Studies on the Biology of Silver Catfish (Chrysichthys Nigrodigitatus Lacèpède 1803) in Jebba Lake, Nigeria
CHAPTER ONE
im of the study is to investigate the biology of Chrysichthys nigrodigitatus in Jebba Lake with the following specific objectives:
- Determine the physico-chemical parameters of Jebba Lake
- Determine the morphometric and meristic parameters of Chrysichthys nigrodigitatus in JebbaLake
- Determine age and growth parameters of Chrysichthys nigrodigitatus in Jebba Lake
- Determine food and feeding habit of Chrysichthys nigrodigitatus in Jebba Lake
- Determine reproductive parameters of Chrysichthys nigrodigitatus in Jebba Lake
- Determine the abundance and distribution of Chrysichthys nigrodigitatus in Jebba Lake
CHAPTER TWO
LITERATURE REVIEW
Physico-chemical Characteristics of Water Bodies
Water is essential for the survival of life on earth. The availability of water plays a significant role in the location, and activities of human beings, because growth explosion is placing great demands on natural fresh water resources (Waziri and Ogugbuaja, 2010). Fresh water bodies are important source of water for human consumption and activities, such as drinking, agriculture, domestic use (including cooking, washing), transportation, recreation and electricity generation (Andem et al., 2012).
Fresh water bodies, supports diverse plants and animals community that is affected due to changes in the physico-chemical parameters, as a result of untreated discharge of pollutants from domestic sewers, industrial waste and agricultural runoff (Singh, 2007). Changes in physico-chemical parameters affect the survival and growth rate of organisms in water bodies, which cause their disappearance (Edward and Ugwumba, 2010). To protect fisheries, either in culture or capture, water quality requirements in terms of physico chemical parameters are of paramount importance. Any chemical,
physical and biological changes in water quality could have a harmful effect on organism and makes water unsuitable for the desired use (Araoye et al., 2007). Physical parameters include length, width, area, volume and depth of water, water temperature, total suspended and dissolved solids, turbidity, transparency and total surface area of the water body. Chemical parameters include conductivity, pH, dissolved oxygen, biochemical oxygen demand, total alkalinity, salinity, nitrate, phosphate, etc.
Knowledge of the physico-chemical parameters, fish and fishery of a body of water are invaluable in the determination of its productivity, stock assessment and management tools for sustainable fishing (Atobatele and Ugwumba, 2008). In addition, these parameters form the basis for enlightened fisheries and water resources management (Araoye et al., 2007). Natural waters, whether rivers, lakes, dams and estuaries, contains some level and types of impurities at various state and concentration, which are subjected to continuous change (Araoye et al., 2007). Direct interactions of many frequently measured water quality parameters with biotic components, which affect productive potentials of fish species, have been documented (Adakole, 2002).
Water Temperature
Temperature has a pronounced effect on chemical and biological processes being an important water quality parameter and relatively easy to measure. Many aquatic organisms are sensitive to changes in water temperature (Bellingham, 2012). It is known that temperature affects the feeding, growth and behaviour of fish. Water bodies will naturally show changes in temperature seasonally and daily; however, man made changes to water temperature will affect fish’s ability to reproduce. The recommended value of temperature in natural water bodies is 25oC (WHO, 2004) and 20oC-30oC for aquatic life in tropical region (Horsfall and Spiff, 2003). Many lakes and rivers exhibit
vertical temperature gradients as the sun warm the upper water and the deeper water remains cooler. Fish has poor tolerance to sudden changes in temperature, but readily tolerate gradual changes in temperature (Schwarzenbach et al., 2003). Aremu et al. (2011) recorded temperature range of 22oC-23oC and 23oC-24oC, for wet and dry seasons respectively in Doma, Farin ruwa and Mada Rivers. Temperature ranges of 22oC-26oC and 26oC-28oC for wet and dry seasons were recorded by Mustapha and Omotosho (2005) in Moro Lake and concluded that there was variation in temperature, but fall within the optimal for normal fish growth and survival of aquatic organisms. In Ona River, temperature range of 26.17oC- 27.50oC was recorded, where the discharge of effluents had influence in the water quality (Andem et al., 2012). Idowu et al. (2004) recorded temperature range of 25.05 oC -27.24oC and asserted higher altitudes as responsible for extreme temperature in Lake Alau. Temperature range of 22.50oC- 27.00oC was recorded in Lake Kubanni (Adakole et al., 2003), Anago et al. (2013) reported 24.00oC-26.5oC in Awba Reservoir. Edward and Ugwumba (2010) in Egbe Reservoir recorded temperature of 31.8oC-26.8oC.
CHAPTER THREE
MATERIALS AND METHODS
Study Area
Jebba Lake is a man-made lake that was created in July 1983 by damming the Niger River about 100km below Kainji Lake at Jebba for the generation of electricity. It is located in the north – western part of Nigeria, situated between Latitudes 9o 35◻ N and 9o 50◻ N and Longitudes 4o30◻ E and 5o00◻ E.
The lake has an estimated surface area of 303km2, which is about 35000ha and a volume of 3.31x109m3. The lake is about 100km long and about 12km at its widest point. The maximum depth is 105m while the mean depth is about 11m. The lake gets the major bulk of its water supply from the discharge of Lake Kainji, while tributaries like Rivers Eku, Awun and others also discharges their water into the lake (Ita et al., 1983).
