African Journals Online
JOURNAL OF AQUATIC SCIENCES

Volume 18, Number 2, October 2003
ABSTRACTS

Acute toxicity and bio-accumulation of mercury and copper in Clibanarius africanus (Aurivillius) and Tympanotonus fuscatus (Linne)

E. O. OYEWO AND K. N. DON–PEDRO*

Nigerian Institute for Oceanography and Marine Research, P.M.B. 12729, Lagos, Nigeria

*Department of Zoology, Marine Biology and Fisheries, University of Lagos, Lagos, Nigeria

Abstract

The acute toxicity of Mercury and Copper on C. africanus and T. fuscatus and the bio-accumulation potentials of the metals were investigated in laboratory experiments employing standard bio–assay techniques. On the basis of LC₅₀ values, both metals had similar magnitudes of toxicity against C. africanus. However, Mercury was more toxic than Copper when tested against T. fuscatus. Against either of the test metals, C. africanus was more susceptible than T. fuscatus by orders of magnitude that varied between 6 and 23. Under sub-lethal concentrations (0.00038 - 0.08 mg L^-1 for either Copper or Mercury against C. africanus; 0.0088 - 1.08 mg Cu L^-1 and 0.0025 - 0.25 mg Hg L^-1 against T. fuscatus), C. africanus and T. fuscatus were shown to bioaccumulate these test metals in amounts that increased with time of exposure as well as dosage. Computed bioaccumulation factors for Mercury and Copper against C. africanus, at the same test concentration were 313 and 20974 respectively. Against T. fuscatus however, the bioaccumulation factors for Mercury and Copper after 28 days of exposure under the test conditions were 7.6 and 153 respectively; indicating that C. africanus was a much more efficient bioaccumulator of these metals than T. fuscatus. The implications of these findings for ecosystem viability, environmental management and public health considerations are discussed.

Key Words: Acute toxicity, Bioaccumulation, Public Health, Ecosystem viability, Environmental management.

Benthic macroinvertebrates as indicators of environmental quality of an urban stream, Zaria, Northern Nigeria

J. A. ADAKOLE¹ AND P. A. ANUNNE²

¹Department of Biological Sciences, Ahmadu Bello University, Zaria. Nigeria

 ²Department of Fisheries and Aquaculture, University of Agriculture, Makurdi, Nigeria

Abstract

For a period of 2 years (from July, 1997 to June, 1999), 87 benthic macroinvertebrate taxa, composed of 12,078 individuals were collected from four stations of Bindare stream and one station on River Galma. Samples were collected monthly, using a Van Veen grap. Physicochemical variables were also determined using standard methods. The catchment areas of Bindare upstream (stations 1 and 2) are farmlands, with few isolated human settlements suggesting a less polluted water environment. The BOD which ranged between 1.88 ± 1.67 mg/l to 8.0 ± 4.76 mg/l increased downstream of the point of discharge. This allowed the survival of sensitive species such as Ephemeroptera, Hemiptera, Plecoptera, Odonata and Neuroptera at upstream. The great preponderance of the class Diptera and Oligochaeta at stations 3 and 4 are attributed to various domestic and agricultural effluents discharged into the stream at these points. The organic pollution of Bindare stream resulted in a decrease in benthic macroinvertebrate species richness and an increase in species density. Compared to background values, these changes in both species richness and density contributed to a reduction in the calculated Magarlef water quality index, hence a deteriorated water quality.

Key words: stream, effluents, water quality, macro benthos, indicator species.

