Tanzania: Crayfish Invasion Threatens Local Marine Life in Lakes

by Jan 16, 2012Marine & Coastal

Tanzania needs to be constantly on alert following the invasion of the Louisiana crayfish that are infamous for eating small freshwater fish, fish eggs, other aquatic organisms and plankton.

Tanzania Fisheries Research Institute (TAFIRI) Director General Benjamin Ngatunga told ‘Daily News’ in an exclusive phone interview that there were no reported cases yet, but cautioned that the menace could be on its way coming.

The 15-centimetre long freshwater crustacean, also known as the red swamp crayfish, is already widely distributed in lakes and other bodies of water throughout Kenya, as well as in Rwanda, Uganda, Egypt, Zambia, the Seychelles, Mauritius and South Africa. “We are on alert. Signs show that should they come they will come via Lake Victoria though not in the main lake,” he said.

Dr Ngatunga revealed that the threat of the Louisiana Crayfish lies more in smaller water bodies and not the main lake and thus the need to be constantly on the look out. “Taking into account that our neighbours have been affected, the government through its various institutions is expected to issue reports immediately upon sighting of these creatures so we can control them,” he said.

According to the National Geographic website, conservationists are now concerned that the crayfish will reach the East African lakes of Malawi, Tanganyika and Victoria, which are home to hundreds – and probably thousands – of species found nowhere else.

Dr Ngatunga said that one characteristic of the crawfish is that it doesn’t affect all lakes but usually prefers shallow waters and at the base of them.

“There shouldn’t be alarm over the risk of losing rare species indigenous to Tanganyika because these species live in isolated areas and are rock based,” he elaborated. Last November, the International Union for Conservation of Nature (IUCN) issued an alert to raise awareness about the possibility that these alien creatures could come to East African lakes – the results of which could be disastrous for the fauna and flora of the lakes as well as for the livelihoods of many of its peoples.

The IUCN programme provides the framework for planning, implementing, monitoring and evaluating the conservation work undertaken by the Commissions and the Secretariat with and on behalf of IUCN Members.

Through its Invasive Species Initiative, IUCN is working with the Lake Tanganyika Authority and with support from United Nations Development Programme-Global Environment Facility to develop an Invasive Species Monitoring and Management Programme for the lake and its four riparian countries (Burundi, DRC, Tanzania and Zambia).

IUCN is gradually accumulating information on existing and possibly developing biological invasions and also sensitizing the lake and catchment managers to the possibility of alien species entering the area and establishing themselves as invasive. One group of aquatic and semi-aquatic animals that is not so far present in the lake is the freshwater crayfish – whose group is not represented by any indigenous species in the lake basin (or indeed, anywhere on the continent of Africa).

Louisiana crayfish were first imported in the 1970s into Kenya and South Africa, where the species was grown in aquaculture operations. People bred the species in Kenya’s Lake Naivasha and sold the delicacy to Scandinavian buyers after that region’s native crayfish had been wiped out by disease.

The crayfish were also introduced into dams around the Kenyan cities of Nairobi, Kiambu and Limuru to rid those areas of parasite-carrying snails. But by burrowing into the edges of dams, rivers and lakes to make their nests, the crayfish have damaged local infrastructure and landscapes. For instance, their burrowing has caused water canals to leak, earth dams to collapse and banks of rivers and lakes to erode.