Poisoning fish as part of nature conservation

Robert Oppenheimer was the scientific director of the project to build the first nuclear bomb.

In an interview from 1965, Oppenheimer describes the initial reactions as the very first nuclear bomb (the Hiroshima bomb was the second one, detonated early in the morning of July 16, 1945): "We knew the world would not be the same. A few people laughed . . . A few people cried . . . Most people were silent. I remembered the line from the Hindu scripture, the Bhagavad Gita: Vishnu is trying to persuade the prince that he should do his duty, and, to impress him, takes on his multiarmed form, and says, 'Now I am become death, the destroyer of worlds.' I suppose we all thought that, one way or another . . ."

One thing that has never been really satisfactorily explained is why they tested the first bomb where they did – at White Sands Proving Ground, in New Mexico, US. There were many areas of the US they could have chosen but, instead, they chose White Sands.

My theory is that fission bombs (like that of the first test at White Sands) produce lots of heat – in fact, about 10 000 000 degrees Kelvin (certainly enough to fry an egg on a car bonnet). I think that the scientists knew that it was possible to make a fusion bomb (in which hydrogen isotopes are brought together to give off energy) and there was a small possibility that, if they did their ten-million-degree test in a humid atmosphere (containing H2O), then their fission bomb would become a fusion bomb and blow up the whole planet.

So they chose White Sands because it was very, very dry. Which brings us (quite obviously) to the plan to poison fish in four rivers in the Cape. CapeNature has embarked on an environmental-impact assessment (EIA) to look at the best methods of eradicating alien fish (such as trout), and has indicated that a poison called Rotenone is the preferred option.

CapeNature has identified the Krom, the Suurvlei and the Rondegat rivers, in the Cederberg, and the Krom river, in the Eastern Cape, where it believes alien fish should be eradicated.

It is not the first time Rotenone has been used to kill off fish (and everything else in the river) – it has been used to kill off fish in the US. But it is the first time it will be used in South Africa with the blessing of an EIA. (Oh, CapeNature has used Rotenone to kill off carp in the Cape Flats area but nobody knows about that).

There's much debate on the subject. All those in favour say that alien fish do a lot of damage – they kill off indigenous fish, and so on. All those against say that they like fishing and the trout have been around for 100 years and there are still plenty of indigenous fish in the rivers after 100 years.

The argument that nobody seems to address is that Rotenone is a poison. It has been linked to Parkinson's Disease symptom in rats. And we will be dumping a poison into a river from which people and animals drink! This makes the idea of doing this very, very stupid, to say nothing of the ecological effect of 50 tonnes of dead fish in any river.

So why am I writing about this in a column about electricity? Simply this – there are, on the market, plenty of electric fish fences. In Lake Seminole, they successfully confine grass carp to an embayment using a pulse fish fence operating at about 5 V dc. So, what you do is this: decide that, say, the upper part of the river must be trout free. Put up an electric fish fence. Using nets or electrofishes fish out the river above the fence. Or even better, use blasting shock cord to kill them. Put in indigenous fish. Sit back, watch them grow up to a mighty three inches long. But poison? Does CapeNature know its long-term effects? Did Oppenheimer know if the first bomb would blow up the world? Is CapeNature insane?