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Journal of Threatened Taxa Building evidence for conservaton globally www.threatenedtaxa.org ISSN 0974-7907 (Online) | ISSN 0974-7893 (Print) Communication Ecology of the Critically Endangered Singidia Tilapia (Teleostei: Cichlidae: Oreochromis esculentus) of lake Kayanja, Uganda and its conservation implications Richard Olwa, Herbert Nakiyende, Elias Muhumuza, Samuel Bassa, Anthony Taabu-Munyaho & Winnie Nkalubo 26 July 2020 | Vol. 12 | No. 10 | Pages: 16251–16256 DOI: 10.11609/jot.5700.12.10.16251-16256 For Focus, Scope, Aims, Policies, and Guidelines visit htps://threatenedtaxa.org/index.php/JoTT/about/editorialPolicies#custom-0 For Artcle Submission Guidelines, visit htps://threatenedtaxa.org/index.php/JoTT/about/submissions#onlineSubmissions For Policies against Scientfc Misconduct, visit htps://threatenedtaxa.org/index.php/JoTT/about/editorialPolicies#custom-2 For reprints, contact <[email protected]> The opinions expressed by the authors do not refect the views of the Journal of Threatened Taxa, Wildlife Informaton Liaison Development Society, Zoo Outreach Organizaton, or any of the partners. The journal, the publisher, the host, and the part- Publisher & Host ners are not responsible for the accuracy of the politcal boundaries shown in the maps by the authors. Member Threatened Taxa Journal of Threatened Taxa | www.threatenedtaxa.org | 26 July 2020 | 12(10): 16251–16256 ISSN 0974-7907 (Online) | ISSN 0974-7893 (Print) PLATINUM OPEN ACCESS DOI: htps://doi.org/10.11609/jot.5700.12.10.16251-16256 #5700 | Received 14 January 2020 | Final received 16 June 2020 | Finally accepted 19 June 2020 C o m Ecology of the Critcally Endangered Singidia Tilapia m u n (Teleostei: Cichlidae: Oreochromis esculentus) of lake Kayanja, Uganda i c and its conservaton implicatons a t 1 2 3 4 i Richard Olwa , Herbert Nakiyende , Elias Muhumuza , Samuel Bassa , o Anthony Taabu-Munyaho 5 & Winnie Nkalubo 6 n 1,2,3,4,6 Natonal Fisheries Resources Research Insttute (NaFIRRI), Plots 39-45, Nile Crescent P.O. Box 343, Jinja, Uganda. 5 Lake Victoria Fisheries Organizaton (LVFO), Plot 7B/E Busoga Square Bell Avenue P.O. Box 1625, Jinja, Uganda. 1 [email protected] (corresponding author), 2 [email protected] , 3 [email protected], 4 [email protected], 5 [email protected] ,6 [email protected] Abstract: Singidia Tilapia Oreochromis esculentus is a Critcally Endangered natve tlapia fsh species endemic to lakes Victoria and Kyoga basins of East Africa, however, it disappeared from these main lakes due to overfshing, environmental degradaton and predaton by the introduced Nile Perch Lates nilotcus. Remnant populatons of this fsh species is now restricted to satellite lakes including Lake Kayanja of the Victoria basin. This study provides updated informaton about the populaton abundance, critcal habitat, threats and diet of Singidia Tilapia to inform conservaton decisions to revive its populatons in the wild. Fish data collecton and mapping of nursery and breeding habitats of Singidia Tilapia on Lake Kayanja was conducted between February 2016 and October 2017. In all the areas mapped and sampled, Singidia Tilapia (with a size range of 11–27 cm TL) was the most abundant (43%) relatve to exotc Nile Tilapia Oreochromis nilotcus (21%) and Redbelly Tilapia Coptodon zillii (36%). The emergence of introduced (exotc) tlapias like Nile Tilapia recorded in this study could be atributed to cage fsh farming being carried out in this Lake. The diet of Oreochromis esculentus consisted mainly of detritus (60.8 %), plant materials (27.7%) and blue-green algae (5.5%). Destructon of critcal habitats and presence of introduced fsh species were noted as the major threats to this fsh and its habitats. The generated informaton could contribute to guiding stakeholders to undertake appropriate actons to conserve this threatened fsh species and its habitats. Keywords: Africa, conservaton, Cichlid fshes, recovery, threatened fshes. Editor: Neelesh Dahanukar, IISER, Pune, India. Date of publicaton: 26 July 2020 (online & print) Citaton: Olwa, R., H. Nakiyende, E. Muhumuza, S. Bassa, A. Taabu-Munyaho & W. Nkalubo (2020). Ecology of the Critcally Endangered Singidia Tilapia (Teleostei: Cichlidae: Oreochromis esculentus) of lake Kayanja, Uganda and its conservaton implicatons. Journal of Threatened Taxa 12(10): 16251–16256. htps://doi. org/10.11609/jot.5700.12.10.16251-16256 Copyright: © Olwa et al. 2020. Creatve Commons Atributon 4.0 Internatonal License. JoTT allows unrestricted