Ecology of the Critically Endangered Singidia Tilapia (Teleostei: Cichlidae: Oreochromis esculentus) of lake Kayanja, Uganda and its conservation implications

Richard Olwa,Winnie Nkalubo,Samuel Bassa,Elias Muhumuza,Anthony Taabu-Munyaho,Herbert Nakiyende

doi:10.11609/jott.5700.12.10.16251-16256

Abstract

Singidia Tilapia Oreochromis esculentus is a Critically Endangered native tilapia fish species endemic to lakes Victoria and Kyoga basins of East Africa, however, it disappeared from these main lakes due to overfishing, environmental degradation and predation by the introduced Nile Perch Lates niloticus. Remnant populations of this fish species is now restricted to satellite lakes including Lake Kayanja of the Victoria basin. This study provides updated information about the population abundance, critical habitat, threats and diet of Singidia Tilapia to inform conservation decisions to revive its populations in the wild. Fish data collection 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%) relative to exotic Nile Tilapia Oreochromis niloticus (21%) and Redbelly Tilapia Coptodon zillii (36%). The emergence of introduced (exotic) tilapias like Nile Tilapia recorded in this study could be attributed to cage fish 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%). Destruction of critical habitats and presence of introduced fish species were noted as the major threats to this fish and its habitats. The generated information could contribute to guiding stakeholders to undertake appropriate actions to conserve this threatened fish species and its habitats.

Highlights

Singidia Tilapia Oreochromis esculentus is a Critically Endangered indigenous tilapiine cichlid (Twongo et al 2006), endemic to lakes Victoria and Kyoga basins of eastern Africa (Nagayi-Yawe et al 2006)
Many researchers have documented factors attributing to the decline in the populations of Singidia Tilapia including the aggressive competition for food, spawning, and nursery grounds with introduced Nile Tilapia Oreochromis niloticus, predatory actions of Nile Perch (Mwanja et al 2012), and environmental degradation like pollution, habitat modification, fragmentation & loss (Balirwa et al 2003;Dudgeon et al 2006; Ogutu-Ohwayo & Balirwa 2006; Chapman et al 2008; Njiru et al 2008; Lowe-McConnell 2009)
Since this species was assessed and published as Critically Endangered (Twongo et al 2006), no active research has been carried out to learn more about its distribution patterns and population status, additional research was needed to provide updated information and data about the feeding behavior, population status, threats to its critical habitat and distribution to inform conservation actions to halt the extinction of this species in the wild

Summary

Introduction

Singidia Tilapia Oreochromis esculentus is a Critically Endangered indigenous tilapiine cichlid (Twongo et al 2006), endemic to lakes Victoria and Kyoga basins of eastern Africa (Nagayi-Yawe et al 2006) This fish species has suffered a large reduction in extent of occurrence and is restricted to a few refuge impoundments and satellite lakes such as Kayanja of the Victoria basins (Balirwa et al 2000; Ogutu-Ohwayo & Balirwa 2006). Since this species was assessed and published as Critically Endangered (Twongo et al 2006), no active research has been carried out to learn more about its distribution patterns and population status, additional research was needed to provide updated information and data about the feeding behavior, population status, threats to its critical habitat and distribution to inform conservation actions to halt the extinction of this species in the wild

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Conclusion