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Fish Biology and Fishery Management of Commercial Stocks in a Tropical Rift

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Fish Biology and Fishery Management of Commercial Stocks in a Tropical Rift Fish biology and fishery management of commercial stocks in a tropical rift valley lake, Lake Langeno, Ethiopia Mathewos Temesgen Kebede A dissertation submitted to the Department of Zoological Sciences, Addis Ababa University in Partial Fulfillment for the Requirements of the Degree of Doctor of Philosophy in Biology (Fisheries and Aquatic Sciences) March 2018 Addis Ababa, Ethiopia 1 2 DEDICATION This Dissertation is dedicated to my family and my beloved wife Obse Fikiru for their outstanding guidance, motivation and helped me to achieve my vision with the help of God. I also dedicate it to my daughter Soni Mathewos, and my son Kena Mathewos, for their unreserved love and affection. 3 STATEMENT OF THE AUTHOR I hereby affirm that this Dissertation “Fish biology and fishery management of commercial stocks in a tropical rift valley lake, Lake Langeno, Ethiopia" is the product of my own research, and no part of the Dissertation has been copied from any published source; except the references, standard mathematical equations and protocols. This Dissertation has been submitted in partial fulfillment for the requirements of the Doctor of Philosophy in Biology (Fisheries and Aquatic Sciences) at Addis Ababa University (AAU), Ethiopia. I declare that this Dissertation is not submitted to any other institution for the award of any academic degree, diploma, or certificate. The paper is permitted to be deposited at the University Library to be available to borrowers under the rules of the library. Brief quotations from this Dissertation are allowable without special permission provided with accurate acknowledgements of the source is made. Requests of permission for extended quotation or reproduction of this Dissertation in whole or in part for academic purpose may be granted by the Head of the Department or the Dean of the College and Director of Postgraduate Studies of AAU. In all other instances, however, permission must be obtained from the author. Finally, all sources of materials used in this Dissertation have been duly acknowledged. Name: Mathewos Temesgen Signature _____________________ Addis Ababa University, Addis Ababa, Ethiopia Date of submission: ______________________ 4 ABSTRACT The study of status and trends of fish and fisheries in Lake Langeno (also known in the literature as Langano), Ethiopia was conducted from March 2014 to February 2016. The basis for this study was that fish stocks were subjected to uncontrolled fishing over many years and available data on the status and trends of fishes in the lake has become unreliable for management and sustainability of the sector. In order to examine the diversity, habitat preference and seasonal distribution, spatial and seasonal data were collected from six different sampling sites by using gillnets of various mesh sizes and long lines. Data were analyzed by Canonical Correspondence Analysis (CCA), SPSS software and by various descriptive statistics. The results indicate physico-chemical parameters showed no significant spatial variation, but high seasonal variation. A total of seven fish species dominated by family Cyprinidae were identified (H’=1.264). Carassius carassius, was not reported in previous studies, now comprise 0.64% of the total collected specimens. All the fish species were collected from all of the sampling sites, except at one site (Middle), where Carrasius carassius and Garra dembecha were absent. Index of relative importance (IRI) was essentially similar for all the sampling sites, but differed in the relative importance of each species with the high importance of Oreochromis niloticus. Principal Component Analysis (PCA) did not produce distinct habitat-associated species patterns across the sampling sites. However, temperature and depth seemed to be the key environmental factors determining fish community structure in the lake. The results showed that the composition of the fishes has undergone some changes during data collection from what was reported in the literature. The Length-weight relationships of O. niloticus, E. paludinosus, C. gariepinus, L. intermedius and C. carpio were curvilinear (b=2.872, 2.554, 2.823, 2.771 and 2.919, respectively), and statistically significant (p>0.05) except for Enteromius paludinosus. For both sexes, the mean Fulton Condition Factor values of Oreochromis niloticus, B. paludinosus, Clarias gariepinus, Labeobarbus intermedius and C. carpio were 1.77±0.37, 1.06±0.44, 0.60±0.5, 1.33±0.44 and 1.47±0.83, respectively. A better body condition was recorded in the dry seasons for all species except for O. niloticus. All fish species had relatively smaller maximum size and poor body condition than what was reported for fishes in most of the Ethiopian water bodies. Females were more abundant than males for all fish species, and the sex ratio of O. niloticus (1.13:1)and E. paludinosus (1:.24:1) was significantly different from the hypothetical distribution of 1:1 (χ2, p<0.05. The identified peak breeding