Academia Journal of Agricultural Research 1(1): 187-192, October 213 DOI: http://dx.doi.org/1.15413/ajar.212.19 ISSN: 2315-7739 213 Academia Publishing Research Paper Seasonal numerical abundance and determination of size distribution of Chrysichthyesnigrodigitatus from lake Akata, Benue State, Nigeria Accepted 15 th July, 213 ABSTRACT Ikongbeh, Okwoli Anthony, Solomon, Shola Gabriel, Ogbe, Friday Garuba Department of Fisheries and Aquaculture, University of Agriculture, Makurdi, P.M.B. 2373 Makurdi, Nigeria Department of Biological Sciences, Kogi State University, P.M.B. 18, Anyigba, Kogi State, Nigeria Department of Fisheries and Aquaculture, University of Agriculture, Makurdi, P.M.B. 2373 Makurdi, Nigeria. *Corresponding Author email: tonikongbeh@gmail.com, (234) 7355155 Seasonal numerical abundance and determination of size distribution of C. nigrodigitatus from Lake Akata in Benue state of Nigeria was conducted from May 28 - April 29. The result revealed that C. nigrodigitatus were caught throughout the year but were more abundant from May, June, July, August, and in March. These periods accounted for 28.9, 37.8, 36.9, 28.6 and 28.% respectively. The highest monthly mean size shows that C. nigrodigitatus had a mean standard length and weight of 26.56±1.46cm and 298.6±41. g. These values were obtained in the month of April. In recent times, fish populations and species sizes have dwindled and this situation is traceable to non rational and unsustainable exploitation of the resource. Such downward trend in annual catch can be eradicated or reduced through planning and management of the lake policy decisions. It is important in the exploitation and management of the fish species in Lake Akata. Key word: Seasonal abundance, length frequency distribution, C. nigrodigitatus, Lake Akata, Nigeria. INTRODUCTION Chrysichthyes nigrodigitatus is a prominent member of family Claroteidae, a family of catfish found in Africa (Nelson, 26). Distribution includes the Nile River basin, most of west and central Africa south to the tropic of Capricorn, including the East African lakes. C. nigrodigitatus is found in Africa from Senegal to Cabinda, Angola, (Risch, 1986). This species is probably more commonly found in rivers than in swamps and it also occurs in shallow waters of lakes less than 4 m. Some aspects of the biology of this fish have already been studied (Fagade, 198), (Kusemuji and Ezenwa, 1981), and (Entsua-Mensah et al., 1995).The family Claroteidae is of considerable commercial importance and C. nigrodigitatus is among the best priced as a result of flesh quality. There is no published account on the biology of this fish species of Lake Akata. A comprehensive study on the biology of fishes from Lake Akata is necessary in order to help the management either of the fisheries resources or also of this water body of recreational importance. The objective of this paper is to make information available on the numerical abundance and size distribution of C. nigrodigitatus, an ecologically and commercially important fish species from Lake Akata, what is useful in the exploitation and management of this fish species in Lake Akata. MATERIALS AND METHODS Study area The study area, Lake Akata is an ox-bow lake of the River Katsina-Ala. It is located between longitude 9 16 and 9 17 East and latitude 7 11 and 7 13 North (Figure 1). The host town, Katsina-Ala is a riverside resort with a unique extensive fadama flood plain feature. The flood plain is used for irrigation farming and fishing. Many small lakes are scattered over the flood plain one of such lake is the Lake Agbo (MANR Makurdi, 1984). Two distinct seasons is usually observed in a year. They include the rainy and dry
Academia Journal of Agricultural Research; Ikongbeh et al. 188 Figure 1. Map of Lake Akata. Source: Ministry of Agriculture and Natural Resources, Makurdi, Benue State. season. The rainy season commence in April - October. The river floods and merges with the lake between August - October. The dry season starts from November - March. During the dry season period the lake is cut-off from the river due to reduction in the water level. Samples were collected from fishermen catches along Lake Akata (Figure 1), between April 28 and May 29, by the use of various fishing gears including hand nets, cast nets, gill nets of various standard mesh sizes (2.2, 25.4, and 3.5 mm) and canoe. A total of 92 Fish species were randomly sampled monthly for one year and usually between 7.am 9.am in the morning and 4:3pm 6:3pm in the evening. The fish samples were transported in an ice chest with ice cubes to reduce posthumous
