Age and growth of Mugil cephalus (Linnaeus, 1758) (Perciformes: Mugilidae) in Bonny Estuary

The age and growth of Mugil cephalus was investigated in Bonny Estuary, Nigeria, from January, 1995 to December, 1996. Length-weight relationships were isometric with length exponents of 2.84 (males), 2.90 (females) and 2.88 (overall). Modal length at age were 12.0cm, 20.9cm, 25.0cm, 28.4cm and 30.2cm TL for ages 0+, 1+, 2+, 3+ and 4+ respectively. Corresponding total weights were 20.01g, 78.93g, 173.12g, 217.61g and 247.50g, respectively. Asymptotic length (Lo) was estimated 33.2cm TL, asymptotic weight (W sub(o)) was 484g, growth coefficient K=0.55847 super(-1) and hypothetical age at zero length To = 0.152yr. Longevity, Tmax, was 5.0yr, length and weight growth performance indices were Q super(1)=2.79 and Q = 1.44, respectively. Total mortality, natural mortality and fishing mortality were z = 1.02yr super(-1), M=0.607yr super(-1) and F=O. 3129yr super(-1), respectively. The exploitation ratio E was 0.4048 and exploitation rate U = 0.2302yr super(-1

Market survey of the periwinkle Tympanotonus fuscatus in Rivers State: Sizes, prices, trade routes and exploitation levels

Tympanotonus fuscatus was collected from 23 markets through Rivers State (Nigeria), a few in neighbouring states, and from an unexploited population at Buguma. The size distribution of shells was determined,and information on prices and trade routes was also obtained. The mean shell length of specimens from the unexploited Buguma population was 46.4 mm, compared to 30.4 mm for the Buguma market samples. Mean sizes in other markets showed a geographic pattern: the smallest were from the Adoni-Ogoni-Opobo sector (28.1-30.9); the largest were from the Nembe-Brass sector (37.7-44.2) and Bendel State (35.7-45.6); The results suggest the population structure of Tympanotonus in much of Rivers State has been strongly impacted by overharvesting. They show that local market as well as some in Cross River State, are increasingly being supplied by road with specimens from the Benin River area of Bendel State. Differences between shell types; and relations between shell size, selling price and market distance from source, are also discusse

Functional roles of mangroves of the Niger Delta to the coastal communities and national economy

Mangrove swamps supply various goods and provide invaluable ecological services, especially as critical habitats for fish breeding. These functions are discussed in the context of rural livelihoods of coastal dwellers in the Niger Delta in particular, and the contribution to national economies in general. The decline in capture fisheries production in Nigeria is partly linked to massive mangrove loss in the Niger Delta. This provides basis for urgent evolution of effective mangrove conservation schemes in the Niger Delta and for focused research on the interaction between the delta mangroves and inland/coastal fish recruitment and production dynamics

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

Some ecological factors of the tropical floodplain influencing the breeding and conservation of Gymnarchus niloticus (Cuvier 1829): a review

Gymnarchus niloticus is the only species of the family Gymnarchidae. It is a popular food fish in most parts of Africa where it is greatly esteemed. In some culture, it is offered as a special gift to leaders during festive seasons, while in some others it is an important part of items presented by a suitor to the parents of a girl at the time of betrothal. It can therefore be inferred that G. niloticus is not only important as food fish with economic significance, but also plays vital roles in the socio-cultural life of some African tribes. The supply of this important species still depends largely on the catch from the wild. However, based on the method of catch, it has been classified as endangered. A close examination of the ecological factors in the floodplain (where it migrates to breed), revealed strong influence on the breeding and survival of the fish. The level of rainfall determines the extent of floodplain inundation, and the abundance and survival of the flora and fauna in the area. These in turn determine the availability of breeding substrates and natural food sources for the various stages of G. niloticus. Therefore, rainfall, the flora and the fauna of the floodplain play vital roles in the breeding and survival of G. niloticus in nature. To ensure the conservation of this important species, controlled propagation strategies that draws on the influence of prevailing ecological factors in the floodplain is recommended. This will ensure conservation, and protect the economic and socio-cultural significance of G. niloticus

Identification of West African estuarine shrimp and crab larvae

The paper deals with the decapod crustacean larvae likely to be found in fresh and brackish waters in tropical west Africa. It summarizes results from an ongoing program of describing larvae hatched directly from adults of known species, to provide the identification keys necessary for applied research on nursery grounds, plankton ecology and pollution effects. A preliminary key to stage - 1 larvae is given for approximately 40 species. In includes all the genera, and nearly all the species, known to produce larvae in fresh and low-salinity waters. The common species of higher salinity waters are also include

