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The Congo Basin Piedmont Rivers and Streams ecoregion contains many types of fish that can't be found anywhere else. On the rivers and streams of the Congo River Basin, you may hear the splash of swamp otters hunting for food, see a group of Allen’s swamp monkeys resting in a tree, or snoutfishes that use electric currents to find their prey. You will also hear the sound of raindrops hitting the trees -- it rains year-round in this ecoregion. More than 700 fish species live in the rivers and streams that flow through this vast rain forest, and 80 percent of them are found nowhere else.
Floodwaters flow from the northern tributaries between August and November and from the southern tributaries between May and June. During flooding, the river spills from the main channel over the floodplain and into the rain forest. Synchronized with this flooding is the spawning of many fish. Most species move upstream with the onset of flooding, then onto the floodplain to mate and lay their eggs. Here the fish and their young take advantage of the abundant food. The flooding allows nutrients from the land to enter the aquatic food chain and support the Congo Basin’s extremely rich diversity of fish species. A network of connecting waterways crisscrosses the Congo Basin. For example, the Kasai starts in the hills of Angola and feeds several rivers on its journey toward the Congo. When the Bomu and Uele rivers meet, they become the Oubangi, one of the Congo's largest tributaries. And it's only when the Lualaba tumbles across Boyoma Falls that the Congo begins.
Nearly 700 species of fish have been identified here, but scientists think there could be many more. About 80 percent of fish species are found only in the Congo basin and some may live only in one forest stream. The snoutfishes, which are mostly active at night, use electric currents to detect prey and predators and to communicate with one another. When body weight is taken into consideration, the brain size of this unique fish is comparable to that of humans. Endemic or near-endemic aquatic mammals include the aquatic genet, swamp otter, Ruwenzori otter shrew, giant otter shrew, and Allen’s swamp monkey.
Several urban centers in the Congo Basin are growing, and with their growth comes the potential for an increase in untreated sewage and other sources of pollution that could harm nearby freshwater systems. Sedimentation and erosion also occur near logging operations. A few industrial-scale mining operations exist in the Congo, but they probably affect only localized areas.
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