African Journals Online
JOURNAL OF AQUATIC SCIENCES

Volume 16, April 2001
Abstracts

 OBSERVATIONS OF FRY CANNIBALISM IN CLARIAS GARIEPINUS (BURCHELL, 1822)

P. O. ALUKO¹, A. A. NLEWADIM² AND A. AREMU¹

¹National Institute for Freshwater Fisheries Research, P.M.B. 6006, New Bussa, Nigeria
² Federal University of Agriculture, Umudike, Nigeria

ABSTRACT

Fry cannibalism was investigated in Clarias gariepinus with a view of understanding the underlying embryological and early larval life factors responsible for the behaviour. A total of 5.6% of the fertilized egg attained 2-cell cleavage stage than others and 2.3% of the eggs hatched within the first one hour of onset of hatching. About 80% of fertilized egg hatched between 4 and 5 hours after onset of hatching, indicating that 2.3% of hatchlings are more advanced in growth than the rest. Larval survival was highest (70.6%) among the eggs that hatched at 5 hours after onset of hatching and the least was in the eggs that hatched at 6 hours after onset of hatching. The ‘medium jumper’ attained the highest weight gain per day (0.056 g / day) while the large jumper recorded the least weight gain per day (0.043 g/day). The ‘small jumper’ recorded the highest specific growth rate (2.46% /day) while the least was the ‘large jumper’ (1.55% /day). ‘Tail first ‘ cannibalistic behaviour was exhibited by one week old fry while ‘head first’ cannibalistic behaviour was recorded in 4-week old post-fry.     

Key words: Cannibalism, Clarias gariepinus, Growth

DISTRIBUTION AND ABUNDANCE OF INSECT ORDERS IN RELATION TO HABITAT TYPES IN OPA STREAM-RESERVOIR SYSTEM, NIGERIA

S. S. OGBOGU AND  T. O. AKINYA

Department of Zoology, Obafemi Awolowo University, Ile-Ife, Osun State, Nigeria.

ABSTRACT

Aquatic insects collected from the stream below the dam, the pool and the spillway of Opa stream-reservoir system in Ile-Ife, Nigeria, were compared.  The primary purpose of this collection is to carry out an assessment of the relation between habitat structure and the distribution and abundance of aquatic insects in the water body.  There was a marked difference in the taxonomic composition of insects in the spillway from those in the pool and stream.  Only the larvae of the Trichoptera family, Hydropsychidae were present in the spillway while Ephemeroptera, Odonata, Plecoptera, Coleoptera, Hemiptera and Diptera occurred in the other sampling locations.  Jaccard’s similarity index and similarity ratio were 0.667 and -1.09 respectively, when the taxa composition and insect abundance from stream and pool were compared.  This indicates that both sampling locations are considerably similar.  The Trichoptera larvae occurred in large numbers and closely associated with a moss, Fontinalis (Bryophyta), recording 1232.5, 900 and 1178 larvae per sq.m as densities in August, September and November respectively. With Trichoptera larvae alone, the spillway recorded the highest total number of individuals among the three sampling locations throughout the period of study.  It was inferred that Fontinalis provided strong foundations for larvae, refuge from predators, and substratum for algae and diatoms which serve as food resource for larvae.  The moss - Trichoptera association in an unstable habitat such as the spillway was discussed with reference to the ability of hydropsychid caddisflies to survive in a wide range of habitats.  However, the association observed in this study needs further investigation.

Key words: Bryophyta, Fontinalis, reservoir spillway, Trichoptera, Insecta, habitat preference.

ASPECTS OF WATER QUALITY OF FRESHWATER SYSTEMS HARBOURING SNAIL VECTORS OF SCHISTOSOME PARASITES IN JOS, NIGERIA

P. I. AGI* AND V. N. OKWUOSA

Department of Zoology, University of Jos, P.M.B. 2084, Jos, Nigeria
*Present Address: University of Port Harcourt, P.M.B. 5321, Port Harcourt, Nigeria


ABSTRACT

A study of some aspects of water quality of freshwater systems harbouring snail vectors of schistosome parasites was conducted in Jos, Nigeria. Calcium ion concentration of the water bodies was a mean value of 31 mg.l-1. The range of temperature was 15 - 30OC. The occurrence of Biomphalaria pferifferi was attributed to the existence of low temperature regimes in the area. pH values were on the alkaline side. High pH values were associated with conductivity and low dissolved oxygen values. Range of conductivity values for the occurrence of snail vectors was 27 - 200 micromhos. Dissolved oxygen in the water rangefrom 1.2 - 8.0 mg.l-1. Thus the water quality parameters were within the tolerance limits of the snail vectors and this was responsible for the wide distribution of the snails.Key words: Freshwater, water quality, snail vectors, schistosome.

