(Published Todays Aquarist 1989: Vol. 2)
The Victoria basin in comprised of a group of low-lying lakes, which at various points throughout history have been connected and re-separated by fluctuating water levels. These lakes are Victoria, Kioga, Kivu, Edward and George.
Ecologically and geologically, Lake Victoria is extremely young and represents an awesome but messy evolutionary explosion. Located in equatorial East Africa, adjacent to the Great Rift Valley, Victoria, like the Rift lakes, boasts an incredibly diverse cichlid fauna, 90% of which is endemic to the lake with 100% endemic to the basin.
Little Competition Til Now
The restricted access to these lakes after their formation less than 750,000 years ago gifted the endemic Haplochromines with little or no competition and the run of at least one immense body of water. The resulting rapid rate of speciation exhibits itself today as over 250 species and, until the introduction of the Nile perch, Lates nilotica (see Todays Aquarist Vol. 2 No. 11); there was no reason to believe that it was finished.
Although Lake Victoria’s taxonomic problem is not unique, it is certainly the largest problem of its kind. Many of these 250+ species (now know to be 600+ spp.) are so closely related and so variable that classification by the usual means of comparative morphology is impossible.
Dr. P.H. Greenwood, Department of Zoology, British Museum, revised many of the Haplochromines into several single-species genera. The haplochromine “species-flock” is in an early and apparently very plastic stage of evolution. All the species are different but not different enough to define evolutionary connections. Where discernible characteristics are found they are used but, in many cases, it just is not possible to tell where the relations lie. Adding to the problem is the plasticity of the progeny, even within a discernible species. Teeth bones and meristics are plastic. They are all capable of changing with the diet of the animal.
As reported here last month, this vast treasure house is in grave danger of partial or total destruction at the hands of an. Recently, a multinational team of researchers visiting Kenya concluded that the introduction of the Nile perch is the most destructive of the three possible factors in the collapse of the lake. Regional development and over-fishing were also evaluated.
Many May Already Be Extinct
Hardest of those species hit occur in open water: planctivores and piscivors. Many of the lake’s predators may already be extinct, unable to compete with the perch for food as well as for space. Much of the shallows, shoreline and certainly the swamps remain reasonably intact. In various locations, sexually active adults are just half the size of those reported only recently; their larger counterparts presumably picked off. A large section of the deep lake, previously inhabited, has been found to be anaerobic, possibly due to the perch’s devastation of the lake’s planctivores fishes. The additional organic matter decomposing in the depths of the lake could be responsible. Oddly enough, there seems to be at least one haplochromine capable of surviving in water where the oxygen concentration is so low the perch cannot live. An adaptation of this sort is an indication that the deep lake may have a history of a fluctuating dead zone. This might turn out to be a haven for those endemic fishes capable of surviving since the oxygen level is too low for the perch.
Around the world, there are numerous species, which are threatened, endangered or even extinct for one reason or another. The black ruby barb, Barbus nigrofasciatus, a reasonably common fish in the aquarium hobby, is now extinct in its Sri Lankan native habitat due to over-fishing and habitat destruction. Because of commercial reproduction, this particular species will survive but others will not.
The key words for the future of the aquarium hobby are conservation biology. Few aquarists will have access to wild founder stock of endangered species, but any stock, which is traceable, will suffice. In the interests of conservation biology, where endangered species are concerned, we need to make every fish count.
Become Aware of Fishes’ Ecosystems
As conservation biologists, aquarists need to be more aware of the ecological systems, which supply our aquarium fishes. We also need to be more aware of the aquarium hobby as it relates to the scientific community.
With access to information, it becomes a simple matter of common sense. Obviously, if a species is threatened by over-fishing then a large-scale collection of wild stock would be detrimental to that species. The solution in a case of habitat destruction would be quite different. Aquarists not informed of the facts could well be causing a problem instead of working towards its solution. The attitude of the aquarium hobby must shift from one of individualism to one of teamwork. If, for instance, a dealer were besieged by customers wanting the collection locations or sources of any cichlids they purchased, that dealer will respond with questions to his supplier and become a team player himself in the process.
Hobbyists on the Front Lines
The hobbyists, even today, is on the front line of ichthyology. Yet this front line is under-utilized because it has little organization and no goals. Consider the example of an enthusiastic hobbyist, having learned much about fish, but refusing to keep a notebook. No lasting contribution will have been make after his of her passing. All that information will be lost and, typically, re-learned and re-lost again and again. A team player’s notebook can, long after their death, communicate in hours what has taken years to compile.