Percentage Abundance Academia Journal of Agricultural Research; Ikongbeh et al. 189 4 35 3 25 2 15 1 5 May June July Aug Sept Oct Nov Dec Jan Feb Mar Apr Months Figure 2. Monthly percentage abundance of Chrysichthyes nigrodigitatus from Lake Akata. digestion to the minimum to the Fisheries Laboratory of the University of Agriculture, Makurdi. Fish samples were collected and identified in the field according to Olaosebikan and Raji (1998) and FAO (1992). Total and standard lengths and weight measurements were taken directly from the landing sites. In fish with forked tail like C. nigrodigitatus, the two lobes were pressed together to give the maximum length measurement. These data obtained when pooled together were used to determine age and growth pattern, size, and abundance as described by Ogbe et al. (23). Mean monthly length and weight were computed for each species and length frequency histograms were plotted using 5 cm length class for both sexes. The sex of each fish sample was determined by visual observation using genital evidence. RESULTS Abundance C. nigrodigitatus were caught throughout the year but were more abundant in May, June, July, and August accounting for 28.9, 37.8, 36.9, and 28.6% respectively. The relative monthly percentage abundance of C. nigrodigitatus is presented in Figure 2. Field observation showed that C. nigrodigitatus had a seasonal trend in abundance. Size and weight distribution Standard length-frequency histograms for males and females of C.nigrodigitatus are shown in Figure 3. Most males whose standard lengths were 16 to 2 cm occur with frequency of 13 which is 28.1% of the total. The females, whose standard length ranges from 26 to 3 cm occur at frequency of 159 which represents 34.7%. Figures 4 and 5 illustrate the monthly mean variation in standard length and weight of C. nigrodigitatus. The monthly mean sizes of C. nigrodigitatus show that male specimens had a mean standard length and weight of 2.16±.4 cm and 25.2±9. g respectively. The highest monthly mean standard length of 26.56±1.46 cm and mean weight of 298.6±41. g were obtained in the month of April and December respectively while the least standard length of 17.1±1.17 cm and weight of 11.8±23.1 g were recorded in March. Months that also had high mean sizes were May, September, December, and February with respectively standard length of 22.2±1.99 cm and weight of 285.5±42.4 g, standard length of 22.41±1.19 cm and weight of 29.7±3.4 g, standard length of 26.16±2.1 cm
Standard Length (cm) Frequency Academia Journal of Agricultural Research; Ikongbeh et al. 19 18 16 14 12 1 8 Male Female 6 4 2 1 to 5 6 to 1 11 to 15 16 to 2 21 to 25 26 to 3 31 to 35 36 to 4 Length Groups (cm) Figure 3. Length Frequency distribution of Chrysichthyes nigrodigitatus from Lake Akata 3 25 2 15 Male Female 1 5 May Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr Months Figure 4. Monthly mean variation in standard length of Chrysichthyes nigrodigitatus from Lake Akata.
Weight (g) Academia Journal of Agricultural Research; Ikongbeh et al. 191 4 35 3 25 2 Male Female 15 1 5 May Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr Months Figure 5. Monthly mean variation in weight of Chrysichthyes nigrodigitatus from Lake Akata. and weight of 35.4±46.8 g, and standard length of 21.58±1.22 cm, and weight of 22.9±28.8 g. The mean standard length and weight for the females were 2.71±.44 cm and 218.2±9. g respectively. The mean monthly standard lengths and weights for the females ranged from 17.79±1.72 cm and 172.7±36.3 g in September and 22.6±1.28 cm and 253±26.5 g in December. The variation in the monthly mean standard lengths and weights was not significant in males (p>.5) and females (p>.5). Male specimens had slightly bigger mean sizes than female in the months of May, September, December, and April. While the female were slightly bigger in July, October, November, and March. DISCUSSION The monthly abundance observed for C. nigrodigitatus in this study is similar to that reported for four mormyrid species in Lower Benue River (Ogbe and Fagade, 23).C. nigrodigitatus mostly exhibiting peaks abundance in the rainy months. The slight differences in the period of peak abundance for Lower Benue River fishes and those obtained from Lake Akata, could be due to the difference in the geo-hydrological factors of the two water bodies especially the flooding regime, rain distribution pattern and the nature of the water body. The results of the present study provided evidence that fluctuations in river flow can influence the seasonal occurrence and distribution patterns of several freshwater fish species in Lake Akata. Lucas et al. (21) reported effect of river flow variability on fish distribution of different species in different river systems. The month of May marks the beginning of the rainy season. During the peak of rainy season the River flood, and merges with the lake. The month of November marks the beginning of the dry season. During the dry season period the lake is cut-off from the river due to reduction in the water level. The peak in abundance of C. nigrodigitatus, in Lake Akata could be due to rise in water level of the lake, availability of food, spawning rates, breeding grounds, coupled with shelter, presence of current, vegetation, depth of water, temperature, salinity and low predation. Another reason could be due to the rise in water level of the lake, this helps
