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Itambi A.C.,University of Bremen | von Dobeneck T.,University of Bremen | Adegbie A.T.,Nigerian Institute for Oceanography and Marine Research
Journal of Quaternary Science | Year: 2010

We combine environmental magnetism, geochemical measurements and colour reflectance to study two late Quaternary sediment cores: GeoB 4905-4 at 2° 30′ N off Cameroon and GeoB 4906-3 at 0° 44′ N off Gabon. This area is suitable for investigating precipitation changes over Central and West Africa because of its potential to record input of aeolian and fluvial sediments. Three magnetozones representing low and high degree of alteration of the primary rock magnetic signals were identified. The magnetic signature is dominated by fine-grained magnetite, while residual haematite prevails in the reduced intervals, showing increase in concentration and fine grain size at wet intervals. Our records also show millennial-scale changes in climate during the last glacial and interglacial cycles. At the northern location, the past 5.5ka are marked by high-frequency oscillations of Ti and colour reflectance, which suggests aeolian input and hence aridity. The southern location remains under the influence of the Intertropical Convergence Zone and thus did not register aeolian signals. The millennial-scale climatic signals indicate that drier and/or colder conditions persisted during the late Holocene and are synchronous with the 900 a climatic cycles observed in Northern Hemisphere ice core records. © 2009 John Wiley & Sons, Ltd.

Edun O.M.,Nigerian Institute for Oceanography and Marine Research
Journal of Fisheries and Aquatic Science | Year: 2012

Global aquaculture production has grown rapidly over the last 50 years. It is generally accepted that there is limited potential to increase trahtional fisheries; consequently, increased aquaculture is required in order to maintain global per capita fish consumption at the present level. With nearly half of all fish eaten today coming from farms and some 12 million people dependent on fish farming for their daily income, ensuring that farmed fish products are safe to eat and of the highest possible quality is crucial. Most of the work reviewed in this article describes the safety and quality issues in farmed fish, implications for consumers and presents methods to improve product characteristics. © 2013 Academic Journals Inc.

Soyinka O.O.,University of Lagos | Kuton M.P.,University of Lagos | Ayo-Olalusi C.I.,Nigerian Institute for Oceanography and Marine Research
Estonian Journal of Ecology | Year: 2010

We recorded 37 fish species representing 21 families in the Badagry Lagoon, south-west Nigeria. Adult stages of 13 (35.14%) of them were freshwater, 7 (13.51%) estuarine, and 19 (51.35%) near-shore marine species. The seasonal variation in the fish catch composition of the lagoon was attributed to the seasonal fluctuation in salinity. Availability of food organisms was also noted to affect the seasonal distribution of the fish fauna. Other physical features such as temperature and pH varied slightly, while the concentration of dissolved oxygen was higher in the dry season than in the rainy season. The highest species richness was observed in September with 11 species, while the lowest with the smallest abundance was observed in February with 5 species. The most abundant species during their occurrence were Cynoglossus senegalensis (7.92%), Tilapia mariae (7.17%), and Ilisha africana (6.04%). Species richness and total abundance were found to increase during the rainy season.

Abohweyere P.O.,Nigerian Institute for Oceanography and Marine Research
European Journal of Scientific Research | Year: 2011

A cohort analysis was carried out on a 24-month length-frequency data of Macrobrachium macrobrachion Herklots, 1851 (Brackish River Prawn) from the Lagos - Lekki lagoon system, via modal progression analysis using Bhattacharya's method in FISAT (FAO-ICLARM Stock Assessment Tools) software. A total of 12,168 specimen of M. macrobrachion was used for the analysis. Three cohorts were decomposed from the composite length frequency sample. The residual of the Gulland and Holt plot, from the length at age derived from the linking of cohort means gave the value of the amplitude of growth oscillation C as 0.20 and the winter point WP as 0.58 or July. The amplitude of seasonal growth oscillation and the winter point derivable from the cohort analysis are of paramount importance in the stock assessment and ultimately management of the resource as they revealed the strength of growth oscillation along with the period of slowest growth which can be inferred as the most susceptible period for the stock. Therefore resource sustainability require that fishing mortality be minimized in this period (July) in the Lagos - Lekki lagoon system. © EuroJournals Publishing, Inc. 2011.

Agwu O.A.,Nigerian Institute for Oceanography and Marine Research
African Journal of Aquatic Science | Year: 2013

Antibiotic-resistant bacteria in the aquatic environment are considered reservoirs for drug-resistant genes. Therefore, culturable heterotrophic bacteria isolated from Lagos Lagoon surface waters between 2011 and 2012 were screened for their susceptibility to 14 commonly used antibiotics belonging to six major classes. The sampling stations had temperature, pH and salinity ranges of 28 to 33 °C, 8.2 to 8.1 and 14.6 to 20.1, respectively. The high microbial load of the sampling stations was evident, the mean most probable number being between 400 and 1 100 per 100 ml. The bacteria encountered were Pseudomonas sp., Citrobacter sp., Vibrio sp., Micrococcus sp., Streptococcus sp., Bacillus sp. and Aeromonas sp. Resistance to the tested antibiotics was widespread; the incidences of isolates resistant to ampicillin (55.3%) and amoxicillin (52.6%) were the most common, while all tested isolates were susceptible to the fluoroquinolones, with the exception of sparfloxacin which was resisted by 26.3% of the isolates. The frequency of resistant isolates for aminogylcosides, macrolides, phenicols and sulfonamides ranged between 2.6% and 18.4%. The most resistant strain had a multiple antibiotic resistance value of 0.57. Although susceptibility to some drugs was noted, resistance to the beta-lactam antibiotics suggests that bacteria in Lagos Lagoon harbour genes for resistance. © 2013 Copyright © NISC (Pty) Ltd.

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