Bacterial and helminth bioload of cultured Channa obscura fish

J. N. OGBULIE, I. O. C. OBIAJURUand T. E. OGBULIE^**

Parasitology and Public Health Unit, Dept of Zoology, Imo State University, Owerri, Nigeria

** Imo State Environmental Protection Agency, Owerri, Imo State, Nigeria

Abstract

An investigation of the bacterial and helminth fuana of organs of diseased and healthy African snake head fish (Channa obscura) from Nigeria Agip Green River project, River State, Nigeria was undertaken. The intestine, skin, fin, gill, tissue and liver of the fish were examined for both bacterial and helminth load. The results indicated that the bacterial load of the diseased fish samples were higher than those of the apparently healthy fish. Identification tests of the probable isolates revealed the isolation of the following genera: Aeromonas, Citrobacter, Enterobacter, Klebsiella, Lactobacillus, Pseudomonas, Campylobacter, Proteus, Serratia, Staphyloccocus, Yersinia and Vibro sp. Whereas helminth fauna isolated were Camallanus sp., Capillaria sp., Acetodoxtra sp., Chimostomum sp, Diphostomum sp. and Polyonchobethium sp. Percentage helminth infestation was found to be higher in adults than sub-adults and juveniles, while the percentage prevalence of the helminth infections amongst the fishes examined was found to be 41%. Helminth infection therefore varies amongst age groups. This study reveals the bacteria and load of cultured Channa obscura

Key words: Bioload, helminths, Bacteria, Cultured fish

Effects of sub-lethal concentrations of NPK (15:15:15) fertilizer on growth and feed utilization by the toothed carp Aphyosemion gairdneri under laboratory conditions

E. OMOREGIE, M. N. O. AJIMA AND I. R. KEKE*

Department of Zoology, University of Jos, Jos, Nigeria

*Department of Animal and Environmental Biology, Imo State University, Owerri, Nigeria

Abstract

The effect of sub-lethal concentrations of NPK (15:15:15) fertilizer on growth and feed utilization by the toothed carp, Aphyosemion gairdneri was investigated under static bioassays during an eight week exposure period. The concentrations of the fertilizer used were 0.50, 0.25, 0.125, 0.063 and 0.031 g/l. Weight of the exposed fish decreased proportionally with increase in the fertilizer concentrations. However, at 0.0312 g/l, no significant weight loss (P > 0.05) was observed. With the exception of the groups of fish exposed to 0.031 g/l, the fertilizer led to poor food conversion ratio (FCR) and protein efficiency ratio (PER). The groups of fish exposed to 0.50 g/l almost rejected the food offered and consumed less than 40% of food offered, these groups recorded a 100% mortality before the end of the eight week exposure period. Environmental implications of the results are discussed.

Key words: Inorganic fertilizers, growth, Aphyosemion gairdneri, pollution

Bacteriological water quality changes and substratespecificity of isolates associated with Clarias lazera culture system

J. N. Ogbulie AND I. O. COBiAJURU

Department of Industrial Microbiology, Federal University of Technology, Owerri, Nigeria.

Abstract

This study was undertaken to ascertain the impact of seasonal changes on the bacteriological water quality and substrate specificity of isolates in a Clarias lazera culture system at Obirikom, Rivers State, Nigeria. Bacteriological changes and substrate specificity were determined using standard microbiological techniques. Stratification was observed in the bacterial distribution with the pond sediment habouring more aerobic and anaerobic bacterial genera than the pond water. Obvious seasonality in the occurrence of bacterial genera was also observed with higher occurrence obtained in the dry than wet (rainy) season. Identification test revealed the presence of Pseudomonas, Proteus, Micrococcus, Escherichia, Chromobacterium, Serratia, Klebsiella, Bacillus, Staphylococcus, Lactobacillus, Pediococcus, Norcadia, Vibro, Salmonella, Aeromonas, Cytophaga, Corynebacterium, Campylobacter and unidentified gram-positive cocci. About 50 – 55% and 80 – 90% of these bacteria genera were isolated from the pond water and sediment samples respectively, with the latter having a preponderance of Micrococcus, Cytophaga, and Bacillus. Substrate specificity test of these isolates revealed variation in the ability of the bacteria genera to hydrolyse gelatin casein, tributyrine, starch and cellulose. The ability of bacterial isolates to utilize these macromolecules occurred more in the sediment than in the water column. Majority of the bacterial population hydrolysed all the substrates while only a small percentage of the population was able to hydrolyse cellulose. This study revealed that seasonal variation affects the bacteriological quality of Clarias lazera culture systems and the substrate specificity by isolates.

