Opportunities for shrimp farming in the Niger Delta: dilemma of sustainable production in the absence of regulatory framework

Commercial shrimp farming has been practised for several decades in many countries of the world over. High demand for shrimps and corresponding high returns on investment has played major roles in the expansion of the industry. In Nigeria, farming shrimps is still novel. Notable research work includes studies conducted at the Nigerian Institute for Oceanography and Marine Research, African Regional Aquaculture Centre and Institute of Oceanography, University of Calabar. Niger Delta has potentials for farming shrimps - suitable sites, good candidate shrimp species, high local demand with potentials for export. However the major challenge would be the availability of guidelines to regulate farming activities especially as concerns the use of potentially toxic compounds in shrimp farms which could lead to deleterious effects in the environment. Efficient regulatory bodies/agencies to ensure sustainability of production system and compliance to stipulated guidelines will go a long way in the protection of the environment

Impact of calcium carbonate on the juveniles of brackish river prawn, Macrobrachium marobrachion under laboratory conditions

The acute toxicity and the effect of sub-lethal concentrations of calcium carbonate on the morphology of M. macrobrachion were investigated under laboratory conditions. The prawns were exposed at 0, 160, 320, 640, 1280, 2560 and 5120 mg/l of CaCO3 using static renewal bioassay for 96 hours for the acute toxicity test. The prawns were also exposed for the chronic test at 0, 20.0, 40.0, and 80.0 mg/1 for a period of two weeks. Mortality occurred in the bioassay tanks at random and the bioassays were monitored throughout the exposure period. Results showed that exposed prawns were not significantly impacted when compared with the control group and correlations were significant at P<0.05. There were no mortalities in the tanks with the highest concentrations while one death was recorded in the control tank and in the tank with the 160 and 320mg/1 of CaCO3 respectively. The gills of exposed prawns were analyzed using photomicrography and the results showed that the organs had their normal morphological status after the exposure time, implying that CaCO3 is non-toxic to M. macrobrachion. The applications of the result to prawn culture and water quality management were discussed in details

The effects of culture system on growth and appearance of the mangrove oyster, Crassostrea gasar

The effect of culture system on the growth and appearance of the mangrove oyster, Crassostrea gasar, was studied. The off-bottom culture method was used under two culture systems of continuous and periodic submergence in two tidal ponds, designated A and B, respectively. The level of water was regulated in pond A while it was allowed to flow freely in pond B. The oysters were submerged in pond A and in pond B, were only submerged at high tide and exposed to air at low tides. A total of 375 oysters were used in each of the ponds at a stocking density of 75 per cage. Growth and appearance in the oysters were monitored monthly. Final mean length and weight: 50.3 mm ~c 6.68 SD, 20.8 g ~c 6.53 SD, and 52.3 mm ~c 7.14 SD, 18.8 g ~c 5.73 SD recorded for ponds A and B, respectively. No statistically significant differences were observed (P<0.05). Oysters from pond A appeared brittle, rough and unattractive and oysters from pond B were strong, neat and attractive. Salinity of 10-18 ppt and water temperature of 26~'C - 35.7 ~'c was recorded. The results revealed favourable growth under both culture systems but the unattractive appearance of oysters from pond A, made the oysters from pond B to show comparative consumer preference. However based on yield only, pond A is of greater advantage for the culture of mangrove oysters

Food habits, sexual dimorphism and sex ratio of three Palaemonid prawns of the Nun River, Niger Delta, Nigeria

The food habits, sex ratio and differences of three freshwater prawns ? Macrobrachium vollenhovenii, M. macrobrachion and M. felicinum from Nun River, Niger Delta were studied. It was found that although the prawns had an omnivorous diet feeding on a wide range of organisms including plants, detritus, insect parts, phytoplankton and zooplankton the food habits indicate a tendency towards a plant-based (herbivorous) diet. The adult prawns exhibit sexual dimorphism with males being larger than females; however the males were fewer in number than the females with mean ratios of 1:2.79, 1:1.58 and 1:9.12 for M. vollenhovenii, M. macrobrachion and M. felicinum. Sexual dimorphism exists in the species and brood-stock are available in the Nun River system of the Niger Delta region