THE FOOD AND FEEDING HABITS OF PHRACTOLAEMUS ANSORGII (BOULENGER) FROM WARRI RIVER, NIGERIA  

O. ODUM AND M. ANUTA

Department of Zoology, Delta State University, Abraka, Nigeria

ABSTRACT

The food and feeding habits of Phractolaemus ansorgii (Boulenger) obtained from the Warri River, Nigeria are discussed. The main food items were detritus, algae, dominated by the Bacillariophyceae and sand grains. The feeding habits varied seasonally and with fish size. The fish fed more actively in the dry season while diet diversity decreased with increased size. It is argued that as fish grew older, it became more specialized in its dietary habits.

HAEMATOLOGICAL RESPONSE OF CLARIAS GARIEPINUS  TO BACTERIAL INFECTION AND PROPHYLACTIC TREATMENT WITH ANTIBIOTIC

G. N. O. EZERI

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

ABSTRACT

A total of thirty Clarias gariepinus were used for the experiment. Ten C. gariepinus of 357.76 g mean weight were artificially challenged by injecting 2 ml each of live Pseudomonas fluorescences suspended in Ringers solution and containing 12.5 x 10⁵ bacterial cells (3.5 x 10⁵ cells/g wt) respectively. They were prophylactically treated by injecting 1ml each of Chloramphenicol (1g in 10 ml distilled water). Another ten C. gariepinus of 270.51 g mean weight were also challenged by injecting 2 ml each of live P. fluorescens in Ringers solution containing 12.5 x 10⁵ cells (4.6 x 10³ cells g/wt) without any prophylactic treatment.  Finally, another ten C. gariepinus of 267.8 g mean weight which served as the control, were injected with 2ml Ringer’s solution only.  60% mortality among the infected and treated fish was recorded, 80% mortality among infected and untreated C. gariepinus while no mortality was observed for the control.  Some haematological indices revealed that the infected and treated fish had haematocrit (25.3 ± 1.883%), Erythrocyte sedimenutation rate (5.25 ± 1.192 mm/h), Mean Haemoglobin (5.2 + 0.48 g/100cm³), and white blood cells (11.33 x 10³m³).  The infected and untreated fish had haemalocrit (22.8 ± 3.61 %), ESR (5.9 ±  0.38 mm/h), mean haemoglobin (5.6 + 0.25 g/100cm³) and WBC (13.52 x 10³/mm³), while the control fish had haemalocrit  (31.0 + 3.24%), mean ESR (5 ±  2.05 mm/h), mean haemoglobin (6.9 ±  0.85 g/100cm³) and mean WBC (7.54 x 10³/mm³).

GROWTH AND SURVIVAL OF FIRST FEEDING LARVAE OF CLARIAS GARIEPINUS FED LIVE AND PRESERVED ZOOPLANKTON

E. I. AMALI AND S. G. SOLOMON

Department of Fisheries, Unviersity of Agriculture, Makurdi, Nigeria.

ABSTRACT

The study was designed to evaluate the growth performance and survival of Clarias gariepinus larvae fed live Zooplankton (LZ), Frozen Zooplnakton (FZ), Dried Zooplankton (DZ) and a mixture of Live and Frozen Zooplankton (LFZ) as well as Live and Dried zooplankton (LDZ). The experiments were conducted in plastic baths of 10 L capacity filled to 5 L mark with dechlorinated domestic water supply (tap). Every bath was stocked with 30 first feeding larvae (3 days old) weighing 12.25 mg – 12.70 mg and randomly assigned the feeding treatments in triplicate. The larvae were fed to satiation twice daily between 09.00 – 10.00 and 15.00 – 16.00 hours. The length and weight of the larvae under the various treatments were measured prior to stocking and weekly for a period of 4 weeks. Also monitored in like manner were pH, temperature and dissolved oxygen content of the culture medium. The percentage survival rate of the larvae were determined per treatment at the end of the feeding trial.  The average daily length increase of 0.38 mm, 0.36 mm and 0.35 mm by fish fed LZ, DZ and LDZ respectively are not significantly different (P >0.05) from one another but were however significantly higher (P<0.05) than the 0.29 mm and 0.27 mm length increase by larvae fed FZ and LFZ respectively. The percentage increase in length by all the fish followed the same pattern above within a range of 55 – 63.63%. The average daily weight gain of 9.0mg by larvae fed on LZ is significantly higher (P < 0.05) than the weight gains on the rest feed treatments which were however not significantly different from one another. While the specific growth rate followed the same pattern as weight gain, the percentage weight gain in the range of 94.17% - 95.30% did not vary significantly (P > 0.05) with the treatments. The larval survival rates which was similar for FZ, LZ, and LFZ were within the range of 65.56% - 68.89%. This is followed by the survival rate of 56% by larvae fed DZ. It was concluded therefore that preserved zooplankton was suitable for the rearing of Clarias gariepinus larvae with the frozen zooplankton giving a better rate of larval survival. The strategy for using preserved zooplankton in larval rearing is also advanced.

