Lake Malawi

Lake Malawi / Lake Nyasa
View from orbit
Coordinates	12°11′S 34°22′E / 12.183°S 34.367°E / -12.183; 34.367Coordinates: 12°11′S 34°22′E / 12.183°S 34.367°E / -12.183; 34.367
Lake type	Rift lake
Primary inflows	Ruhuhu River[1]
Primary outflows	Shire River[1]
Basin countries	Malawi, Mozambique, Tanzania
Max. length	560 km[1] to 580[2]
Max. width	75 km[1]
Surface area	29,600 km2 (11,400 sq mi) [1]
Average depth	292 m[3]
Max. depth	706 m[3]
Water volume	8,400 km³[3]
Surface elevation	500 meters above sea level
Islands	Likoma and Chizumulu islets
References	[1][3]

Lake Malawi, also known as Lake Nyasa in Tanzania and Lago Niassa in Mozambique, is an African Great Lake and the southernmost lake in the East African Rift system, located between Malawi, Mozambique and Tanzania. It is the ninth largest lake in the world and the third largest and second deepest lake in Africa. It is home to more species of fish than any other lake,^[4] including about 1000 species of cichlids.^[5] The Mozambique portion of the lake was officially declared a reserve by the Government of Mozambique on June 10, 2011,^[5] and in Malawi a portion of the lake is included in the Lake Malawi National Park.^[4] Lake Malawi is a meromictic lake; permanent stratification and the oxic-anoxic boundary are maintained by moderately small chemical and thermal gradients.^[6]

Geography

Lake Malawi is between 560 kilometres (350 mi)^[1] and 580 kilometres (360 mi) long,^[2] and about 75 kilometres (47 mi) wide at its widest point. The total surface area of the lake is about 29,600 square kilometres (11,400 sq mi).^[1] The lake has shorelines on western Mozambique, eastern Malawi, and southern Tanzania. The largest river flowing into it is the Ruhuhu River, and there is an outlet at its southern end, the Shire River, a tributary that flows into the very large Zambezi River in Mozambique.^[2]

The lake lies in a valley formed by the opening of the East African Rift, where the African tectonic plate is being split into two pieces. This is called a divergent plate tectonics boundary. It is variously estimated at about 40,000 years old^[1] or about one to two million years.^[7] The lake is about 350 kilometres (220 mi) southeast of Lake Tanganyika, another of the great lakes of the East African Rift.

The Lake Malawi National Park is located at the southern end of the lake.^[8]

European discovery and colonization

Mwaya Beach on Lake Malawi

The Portuguese trader Candido José da Costa Cardoso was the first European to visit the lake in 1846.^[9] David Livingstone reached the lake in 1859, and named it "Lake Nyasa".^[2]

On 16 August 1914, Lake Malawi was the scene of a brief naval battle when the British gunboat SS Gwendolen, commanded by a Captain Rhoades, heard that World War I had broken out, and he received orders from the British Empire's high command to "sink, burn, or destroy" the German Empire's only gunboat on the lake, the Hermann von Wissmann, commanded by a Captain Berndt. Rhoades's crew found the Hermann von Wissmann in a bay near "Sphinxhaven", in German East African territorial waters. Gwendolen disabled the German boat with a single cannon shot from a range of about 1,800 metres (2,000 yd). This very brief gunboat conflict was hailed by The Times in England as the British Empire's first naval victory of World War I.^[10][11]

Lake of Stars

"The Lake of Stars" is the nickname for Lake Malawi coined by David Livingstone.^[12] This name came about due to lights from the lanterns of the fishermen in Malawi on their boats, that resemble, from a distance, stars in the sky.^[13]

The lake is also known as the Lake of Storms, for the unpredictable and extremely violent gales that sweep through the area.^[13]

Borders

The largest portion of the area of the lake is in Malawi. However, about a quarter of the area belongs to Mozambique. This area includes the waters surrounding the Malawian islets of Likoma and Chizumulu, which are this lake's only two inhabited islets.

