East African Rift Valley Lakes
The East African rift runs for thousands of miles, and is
a result of ancient plate tectonics. It begins in Syria, and
cuts through the eastern slice of Africa, running southwards.
Below Ethiopia, it divides into the Eastern and Western rifts.
The Western or Albertine Rift is the region I'll focus on; it contains what are sometimes termed Africa's "Great Lakes". Technically speaking, Lake Victoria is not a Rift Valley Lake - it occupies a depression between the eastern and western rifts, formed by the uplift of the rifts to either side. Other of the "Great Lakes" include Lake Tanganyika, Lake Albert (Victoria is going to need her Prince Albert, after all), Lake Edward, Lake Kivu and Lake Malawi. Victoria, Tanganyika, and Malawi are the largest and most important of these lakes.
The region is a heavily populated area in Africa - climate is moderate due to high elevation, despite the nearby crossing of the equator. Unfortunately, much of the region has lately been wracked by civil conflict, leading to bloodshed and economic disaster in many of the nations located here.
Lake Victoria: The countries of Uganda, Kenya, and Tanzania border it. Also known as Victoria Nyanza, Ukerewe, or Nalubaale, it is the world's third-largest lake, the world's second-largest freshwater lake, and the largest in Africa. Surface area coves 26,830 square miles, and it is 260 miles in length. It is the headwaters of the White Nile, the largest tributary of the Egyptian Nile. Of the lakes we will consider, it is the youngest and the shallowest (not being a true rift lake). There are over three thousand islands dotting the lake, many settled, and some currently tourist destinations.
The Arabic Al Adrisi map, dating from the 1160s, provides one of the earliest recorded views of Lake Victoria, correctly pinpointing it as the source of the Nile (which later Europeans went through much effort to find out for themselves). In 1858, John Hanning Speke re-discovered all this provoking a well-publicized battle with the explorer Richard Francis Burton.
Up until the 1950's, Lake Victoria was home to over 500 species of cichlid fish, mostly haplochromids. Unfortunately, the locals decided that a Nile perch fishing industry would be a good idea, and so the latter species was introduced. This has had devastating effects on the endemic fish. While currently, with help, there is some comeback of the original population, the situation remains iffy, and perhaps half the original species are gone for good.
Lakes Albert and Edward are also part of the Nile watershed.
Lake Tanganyika: This is the second largest lake in the world, by volume (not surface area). The honors for the world's largest lake by volume goes to Siberia's Lake Baikal. Geologists believe that Lake Tanganyika was formed some 7-10 million years ago. A true rift lake, it is elongated and deep, and at 420 miles in length, it is the longest lake in the world. Its maximum width is 45 miles. Maximum depth is 1,470 meters. Countries surrounding this lake are Tanzania, Burundi, Congo, and Zambia.
As this lake has only one outlet, which leads to the Congo River, it has a high mineral content, the water is quite hard, and its ph is high (alkaline). Much of the upper underground area is sandy.
The water requirements for fish living in this lake make it particularly challenging to keep them in aquaria, although with close monitoring it can be done. Over 200 species of cichlids, many of them quite unique in adaptations, reside here. The water is exceptionally clear, and the upper layers highly saturated with oxygen, while the lower zones are extremely oxygen-starved. Crocodiles and hippos make their home by the the lake. Many of the Tanganyikan species of cichlid fish are small. Those which are, can often survive well in well-areated and maintaned 10 or 20 gallon acquaria. Such types include the shell-dwelling Neolamprologus and Lamprologus.
Lake Kivu's waters eventually end up in Lake Tanganyika.
Lake
Malawi: This lake is also known as Lake Nyasa,
Lake Nyassa, or Lake Niassa. Niassa means "Lake" in Yao,
so technically we've got "Lake Lake".It lies between
the landlocked country of Malawi, and Tanzania and Mozambique.
Two islands, named Likoma and Chizumulu, near the center
of the lake belong to Malawi, although waters of Mozambique
surrounds that section. Lake Malawi probably formed about
1-2 million years ago, making it a young lake. It is the
ninth largest lake in the world.