Academia Journal of Agricultural Research; Ikongbeh et al. 192 in the biological productivity of the lake with optimal light penetration. Ita (1978) reported low predation as a major limiting factors affecting the distribution and abundance of various fish families in Kainji Lake. It has been observed that C. nigrodigitatus were annual brooder in the wild, characterized by an annual reproductive cycle with a spawning season around September and November. The reproductive season coincides with the short rainy season which is characterized by lower water temperature and salinity at the beginning (September) and by a progressive rise of these parameters at the end of the season (November). Mature C. nigrodigitatus females were only observed just after the rainy season during July and August (Chauvet, 1972); or the short rainy season during September and October (Otémé, 1993a). The data on monthly size distribution of C. nigrodigitatus showed that large size and matured fish occur mainly during the rainy seasons and high water levels. At the end of the rainy season, fish moves with the receding water to the main river channel. However some remain trapped in cut-off flood pools and become vulnerable to fishing by baskets, nets, and hooks. This is because fish migrate from the Lake and swamps into the river. The movement could be associated with environmental changes brought about by rainfall and spate conditions. In this study, it was observed that the mean standard lengths, and mean total weights of the females of C. nigrodigitatus were higher than the males. In the analysis of size ranges in some catfishes the female s exhibit faster growth rate than males (Olatunde, 1979). The comparatively large sizes of C. nigrodigitatus observed in this study are similar to the findings of Risch (1986) who reported that C. nigrodigitatus attains maximum size of 65. cm standard length (male/unsexed). Nelson (24) reported that C. grandis in Lake Tanganyika attained maximum length of about 2 m. It could be suggested that this fish stock have remained stable over the years due to rational exploitation. The reason could be attributed to a fishing strategy that gives the highest steady yield year after year. Conclusion In conclusion, the result revealed that C. nigrodigitatus were caught throughout the year but were more abundant from May, June, July, August, and in March. The highest monthly mean size shows that C. nigrodigitatus had a mean standard length and weight of 26.56±1.46 cm and 298.6±41. g. These values were obtained in the month of April. The mean standard lengths, and mean total weights of the females of C. nigrodigitatus were higher than the males. ACKNOWLEDGMENTS The authors are grateful to the Head of Department of Fisheries and Aquaculture, College of Forestry and Fisheries, University of Agriculture Makurdi, Nigeria for approving the use of the laboratory and Mr. Ataguba G.A who offered useful advice on data analysis. REFERENCES Chauvet C (1972). Note préliminaire à l étude des stocks de poissons du genre Chrysichthys des lagunes et rivières de la Côte d Ivoire. Tethys. 4:981-988. Entsua-Mensa M, Osei-Abunyewa A, Palomares MCD (1995). Length- Weight relationships of fishes from tributaries of Volta River, Ghana. Part 1: Analysis of pooled data sets, NAGA ICLARM. pp.36-38. Fagade SO (198). The morphology of the otolith of the Bagrid catfish Chrysichthyesnigrodigitatus (Lacepede) and their use in age determination. Hydrobiologia. 71:29-215. FAO (1992). Field guide to the freshwater fishes of Tanzania. Food Agric. Organiz. Rome, pp.145. Ita EO (1978). An analysis of fish distribution in Kainji Lake, Nigeria. 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Olaosebikan BO, Raji A (1998). Field guide to Nigerian freshwater fishes. Federal College of Freshwater Fisheries Technology, New Bussa, Nigeria. 16:88 Olatunde AA (1979). Age determination, length-weight relationship and growth of Eutropiusniloticus and Schilbemystus in Lake Kainji, Nigeria. Arch. Hydrobiol. 87:49-83. Otémé ZJ (1993a). Cycle sexuel et fécondité du MâchoironChrysichthysnigrodigitatus en laguneebrié, Côte d Ivoire. J. Ivoir. Océanol. Lin. Abiqdjan, 1:61-67. Risch LM (1986). Bagridae P. 2-35. Inj. Daget, J.P. Gosse and D.F.E. Thys van den Audenaerde (eds.) check list of the freshwater fishes of Africa (CLOFFA) ISNB, Brussels; MRAC, Tervuren, and Orostom, Paris. 2:22-24. Cite this article as: Ikongbeh OA, Solomon SG, Ogbe, FG (213). Seasonal numerical abundance and determination of size distribution of Chrysichthyesnigrodigitatus from lake Akata, Benue State, Nigeria. Acad. J. Agric. Res. 1(1): 187-192. 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