Sampling Zones
The Lake was divided into three sampling zones with two stationseach (Figure1). These stations were sampled for Chrysichthys nigrodigitatus and other fish species. These zones were chosen because of accessibility, high fishing activities around the areas and low water current. The first zone, designated as Zone I – Kpatachi; secondly, Zone II – New Awuru and finally, Zone III – Old Awuru (Figure 1).
CHAPTER FOUR
RESULTS
Mean physico-chemical parameters of Jebba Lake, Nigeria
Table 4.1 shows the mean measurements of each of the physico-chemical parameters in Jebba Lake.
The various parameters measured fluctuated (that is, decrease and increase) during the period of study. While electrical conductivity (6.30-75.90µs/cm, = 66.41±13.80), depth (3.00-18.50m, = 10.00±4.75), and phosphate (0.006-0.511mg/l,
0.20±0.15) showed high variation, nitrate (0.001-0.006, 0.003±0.0001) showed low variation.
Monthly physico-chemical parameters showed fluctuations (Table 4.2).Temperature was highest in Mayand lowest in January; dissolved oxygen in Julyand lowest in June; transparency highest in October and lowest in May. Electrical conductivity was highest in January and lowest in August with less fluctuations; pH in March and lowest in June; phosphate in September and lowest in January, and nitrate was highest in November.
CHAPTER FIVE
DISCUSSION
Physico-chemical Parameters of Jebba Lake
Physico-chemical parameters, which include pH, temperature, dissolved oxygen, electrical conductivity, transparency, phosphate and nitrate, plays an important role because it determines the survival and existence of living organisms found in the aquatic environment. These parameters are known to operate in the lake ecosystem, amongst others. Mustapha and Omotosho (2005) reported that interaction of both physical and chemical properties of water play a significant role in the composition, distribution and abundance of aquatic organisms. In addition it gives understanding of the relationship between the organism and their environment; determine the quality of water and its productivity. Temperature, pH and depth showed marked variation during the period of study. Temperature ranged from 20.60oC – 32.50oC with mean 25.80±3.18; pH ranged from 6.4 – 7.5 with mean 6.98±0.35 and depth ranged from 3.00m – 18.50m with mean 10.00±4.75. pH is a crucial factor in the aquatic environment because most metabolic activities depend on that (Wang et al., 2002). The values recorded during the study, though showed show some level of fluctuation falls between 6.0 – 7.5 and 6.5 – 8.2 as reported by Boyd (1978) and Murdock et al. (2001) as tolerable level by fish and for sustainable aquatic life in freshwater environment.
CHAPTER SIX
SUMMARY AND CONCLUSIONS AND RECOMMENDATIONS
Summary
The physico-chemical parameters of Jebba Lake varied throughout the study period but where within the accepatable range for fish survival.
Length-weight relationship showed allometric and isometric growth for males and females. Condition factor (K) of C. nigrodigitatuswaswithin the favourable range. Length-length relationship showed strong relationship between theseparameters.
Morphometric parameters and meristic counts were used to validate the identity of
- C.nigrodigitatusin the Correlation coefficient showed positive relationship among these parameters.
- Size or body measurements showed various range of sizes of C. nigrodigitatus; females were heavier than males.
Age composition of C. nigrodigitatusranged from 0+ and 3+ with the bulk of the samples falling within ages 2 and 2+. Growth performance index showed that the species can grow bigger and better if properly managed.
Nine major items were eaten by C. nigrodigitatus, whichincludedplant and animal materials. Insects, fry/remains, vegetable matter, detritus, algae and crustaceans were major food items, nematodes, sand/mud and unidentified materials were minor items.These items fluctuated in months and seasons at various stages of life.
Conclusions
Physico-chemical parameters measured, which include temperature, phosphate, pH, electrical conductivity, dissolved oxygen showed significant difference (p<0.05) in seasons and months, but did not differ significantly (p>0.05) in zones.
Males exhibits allometric growth (increase in weight and length are not proportional), females exhibits isometric growth (increase in weight and length are proportion).Morphometric and meristic parameters is reliable, and can be use to confirm the presence of C. nigrodigitatus in the lake.
The age of males and females differs, and fall within the range 0+ and 3+ with males bigger than females. C. nigrodigitatus can be a good candidate for culture based on growth performance index.
Chrysichthysnigrodigitatusis an omnivore with changes in items ingested from insects at juvenile and sub-adult to fish at adult stage.
There are more males that females in the population; female attained maturity than the male.
Chrysichthysnigrodigitatus is among the abundant fish found in the lake, common especially during the wet season, and mostly distributed at the bottom of the lake.
Recommendations
Morphometric parameters, especially those with strong correlations and meristic parameters should be used to identifyC. nigrodigitatus.
More study should be done on the population structure to ascertain if there are sizes bigger than the onesreported in this study.
Plant and animal components should constitute the diet of C.nigrodigitatus.
C.nigrodigitatusfrom the lake has aquaculture potential, therefore culture trials should be carried out.
Nets should be set to cover the bottom of water body in order to catch C. nigrodigitatus.
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