Meet the Rotenone experts.... 1 March 2012

[JustinM]

If the extremist few rotenone the trout out of the Western Cape streams I'd say there's a very good chance of someone simply sneaking a few back into the system after it has recovered... I don't believe trout are the monsters they are made out to be and I'm struggling to find a reason why I would morally object to this...

The great pity would be the loss of a hundred's years worth of wild evolution which has seen the trout adapt completely to the local environment and at times pretty high water temperatures.

Just my two cents worth.

[Andre]

May be a bit heavy for a Monday morning...

What are the effects of rotenone on DNA and the cell damage to animals / people ?
If Roundup can still cause cancer and DNA damage when diluted 99.8%, what damage is going to be done to those animals that drink the water or fisherman ?

Everyone is concerned about the killing of trout, but what are the long term effects on us and animals further done te food chain ?

Apparently no ill effects to any of these. Or so we are led to believe. It only effects animals with gills, and works by preventing them from diffusing oxygen, so it would kill the fish, tadpoles, most insect larvae etc. Also because it is a natural non chemical poison, (made from cactus leaves of the euphorbia group), it biodegrades very quickly, and allows the system to repair very shortly after application.
This is what I have been told, so if it's all lies, blame the pundits.

[JustinM]

Leaving aside the question of what further 'harm' trout can do than what has already been done by their introduction and existence in the ecosystem for circa 100 years. If the purpose of removing the trout in the first place is to protect the native minnow species and native frogs from trout predation, how will rotenone discriminate between exotic and native species? Or do the native minnows face utter annihilation too?

[ebf]

Interesting to see this saga still going on.

You guys might be interested in Rotenone use halfway round the world.

I do some volunteer work at a "onshore island" - mammalian predator fenced - sanctuary over here. Majority of the work around bird species, but there is a doctoral thesis student doing research into native fish species called banded kokopu.

The sanctuary has two dams (with perch and brown trout), connected by a stream. Dept of Conservation has previously used Rotenone on lakes over here in NZ, but this is the first trial they know of in running water.

The kokopu seem to be doing ok, as well as the native freshwater crayfish (koura). Also started doing feeding of the freshwater eels as part of the visitor education program :-)

As you can imagine in a country where nature conservation and agriculture are the main economic drivers, there are all kinds of heated debates around conservation. 1080 poison use against possums (and the resulting effect of native birds, koura) probably being the largest debate.

[William Ewels]

Apparently no ill effects to any of these. Or so we are led to believe. It only effects animals with gills, and works by preventing them from diffusing oxygen, so it would kill the fish, tadpoles, most insect larvae etc. Also because it is a natural non chemical poison, (made from cactus leaves of the euphorbia group), it biodegrades very quickly, and allows the system to repair very shortly after application.
This is what I have been told, so if it's all lies, blame the pundits.

Thanks Andre - good info.

Yes that sounds correct and it is a VERY scary thing. The fish, frogs, insect larva etc carry localised genetic diversity which has taken thousands if not hundreds of thousands of years to develop. It certainly is possible to recolonise/restock organisms in a stream after it has been cleaned out - from specimens taken before the rotenone or from elsewhere - but it will always cause some degree of GENETIC BOTTLENECK so the local genetic diversity will always be poorer in EVERY SPECIES affected - leaving the total ecosystem more fragile than before.

When they re-seed the river after rotenone treatment, can they guarantee they've included rare copies of genes in every species that helped those species survive extreme conditions or diseases 1000 years ago and might be needed again in the next 1000 years? Of course not!

Netting and electrofishing can be highly effective on target alien species in a river if done with a bit of thought and tenacity - with near zero impact on genetic diversity of the underlying ecosystem they claim to be trying to save.

[ArcherFish]

Just an aside.

On Sunday I found galaxias in a trout stream, the jan du Toits is full of cape kurper and redfin.
Indigenous fish survive in trout streams so whats all the rotenone shit about?

[MarkK]

Just an aside.

On Sunday I found galaxias in a trout stream, the jan du Toits is full of cape kurper and redfin.
Indigenous fish survive in trout streams so whats all the rotenone shit about?

Indeed. I occasionally fish tiny Cape streams that have harboured trout for as long as they've been in the country, and several of them have strong populations of Galaxias / Sandelia and/or redfins. The simple truth is that habitat controls what survives where. In addition, there are better and less destructive treatments than Rotenone available - the podcast link below is interesting in that respect. Now if trout aren't really that destructive and Rotenone isn't the best tool for the job, then what's really going on here? Sadly I've given up trying to find out - after their rigged EIA what's the point?

http://www.itinerantangler.com/podca...podcast_s.html

[Ryan]

The only fish I care about getting rid of, is the bass in the olifants system and out in the Cederberg.

[Appin69]

Right, so we will be deliberately polluting, sorry poisoning, oops cleansing a river to restore the ecological balance of said river to predetermined period in its history. So lets forget the water abstraction, the farming prctices right up to the banks, the buiding of dams and weirs (legal & illegal), gravel mining, sewage overflow, fertilizer and pesticide runoffs that affect rivers. To create these utopian ideals of our rivers we need to remove all our influence. The reality is that we can't.
My opinion is that too many reputations have been placed on the outcome of this issue for it not to happen. The only loser at the end of the day is the very thing that is meant to be protected!

[Fario]

I don't recall any threads being deleted but maybe I am wrong? If this one wasn't deleted then I wonder about the others?
http://www.flytalk.co.za/forum/showt...light=Rotenone

stirrer