International Journal of Fisheries and Aquatic Studies 2018; 6(2): 562-570 E-ISSN: 2347-5129 P-ISSN: 2394-0506 (ICV-Poland) Impact Value: 5.62 Spatio-temporal distribution of Labeobarbus species in (GIF) Impact Factor: 0.549 IJFAS 2018; 6(2): 562-570 Lake Tana © 2018 IJFAS www.fisheriesjournal.com Received: 21-01-2018 Takele Shitaw, Shewit G Medehin and Wassie Anteneh Accepted: 22-02-2018 Takele Shitaw Abstract Department of Fisheries Wetland This study was conducted from May to December 2016 and the aim was to investigate the spatio- and Wild Life Management, temporal distribution of Labeobarbus species of Lake Tana. Descriptive statistics was used to present the Bahir Dar University College of data. Chi-Square Test was used to compare the spatial variations of species between areas, the temporal Agriculture and Environmental variations between seasons. Labeobarbus intermedius was the most dominant specie, containing 38.8 % Sciences, Ethiopia of catch followed by L. tsanensis, L. platydorsus, L. brevicephalus within a catch composition of, 18.96%, 13.1%, 10.5%, respectively. Labeobarbus dainellii and L. gorguari were rarely collected. Shewit G Medehin Labeobarbus species of Lake Tana showed significant variation in catches at four sampling sites Department of Fisheries Wetland (p<0.01) and also these species showed significant variation in dry and rainy seasons (p<0.01). L. and Wild Life Management, intermedius, L. tsanensis, L. brevicephalus, L. nedgia, L. gorgorensis, L. truttiformis were significantly Bahir Dar University College of more abundant in rainy season than dry season. The maximum possible diversity of four sampling site. Agriculture and Environmental The highest ‘J’ value was obtained at Gumara site with the value of 0.5. Effort control regulations, Sciences, Ethiopia limiting the gillnet fishery in spawning seasons and/or areas, will be appropriate to prevent the Wassie Anteneh Labeobarbus fish species of lake Tana. Department of Fisheries Wetland and Wild Life Management, Keywords: relative abundance, diversity, gillnet selectivity, lake tana, labeobarbus Bahir Dar University College of Agriculture and Environmental 1. Introduction Sciences, Ethiopia Ethiopia is rich in its fish fauna, having a diversified species in the inland water bodies [1]. The three major fish families (Cichlidae, Clariidae and Cyprinidae) are widely distributed throughout the country. In Lake Tana, Cyprinidae is the largest family and is represented by four genera. These are the genera Barbus represented by three species: B. humilis, B. pleurograma, and B. tanapelagious [2], Varicorhinus represented by one specie: V. beso, Garra represented by four species: G. dembecha, G. tana, G. regressus and G. small mouth [3] and Labeobarbus, which is the most abundant genus of the family and consists of 17 species [4] forming a unique species flock in Lake Tana . It is the most abundant genus of the family and consists of 15 species (L.acutrostris, L. brevicephalus, L. macrophtalmus, L. megastoma, L. platydorsus, L.truttiformis, L. dainellii L. tsanensis, L. surkis, L. gorgorensis, L. Crassibarbis, L. gorguari, L. nedgia, L. longissimus and L. intermedius forming a unique [4] species flock in Lake Tana . Labeobarbus species of Lake Tana, belonging to the family of [4, 5, 6] large Cyprinidae are the only species flock in the world . Stock reduction of Labeobarbus species has been reported by several authors. However, recently nothing is known about spatio-temporal dynamics of Labeobarbus species in Lake Tana. At the current situation the distribution and abundance of 15 Labeobarbus fish species of lake Tana is not well known (three is no any clear information which is recently documented on the distribution of Labeobarbus species of Lake Tana), since there is no any information about which species are threatened or rarely occur and which are more abundant. In addition to this fishing at the spawning ground during spawning season using minimum gillnet mash size in Lake Tana is set long time back. Dramatic reduction of the adult Labeobarbus and the even lower proportion of recruits at the end of the 1990s, show the Correspondence necessity for the development, implementation and control of fisheries legislation in Lake Takele Shitaw Tana [7]. Their aggregations at the river mouth during spawning migrations makes them Department of Fisheries Wetland vulnerable to recruitment overfishing, because their exploitation can, in extreme cases, lead to and Wild Life Management, a dramatic decrease in the number of recruits. Moreover, at present there is no limitation on the Bahir Dar University College of Agriculture and Environmental number and type of gillnets used. Information about distribution, abundance of Labeobarbus Sciences, Ethiopia species is required in order to advise on management measures to protect the reproductively ~ 562 ~ International Journal of Fisheries and Aquatic Studies active part of the population. Proper