An African fish eagle catches a fish on Lake Malawi

Tanzania–Malawi dispute

Dashed line: current Malawi border
Dotted line: Tanzanian claim

The partition of the lake's surface area between Malawi and Tanzania is under dispute. Tanzania claims that the international border runs through the middle of the lake.^[14] On the other hand, Malawi claims the whole of the surface of this lake that is not in Mozambique, including the waters that are next to the shoreline of Tanzania.^[15] Both sides cite the Heligoland Treaty of 1890 between Great Britain and Germany concerning the border. The wrangle in this dispute occurred when the British colonial government, just after they had captured Tanganyika from Germany, placed all of the waters of the lake under a single jurisdiction, that of the territory of Nyasaland, without a separate administration for the Tanganyikan portion of the surface. Later in colonial times, two jurisdictions were established.^[16]

The dispute came to a head in 1967 when Tanzania officially protested to Malawi; however nothing was settled.^[17] Occasional flare-ups of conflict occurred during the 1990s and in the 21st century.^[18] In 2012, Malawi's oil exploration initiative brought the issue to the fore, with Tanzania demanding that exploration cease until the dispute was settled.^[19]

Malawi–Mozambique border

In 1954, an agreement was signed between the British and the Portuguese making the middle of the lake their boundary with the exception of Chizumulu Island and Likoma Island, which were kept by the British and are now part of Malawi.^[16]

Transport

Large-scale transport between villages on the shores of Lake Malawi, and also between the lakeshore and the inhabited islets, is provided by steamboats or motor ships on the lake, or else by air transport.

A jetty juts into the lake at Nkhata Bay

MV Chauncy Maples began service on the lake in 1901 as the SS Chauncy Maples: a floating clinic and church for the Universities' Mission to Central Africa. She later served as a ferry and is currently being renovated into a mobile clinic at Monkey Bay. The renovation is expected to be complete during the first half of 2014. MV Mpasa entered service in 1935.^[20] The ferry MV Ilala entered service in 1951. In recent years she has often been out of service, but when operational she runs between Monkey Bay at the southern end of the lake to Karonga on the northern end, and occasionally to the Iringa Region of Tanzania. The ferry MV Mtendere entered service in 1980.^[20] By 1982 she was carrying 100,000 passengers each year.^[20] She normally serves the southern part of the lake but if Ilala is out of service she operates the route to Karonga. The Tanzanian ferry MV Songea was built in 1988.^[21] Her operator was the Tanzania Railway Corporation Marine Division until 1997, when it became the Marine Services Company Limited.^[22] Songea plies weekly between Liuli and Nkhata Bay via Itungi and Mbamba Bay.^[21]

Wildlife

Various mbuna cichlids from Lake Malawi

The painted hunting dog was believed to be extinct in Malawi, however recent research in Kasungu National Park near the western boundary of Malawi has found a pack of 17 painted dogs. Researcher Duncan Yearly has begun a project called Carnivore Conservation Malawi and is trying to raise awareness and funding to further the protection of these endangered mammals in Malawi. It is believed that these painted dogs seasonally move across the border from Malawi into Zambia to hunt in The South Luangwa Valley but seemingly they have plenty of success within Malawi as the pack consists of 7 adults and 10 pups.^[23] Other wildlife that is found in and around Lake Malawi or Nyasa include Nile crocodiles, hippopotamus, monkeys,^[24] and a significant population of African fish eagles that feed off fish from the lake. ^[25]

Fish

Fishing

Lake Malawi has for millennia provided a major food source to the residents of its shores since its waters are rich in fish such as the chambo, consisting of any one of five species of the cichlid subgenus Nyasalapia (Oreochromis karongae, O. lidole, O. saka, O. shiranus and O. squamipinnis), the lake sardine (Engraulicypris sardella) and the kampango (Bagrus meridionalis), a large catfish.^[26] Some of the fish that are caught are exported from Malawi, but the wild population of fish is increasingly threatened by overfishing and water pollution. ^[27]

Cichlids

Lake Malawi is home to numerous cichlid species including Livingston's cichlid (Nimbochromis livingstonii).

