Perch Precariously

The Daily Nation is reporting that populations of introduced Nile perch (Lates niloticus) in Lake Victoria are dwindling, causing strife for fishermen in Uganda, Kenya and Tanzania. The perch in Lake Victoria were once so numerous that they overwhelmed the lake and many of the native fish that lived there, causing a ripple effect that extended to the lives of the people that live in countries surrounding the lake and spawned a movie about the consequences. Now the perch are getting much harder to find, with fishermen being to forced to venture into the deeper waters of the lake in search of their catch. General consensus is that the drop in Nile perch numbers is likely due to water pollution, which likely doesn't bode well for the other creatures that call the lake home.

Unwelcome Mat

From the Daily News in Tanzania comes this update about the water hyacinth invasion in Lake Victoria. The Lake Victoria Environment Management Project, which entered its second phase in 2006, now says populations of water hyacinth (Eichhornia crassipes) have doubled over the past year, and the plants now cover over 700 hectares (1700 acres) of the lake's surface. Back when the LVEMP was first starting up, they had reduced populations by 80%. There is quite a lot of diversity in the potential vectors behind this resurgence: agricultural activities that release silt and fertilizer into the lake, untreated sewage that is dumped in the lake, failure of biocontrols due to excessive water movement in adjacent rivers, and car washes along the shore of the lake that lead to oil and polluted water entering the lake.

You can actually observe for yourself the extent of the water hyacinth invasion in Lake Victoria in this feature from NASA's Earth Observatory. NASA scientists used satellite imagery to estimate the surface area of the lake that was covered by water hyacinth. The photos show that the water hyacinth completely took over the lake's Kisumu Bay between Dec. 2005 and Dec. 2006.

For previous ISW stories about water hyacinth in Lake Victoria, go here and here. Thanks to Xris over at the Flatbush Gardener for sending in the NASA link.

Darwin's Nightmare

One of the indie films scooping up awards this season is a foreign documentary named "Darwin's Nightmare." It's the true story of the introduction and subsequent domination of the Nile perch (Lates niloticus) in Lake Victoria. While the Nile Perch is native to Africa, it was not known in Lake Victoria until it was intentionally introduced there in the 1960s. Its arrival irrevocably altered both the ecology of Lake Victoria and the economies of the countries where the lake is situated: Tanzania, Uganda and Kenya. "Darwin's Nightmare" focuses on Tanzania. The director of the film, Hubert Sauper, paints a grim picture of a country that processes and exports tons of nile perch flesh to wealthy countries while native Tanzanians teeter on the edge of famine. The planes that take away the perch for sale and consumption arrive with guns and ammunition that will make their way to the wars in surrounding African countries.

It doesn't look like I will be able to catch any of the screening of this film, but I look forward to the DVD release. Tip of the virtual hat to SFStation for posting about a screening of the film in San Francisco.

Hating Hyacinth

Water hyacinth (Eichhornia crassipes) is threatening to take over Lake Victoria...again. It seems that the contract between the Kenyan government and the company in charge of water hyacinth control expired, according to this story at AllAfrica.com. Now that the company's control measures, which consisted of harvesting the plants and shredding them, have ceased, the plants are once more clogging irrigation canals, crowding the lake edge, and blocking passageways on the lake. Maybe they should just start making more furniture.