fishery management and the trophic status is oligotrophic to mesotrophic [4, 13, 14]. requires that fishing gear harvest large mature fish while The Lake Tana area has a warm climate with four years mean allowing the small juveniles to escape [8]. Such measures annual rainfall of about 1564 mm, of which 59 percent fall in could involve the introduction of a minimum mesh size and the months of July and August, when the mean rainfall can be closed seasons and/or areas. Therefore, this study was intends 444-483 mm per month. The seasonal rains cause the lake to generate scientific information about the distribution and level to fluctuate regularly with an average difference composition of these species for the management of Lake between the minimum, in May-June, and maximum in Tana fish resource. September-October of about 1.5 m. Lake Tana and its adjacent wetlands both directly and indirectly provide a 2. Materials and Methods livelihood for more than 500 000 people [15] and about three 2.1 Description of the Study Area million people live in the catchment. The population Lake Tana, is the largest lake in Ethiopia with an area of distribution is high in those areas to the northeast and south of about 3200 km2 and it is located in the northwestern highlands Lake Tana [16]. This Ethiopia’s largest lake is source of Blue of Ethiopia at an altitude of about 1800 m with an average Nile. The only out flowing river is Blue Nile. Ichthyo (fish) depth of 8 m and maximum depth of 14 m and it is the only fauna is isolated from the lower Blue Nile by a 40m waterfall source of the Blue Nile River and constitutes almost half of located 30 km from Lake Tana. Fogera and Dembia the freshwater bodies of the country [9, 10]. Lake Tana, the Floodplains are the largest wetlands of the country and border third largest Lake in Africa next to Victoria and Tanganyika, Lake Tana in the eastern and northern parts, respectively [17]. originated by the blocking the Blue Nile River with volcanic The population density ranges from 151-200 persons km2 in basalt two million years ago [11, 12]. It is characterized by low the north and in some parts of Fogera plain to the east, and nutrient concentrations, relatively high silt concentrations from 101-150 persons km2 in the more fertile lowland areas to with a loading rate of 8.96-14.84 million tons of soil per year the east and southwest [17]. Fig 1: map of Lake Tana and sampling sites 2.2 Sampling and Data Collection long panel was set around sunset and retrieved at dawn. Thus, Both fisheries independent and dependent data were used. For the average gillnet setting time was 12 hrs throughout the fisheries independent data collection four sampling sites sampling period. After the retrieval of the sampling gear, fish (Gorgora from North, Bahir Dar Gulf from South, Nabega caught in the five gillnets were collected separately in five from East and Kunzla from West direction of the lake), which labeled boxes and the variable such as total length, weight, are a good representatives of the whole lake in its North- sex and maturity stage were measured on each specimen in South and East-West direction, were selected (Fig.1). Fish the field. The commercial data was collected at the landing samples were collected monthly at each site for eight months. site of four selected site (Bahir Dar, Gorgora, Kunzla and Gillnets of 6, 8, 10, 12 and 14 cm stretched mesh were used Gumara). The commercial catch was recorded monthly from and set overnight in the lake at a depth of about 3m. The five three landing site but samples were collected 3-4 days weekly gillnets were connected end to end and the resulting 150 m from Bahir Dar site. Labeobarbus species were identified into ~ 563 ~ International Journal of Fisheries and Aquatic Studies species level using keys developed by [4, 18]. S = number of species encountered ∑ = sum from species 1 to species S 2.3 Data Analysis H’ was used to indicate diversity at different sampling sites Chi-Square test was used to compare the spatial variations of and/or rivers. A high value indicates high species diversity. species between areas, the temporal variations between seasons. SPSS version 16 and Microsoft Excel sheet 2007 was Species equitability used to analyze and manage the data. Descriptive statistics Species equitability or evenness Index (J) that refers to the was used to present the distribution of the data with respect to degree of relative dominance of each species in the sampling the minimum, maximum and mean values as well as the station was calculated according to [21] as: dispersion of the data through standard deviation. An index of relative importance (IRI) and Shannon diversity index (H`) were used to evaluate relative abundance and species diversity of fishes, respectively. IRI gives a better representation of the H'max (the maximum possible diversity of the site) was ecological importance of species rather than the weight, determined as follows: LN(S) [22].