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Time to mop up the 'alien fish spill!'
By Dr Jim Cambray
Albany Museum, Somerset St. Grahamstown, 6139, South
Africa.
 Think about that fish you just caught? There you stand with your proud catch of a 2 kilogram rainbow trout. Have you ever stopped to think if this fish is indigenous
or not? You look around, the river is beautiful, a nice flow, lovely indigenous vegetation, a lovely rock face in the distance where the river meanders towards you, cool clear weather, ah this is perfect. Not
so.
That fish in your hands is a North American species which has been introduced into over 80 countries around the world. It has seriously impacted on the diversity of freshwater fish in the world. Those waters in which you cast your trout fly should hold populations of indigenous species which have evolved with the system over many thousands of years.
But why should you care? You should be proud of South Africa's natural heritage. Not only is the elephant, lion, buffalo, hippo, kudu part of this heritage so are the indigenous aquatic animals. These fish are more or less trapped in the river, there is no escape for them. If we pollute the stream with chemicals or pollute it with alien fish species which will eat or compete with them for resources we loose aquatic biodiversity.
But how did this problem start?
There is quite an interesting history about fish introductions into South Africa. I will not go into this in any detail. One interesting aspect is that some of the provincial nature conservation departments started off with hatcheries which bred alien species, such as bass and trout to stock in inland waters. Even in the Olifants River in the Western Cape bass and trout were introduced as angling species. This was, even at that time, ridiculous as this river had one of the finest and largest species of yellowfish, the Clanwilliam yellowfish, which was an excellent angling species. Suffice it to say that these embryonic conservation bodies made a huge mistake. This is historical and at the time it was happening around the world. That it still happens today is difficult to defend with the knowledge we have. Introduced predatory, as well as non-predatory, aquatic species have had and are having a major impact on South Africa's indigenous aquatic biodiversity.
What are the solutions?
Rivers by their nature are difficult to manage. They usually flow through many farms, villages and towns and sometimes different countries. For example you may be perfectly environmentally aware of the dangers of introducing alien species into the river that flows through your property BUT your neighbour puts in bass or trout. They are not confined to one section of the river and depending on water quality and temperature they can penetrate into your conserved section!
But all is not lost there are solutions:
Solution one:
Legislation - it is illegal to transport live fish without a permit. There are fines if you are caught. I believe these fines should be increased and include confiscation of the vehicle and trailers used. Environmental Impact assessments (EIA) have to be done prior to any stocking. If there are sensitive indigenous aquatic species present then a proper EIA will stop the introduction.
Solution two:
Educate the public. This would make people more aware of the dangers of introducing these alien species. In fact this article is part of the awareness campaign. My web-site is also part of this campaign:
http://www.ru.ac.za/albany-museum/m&g.html
Solution three:
It would then be up to the public to watch and inform the authorities of illegal movement of fish. You can imagine that the understaffed and under-resourced nature conservation departments can not be always in the right place at the right time. If you have no joy with the conservation department then approach an organisation that is an environmental watchdog, such as the Wildlife and Environmental Society of South Africa ( WESSA).
Solution four:
Some rivers can be rehabilitated. This will cost money as the alien species have to be removed and the indigenous species re-introduced in some cases. But it is a positive step and one in which conservation clubs can help. You may even equate it to the recent oil spill disaster which threatened penguin colonies in the Cape. On the freshwater fish side we have had a ‘spill of alien fish species' these now have to be mopped up.
Future implications for biodiversity:
The future scenario is quite bleak. There are 10 000 species of freshwater fish in the world. This is about 25% of the known vertebrate species. Of these 10 000 species we have estimated that as many as 3 000 will be extinct, gone forever, within 20-30 years. This is an alarming statistic and should make us all want to help where we can. One easy way is to not stock any more alien fish species into our rivers.
Paradigm shift:
So the next time you are near a river, try looking at the freshwater systems from a different light. Not for what angling fish they have in them, but for what indigenous species are there. Watch the dragonflies mating, the kingfishers catching small minnow species, listen to the soothing flow of the water. Take a walk along the bank note the frogs, the weaver's nests, the loud splash of a leguaan which had been sunning itself and now retreated to the water for safety. Think about the hidden treasures under the water, the minnows and the wide variety of aquatic invertebrates. This is the kind of experience that will keep freshwater ecosystems in tact. These sources of freshwater are essential for our own continued existence, after all we are ourselves 70% water!
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