2School of Biological Sciences, Imo State University, Owerri, Nigeria

The Citharinid fishery of Lake Oguta, the largest lentic natural water body in South eastern Nigeria is biologically and economically overfished. Technological innovations in the lake fishery between 1975 and 1985 by the Fisheries Division of the Imo State Ministry of Agriculture and the Anambra-Imo River Basin Development Authority (AIRBDA) are largely responsible. These had resulted in unhealthy dramatic fishing transitions, excessive fishing pressure and resource over-exploitation. Restocking programme has been advocated as the most effective and accelerated management strategy for resuscitating lake bodies whose fishery resource are depleted. However, the unclear identity of the young stage of the fauna for use in restocking programmes, especially the fingerlings from the wild is a major set-back. The present study ascertains the identity of Citharinus latus (Family: Citharinidae) through the analysis of Morphometric and meristic features. Other characeristics that make field identification practicable are also discussed.

Key words: Morpho-meristic analysis, Citharinus latus, restocking policy.

K. A. ABUBAKAR AND A. EDWARD

Department of Biological Sciences, Federal University of Technology, Yola, Nigeria

Investigation was carried out on food and condition of the Catfish, Synodontis species in the Upper Benue River Basin, Nigeria from March to June, 2000. Fish samples were obtained twice monthly from different fish landing sites. Analysis showed that there was no significant difference between the sizes of males and females. Length-weight regression analysis indicated isometric growth of the species sampled. Correlation analysis between length and weight was highly significant. Monthly mean condition factor was constant during the period of investigation. The fish species exhibited diversity in their diets with insect parts, larvae and Algae as the main diets. The overall sex ratio showed a close proximity to 1:1 ratio.

Key Words: Food, condition, Synodontis sp.

K. V. ABSALOM, S. O. MUSA, L. E. AKPA AND A. OYINDASHOLA

Hydrobiology and Fisheries Unit, Department of Zoology, University of Jos, Jos, Nigeria

A survey of the Protozoan species diversity in a productive fishpond of the Jos Plateau, Nigeria was investigated at 7 day interval over a period of 11 months. Samples were collected from water column and sediment. Protozoans were found to compose of the flagellates sarcodines and cilliates. There was a significant variation (P < 0.05) between the sampling periods for the flagellates. In the water column, the flagellates ranged 38 - 1035 cells.l^-1 in July (atmospheric temperature ranged from 22 - 24⁰C and water temperature was 22 - 25⁰C) while the sediment contained 5 - 860 cells.1^-1 in August (atmospheric and water temperature coincided at a range of 22 - 26⁰C). Sarcodina abundance showed significant variation (P < 0.05) between sampling period. The density ranged from 3 - 140 cells.l^-1 in the water column of temperature range between 23 and 26⁰C while atmospheric temperature was between 23 and 28⁰C. In the sediment of the same sampling period (i.e. June - November) numbers ranged from 32 - 480 cells l^-1. The cilliates showed no significant difference in abundance (P > 0.05) between the sampling period. The highest number ranged from 3 - 145 cells.l^-1 in the sediment while the water column was 0 - 4 cells. l^-1. The low numbers recorded for the sacodines and cilliates could have been due to predation by the planktivorous fish species in the pond. The study has revealed the dynamic nature of the pond ecosystem interacting to maintain an ecological balance through the contribution of the protozoans.

Key words: Protozoa diversity, homestead fishpond, Jos Plateau.

RICHARD P. KING & BASSEY E. AKPAN*

Centre for Wetlands & Waste Management Studies, University of Uyo, Uyo, Nigeria

*Department of Zoology, University of Uyo, Uyo, Nigeria

Aspects of the ecology of Nanaethiops unitaeniatus were studied in a rainforest wetland ecosystem (Mfangmfang pond) in Uyo, Nigeria. This fish occurred through out the year and was commonly found in association with the cyprinid, Barbus callipterus. They were often found in shoals of 20 or more fishes. They remained in open water during the day and retreated into shallow vegetated shore water at night. Total lengths varied between 32 and 76 mm. The length-weight relationship was negatively allometric. Feeding intensity increased with fish size and was higher during the night than day. Feeding occurred at the surface, mid water and bottom. The fish had a broad trophic spectrum with 21 dietaries. Algae and detritus were of primary importance.