Key words: Bacteriological, water quality, Clarias lazera, culture system

Freshwater Ostracoda from Jamieson River, Niger Delta Region, NIGERIA

T. O. T. IMOOBE

Department of Zoology, Faculty of Science, University of Benin, Benin City, Nigeria

Abstract

An investigation of ostracods along the entire stretch of Jamieson River, Delta State, Nigeria was carried out to determine the species composition and ecology. A total of four species of freshwater ostracods, three of which are new records in Nigeria are reported. All the four species were widely spread across the five sampling stations; however percentage co-occurrence of species of Ostracoda indicate that none of the ostracods species showed significant co-occurrence. At stations one and two no significant correlation existed between ostracods and any of the environmental factors investigated, however, at station three air and water temperatures significantly correlated negatively with the ostracods (P < 0.05), while at stations four and five Transparency and Calcium respectively showed highly significant correlation with ostracods (P < 0.01), while transparency was negatively correlated, Calcium showed positive correlation.

Keywords:Freshwater, Ostracoda, Crustacea, Nigeria

Leaching of feed nutrients, economic losses to fish farming

B. A. FALAYI¹, A. M. BALOGUN², O. T. ADEBAYO² , C. T. MADU¹ AND A. A. EYO¹

¹National Institute for Freshwater Fisheries Research, New Bussa, Nigeria

²Department of Wildlife and Fisheries, Federal University of Technology, Akure, Nigeria

Abstract

Seven isoproteic 40% crude protein diets were formulated and each diet was bound with different binding agents from wheat flour (WFS), Cassava tuber (CS), Maize offal (MOS), Paddy rice (RS), Yellow maize grains (YMS), Sorghum grains (SS) and Synthetic Carboxymethyl-Cellulose (CMC) as control binder. All binding agents were incorporated at 2%. Total proteins and total lipids retention at 10, 20, 30 and 60 minutes were observed in the laboratory. There were decreasing trends in the nutrients retention at increasing time of immersion in water with the lipids nutrients retention higher (P > 0.05) than the proteins. The diets were also fed to groups of Clarias gariepinus fingerlings (mean weight 2.12 ± 0.02 g) in outdoor concrete tanks. The growth and feed utilization were very related to the records produced from the nutrients retention with the WFS, CS, MOS and RS fishes recording significant differences (P < 0.05) in mean final weight; mean weight gain and feed conversion ratio over YMS and SS among the local binding agents. The economic evaluation was highest (P < 0.05) in CMC in net production value, value of fish, cost of feed, gross profit, incidence of cost and the least in profit index. However, CS binder was recommended because of its abundance in the tropics; higher nutrients retention; higher growth and feed utilization and higher economic evaluation indices among the local binders.

Keywords: Retention, Leaching, Diets, Catfish, Binding agents, Economic values.

Surveillance of potential pathogenic fungi associated with water hyacinth in Lake Kainji, Nigeria

F. DADDY, B. M. B. LADU, F. D. BEED*, Y. A. BIRNIN-YAURI AND S. OWOTUNSE

National Institute for Freshwater Fisheries Research, PMB 6006, New Bussa, Nigeria

*International Institute of Tropical Agriculture, Plant Health Management Division, Cotonou, Republic of Benin.

Abstract

The entire Kainji Lake and the riverine areas upstream of Yauri were surveyed monthly between February and May 2002 with a motorboat to make full inspection of fungi-infested water hyacinth plants. Various parts of water hyacinth plant showing symptoms of fungal infection were collected, dried between paper towels, labeled, treated and planted onto growth agar media in petri dishes sealed with parafilm. All isolates were characterised for identification. On some older plants with larger leaves were found sporulating Myrothecium roridum. On the smaller plants with purple flecking lesions were isolates of Alternaria eichhorniae of, which were necrotic patches surrounded by chlorotic halos. The presence of A. eichhorniae in Nigeria indicates a great promise as its choice in most African environment by the International Mycoherbicide Programme for Eichhornia crassipes Control in Africa (IMPECCA) for development into a mycoherbicide. Other fungal pathogens isolated included Rhizoctonia solani, Acremonium zonatum and Cercospora piaropi.