time was April- June, May-July, June-July and March-May for O. niloticus, C. gariepinus, L. intermedius and C. 5 carpio, respectively. Their respective length at L50 for females and males during these breeding times were 16.4 cm & 15.8 cm TL, 28.5 cm & 29.5 cm TL 30.5 cm & 29.5 cm FL and 28.2 cm & 27.6 cm FL. The mean fecundity of these fish species were 463.83±114, 141,466±40,982, 3,055±2,234 and 105,631±46,680, respectively. The results also showed significant seasonal variations of GSI for all fish species (ANOVA, P< 0.05). In addition, seven food items, namely phytoplankton, zooplankton, insects, detritus, macrophytes, fish parts and nematodes were identified from the stomach contents of O. niloticus. Phytoplankton was the main food grazed followed by detritus, zooplankton and macrophytes. The other food items were occasionally and randomly consumed. The volumetric contribution of these food items showed high variation in the study months (p<0.05). Phytoplankton and detritus were the dominant food items in the dry season and zooplankton and macrophytes were the highest in the wet months. The contribution of phytoplankton, zooplankton and insects were slightly high in small sized groups (<10 cm), whereas detritus, macrophytes and fish parts were the highest in larger size groups (>20 cm). Generally, food items of plant origin dominated the stomach contents, typically associated with less protein content than food item of animal origin. The result also showed that the lake supported small-scale beach seine fishery for small income generation and alternative employment opportunity of fishermen. The catch composition was dominated by O. niloticus (87.58%) followed by C. gariepinus (5.89%). Fisheries value chain was also developed and major related issues were addressed, fishers’ perceptions about the resources condition and management status were identified and discussed. Generally, the total annual fish production from the lake was estimated to be 1,137.67 tonnes/ year, and the mean gross annual revenue was about 8,622,158 ETB. Extrapolation of annual production and annual revenue from the sector showed a significance variation among the landing facility owners and those that do not have landing facilities (ANOVA, p<0.05), and between the fulltime and part time fishermen (ANOVA, p<0.05). The estimated annual per capita consumption of fish/ person was about 23.65 kg. The majority of the fishermen had positive attitude towards the fish resources, but due to lack of knowledge and follow up, the current harvest system and fishing methods put these resources at risk. Therefore, appropriate management action should be in place in order to sustain the fish resources in Lake Langeno. Key words: Fish; Fishery; Fish biology; Ethiopia; Lake Langeno; Feeding habits; Fish reproduction; Length-weight relationship 6 ACKNOWLEDGMENTS This Dissertation would not have been successfully completed without the combined supports of many people and institutions. First of all, I would like to extend my heartfelt thanks to my supervisors Prof. Abebe Getahun and Prof. Brook Lemma for their keen interest, limitless advice, encouragements, guidance, support and patience from proposal development to the final stages of my work. They were always ready to give me a hand at all stages of my research endeavors, and they made me feel more confident. Their support in securing other sources of funds, facilitating all the necessary process to do my laboratory works at an appropriate laboratory and shaping the data collection process are also unforgettable in my life. I would also like to extend my sincere gratitude to Ambo University and Addis Ababa University for granting me this great opportunity, for the financial sponsorship and material support. In addition, many people from the Department of Zoological Sciences, Addis Ababa University, have contributed for the success of my professional works. With this regard, I am very grateful to Prof. Seyoum Mengistou and Dr. Demeke Admassu for their constructive guidance during the entire course work. In addition, I would like to appreciate Mr. Neway Andarge and Mr. Kasahun Tessema for all their support during the laboratory work. I would also like to thank the Zeway-Shalla basin thematic research project for the financial support during the research work. In addition, I would like to express my gratitude to my colleague, Dr. Lemma Abera, for all of his unforgettable assistance during data collection and laboratory work, and for arranging all the necessary materials and facilities at his home institution, Zeway Fishery Resources Research Center, Zeway (Batu) (ZFRRC). Many thanks also go to ZFRRC staff for the materials, laboratory and human power support during the data collection and laboratory work. In this connection, I am 7 very grateful to Mr. Getachew Senbete, Mr. Megersa Endebu, Mr. Alemu Lemma, Mr. Bedane Delu, Mr. Mitiku Bonta and all of the other staff. I also kindly thank Prof. Geert. P. Janssens, the head of Animal Nutrition Laboratory, Ghent University, Belgium for his hospitality at his home institution, and for his material and technical supports during the laboratory work.
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