The study was conducted from July, 2013 to July, 2015 in the North-Eastern part of lake Tana. Six sites were selected from Fogera, Libokemkem and Dembia districts based on water hyacinth infestation and free area. Plant sample was collected from infested areas using quadrant and different parameters were recorded using sensitive balance and tape meter. The physical parameters were measured in situ using YSI 556 multi-probe system, while the chemical parameters were carried out using a portable water analysis kit. Zooplankton and phytoplankton samples were collected by 80 and 50 µm mesh net filtering device. Moreover, structured questionnaire, focuses group discussion, key informant interview has been used to collect some quantitative and qualitative data. 104 plants/m 2 and 8.216 ± 0.45 kg fresh weight/m 2 which equals 82,160 kg/ha or 82.16 tones/ha fresh weight can be harvested during the dry season of a year. But 583 plants/m 2 which equals 270,000 kg/ha = 270 tones/ha fresh weight can be harvested during the wet season of a year. The present assessment also noted that no major management strategy had been employed in the infested water body areas, despite many efforts had been applied by the community and the government. Water hyacinth poses serious problems on the community living around Lake Tana by affecting fishing process, farmland, livestock and the environment of in a variety of ways.
The status of Lake Tana Fishery was evaluated from analysis of commercial catch data of number I fishers cooperative. The data collection has been carried out from September 2003 to September 2009. Results indicated that Nile tilapia (Oreochromis niloticus), African catfish (Clarias gariepinus) and species flock of endemic, large Labeobarbus spp. were the three main species groups targeted by commercial gillnet fishery of Lake Tana and form 65 %, 20 % and 15 % of the annual catch compositions of fish species during the study period respectively. There was significant variability among sampling years encompassing temporal aspects. Especially, commercial catch of O. niloticus were significantly booming up to 2007 and declining after wards. The most likely explanations for the declining catch of O. niloticus and others are the illegal use of undersized monofilament gillnet imported from Sudan town (Gelabat) and the harmful increase of the commercial gillnet fishery targeting the spawning aggregations of L. barbus spp. and C. gariepinus in the river mouths and littoral areas. The observed decline in the commercial catch of O. niloticus and others stress the need for the urgent development of a management plan focusing on controlling import of undersized monofilament gillnet, fishing effort and gear restrictions in the river mouths and major tributaries during the breeding seasons and implementing the regional fishery legislation.
The aim of the present study was to determine the physical, chemical and biological characteristics and to characterize the fishery of Geray reservoir. Three sites from the inlet site, the open water and the outlet has been selected and samples were collected using YSI 556MPS model multimeter and Palin test photometer 5000 .Temperature, pH, dissolved oxygen, salinity, Total Dissolved Solid, conductivity, secchi disk measurement, alkalinity, nitrate, phosphate, ammonia and turbidity were the parameters measured. Plankton sample collected using 55 and 80 micrometer mesh net. The most abund taxon was copepoda (666 ind. /m 3 of water with their juvenile stages "Nauplia" or contributed 85% of total zooplankton taxa), which was followed by Cladocera (190 inds. /m 3 or 15%). Among the 3 study sites the open water site showed higher density of zooplankton, especially cyclopod followed by outlet site. The inlet site was relatively low in zooplankton density. Cyprinus carpio, Varicorhinus Beso, Carasius Auratus and Oreochromis niloticus were species found in the reservoir. Almost all the physical and chemical parameters sampled of this reservoir water were within desirable limits for aquatic biodiversity the current state of the water quality of the reservoir is conducive for fish production. But the current management is not good for its sustainability, knowingly or unknowingly the activities done on and around the reservoir will shorten the sustainable utilization of the reservoir. The community should be awaked while they are starting to overexploit the resource.chemical and biological parameters of Geray reservoir and to identify the fish species in the reservoir. Materials and Methods Study areaGeray is located in Amhara Regional state Ethiopia, West Gojjam Administrative Zone, Jabitehnan and Finoteselam district, bordering, Shembekuma-Yedafas and Arebayitu-Insesa Kebeles. Three sites one from the inlet site, one from the open water and the other from the outlet was selected. In situ measurements in the morning at 4 o'clock samples of temperature, pH, dissolved oxygen, salinity, Total Dissolved Solid, conductivity were done using YSI 556 multiprobe meter. Secchi measurement was done using secchi disk.Palin test photometer 5000 was used for analysis of total hardness, alkalinity, nitrate, phosphate and ammonia test. Fish samples collected using 6, 8, 10 and 12 cm stretched size mesh gillnet by setting the net overnight. Descriptive statistics has been used to calculate the mean and standard deviation values of the parameters.
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