- Fishery Studies of Ribb River, Lake !Ib @b Tana Basin, Ethiopia #!b Public Disclosure Authorized * m b !!B Final Report lib- Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized Presented to the World Bank-financed Ethiopian-Nile Irrigation and Drainage Project Coordination Office, Ministry of Water Resources BY: Abebe Getahun (PhD) ------LeadAquatic Ecologist Eshete Dejen (PhD) -------Aquatic Ecologist Public Disclosure Authorized Wassie Anteneh (MSc) -------Aquatic Ecologist January 2008 Addis Ababa, Ethiopia Ribb River Fishery Studies: Final Report January 2008 Table of Contents Content Page Table of contents i List of Tables 11 .. List of Figures 111 Acknowledgments iv Acronyms vi Executive Summary 1 Background 5 Ethiopian Drainage basins 5 Ethiopian Freshwater fishes 5 Lake Tana 7 Lake Tana fishes and fisheries 8 Migration in fishes 9 The effects of dam building on fishes 10 The initiation and execution of this study 13 Objectives of the study 14 Study sites, Materials and Methods 14 Study sites 14 Materials and Methods 19 Results and Discussions 22 Fish species diversity from Ribb River and its tributaries 22 Fish species abundance in the Ribb River and its tributaries 2 5 Length-weight relationship of the dominant Labeobarbus spp. 2 8 Role of Labeobarbus spp in the food web of Lake Tana 30 Gonad Maturity status and migration behavior of Labeobarbus spp. 3 1 Spawning Segregations 36 Spatial segregation 36 Temporal segregation 38 Suitable spawning habitats in the Ribb River and its tributaries 3 8 Farmer's use of fish from Ribb River and its tributaries 43 The contribution of Ribb fishes to Lake Tana fish ecology and production 44 Species composition of Labeobarbus spp. from Lake Tana 46 Ribb River Fishery Studies: Final Report January 2008 Fish catch trends from Lake Tana 4 8 Fish production and marketing from Lake Tana 50 The nature and number of Lake Tana fishers, their bases and organizations 5 1 Fishery Policy and Management 54 Major Findings, Conclusions and Recommended Mitigation Measures 56 Major Findings and Conclusions 56 Recommended Mitigation Measures 59 References 62 Appendices 67 Appendix I: Names of contacted individuals and Institutions 67 Appendix 11: Questionnaire for the socio-economic studies 68 Appendix 111: Pictures showing activities 69 Appendix IV: Raw data collected 7 8 Ribb River Fishery Studies: Final Report January 2008 List of Tables Table Content Page Table 1. Average value of oxygen, temperature, pH and depth at the sampling sites. 18 Table 2. Gonad maturity stages and descriptions for cyprinids 2 1 Table 3. The species of fish identified from the different sampling sites of Ribb Ever 24 Table 4. Occurrence and total number of species of fish from the different sampling 24 sites of Ribb River. Table 5. Total abundance of species from all the sampling sites of Ebb River 26 Table 6. Number of species and their percentage composition fiom the different sampling sites of Ribb River 27 Table 7. Spatial distribution of gonad stages of the Labeobarbus spp. of Lake Tana 34 spawning in Ribb River Table 8. Tributaries of Ribb River and the distance fiom their origin to the main Channel 40 Table 9. Species number and percentage composition pooled from all monthly 47 samples per site from January 2000 to December 2004 (BAFLRC, 2007) Table 10. Species composition of the Labeobarbus species in Lake Tana 48 Table 11. Fish catch data in tons for Motorized and Reed Boat fishery in Lake Tana 49 Table 12. Fish prices at Bahir Dar 5 1 Table 13. Dependents on the fishery sector that are directly involved in fishing and post 54 harvest processing Ribb River Fishery Studies: Final Report January 2008 List of Figures Figure Content Page Fig. 1. Ribb River water shed and the sampling sites 15 Fig. 2. Length-weight relationship of Labeobarbus species of Lake Tana spawning in Ribb River 29 Fig. 3. Simplified food web of Lake Tana Fig. 4. Maturity stages in the most common Labeobarbus spp. Fig. 5. Temporal variation of gonad stages of Labeobarbus of Lake Tana in Ribb River 3 5 Fig. 6. Spatial segregation of Labeobarbus species of Lake Tana spawning in Ribb River. Fig. 7. The planned dam site on Ribb River and the reservoir area Ribb River Fishery Studies: Final Report January 2008 Acknowledgments : We thank the Ministry of Water Resources (World Bank Financed Ethiopian-Nile Imgation & Drainage Project Coordination Office) for the great cooperation we received during our entire working period. We are thankful to the Bahirdar Fisheries and Other Living Aquatic Resources Research Center, the Amhara Regional Agricultural Research Institute, Ministry of Water Resources (Amhara Region), South Gondar Zone Administration, Libo Kemkem Woreda Agriculture Office, Ebenat Woreda Agriculture Office and several other institutions for providing us most needed information and logistics. Fishery experts (Belay Abdissa, Goraw Goshu and Mesfin Tsegaw) and a number of fishermen (Gebresellassie Meseret, Getnet Temesgen, Ayenew