Histopathological variations in gills, liver and kidney of nile tilapia - Oreochromis niloticus exposed to benzalkoniumbhloride mixture with treated produced water

The microscopic examination of tissue in order to study the manifestations of disease is very important. This paper investigated the histopathological variation in some organs of juveniles of Nile tilapia-Oreohromis niloticus exposed to benzalkonium chloride (BAC)-treated produced water (TPW) mixture in a 96hour acute toxicity test. Fish specimens of average body length and weight 7.80 cm and 25.05g, respectively were used. At the end of exposure 2 survivor fish in each concentration across triplicates were randomly harvested for the histological examination. Histological preparations of gills, kidney and liver were analysed for histopathological alterations. Results of histological examination revealed various degrees of legions ( gills- cellular necrosis and epithelial rupture (CN), kidney - glomerular expansion (GE) and dilation of Bowman’s space (BC) and liver - expanded central vein (CV) and melanomacrophages aggregate (M)) depending on concentrations of the toxicant as against untreated (control) that recorded no abnormality. The results showed that the severity of tissue alterations recorded was a function of toxicity ofbenzalkonium chloride (BAC) mixture with treated produced water (TPW). It is strongly recommended its disposal followed a thorough treatment.Keywords: Benzalkonium-chloride, treated-produced-water, histopathology, cellular necrosis, O. niloticu

Heavy Metal Uptake and Bioaccumulation by Mangrove Grab (Goniopsis pelli) from used Drilling Mud, Niger Delta, Nigeria

This study was carried out to evaluate some heavy metal uptake and bioaccumulation in the meat, egg and shell of G. pelli from used drilling mud. The experimental approach involved the exposure of ten of the test organism G. pelli to six acute concentrations of drilling mud representing 0% (control), 10%, 20%, 30%, 40% and 50% for 96 hours in three replicates after the range finding test was conducted to determine the LC50. From the LC50, the test organism was further exposed to four sub-lethal concentrations of drilling mud (0%, 5%, 10% and 15%) for 21 days to evaluate the heavy metal uptake by the test organism. the result showed that heavy metal uptake increased in the order of meat (&lt;0.001-2.36±0.12), shell (&lt;0.001-3.31±0.19) and egg (&lt;0.001-0.54±0.05) when compared with those in control tank. Copper was highest (3.31μg/g) in the shell and lowest (0.26μg/g) in the egg; zinc was highest (2.36μg/g) in the meat and lowest (0.22μg/g) in the shell; chromium was highest (0.12μg/g) in the meat and lowest (0.06μg/g) in the egg; cadmium was highest (0.2μg/g) in the shell and lowest (0.001μg/g) in the egg while lead had equal value (&lt;0.001) in the meat, shell and egg of the test organism. This could pose a very serious health challenge to the consumers of G. pelli and other aquatic fishery resources if nothing is done to ensure the best practice in drilling activities in other to avoid pollution of the water bodies through drilling. Keywords: Heavy metals, bioaccumulation, drilling mud, Goniopsis pell

Acute toxicity of benzalkonium chloride mixture with treated produced water to juveniles of freshwater tilapia - Oreochromis niloticus

This research was conducted to determine the lethal concentration (LC50) of benzalkonium chloride (BAC) mixture with treated produced water capable of causing mortality of at least 50% of the Nile-tilapia-Oreochromis niloticus juveniles in a static 96h acute toxicity. Juveniles of mix sexes of O. niloticus of average length (6.80 cm) and weight (25.05g) were exposed to various concentrations (20.20, 50.50, 101.00 and 202.00 ppm.) of the toxicant with tap water used as control under laboratory condition. The LC50 values at 24, 48, 72 and 96hours were determined to be 96.427, 73.799, 73.799 and 69.772 ppm, respectively. Water quality check and general fish behaviour (respiratory distress, loss of balance, erratic swimming and death) were observed. Regression equation(y =-0.270 + 93.44) and correlation (R2 = 0.751) obtained from the study depict direct positive relationship between fish mortality and BAC mixture. Hence, unregulated release of benzalkonium chloride and treated produced water into aquatic environment is capable of causing acute toxicity to juveniles of O. niloticus. Its disposal into the environment should therefore be discouraged.Keywords: Acute-toxicity, LC50, Benzalkonium-chloride-mixture, Nile tilapi

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