FOOD AND FEEDING BEHAVIOUR OF NYMPHON GRACILE (PYCNOGONIDA:NYMPHONIDAE)  AROUND THE MUMBLES PIER AREA  OF SWANSEA, UNITED KINGDOM.

N. G. IMANDEH* AND P. E. KING

Marine, Environmental and Evolutionary Research Division, School of Biological Sciences, University of Wales, Swansea SA2 8PP, UK.

*Present address: Applied Entomology and Parasitology Unit, Department of Zoology,
University of Jos, P.M.B. 2084 Jos, Nigeria. E-mail:[email protected]

ABSTRACT

The feeding behaviour of the “sea-spider” Nymphon gracile (Pycnogonida: Nymphonidae) and its  association with other organisms, around the Mumbles pier area of Swansea, United Kingdom is described and compared to the reported cases in other families of the order Pycnogonida.

SURF DIATOMS OF THE LAGOS LAGOON BEACH, NIGERIA

D. I. NWANKWO AND M. A. JAIYEOLA

Department of Zoology, Marine Biology and Fisheries, University of Lagos, Akoka, Lagos.

ABSTRACT

Investigations into the dry season surf diatoms of the Lagos lagoon along the University of Lagos beach were carried out for six months (Dec. 1989 – May 1990). Forty-two diatom taxa belonging to 23 genera were recorded. The diatoms recorded, showed euryhaline tendencies. On the whole the more frequent species were Navicula expansa, Achanthes coaractata, Cymbella minuta, Nitzschia irresoluta, Nitzschia closterium, Gyrosigma tenuissimum, Amphora ovalis and Hantzschia amphioxys. The importance of these diatom to the shore–line sandy habitat fauna was highlighted.

Key Words: Surf, diatoms, Lagos lagoon, Nigeria

HELMINTH EGGS RECOVERED FROM POLLUTED IRRIGATION WATER IN SOME PARTS OF PLATEAU STATE, NIGERIA

 O. OKORONKWO* AND C. O. E. ONWULIRI
Department of Zoology, University of Jos, Jos, Nigeria
*Department of Community Health, University of Jos,Jos, Nigeria

  ABSTRACT

Irrigation waters from rivers and mining ponds insome parts of Plateau State were examined from the presence of helminth eggs using centrifugal-floatation technique between 1996 and 1997. The results showed that helminth eggs were present in varying amounts in all the 672 samples of water taken from each of the fourteen sources examined. Hookworm eggs occurred in the highest concentration in both the river and pond samples. Ascaris eggs were detected from the pond samples, and at levels comparable to river samples except for the Dilimi and Farin-Gada river samples which were significantly higher. Toxocara eggs were detected more frequently from pond samples than from the river water sources, while Trichuris eggs were more evenly distributed in the two water sources. The public health risks associated with the helminth eggs recovered are further discussed.

Key words: Helminth eggs, irrigation, polluted water.

DISTRIBUTION, DENSITY AND DIVERSITY OF DIPTERANS IN A TEMPORARY POND IN OKOMU FOREST RESERVE, SOUTHERN NIGERIA

A. E OGBEIBU

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

ABSTRACT

Some aspects of the ecology of Diptera were studied in a temporary pond in Okomu Forest Reserve, southern Nigeria between January 1988 and December 1989.  Twenty six morphologically distinct taxa were identified, of which 14 were chironomids.  The dominant taxa were Polypedilum (43%), Alluaudomyia (21%), Culex (11%), Pentaneura (10%), and Chironomus (5%).  Spatial and temporal variations in the individual dipteran taxa during this period are considered in relation to inter-station differences in macrophyte cover, exposure to sunlight, substratum, and changing environmental factors, such as temperature, water level, conductivity, dissolved oxygen, pH and nutrients.  The distribution, density and diversity of dipterans were principally influenced by macrophytes, substratum, water level, temperature and pH.  The ecology of ceratopogonids, chironomids, culicids and stratiomyids are discussed in this paper.

Key Words: Temporary pond, Diptera, distribution, density, diversity.

