Aspects of mineral composition of male and female Heterobranchus bidorsalis adults exposed to different concentrations of Bonny-light crude oil

Studies were carried out to assess some macro and trace elements of mineral composition of the male and female Heterobranchus bidorsalis adults exposed to graded concentrations (1.00-8.00m/L-1) of Bonny-light crude oil (BLCO). The experiment was monitored for 4 days (toxicity) and 42days (recovery) periods. Significant decreases (P < 0.05)in the sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), phosphorus (P), zinc (Zn), iron (Fe), vanadium (Va), lead (Pb) and manganese (Mn) contents of the male H. bidorsalis corresponded with the increasing concentrations of BLCO. In contrast, the female fishes recorded significant increases (P < 0.05) in the values of the above elements in their tissues as the concentrations of BLCO increased. Furthermore, the values of Na, K, Mg, Ca, P, Zn, Fe, Va, Pb and Mn recorded in the male fishes where generally lower than those of their female counterparts and the control fish. Increased values of these elements were also recorded during the recovery periods (days 14, 28 and 42) of this study in the magnitudes of 15% at day 14, 20% at day 28 and 20% at day 42. This implied that the removal of crude oil stress during this period improved the quantity of these minerals deposited in the fish tissues. The highest percent proportion of Zn and the lowest proportion of Pb recorded in both male and female H. bidorsalis adults agreed with the report of other workers for other fish species. KEYWORDS: Heterobranchus bidorsalis, Mineral composition, Bonny-light crude oil, Toxicity, Recovery.

Qualitative and quantitative aspects of the food of Ethmalosa fimbriata (Bowdich) in the Ebrié lagoon (Côte d'Ivoire)

The food of Ethmalosa fimbriata in the central part of the Ebrié lagoon, where the salinity is low, consists on limnic phytoplankton. In the region near Abidjan, which is more strongly influenced by coastal water, it consists of marine phyto- and zooplankton. The daily ration of a 12.5 cm fork-length fish is estimated to be between 2 and 3 % of its body weight.

Salmon and freshwater fisheries in the Solway Firth. Report of the Working Party of North West Water Authority and the Annan District Salmon Fishery Board.

The Workinq Party of North West Water Authority and the Annan District Salmon Fishery Board's aims were to identify the current problems relating to the salmon and freshwater fisheries in the Solway Firth and its tributaries (embracing the catchments of the Annan, Kirtle Water, Sark, Esk, Eden, Wampool and Waver - and possibly also the Lochar Water and the Nith) to produce agreed outline solutions, and to consider the financial aspects of the future administration of these fisheries.

Aspects of the ecology of the crustacean zooplankton in the Sanyati Basin, Lake Kariba

Investigations on the zooplankton in Lake Kariba were carried out as part of a broader programme investigating components of the sardine, Limnothrissa miodon, food chain and factors affecting their productivity. This report deals mainly with the crustacean zooplankton, Bosmina longirostris and Mesocyclops leuckarti, which are the most important species in the sardine's diet. Factors which influence the number and distribution of the zooplankton are discussed. The relationship between the zooplankton and Limnothrissa are also briefly discussed.

Aspects of the biology and population dynamics of freshwater mussels in Lake Kariba and Lake McIlwaine

The essential aim of this study was to provide a broad foundation of biological knowledge upon which a programme of mussel utilization and management could be built. Results of the study are presented in three main sections. Part 1 describes the stock of Lake Kariba and Lake McIlwaine; part 2 describes various aspects of the breeding biology of the three species; and part 3 presents the results of morphological, biochemical and age analyses - aspects which are used for initial standing crop and production calculations. The final discussion concludes the thesis with a general examination in ecological terms of the factors which have influenced the development and nature of the mussel faunas of the two lakes under consideration.

Aspects of quality control of wind profiler measurements in complex topography

It is well known in the scientific community that some remote sensing instruments assume that sample volumes present homogeneous conditions within a defined meteorological profile. At complex topographic sites and under extreme meteorological conditions, this assumption may be fallible depending on the site, and it is more likely to fail in the lower layers of the atmosphere. This piece of work tests the homogeneity of the wind field over a boundary layer wind profiler radar located in complex terrain on the coast under different meteorological conditions. The results reveal the qualitative importance of being aware of deviations in this homogeneity assumption and evaluate its effect on the final product. Patterns of behavior in data have been identified in order to simplify the analysis of the complex signal registered. The quality information obtained from the homogeneity study under different meteorological conditions provides useful indicators for the best alternatives the system can offer to build wind profiles. Finally, the results are also to be considered in order to integrate them in a quality algorithm implemented at the product level.

Some reproductive aspects of Chrysichthys nigrodigitatus (Lacépède) from Cross River, Nigeria

Between May and October 1990, fecundity, egg size and condition factor of Chrysichthys nigrodigitatus (Lacépède) in the Cross River, Nigeria, were studied. The fecundity (F) of this population varied from 3 046 eggs (total length, L=28.5 cm) to 28 086 eggs (L=64 cm). A mean relative fecundity of 231 eggs/cm or 13 eggs/g of fish was obtained for this population. The fecundity of this population can be estimated with the formula F=2.511 · L 2.30 or F=52.893 · W 0.78 , total length being in cm and weight (W) in g. The mean egg diameter of this population varied from 0.65 mm to 3.54 mm. Condition factor (CF) of the population varied from 0.24 to 1.34 with 0.977 as the mean; 52.8% had CF higher than the mean and 47% had CF above unity. Smaller fish in this population were in better condition than bigger ones. The egg size and condition factor obtained in this study are evidence that the Cross River population of C. nigrodigitatus can provide excellent broodstock.

Aspects of phosphorus pollution from aquaculture

Phosphorus is an essential element for living organisms and exists in waterbodies as dissolved and particulate forms. Phosphorus is required for optimum growth, feed efficiency, bone development and maintenance of acid-base regulation in fish. The presence of high concentration of phosphates in water may indicate presence of pollution as it may accelerate plant growth and disrupt the aquatic ecosystem thereby benefiting certain species and altering species diversity in affected areas. Eutrophication of waterbodies is often correlated with the phosphorus loading into the environment and aquaculture has been identified as one of the sources of phosphorus pollution. Details of the impacts of eutrophication is given in Bernhardt (1981). Phosphorus must be provided in fish feed because of its low concentration in water. Studies made in Europe and Northern America have revealed a phosphorus surplus in most commercial feeds which is above actual requirements; or is supplied in a form which is unavailable to the fish. Surplus phosphorus is excreted, while unavailable phosphorus is passed out in the feces. Discharge of phosphorus from fish farms and hatchery effluents have caused phosphorus pollution in Nordic countries, North America and Europe. This article examines the path of phosphorus pollution, quantification/prediction of phosphorus load from aquaculture and remedial measures.

Comparison of some traits of economic importance in tilapias (Orechromis niloticus and Sarotherodon galilaeus) with particular reference to their culture in Ghana

This study was conducted to determine which of the two major tilapia species in freshwater capture fisheries in Ghana, Oreochromis niloticus or Sarotherodon galilaeus, is more suitable for breed improvement and pond culture. It compares traits of economic importance, including seed output, specific growth rate, survival and sex ratios following androgen sex reversal. The results of the study showed that the aquaculture potential of S. galilaeus compares favorably with that of O. niloticus. However, S. galilaeus may be preferred because the males and females have an equal growth rate, which allows for manual sorting to raise both sexes in monosex culture, an inexpensive appropriate technology that an ordinary smallscale fish farmer can apply.