| Lake Ejagham | |
|---|---|
  Lake Ejagham  Lake Ejagham | |
| Coordinates | 5°45′N8°59′E / 5.750°N 8.983°E /5.750; 8.983 |
| Type | Solution basin |
| Primary outflows | Munaya River (part of theCross River system) |
| Basin countries | Cameroon |
| Max. length | Approximately 1,050 metres (3,440 ft)[1] |
| Max. width | Approximately 700 metres (2,300 ft)[1] |
| Surface area | 0.49 square kilometres (0.19 sq mi)[2] |
| Max. depth | Approximately 18 metres (59 ft)[1] |
Lake Ejagham is a small lake nearEyumodjock in theSouthwest Region ofCameroon. Unlike many other lakes in the region, it is not avolcanic lake, but is likely asolution basin formed bygroundwater during thelast Ice Age.[1] This highly isolated lake is roughlyoval in shape, lacks an inflow, but has an outflow into theMunaya River (part of theCross River system).[1][3] The outflow is impassable to most fishes because of a waterfall.[1]
Despite its very small size, it supports 7endemic species ofcoptodonine andoreochromine cichlid fishes (Coptodon deckerti,C. ejagham,C. fusiforme,C. nigrans,Sarotherodon lamprechti, andS. knauerae). Of these, 6 were onlyscientifically described in 2010 and 2011, and have therefore not been rated by theIUCN, but they likely face the same threats asC. deckerti (the single older species that has been rated by the IUCN).[2][4][5]C. deckerti is consideredcritically endangered due topollution andsedimentation from human activities. It could also be threatened by large emissions ofcarbon dioxide (CO2) from the lake's bottom (compareLake Nyos),[5] although Ejagham is too shallow to contain very high amounts of this gas.[6] A species of catfish from the genusParauchenoglanis has beenintroduced to the lake, and this probably presents a serious threat to the endemic cichlids.[2]
The Ejagham cichlids are commonly considered a prime example ofsympatric speciation within its two genera. Studies indicate a level of secondarygene flow between the lake's species and relatives from nearby regions, and this likely facilitated thespeciation (i.e., the Ejagham species not strictly the result of sympatric speciation).[7]