ULTRASTRUCTURAL CHANGES IN THE KIDNEYS OF THE STICKLEBACK, GASTEROSTEUS ACULEATUS (L) EXPOSED TO DISSOLVED CADMIUM

J. A. O. ORONSAYE

Department of Fisheries, Faculty of Agriculture, University of Benin, Benin City, Nigeria

ABSTRACT

The cytological alterations in kidney tissues of the stickleback Gasterosteus  aculeatus exposed to 6 mg Cd.L^-1 on water 299 mg.L^-1 hardness as CaCO₃ at 12 + 2^oC for 30 days are described. The alterations include vacuolation of the haemotopoetic cells, enlargement of nuclei, of renal cells, shrunken and rounded mitochondria increased electron dense materials necrotic cells and electron transparent vacuoles becoming occupied by granulomas. Lysosomes become numerous in all cells notably the collumnar cells towards the microvilli and tubule lumina. The role played by the lysosomes is discussed.

Key words: Cadmiun. kidney ultrastructure  freshwater  fish

STOMACH LENGTH AND FOOD PREFERENCE OF THREE TILAPIA SPECIES (OSTEICHTHYES: CICHLIDAE) IN AGULU LAKE BASIN, NIGERIA. 

C. I. P. Anibeze

Department of Zoology, University of  Nigeria, Nsukka
Correspondence Address: P. O. Box 3322, Enugu, Nigeria

ABSTRACT

A comparative study of the stomach length and food contents of Tilapia  mariae (Boulenger), T. zillii (Garvais) and Oreochromis niloticus (Linneus) was carried out over a 24 month period in Agulu Lake basin, southeastern Nigeria. Results showed that T . zillii was herbivorous while T . mariae  and O. niloticus subsisted mainly on a wide variety of plankton. Generally, considerable quantities of zoo – and phyto-plankton  were present in the food of the three species. Variations were observed in the gut lengths and dental anatomy of the tilapias which related to their food preferences. Nutritive value of food showed no significant difference (P < 0.05) in all species and crude protein evaluation showed that stomach contents were adequate.

CHECKLIST OF PHYTOPLANKTON OF SHENDAM RESERVOIR IN PLATEAU STATE, NIGERIA

E. C. KEMDIRIM
Department of Biological Sciences, Nigerian Defence Academy, Kaduna

ABSTRACT

A qualitative study of phytoplankton flora was carried out in Shendam reservoir, Plateau state of Nigeria.  Seventy one species were recorded indicating a fairly low species number when compared to other Nigerian waters.  The major groups of phytoplankton found were chlorophyceae, bacilliarophyceae, cyanophyceae and dirophyceae.  The study revealed that the reservoir has a high potential for thriving fishery.

Key words: Phytoplankton, Nigeria

ON-SET OF SEXUAL MATURITY: OBSERVED DIFFERENCES BETWEEN POND-RAISED AND RECIRCULATION SYSTEM-RAISED HETEROBRANCHUS LONGIFILIS (TELEOSTEI:  CLARIIDAE) VAL. 1840

 C. O. OFOR

Department of Fisheries, Michael Okpara University of Agriculture, Umudike, Nigeria

ABSTRACT

On-set of sexual maturity in pond-raised and recirculation system-raised Heterobranchus longifilis was studied. Males of both groups matured at 9½ months. The females of the first group matured at 11½  months, while females of the second group matured at 14 months. Histological examination of the ovaries revealed that this difference in onset of sexual maturity was due to the fact that the progression of the gonads of the second group of fish from the immature to the maturing stage suffered a 2½  month delay relative to the first group. The possible reasons for this delay are discussed.

Keywords: Heterobranchus longifilis, Sexual Maturity Onset, Ponds, Recirculation System.

THE EFFECTS OF CROWDING STRESS, DIFFERENT DIETS AND DIFFERENT SIZE CLASSES ON THE GROWTH RATE OF CLARIAS GARIEPINUS

  L. A. CHUDE
Department of Fisheries, Federal University of Agriculture, Umudike, Nigeria

ABSTRACT

Indoor-studies conducted on three growth variables - stocking rate, diets and size classes at fortnightly intervals revealed that out of 460 dterminations of length and weight of Clarias gariepinus (12 cm mean total length and 11 gm mean weight) taken, the results showed that: at constant area, growth rate of Clarias gariepinus reduced by as much as 75% when the density was increased from one to three individuals per square metre - regardless of food supplied. Sinking feed with high carbohydrate content enriched with vegetable protein rather than animal protein is more beneficial to the species. Fish with standard length less than 17 cm grew faster than those with greater lengths. This corresponds to and indeed accentuates the importance of transition pond stage in aquacultural management.The implication of this finding with respect to aquaculture management is discussed herein.

Key words: Growth rate, crowding stress, negative allometry, Clarias gariepinus.