Lake Malawi is noted for being the site of evolutionary radiations among several groups of animals, most notably cichlid fish. In total there are about 1,000 cichlid species in Lake Malawi and the vast majority are endemic.^[5] Many of these have become popular among aquarium owners due to their bright colors. Recreating a Lake Malawi biotope^[28] to host cichlids became quite popular in the aquarium hobby. The cichlids of the lake are divided into two basic groups, loosely referred to as the haplochromines and the tilapiines. Within the first group, Haplochrominae, there are two subgroups. The first one consists of open water and sand dwelling species whose males display bright colors and whose females show a silvery coloration with sometimes irregular black bars or other markings. The second subgroup is known both locally and popularly as mbuna, which means "rockdwellers". The Mbuna species tend to be smaller, often specialized aufwuchs feeders, and often both sexes are brightly colored with males having several egg shaped gold spots on their anal fin. All haplochromines from Lake Malawi are mouthbrooders.^[26]

The second group, the tilapiines, comprises the only substrate-spawning species in the lake (Coptodon rendalli), in addition to the five mouthbrooding species of chambo (Nyasalapia, a subgenus of Oreochromis).^[26]

Non-cichlids

The vast majority of the fish species in the lake are cichlids. Among the non-cichlid native fish are several species of cyprinids (in genera Barbus, Labeo and Opsaridium, and the lake sardine, Engraulicypris sardella), airbreathing catfish (Bathyclarias and Clarias, and the Kampango, Bagrus meridionalis), mochokid catfish (Chiloglanis and Synodontis), Mastacembelus spiny eel, mormyrids (Marcusenius, Mormyrops and Petrocephalus), the African tetra Brycinus imberi, the poeciliid Aplocheilichthys johnstoni, the spotted killifish (Nothobranchius orthonotus), and the mottled eel (Anguilla nebulosa).^[26]

Invertebrates

Lake Malawi (1967)

Molluscs

Lake Malawi is home to 28 species of freshwater snails (including 16 endemics) and 9 bivalves (1 endemic, the unionid Nyassunio nyassaensis).^[29] With the exception of two species of Bulinus, the endemic freshwater snails are all members of the genera Bellamya, Gabbiella, Lanistes and Melanoides.^[30]

Lake Malawi is home to a total of four snail species in the genus Bulinus, which is a known vector of bilharzia. A survey in Monkey Bay in 1964 found two endemic species of snails of the genus (B. nyassanus and B. succinoides) in the lake, and two non-endemic species (B. globosus and B. forskalli) in lagoons separated from it. The latter species are known vectors of bilharzia, and larvae of the parasite were detected in water containing these, but in experiments C. Wright of the British Museum of Natural History was unable to infect the two species endemic to the lake with the parasites. The field workers, who spent many hours on and in the lake, did not find either B. globosus or B. forskalli in the lake itself.^[31]

Crustaceans

Unlike Lake Tanganyika with its many endemic freshwater crabs and shrimp, there are few such species in Lake Malawi. The Malawi blue crab, Potamonautes lirrangensis (syn. P. orbitospinus), is the only crab in the lake and it is not endemic.^[32][33] The atyid shrimp Caridina malawensis is endemic to the lake, but it is poorly known and has historically been confused with C. nilotica, which is not found in the lake.^[34]

2015 mine leak

In January 2015 a sediment control tank collapsed at the Paladin Energy-owned uranium mine in Northern Malawi after a high intensity rain storm hit the area. It was revealed that approximately 50 litres of non radioactive material leaked into a local creek. Despite reports in local media of radioactive contamination the government conducted independent scientific tests on the local river system and found that there was no effect on the environment despite the contrary reports in some parts of the local media.^[35][36]

See also

• 1989 Malawi earthquake
• 2009 Karonga earthquakes
• Lake Malawi National Park
• Rift Valley lakes

References

Further reading

• Mayall, James (December 1973). "The Malawi-Tanzania Boundary Dispute". The Journal of Modern African Studies 11 (4): 611–628. doi:10.1017/S0022278X00008776. 
• Recent study on Lake Malawi water levels reveals drought 100,000 years ago

External links

Wikimedia Commons has media related to Lake Malawi.

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