Key words: Feeding Habits, Nanaethiops unitaeniatus, Nigerian Rainforest Pond

L. A. NWUBA AND J. N. AGUIGWO

Department of Zoology, Nnamdi Azikiwe University, Awka, Nigeria

Hatchlings of clarias anguillaris produced at Nnamdi Azikiwe University, Awka, Nigeria, were cultured in plastic aquaria set up in flow through system and observed for 30 days. The effect of different food items such as artemia, moina, zooplankton (mixture of artemia and moina), mixture of zooplankton and artificially compounded feeds on the survival of hatchlings were monitored. It was observed that the hatchlings on single diet could not survival beyond the 19th day of life. The individuals, were all the live foods plus the compounded feed were given, gave 90% survival after 30 days observation period. It is therefore recommended that live food in a mixture of compounded feed be fed to clarias anguillaris for high percentage survival to be achieved.

Keywords: clarias anguillaris, Hatchlings, survival

A. O. ANYANWU, E. AJADO AND B. EBONWU

Nigerian Institute for Oceanography and Marine Research Victoria Island, Lagos, Nigeria

Isoelectric focusing methodology using LKB 2117 Multiphor 11 electrofocusing apparatus was used for electofocusing and identification of Oreochromis niloticus and Tilapia zilli. The electrographs of the two species suggest clear protein differences producing species specific patterns. There were variations in the protein patterns at the cathode and the middle portions of the gels. The densitometric tracings of the low-resolution (pH 3-10) gels for the species also showed major differences in their banding patterns as shown by graphical representations of the bands. The banding patterns of O. niloticus and T. zilli were closer at the basic (cathodal) and mid pH range than at the acidic zone. Some family resemblance was observed in protein zones of similar mobilities.

Key words: Isoelectric focusing, Oreochromis niloticus, Tilapia zilli, protein profiles,

B. C. ONUSIRIUKA

Department of Biological Sciences, Nigerian Defence Academy, Kaduna, Nigeria

The effect of parasitism on the protein and free fatty acid of the Nile tilapia, Oreochromis niloticus and African catfish, Clarias gariepinus from swimming pool end of River Kaduna was investigated. Nematodes were seen to parasitize the two fish samples and this resulted in lower values of free fatty acid and crude protein content in the two fish types. Water quality parameters showed variation but these are regarded as affecting the parasitized and unparasitized fish samples equally. Proper examination of fish obtained from River Kaduna before consumption is recommended.

Key Words: Clarias gariepinus, fatty acid, Oreochromis niloticus, parasites, protein, River Kaduna.

V. O. AYUBA* AND P. C. OFOJEKWU

Fisheries Research Unit, Department of Zoology, University of Jos, Jos, Nigeria

*Present Address: Department of Fisheries and Aquaculture, University of Agriculture Makurdi, Nigeria

Datura innoxia root extract was exposed to fingerlings of Clarias gariepinus (mean weight: 10.20 + 0.38 g) for 96 hours under laboratory conditions using static bioassays with continuous aeration to determine its acute toxicity. The LC₅₀ of the exposed fingerlings was found to be 204.17 mg/L with lower and upper confidence limits being 125.89 and 384.59 mg/L respectively. The fish exhibited loss of balance, respiratory distress and swam erratically just before death.

Keywords: Catfish, Clarias gariepinus, Datura innoxia, Datura innoxia, toxicity.

A. O. AGBON, G. N. O. EZERI., B. N. IKENWEIWE, W. O. ALEGBELEYE, , O. OKE* AND D. T. AKOMOLEDE

Department of Aquaculture and Fisheries Management, University of Agriculture, Abeokuta, Nigeria.

