status of riparian communities. Using gill nets of various mesh sizes, fishes were sampled monthly and individually identified, weighed and measured for standard and total lengths. Water samples were taken monthly and analysed for physico-chemical parameters. In the Bontanga Reservoir, 21 species belonging to 18 genera and 10 families were encountered. Four families, namely Clariidae, Cichlidae, Cyprinidae and Clarotidae constituted almost 83% of the fishery while Clarias anguillaris, Auchenoglanis occidentalis, Barbus macrops and Sarotherodon galileus were the major species. In the Libga Reservoir, 36 species, representing 27 genera and 15 families, were obtained. Twofamilies, namely Mochokidae and Centropomidae constituted almost 67% of the fishery resources while Synodontis gambiensis and the Nile perch, Lates niloticus, were the dominant species. The fish diversity of the Bontanga Reservoir was lower than that of the Libga reservoir. Carnivorous fishes were dominant in Bontanga Reservoir while fishes offorage feeding habits were the major feeding group in Libga Reservoir. The forage-carnivore ratios of 1.60 and 2.12 for Bontanga and Libga reservoirs, respectively, suggest a suitable ecological balance between carnivorous fishes and their prey populations. The estimated potential fish yield per year for the Bontanga Reservoir (67 tons) was higher than thatof the Libga Reservoir (4.7 tons) mainly due to its larger size although the productivity per hectare for Libga Reservoir was slightly higher. Both reservoirs were well oxygenated all year-round with relatively high oxygen demanding substances and slightly acidic from June to October. The Bontanga Reservoir was characterized by a strikingly high ionic content. The nutrient level and the mean productivity of the Bontanga Reservoir were slightly lower than those of the Libga Reservoir

Fish community structure of Weija Reservoir after 28 years of impoundment

The fish community structure of Weija Reservoir after twenty eight (28) years of impoundment was investigated to formulate management strategies and interventions for sustainable fisheries development. Monthly fish sam-pling was undertaken with gill nets of various mesh sizes from March to December 2005. Sixteen species repre-senting 11 genera and 7 families were recorded, indicating declining fish species richness due to disappearance of marine species and restructuring of the fish community in response to change from riverine to lacustrine con-ditions. Cichlid, mainly, Tilapia guineensis and Hemichromis fasciatus and Cyprinids, mainly B. macrops supp-orted about 69.6 % of total weight (mass) and 93.8 % of total number. About 37.14 % of all fish species ever recorded from the reservoir have disappeared and about 6 % have appeared, indicating that the fish community is undergoing restructuring. Semi-pelagic omnivores and aufwuchs-detritus herbivores constituted the most im-portant trophic groups accounting for about 65 % of both total weight and number. The Forage/Carnivores (F/C) ratio of 4.97 and 2.43 in terms of weight and numbers indicated acceptable ecological balance among the fish population. For effective fisheries development, regular biological monitoring of the major fish species, contr-ol of unapproved fishing practices and anthropogenic activities that accelerate habitat destruction and environm-ental degradation must be instituted

ARthroscopy in Knee OsteoArthritis (ARK-OA): a multicentre study assessing compliance to national guidelines.

INTRODUCTION: The use of arthroscopy to alleviate the symptoms of osteoarthritis has been questioned by recent high quality evidence. This has led to the development of guidelines by specialist and national bodies advocating against its use. AIMS: To examine the trends of the rates of arthroscopy in patients with knee osteoarthritis over the past five years and determining compliance with guidelines. METHODS: Multi-centre, retrospective audit in five hospital trusts in the United Kingdom. The number of arthroscopies performed by month from 2013 to 2017 was identified through hospital coding. Fifty randomly selected records from the year 2017 were further analysed to assess compliance with NICE guidelines. RESULTS: Between 2013 and 2017, the number of arthroscopies performed annually in five trusts dropped from 2028 to 1099. In the year 2017, 17.7% of patients with no mechanical symptoms and moderate-to-severe arthritis pre-operatively had arthroscopy. CONCLUSION: Knee arthroscopy continues to be used as a treatment for osteoarthritis, against national guidelines. Whilst overall numbers are declining, further interventions, including implementation of high-quality conservative care is required to further eliminate unnecessary procedures