The use of aqueous extracts of Vernonia amygdalina in the control of saprolegniasis in Clarias gariepinus, a freshwater fish

Saprolegniasis infection causes severe damage to fish integument. To control this fungal infection in the fish environment, Asteraceous plant (Vernonia amygdalina) extract at varying concentrations (50, 40, 30, 20%, control) was used to test its potency in controlling the infection and to ascertain its inhibitory capacity. The axenic culture of the test fungus was maintained on PDA at 28oC. The rate of the colony forming units was determined and the test inocula adjusted to 1.5 X 105 spores per ml. The Asteraceous plant extract generally depressed the growth of the fungi and cleared the spores earlier noticed on the fish integument. The potency of inhibition of the growth of Saprolegnia increased with increase in concentration. The control fish without the plant extract showed fluffy tufts growing on their body after 28 days and they appeared lethargic. This research hold great promise in elucidating the potency of the plant extract (V. amygdalina) in suppressing fungal growth in the integument of Clarias gariepinus, a freshwater fish

Incidence of feeding, growth and survival of the toothed carp, Aphyosemion gardneri larvae reared on the freshwater rotifer, Brachionus calyciflorus

Comparative analysis of survival and growth in the toothed carp, Aphyosemion gardneri larvae grown on the freshwater rotifer, Brachionus calyciflorus and on commercial diet were obtained. The freshwater rotifers were first isolated and cultured in the laboratory in a rich medium containing algae and Baker's yeast. Larval length and wet weight were measured on day zero (0), 8, 16, 24, and at the end of the experiment (day 32). Results obtained showed that growth were significantly (

Observations on some aspects of the biology of Sudanonautes aubryi (H. Milne Edward,1886) (Crustacea: brachyura: potamoidea: potamonautidae) in Orogodo River, Niger Delta, Nigeria

Investigation into some aspects of the ecology of the amphibious freshwater crab, Sudanonautes aubryi (H. Milne Edwards, 1886) in Orogodo River at Abavo, Southern-Nigeria was carried out between March and August, 1995. The study revealed that the crab species is wide spread and abundant in the river. There was a seasonal trend in the level of abundance both in number and biomass. The crab showed more abundance at the peak of the rainy season (August). Both adults and juveniles showed a progressive increase from late dry season to mid-rainy season (August). The male–female ratio was 1:1.2. The fluctuation in the number and percentage of gravid females indicated that the crab spawned during the mid-rainy season (June–August). The crab attained a maximum total length and weight of 8.4cm and 89.09g respectively. Its growth pattern was isometric. The mean monthly condition factor (k) ranged from 17.15 to 23.52 and generally showed a monthly fluctuation with a peak in April. Keywords: sudanonautes aubryi, biomass, gravid, Orogodo River, condition factorTropical Freshwater Biology 2003/2004 Vol. 12/13: 105-11

Phytoplankton Community Responses in A Perturbed Tropical Stream in the Niger Delta

The effect of abattoir wastes and other anthropogenic activities on the distribution and abundance of phytoplankton and environmental variables were investigated in River Orogodo, southern Nigeria. Samples of phytoplankton were collected monthly from three stations designated as station 1 (upstream of the river course), station 2 (effluent discharge point) and station 3 (downstream of the river course) for a period of six months. A combined total of 46 species of phytoplankton were encountered in the study. Station 1 recorded a total of 45 species, station 2 with 18 taxa and station 3 with 42 representative species, showing recovery in terms of diversity and density of phytoplankton. The order of dominance in the river was Bacillariophyceae > Chlorophyceae >Cyanophyceae > Euglenophyceae. The blue-green algae (Cyanophyceae) were dominant in station 2 in terms of density and diversity indicating their tolerance to organic enrichment. Generally, Spirogyra, Ulothrix, Oscillatoria, and Navicula species were the preponderant species. Euglena viridis was the only member of the class Euglenophyceae recorded in the river and it occurred only sporadically in station 1. The low fauna diversity experienced in station 2 throughout the period of sampling showed strong evidence of impact arising from the abattoir waste discharge and heavy human activities at that station. Pearson correlation coefficient analysis indicated temporal trends in phytoplankton density and composition. This was related to changes in environmental characteristics of the river. Keywords: Phytoplankton, Spirogyra, Ulothrix, River Orogodo, Abattoir wastes, Environmental variables.Tropical Freshwater Biology Vol. 17 (1) 2008: pp. 37-5

Effect of abattoir wastes on the water quality of Aleto River in the Niger Delta, Nigeria

The effects of abattoir effluent on the water quality parameters, pH, dissolved oxygen, nitrate (NO3), phosphate (PO4), sulphate (SO4), hardness, conductivity, faecal coliform and the biochemical oxygen demand (BOD), of the receiving surface water of Aleto River in River State (Niger Delta, Nigeria) was monitored monthly from February to June 2007. The NO3, PO4 and SO4 contents were higher in the downstream than that of the upstream of the outfall points of abattoir effluent, of the river. The quality of Aleto River water was assessed using the National Science Foundation water quality indices. Most of the water sampled during the study period fell in the medium water quality range. Few samples mainly mid reaches fell in the good quality range while WQI index reflect the overall quality parameter of the based on all the parameter, exceptionally low BOD values of the water samples facilitated their classification. The water quality in station 1 deteriorated mainly due to discharges from the abattoir.Key words: Abattoir waste, Aleto River, water quality, water quality inde

Influence of selected biotopes on chironomid-based bioassessment of the Swartkops River, Eastern Cape, South Africa

Impact of pollution on aquatic biota is usually assessed by comparing the assemblage at an impacted site with those at a control or reference site. In South Africa, except in rivers where not all biotopes are represented, the characterisation of a macroinvertebrate-based pollution effect is usually based on samples collected from three distinct biotopes, i.e., stones, vegetation and sediments. In this study, the influence of reducing the numbers of biotopes on chironomid-based bioassessment of pollution in the Swartkops River was investigated. This paper addresses the following questions: (i) can the chironomid species assemblage from any single distinct biotope analysed separately provide sufficiently accurate results similar to those of the composite-biotope group assemblage, and (ii) can chironomid community types be identified based on their biotope preferences? Chironomid larvae were sampled seasonally from three distinct biotopes: stones (stone-inand- out-of-current), vegetation (marginal and aquatic), and sediment (gravel, sand and mud, GSM) at one upstream control site, i.e., Site 1, and three downstream sites, i.e., Sites 2, 3 and 4. Site 2 in Uitenhage was impacted by diffuse pollution sources including runoff from road networks. Site 3, also in Uitenhage, was impacted by wastewater effluent discharges as well as diffuse pollution sources, while Site 4 in Despatch was about 2.5 km downstream of Site 3. The multivariate analysis of similarity (ANOSIM) indicated that the chironomid species assemblages based on the composite biotopes were significantly different between all site pairs in terms of species composition and abundance. However, when the assemblages were analysed separately for each of the three distinct biotopes, only the stone-based assemblage indicated significant differences between all of the site pairs similarly to those of the composite biotopes. Thus, the results suggest that, when resources are limited, sampling only the stony benthos could still provide bioassessment results similar to benthos from all three biotopes combined