Academia Journal of Environmetal Science 5(1): 013-021, January 2017 DOI: 10.15413/ajes.2017.0229 ISSN: ISSN 2315-778X ©2017 Academia Publishing Research Paper An update on the fish and fisheries of Lake Oguta, Nigeria Accepted 18th January, 2017 ABSTRACT The paper attempts to review the current trends in fisheries activities in Lake Oguta, Nigeria with the aim to finding a lasting solution to the declining fisheries of the Lake. Lake oguta is the largest standing freshwater body in South-Eastern Nigeria and is of immense importance to thousands of people in Oguta Local Government, Nigeria. The lake supports about 2, 403 full-time and 154 part-time fishers. About 80% of the fishers in the Lake obtain their protein from the Lake. Virtually, all the households in the Lake participates in fisheries activities from time to time. The fishers employ cast nets, gill nets, fish traps, seines, hooks and line etc most of which are locally made but increasingly, much of the gears are made locally using modern materials like nylon twine or rope in the case of gill nets. Recently, the fishers and fisheries of the Lake are faced with some challenges which include overfishing, pollution, eutrophication, aquatic weeds, decline in fish biodiversity, illegal, unreported and unregulated fishing, ineffective monitoring, control and surveillance (MCS) and poverty, lack of alternative livelihoods and inadequate social legislation as well as, some destructive fishing methods. The free access to the resources of the lake has caused the resources to be biologically and Sanda MK, Kwaji BP, Ajijola KO, economically overfished. The paper recommends the need for regular restocking Sogbesan OA.* programs, effective conservation through controlling the intensity of fishing by Department of Fisheries, Modibbo regulating mesh size of fishing gears, catch quota, closed season and closed areas. Adama University of Technology, Yola, Alternative income source for the fishers will reduce the pressure on the Nigeria. resources. There is need to strengthen the fishers as key stakeholders in the fisheries sub-sector. This will entrust commitment and compliance to regulations. *Corresponding author. E-mail: [email protected]. Tel: +2348161518298. Keywords: Fishers, biodiversity, fisheries resources, management, Oguta Lake. INTRODUCTION Oguta Lake is a fresh water lake. It receives perennial northern section of Imo State (Ahiarakwem and Onyekuru, drainage from Rivers Njaba, Utu and Awbuna, which have 2011). their sources from the Awka-Orlu Cuesta in North central Four rivers (Njaba, Awbana, Utu and Orashi) are Imo State, Nigeria. It also receives overflow from the Niger. associated with Oguta Lake (Ahiarakwem and Onyekuru, Lake Oguta drains into the River Orashi, a main river on the 2011). The Njaba and Awbana discharge into the lake all east bank floodplain of the Niger and which conveys River the year round while Utu Stream flows in during the rainy Niger’s floodwaters directly to the Niger delta. The lake season. The Orashi River flows past the lake in its receives huge volumes of sediment from its tributaries, southwestern portion. The total annual inflow from the particularly, the Njaba, a river that is actively and deeply rivers and stream is about 25,801.60 m3 (Ahiarakwem, incising into the poorly structured soils and unconsolidated 2006). Oguta Lake is one of the natural water resources of sedimentary rock (Ameki Formation, Ogwashi-Asaba non-marine habitat located in a low-lying (elevation < 50 Formation and the Benin Formation) underlying the m) platform. Lake Oguta is situated in Oguta Local Academia Journal of Environmental Science; Sanda et al. 014 Figure 1: Map of Lake Oguta. Source: (Ahiarakwem, 2006). Government Area of Imo State, Nigeria. It is located season but declines to 0.61 m at the peak of the rainy approximately within latitude 5° 41’ and 5° 44’ North of the season consequent upon the inflow of sediment-laden Equator and longitude 6° 50’ and 6° 45’ of the Greenwich waters from the River Njaba/Alusi and Niger floodwaters. Meridian (Figure 1). Although, it is a very small lake The mean pH is 6.0 and ranges from 5.2 to 6.2 while compared to man-made and natural lakes in Nigeria like dissolved oxygen range of 4.8 to 6.0 and a mean Lake Chad, Kainji and Tiga, it is, however, the largest conductivity range of 5.5, 8.6 to 16.5 μS, respectively. The freshwater system in southeastern Nigeria (Anene et al., climate is the Koppen’s Af (that is, humid tropical rain 2010). forest) with a short dry season extending from December to The lake has a maximum depth of 8.0 m and a mean February and a long rainy season during the remainder of depth of 5.5 m, with a water surface area that varies from the year (Ahiarakwem, 2006). 