Again, it is a lake with high mineral content, a high pH and water hardness, but not as extreme as Lake Tanganyika, so there is some wiggle room for the aquarist.
Over 500 types of fish are found here that are found no where else in the world. All of Europe has something like 64 types of unique freshwater fish. All told, there may be over 600-800 species of fish. The diversity here is amazing. Many if not most of these fish are cichlids. Malawi cichlids are roughly divided into two groups: the rock-dwelling largely-vegetarian Mbunga and the sand-preferring piscovore Hap.
Baobab trees grow in abundance on the two islands, and inhabitants grow cassava, bananas and mangos; and they fish the lake waters.
So, anyhow, what is a cichlid, and why do many aquarists like them?
Taxonomists have come up with a rationale for the Family Cichlidae, none of which means much to me, but I'll reprint what Wikipedia has to say:
- a single nostril (a characteristic they share only with damselfish)
- an interrupted lateral line organ (except for genera Teleogramma and Gobiocichla)
- a distinctive shape of one of the otoliths
- the small intestine leaves the stomach from its left side, not from its right side as in other fish
- the presence of teeth in both the jaws and in the throat.
There now, that was informative!
The cichlid is found in Africa and South America, with just a few varieties in Asia - some have specialized for alkaline environments such as the African Rift Lake cichlids. Others prefer a markedly more acidic environment (western Africa, for instance). Your everyday angelfish is a South American cichlid.
The extra teeth do give them more feeding options. Some eat the scales of other fish, for instance. However one thing that aquarists find fascinating about these fish is their reproductive and brooding methods. All species show some form of parental care for both eggs and larvae, often extended to free-swimming young until they are several weeks old. Parental care falls into one of three categories: mouthbrooders, substrate brooders, and delayed mouthbrooding where the eggs are layed in the open or in a cave, and subsequently brooded in the mouth of either or both of the parents. People have also noted that cichlids appear to be extremely intelligent. Some will take food out of the hands of the feeders.
Many tend to be aggressive fish, but by careful searching one can find mellower types of cichlids. With the Malawi mbunga it is best to place more females to males in tanks, as males may harry females during mating. The behaviors of the African rift valley lake fish tend to be more interesting than most, and many - not all - of these fish are less aggressive than the South American oscars and rams. Adaptations these fish have made to survive happily in the African rift valley lakes have been advantagious to this family as a whole.
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If you decide to set up an aquarium, I'm doing well with my twenty gallon tank, although this will limit the types and numbers of fish you can place in it. You will want smaller cichlids, and will want to choose from the less agressive species. SInce many cichlids poke at the ground and eat plants, you may want to avoid the undergravel filter setup, and perhaps limit your plants. I have a filtration system on the tank rated for a 30 gallon. Provide water changes - I do 20% every two weeks (more or less, sometimes I get lazy) for my Lake Malawi fish, and I change the filtration parts by manufacturer's specs. Rule of thumb is one inch of fish per gallon; I think with these fish it is better to err towards less fish per gallon. Be sure not to overfeed, this can be deadly. Not just due to water conditions, but to the fact these guys are voracious and may bloat with over-consumption, and this won't be pretty.
If you do wish to provide appropriate plants, one you may be sometimes able to find in pet stores is Vallisneria, which apparently comes originally from that region, but if being a purist is not an issue, try the Anubias and Java Ferns. These latter can tolerate lower light levels than the Vallisneria. Many of the other plants cannot tolerate the high pH levels required for many African rift lake cichlids. Some crushed coral, which will help keep the water hard, is also not a bad idea. You can also find specific salts for African rift lake fish, but I have not yet tried these.
At the moment I have four electric yellows (see the Labidochromis pic) and two rusty sprengerae (not shown). None of them have bred yet, but I'm waiting. I've gone the plant-free route.
Article Resources:
Wikipedia (all
images, some info)
The
Great Lakes of East Africa
Lake
Malawi Cichlids
Setting
Up an African Lake Aquarium