Sediment Characteristics of the Andoni Flats, Niger Delta, Nigeria

A baseline study of the intertidal and subtidal zones of the Andoni flats was conducted to determine the basic physical and chemical characteristics of the sediment. Sediment characteristics revealed sandy to loamy (muddy) sand soils with pH of 4.09 to 5.04. Values of organic carbon varied from 0.17% in the sandy soil to 3.01% in the muddy sand soil. Other parameters determined include organic matter which varied between 0.29% and 5.22%, conductivity with values varying from 1120\u3bcScm-1 to 1800\u3bcScm-1 and water absorbency with values ranging from 21.74% to 43.73%. Particle density, bulk density and porosity of the sediment were also determined for the flats

Seasonal Variation in Interstitial Fluid Quality of the Andoni Flats, Niger Delta, Nigeria

Physicochemical characteristics of the interstitial fluid of the sediment of the intertidal and subtidal zones of the Andoni flats were studied. The results for the interstitial fluid showed low dissolved oxygen levels (0.1 \u2013 1.3mg/l), high temperature values (26.2 -32.4\ub0C), wide salinity range (8 \u2013 21ppt) and near neutral pH (6.26 \u2013 7.76) across stations. Sampling duration was from January 1999 to December 2000 covering both wet season (April \u2013 October) and dry season (November \u2013 March). The implications of the effects of fluctuating environmental variables on in-fauna inhabiting sediment are discussed

The influence of stocking density on the growth performance and production of tilapia (Oreochromis niloticus) in earthen pond

An experiment was carried out to investigate the influence of stocking density on the growth of the initial stocked tilapia (O.niloticus) in earthen ponds, the effect on the reproductive performance of the fish and impact on the economy of production. Six African Regional Aquaculture Centre (ARAC), Aluu, Port Harcourt earthen genetic ponds split into three compartments representing three replicates were stocked with 666 fingerlings of 4.33g average initial weight and 6.06cm average initial length at 37 per replicate. They were fed with a 28%CP blood meal based diet for nine months. The size of the ponds and depth of water was such as to attain average stocking densities of 6.33, 6.45, 5.05, 3.60, 2.88 and 2.05 fish/m3. The result showed distinct increase in growth as the stocking densities decreased. Ponds 5,6 and 4 with lower densities 2.88, 2.05 and 3.60 fish/m3 having higher final weights of 146.10, 120.79 and 108.69g than ponds 3, 2 and 1 with 85.37, 74.36 and 59.68g respectively (P<0.05). Average final length was higher in ponds 5, 6 and 4 at 14.46, 13.86 and 13.79cm than ponds 3, 2 and 1 with 12.09, 10.62 and 11.36cm. Relative weight gain followed suit with 3274.13, 2689.61 and 2410.16% in ponds 5, 6 and 4 as against 1871.59, 1617.32 and 1277.83% in 3, 2 and 1. Percentage survival increased as stocking density decreased at 28.18, 35.45, 37.27, 40.91, 41.82 and 45.45% for the 6.33, 6.45, 5.05 , 3.60, 2.05 and 2.88 fish/m3 treatment respectively, with the 3.60, 2.05 and 2.88fish/m3 treatment significantly higher (P<0.05). The 2.88fish/m3treatment (treatment 5) also provided the cheapest cost of producing 1kg of fish at N178.74 as against N457.14, N351.44, N312.41, N242.81 and N217.25 per kg fish of treatments 1, 2, 3, 4 and 6 respectively. The total number of off-springs produced all in progressive sizes increased as the stocking density decreased at 1530, 1636, 1674, 2053, 3160 and 3234 for ponds 1-6. The experiment showed that tilapia fingerlings stocked in earthen pond at low densities grow and reproduce more and at a lower cost of production than those with higher stocking densities. The ideal appears to be between 2 and 3 fish/m