*Department of Biological Sciences, University of Agriculture, Abeokuta, Nigeria.

A study was conducted to determine the storage method that will best preserve the quality and quantity of smoke-cured Clarias sp. using boxes made of cardboard and wood, as well as, airtight metal containers. The boxes made of cardboard material was found to be the best medium of storage as all infesting dermestid adult and larvae were found dead at the end of 60 days storage period. There was a significant increase (P < 0.05) in the population of larvae in the metal container, which accounted for the reduction in quality and quantity of the stored product. It is concluded that boxes made of cardboard are the best medium for storing smoke-cured Clarias sp. when a preservative is not added to the stored product.

Keywords: Smoke-cured, Dermestes maculatus, storage, fish.

D. P. YAKUBU, E. OMOREGIE, J. W. WADE AND D. U. FARINGORO

Department of Zoology, University of Jos, Jos, Nigeria

A comparative study of the gut helminths of Tilapia zilli and Clarias gariepinus from river Uke in Plateau State, Nigeria was carried. A total of 100 fishes comprising of 60 T. zilli and 40 C. gariepinus were examined for helminth parasites. The parasites encountered include Camallanus sp., Crepedostomum meteocus, Procamallanus laeviconchus, Proteocephalid sp., and Sphaerostoma bramae. A total of 61% of the T. zilli were found to be infected with one parasite or the other while 55% of C. gariepinus were infected. Chi-square test confirmed a significant difference (P < 0.05) in infection rate between the two species, although no significant difference was observed between the males and females of the two different fish species.

Keywords: Gut Helminths, Tilapia zilli, Clarias gariepinus, Plateau State, Nigeria

V. F. OLALEYE

Department of Zoology, Obafemi Awolowo University, Ile-Ife, Nigeria

Water quality changes after in situ chemical control of water hyacinth (Eichhornia crassipes (Mart.) Solm-Laub. using five chemical products were monitored in a green house experiment. The observed changes in water quality coincided with the loss of treated plant photosynthetic activities, submerging of the dead plants in water and the subsequent decomposition and dissolution processes. Treatment in all cases significantly (P < 0.05) increased the mean alkalinity, pH, conductivity, organic matter, ionic and the solids contents of the water 28 days after treatment. Irrespective of herbicidal treatment, mortality of water hyacinth and subsequent decay in situ significantly lowered (P < 0.05) the amount of dissolved oxygen in the various treated media below 1.0 mg/L.

Key Words: Water hyacinth, water quality, herbicide.

C. U. EDEMA, J. O. AYENI, A. ARUOTURE

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

Some abiotic and biotic habitat characteristics of the shallow Okhuo River (average depth 0.85 m) were determined and are described. Water temperature (25.8⁰C) is slightly lower than 25.9⁰C of air. The mean conductivity was 291.4 m Scm^-1. The pH is low (5.63) as the alkalinity (8.95mg CaCO₃ l^-1). The low biochemical oxygen demand (2.94 mg l^-1) and high dissolved oxygen (11.1mg l^-1) indicate low level of organic matter in the water. Ephemeroptera and Oligochaeta are widely distributed and not inclined to habitat restrictions. Oligochaetes (8.8%), rotifers (72.60%), cladocerans (8.64%), copepods (15.52%), ostracods (3.65%), shrimps (15.9%), insects (75.3%) were sorted out and identified from the collections. Numerically rotifers (72.60% of plankton) and insects (75.3% of benthos) were dominant. The proportions of biota (Ephemeroptera, 67.2%; Chironomidae, 8.1%) interplaying with the physico-chemical characteristics are conducive to cleanliness of the Okhuo River.

Key words: Zooplankton, Macroinvertebrates, Nigeria.

REVIEW ARTICLE

W. O. OGARA¹, A. O. NYANG'WARA² AND I. ABIYA³

1University of Nairobi, Department of Public Health, Pharmacology and Toxicology, Nairobi, Kenya