Key words: Bio-control, pathogenic fungi, Kainji Lake, water hyacinth, identification

Laboratory rearing and distribution of the breeding sites of simulium species in Kaduna State

C. E. MBAH, I. H. NOCK AND C. G. VAJIME

Department of Biological Sciences, Ahmadu Bello University, Zaria, Nigeria

Abstract

Between November 1992 and July 2000, immature and adult simuliid fauna were collected from rivers and streams across four bioclimatic zones comparising 96 sampling stations in 62 sites for rearing and identification. Adult man-biting simuliids were allowed to feed on human bait and later maintained in the laboratory on 10% sucrose solution. They were induced to oviposit by immersion in water contained in capped plastic tubes. Larvae hatched from the single batch eggs were reared to late instar and identified cytologically. Developing larvae from the wild were reared in aerated cylinder system and identified cytologically. Pupae reared in emergence cages and adults of non-anthropophilic species were identified morphologically. A total of 652 man-biting adult females were caught, (and identified using published keys) 3927 larvae reared and 811 larvae identified cytologically. Three sibling species, S. damnosum s.s., S. sirbanum and S. squamosum were identified cylologically from their F₁ larval progeny. Apart from these known vectors of onchocerciasis, seven non-anthropophilic species were identified using morphological keys, namely: S. ruficorne, S, hargreavesi, S, alcocki, S. adersi. S. cervicornutum, S. unicornutum and S. aureosimile.The composition of S. damnosum s.s. larvae within either the rivers or months and the interaction among the months and rivers was not significant (P>0.05). Analysis of variance of biting females of Simulium squamosum with either the rivers or months was not significant.

Keywords: rearing, Simulium, identification

Biodiversity and abundance of fish and plankton of Dan-Zaria Dam, Niger State, Nigeria

S. L. LAMAI AND R. J. KOLO

Department of Fisheries, Federal University of Technology, Minna, Nigeria

Abstract

An assessment of fish and plankton biodiversity and abundance of Dan-Zaria Dam were carried out over a period of one year. Sampling of fish and plankton was conducted monthly. Five (5) sampling stations were randomly established based on their importance to the dam. Fish sampling was conducted using cast net, fleets of gill nets of various mesh sizes, ranging from one inch to seven inches. Fishes caught were identified, counted, weighed and lengths taken and recorded. Results indicated that five fish species existed in the dam during the study period, about three of the species viz. Oreochromis niloticus, Tilapia zilli and Clarias gariepinus were the most common, while the two other species, Laboe senegalensis and Alestes nurse were less common. A total of 2,010 fishes were caught. Of the three common species, O. niloticus dominated with an estimated total catch of about 1,609 accounting for 80.05%. The total catch for, T. zilli was 178 representing 8.86%, that of, C. gariepinus was 137 representing 6.82%, the others represented about 4%. Water and plankton samples were taken simultaneously with fish samples. Results showed that Four (4) common taxa existed in the water body at the time of study viz. Chlorophyceae, Cyanophyceae, Desmidiaceae and Bacillariophyceae. In all about 28 species of phytoplankton were identified. About forty (40) species belonging to 4 taxa of zooplankton, the protozoa with about 26 species, Cladoceran (3 species); Copepoda (4 species) and Rotifers comprising about 7 species %. It was therefore concluded that the biodiversity of fish species and abundance were of a short range however with a good yield. While for plankton, it was concluded that their biodiversity and abundance were great at the time of this study.   

Key word: Biodiversity, Fish, Plankton, Abundance, Dan-Zaria dam