180 ha in the dry season to 300 ha at the peak of the rainy Mean annual rainfall is 2,120 mm with a unimodal season (Njoku and Ejiogu, 2005). Water level varies over a distribution with the peak in September. The period range of 2.7 m between these two seasons. The length of between July and August is characterized by overcast skies the shoreline is approximately 10 km. Surface water and milder temperatures (mean: 25°C). Mean temperature temperature vary from 240°C in December to 31°C in ranges from 25 to 28°C (April). The dry season is March (Njoku and Ejiogu, 2005). A very weak thermal dominated by dusty, Harmattan winds. The catchment stratification occurs towards mid-day between February areas of the Lake comprise the drainage area of the Njabba and May which is as a result of the energy received from the River and a part of the River Niger floodplain in the region Sun. Secchi-disk transparency is 4.0 m early in the rainy south of Onitsha. Tertiary - Recent sediments of the Academia Journal of Environmental Science; Sanda et al. 015 Table 1: Species composition of Lake Oguta. S/No Fish family Species 1 Pantodontidae Pantodon bucholzi Polypterus senegalensis 2 Polypteridae Calmichthys calabaricus 3 Lepidosirenidae Protopterus annectens Papyrocranus afer 4 Notopteridae Xenomystus nigri 5 Osteoglossidae Heterotis niloticus Mormyrus rume Hyperopinus bee occidentalis 6 Mormyridae Gnathonemus petersii Petrocephalus bovei Barbus spp. 7 Cyprinidae Labeo cubei Phargo laricatus 8 Distichodontidae Distichodus rostratus Distichodus brevipinnis Chrysichthys nigrodigitatus Chrysichthys filamentousus 9 Bagridae Auchenoglanis bicustatus Paraauchenoglanis ansorgii Clarotes laticeps Schilbe mystus 10 Schilbeidae Eutropius niloticus Synodontis clarias 11 Mochokidae Synodontis vermiculatus Synodontis schall Source: (Njoku and Ejiogu, 2005). Ogwashi-Asaba, Ameki and Benin Formations underlie the Synodontis sp., and Schilbe sp., etc (Omin, 1983). The Lake catchment area (Ahiarakwem and Onyekuru, 2011). Anene has a high phytoplankton community (258 species of et al. (2010) reported that the artisanal fishery of Lake phytoplankton which falls under 107 genera). The Oguta is lucrative. The gross margin analysis was reported estimated primary productivity of the Lake is 160, 279 to be ₦161, 444.52. mg/cm3 per day, which is generally low. This may be the reason for the low fishery production estimated at 12.5 metric tons/year. BIODIVERSITY OF THE LAKE The species diversity of the Lake contributes to the biological diversity of the Rain Forest ecological zone of The Lake supports 40 fish species such as Chrysichthys sp., southern Nigeria (Ita and Balogun, 1984). Table 1 shows Lates sp., Alestes sp., Tilapia sp.,Citharinus sp., Mormyrus sp., the species composition of Oguta Lake in a survey Academia Journal of Environmental Science; Sanda et al. 016 Table 1Contd: Species composition of Lake Oguta. S/No Fish family Species 12 Malateruridae Malapterurus electricus Hydrocynus lineatus Hydrocynus brevis Hepsetus odoe 13 Characidae Alestes baramose Alestes dentex Mircralestes spp. Citharinus citharus 14 Citharanidae Citharinus latus Citharinus disticholdoides 15 Cyprinodontidae Epiplays bifasciatus 16 Chanidae Chana obscura Heterobranchus bidorsalis Heterobranchus longifilis 17 Clariidae Clarias gariepinus Clarias anguillaris Ophiocephalus forskali 18 Ophiocephalidae Paraophiocephalus africanus 19 Mastacemalidae Mastacembelus niloticus Oreochromis niloticus Tilapia zilli Tilapia mariae 20 Cichlidae Hemichromis fasciatus Tylochromis spp. Hemichromis elongates Source: (Njoku and Ejiogu, 2005). conducted by Njoku and Ejiogu (2005). A survey of fish FISHERIES OF THE LAKE species conducted by Francis et al. (2014) (Table 2), shows a decrease in the families and fish species. Table 3 shows Njoku (2002) and Njoku and Ejiogu (2005) gives good some families and fish species reported by Njoku and accounts of the fishery of Lake Oguta and the transition in Ejiogu (2005) that were not reported by Francis et al. the fishery after 1991. The Lake is of immense value to the (2014). This indicates that many fish species are threatened people of Oguta Local Government area, especially, the and if an urgent measure is not taken, they may become villagers residing around the Lake. They obtain about 80% endangered species in the near future. Lake Oguta has of their protein from the Lake. Lake Oguta supports about 2, experienced loss of biodiversity in terms of fishery 403 full-time and 154 part-time fishers. Virtually, all the resources in recent times. Keke et al. (2008) reported that households in the Lake participate in fishing activities there has been an altitude of free access to the fishery as to alongside other activities like crop and animal farming there was no basic rules