Trout may be the favourite fish of South African anglers, but they are dangerous interlopers who wreak havoc on our ecosystems, argues Jim Cambray
BETWEEN 1850 and 1950, there was a dramatic increase in the rate of animal extinctions, which coincided with European colonial expansion. Many alien plants and creatures were introduced to colonised territories, some with disastrous consequences.
One of these was the rainbow trout, which is still being moved, in many cases illegally, around South Africa, New Zealand, Australia and other countries. It is still being introduced into river systems where local species have been living and evolving for many thousands of years. In the light of present-day knowledge, this is truly eco-terrorism.
Good environmental impact studies must be carried out before any plant or animal species is introduced. The ardent trout angler may say “trout are an important resource” or simply that “a person likes to eat trout”. But one misguided person with a breeding pair of fish can cause irreparable harm to endemic species.
There are enough case histories in the world to warn us. Take, for example, the introduction of Nile perch into Lake Victoria: it is now estimated to have resulted in the extinction of more than 250 fish species.
In the Olifants River in the Western Cape, alien trout and bass were introduced to “improve” the fishing. The result has been catastrophic and this river now has a high number of endemic freshwater species in the Red Data Book, the log of species close to extinction. This is indeed nothing to be proud of. It was also completely unnecessary, as there was already one of the best South African angling species, the Clanwilliam yellowfish, in the river system, a fish that grows larger than trout or bass. It was clearly lack of good impact studies and introducing what one already knows. This is a recipe for disaster.
Recently, a small fish resembling trout was found in the Eastern Cape’s Krom River – the Cape galaxias. The Cape galaxias is an interesting, indigenous freshwater species, with relatives in Australia, New Zealand, South America and on many islands. It is possible that they have been living at the southern tip of Africa since the break-up of Gondawanaland, millions of years ago. They are now threatened by the introduction of alien predatory fish like trout.
In fact, in New Zealand, alien trout have possibly caused the extinction of several near-relatives of our Cape galaxias.
So what is the myth of trout in this arid country of ours? Is it the assault on the mind by all those cigarette and alcohol advertisements with a trout neatly laid out on the damp grass, reel and trout flies artistically arranged near the dead or dying fish? Surely informed and educated people can understand that introducing alien species, whether it is trout or black wattle, may cause species extinctions and environmental impacts on entire aquatic ecosystems.
South Africa has signed an international convention on biological diversity and we need to follow through on those principles. The original introductions of alien species were once thought to be beneficial. But today we should and must know better.
Moving fish around the country is an offence. It is illegal to move fish without permits because these introductions can result in irreparable harm to the biodiversity of aquatic ecosystems. If you are found guilty of introducing fish without permits in some parts of Australia, the fine is $50 000, as well as eradication charges.
I would strongly recommend that South African environmental policy-makers also implement heavy fines for offenders. We have just passed through a period of political terrorism: let us now move away from eco-terrorism, even if it means the end of trout.