Sediment Characteristics of the Andoni Flats, Niger Delta, Nigeria

A baseline study of the intertidal and subtidal zones of the Andoni flats was conducted to determine the basic physical and chemical characteristics of the sediment. Sediment characteristics revealed sandy to loamy (muddy) sand soils with pH of 4.09 to 5.04. Values of organic carbon varied from 0.17% in the sandy soil to 3.01% in the muddy sand soil. Other parameters determined include organic matter which varied between 0.29% and 5.22%, conductivity with values varying from 1120μScm-1 to 1800μScm-1 and water absorbency with values ranging from 21.74% to 43.73%. Particle density, bulk density and porosity of the sediment were also determined for the flats

Toxicity study and the effect of organophosphate pesticide on the gill of Oreochromis niloticus (Linnaeus, 1758)

The exposure of Oreochromis niloticus to perfekthion pesticide revealed the potential destructive impact of the toxicant on living systems using the gill as a parameter. Perfekthion which has dimethoate 400 g/L as the active agent is used in agricultural practices to eradicate pests and parasites to reduce pre and post-harvest losses. Bioassay treatment using perfekthion as the toxicant was administered to test fishes which were randomly selected. Ten (10) fishes were selected and placed all together in each of the treated chambers of 10 L capacity with the following concentrations; 2.8 mg/L, 5.6 mg/L, 11.2 mg/L , 22.4 mg/L , 44.8 mg/L and 0 mg/L which served as the control for the toxicity test. Histological analysis at the end of the 96-h acute test, showed huge damages inflicted on the test organisms. The impact increased as the concentration increased with the highest degree of gill lamellae degeneration in the 22.4 mg/L and 44.8 mg/L concentrations treatment chambers. Erosion of gill filaments were also seen at both concentrations. Lesions of gill tissues were also visible in the treatment medium with 11.2 mg/L concentration. Complete erosion of gill tissues was observed in the treatment with highest concentration of 44.8 mg/L of perfekthion. The gills of test fish exposed at treatments 2.8mg/l and 5.6 mg/L had no observable impact when compared with the control. From the overall inference, the study strongly recommends careful application of pesticides.Key words: Toxicity test, Organophosphate pesticides, Oreochromis niloticus, Bioassay, Gill histology, Dimethoat

OCCUPATIONAL RISK OF INFECTION BY HUMAN IMMUNODEFICIENCY AND HEPATITIS B VIRUSES AMONG HEALTH WORKERS IN SOUTH-EASTERN NIGERIA

Objective: To assess the occupational risk of infection by human immunodeficiency virus(HIV) as well as hepatitis B virus (HBV) among healthcare workers in south-eastern Nigeria.Design: Cross-sectional study.Setting: Three tertiary health institutions in south-eastern Nigeria.Subjects: Doctors, nurses, laboratory staff and cleaners.Main outcome measures: Observation of the availability and use of protective equipment andmaterials in the various departments of the hospitals.Results: Materials and equipments needed for protective and hygienic practices (adequatewater supply, protective clothing and availability of disinfectants) were inadequate in allhospitals. Where available, they were found to be inconsistently used. Health workers in thethree institutions were thus constantly exposed unnecessarily to blood and other body fluidswhich might be potentially infectious as well as injury from used sharps.Conclusion: The risk of acquiring HIV and HBV infections by health workers in this regionof Nigeria in the course of performing their duties is therefore still apparently high. Thoughdistinct viruses, they share similar mode of transmission and risk factors. Use of personalprotective equipment and adoption of standard hygienic practices among health workersmust be encouraged. Supply of protective materials and equipment should be greatlyimproved. It is recommended that reduction of occupational risks among health workersusing this approach should form part of control strategies for both infections in the country