Gediff, Tiruneh Belay, Asrate Wondie, Endalamaw Asres) were involved in the sampling effort and we are indebted to all of them. We are thankful to the able drivers, Asnake Aynekulu, Habte Muche and harethat helped us in very difficult conditions. We are also thankful to several farmers and local residents that have assisted the work in providing information and animals and transporting our equipments. We also thank Geremew Mellese, Abebe Ameha and Fitsum Abebe for their contributions in preparing the Ribb watershed map, organizing data, formatting and other editorial assistance. Ribb River Fishery Studies: Final Report January 2008 Acronyms: ACU: Labeobarbus acutrostris BA: Barya River (tributary of Ribb River) BAFLRC: Bahir Dar Fish and other Living Resources Research Center BRE: Labeobarbus brevicephalus CH: Chibirna River (tributary of Ribb River) CPUE: Catch Per Unit Effort CRA: Labeobarbus crassibarbis DEG: Labeobarbus degeni ETB: Ethiopian Birr FL: Fork Length FPME: Fish Production and Marketing Enterprise GAR: Garra sp. GON: Labeobarbus gorgorensis HA: Hamus River (tributary of Ribb River) INT : Labeobarbus intermedius KI Kirarign River (tributary of Ribb River) KE: Keha River (tributary of Ribb River) LON: Labeobarbus longissirnus LTFRDP: Lake Tana Fisheries Resource Development Program MAC: Labeobarbus macrolepidotus MC1: Main Ribb River at the Bahir Dar-Gondar Bridge near Woreta town MC2: Main Ribb River at the old Broken Bridge (on the old road from Zeha to Debretabor) MC3 : Main Ribb River at the dam site MC4: Main Ribb River above the junction with Hamus River MC5: Main Ribb River above the junction with Melo River ME : Melo River (tributary of Ribb River) MEG: Labeobarbus megastoina NED: Labeobarbus nedgia PLA: Labeobarbus platydorsus RM: River mouth SH: Shini River (tributary of Ribb River) SUR: Labeobarbus surkis TIL: Oreochromis niloticus vi Ribb River Fishery Studies: Final Report January 2008 TRU: Labeobarbus truttiformis TSA: Labeobarbus tsanensis TW: Total Weight VAR: Varicorhinus beso vii Ribb River Fishery Studies: Final Report January 2008 EXECUTIVE SUMMARY A dam is planned to be constructed on the Ribb River some 50 km north east of Lake Tana. This study was designed to investigate the dam's effect on fishes of Labeobarbus spp. that migrate from Lake Tana to Ribb River and its tributaries for spawning. 13 sampling sites were identified at the river mouth, on the main Ribb River and its tributaries below and above the dam site. Fishes were collected from each sampling site in three separate field trips during the main rainy season (end of July to beginning of November). A total of 2457 fish specimens (1287 females, 1143 males and 27 unidentified specimens) were collected using gill nets of different mesh sizes (6, 8, 10, and 12 cm stretched mesh size), hooks and lines, fykes, cast nets, traps and scoop nets and fishes were also purchased from the local fishers for biological investigation. Eighteen species belonging to five genera and three families were represented in the catch. L. intermedius, L. brevicephalus, L. megastoma, L. truttiformis and L. tsanensis were the most abundant species migrating to Ribb River and its tributaries. These Labeobarbus species were found to aggregate at the Ribb River mouth before the onset of migration and they are found to migrate to all the tributaries and up to the most distant site sampled (Main channel above the junction with Melo River located some 15 km above the dam). Most of the Labeobarbus specimens collected during the study period were having gonads that were mature and running; from the total of 2075 Labeobarbus specimens, 887 specimens were mature, 835 specimens were running and 53 were spent. There is no evidence for specificity of habitat at which each species of Labeobarbus spawn and hence spatial segregation is out-ruled. However, there is evidence that they segregate temporally except in the case of L. internzedius. Among the dominant species, L. megastoma was the first to aggregate at the river mouth and run to upstream followed by L. truttiformis and L. tsanensis. The last to aggregate and migrate upstream is L. brevicephalus. All the tributaries and the upstream Ribb main channel can be considered as suitable breeding habitats for Labeobarbus spp. The total estimated length of spawning habitat along the main Ribb River and its tributaries is 351.5 km. The area below the dam contributes 57.3 % while the spawning habitat above the dam contributes 42.7 % of 1 Ribb River Fishery Studies: Final Report January 2008 the total. Moreover it has to be noted that higher relative abundance of Labeobarbus spp. was observed from sampling sites below the dam than above the dam. It has been estimated that 48 % of the fish production from Lake Tana that landed at the Southern Gulf (about 1000 tons) is contributed by the fish caught from the Ribb River mouth and its surroundings. This is about 480 tons contributed by mainly Nile tilapia, cat fish and Labeobarbus spp.