use, reproducton, and distributon of this artcle in any medium by providing adequate credit to the author(s) and the source of publicaton. Funding: This study was carried out with fnancial support from The Ruford Small Grants Foundaton, The Pro Natura Foundaton Japan and The Mohamed Bin Zayed Species Conservaton Fund. Competng interests: The authors declare no competng interests. For Author details & Author contributon see end of this artcle. Acknowledgements: Our outmost credits go to The Pro Natura Foundaton Japan, Ruford Small Grant Foundaton, and The Mohamed Bin Zayed Species Conservaton Fund for providing fnancial support for this study. Appreciatons to associate professor Yasuaki Sato of Osaka Sangyo University, Japan for his guidance, advise, and support which made this study successful. We convey our grattude to government representatves partcularly district fsheries ofcer and assistant fsheries ofcer of Masaka for their guidance, technical support and partcipaton in data collecton and mobilizaton of local communites. Appreciaton goes to the Natonal Fisheries Resources Research Insttute of Uganda for allowing tme for Richard Olwa, Herbert Nakiyende, Bassa Sammuel, and Elias Muhumuza to be away from ofce duty to collect data, write, and review this artcle. We are grateful for the contributon of Dr. Winnie Nkalubo and Dr. Anthony Taabu- Munyaho of Natonal Fisheries Resources Research Insttute for their technical guidance, support, and valuable inputs. Thanks to the lake Kayanja communites, especially the fshermen and local leaders, for sacrifcing their valuable tme in implementng the actvites of the project. 16251 J TT Ecology of the Critcally Endangered Singidia Tilapia Olwa et al. INTRODUCTION Collecton of fsh data Fish surveys were conducted at pre-selected Singidia Tilapia Oreochromis esculentus is a Critcally experimental sites for collecton of primary fsh data. Endangered indigenous tlapiine cichlid (Twongo et al. Experimental gill-netng and electro-fshing techniques 2006), endemic to lakes Victoria and Kyoga basins of (Image 1 and 2) were used to collect fsh samples. At eastern Africa (Nagayi-Yawe et al. 2006). This fsh species each site, three feets of graded mult-flament gill nets has sufered a large reducton in extent of occurrence of mesh sizes ranging from 25.4–139.7 mm at an interval and is now restricted to a few refuge impoundments of 12.7mm and sizes 152.4–203 mm at 25.4mm intervals. and satellite lakes such as Kayanja of the Victoria basins The feets were set parallel to the lake shoreline towards (Balirwa et al. 2000; Ogutu-Ohwayo & Balirwa 2006). open water in the evening (17.00–18.00 h) and retrieved Many researchers have documented factors atributng at dawn (05.00–06.00 h) the following morning. At each to the decline in the populatons of Singidia Tilapia study site, geographical coordinates were recorded including the aggressive competton for food, spawning, using a Global Positoning System (GPS). At the shallow and nursery grounds with introduced Nile Tilapia inshore areas of each site, fsh populatons were Oreochromis nilotcus, predatory actons of Nile Perch sampled using a pulsed electro-fsher with an eight-wat (Mwanja et al. 2012), and environmental degradaton generator and two anodes (Amisah & Cowx 2000). Two like polluton, habitat modifcaton, fragmentaton & loss 30-minute runs were made at each site at an interval (Balirwa et al. 2003;Dudgeon et al. 2006; Ogutu-Ohwayo of 15 minutes to allow processing of the catch and & Balirwa 2006; Chapman et al. 2008; Njiru et al. 2008; recovery of conditons for fsh re-occupancy. All the fsh Lowe-McConnell 2009). Since this species was assessed caught were measured for total and standard lengths and published as Critcally Endangered (Twongo et al. (TL and SL) in centmeters, and identfed to species level 2006), no actve research has been carried out to learn according to Greenwood (1966) guidelines. A total of more about its distributon paterns and populaton 45 fsh stomachs of Singidia Tilapia, Nile Tilapia, and status, therefore, additonal research was needed to Coptodon zillii indicatng presence of any food were provide updated informaton and data about the feeding dissected out, contents evaluated and preserved in behavior, populaton status, threats to its critcal habitat 5% formalin soluton in separate numbered botles for and distributon to inform conservaton actons to halt further analysis in the laboratory. The analysis of gut the extncton of this species in the wild. contents of preserved stomachs followed