Lake Victoria s eye-openers
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CTA. 2002. Lake Victoria?s eye-openers. Spore 99. CTA, Wageningen, The Netherlands.
Permanent link to this item: http://hdl.handle.net/10568/47568
Internet URL: http://spore.cta.int/images/stories/pdf/old/spore99.pdf
Some 20 members of the cichlid fish family supposedly extinct - have adapted remarkably to the changed environment of Lake Victoria and are back in business. Scientists were surprised to learn in 1997 that local fishermen were catching cichlids...
Some 20 members of the cichlid fish family supposedly extinct - have adapted remarkably to the changed environment of Lake Victoria and are back in business. Scientists were surprised to learn in 1997 that local fishermen were catching cichlids again, and hurried to understand why. Way back in the 1950s, fry of the Nile perch was planted in the lake. This large, protein-rich, predator fish, was believed to be more useful and nutritious for the lake-shore communities, than the small, bony collection of more than five hundred, closely related types of cichlids that swam there at the time. By the 1980s, it was clear that an ecological disaster had been triggered off. The Nile perch fed on the local fish, reducing their numbers. The volume of algae, the cichlid s food, rose sharply. This reduced the amount of light and oxygen and threatened some fishes survival, since they could no longer pick out fine algae for feeding, nor potential partners for breeding. All in all, two hundred local fish species disappeared. The 20 species that did recover, owe that largely to their eyes and to natural selection and adaptation. Research by the Institute for Evolutionary and Ecological Sciences, of the Netherlands Leiden University, and local partner institutions revealed, in February 2002 that the least light-sensitive species, such as the Haplochromis pyrrhocephalus, were the least bothered by the changed environment. In addition, they have adapted their eyes to less clear and bright water and started to prey on larger organisms, which are easier to see. The survivors also adapted their gills. Compared to their ancestors from the 1960s, they can now increase the oxygen intake from the oxygen-poorer water. The sieve in the gills became more coarse-threaded enabling them to handle larger prey. The twenty survivors offer a small glimmer of hope about the adaptability of nature, even if they take nothing away from the ecological disaster in Lake Victoria. [caption to illustration] Sleek, smart and adaptive, the Haplochromis pyrrhocephalus can see in troubled waters too