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August 08, 2007

Fish could help fight malaria

...by eating the malarial mosquitos' larvae. [BBC]

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But Rachel Carson eats fish as part of her ongoing attempt to kill people through malaria, so we should abolish the EPA. And cut taxes.

The fish don't eat the malaria parasite's larvae, they eat mosquito larvae.

The malaria parasite is a protozoa, a single-celled animal, which doesn't have a larval stage. Mosquitoes are the vector by which the parasites travel from host to host.

We should be very cautious when distributing fish about, for whatever purpose. Use of fish for mosquito control has a checkered history. The little mosquitofish, Gambusia affinis and G. holbrooki (Recently split into two species from G. affinis.) from the Southeast US has been spread all over the world to the point that it (they) probably now have the greatest range of any freshwater fish. There’s no doubt that they’re voracious little mosquito eaters, I’ve kept them and fed them mosquito larvae. It’s a “Jaws” microcosm, they’d eat until larvae were bloating their bellies and hanging out of their mouths and were still going for more. They were however also eating the fins off of goldfish in the same tank. In waters in which they are not native they’ll eat the fry of other fish, amphibian larvae, and the food that native fish depend on. They have driven several species of fish and amphibians to extinction or to the brink of extinction. They’re also ecologically tolerant and tough as nails, and once established in open waters, basically impossible to eradicate.

Government policy is contradictory with respect to Gambusia. In California for instance, state law prohibits introduction of mosquitofish into open bodies of water, but you can pick up free mosquitofish from county mosquito abatement agencies for your stock pond, irrigation ditches, abandoned swimming pool, or whatever.

Nile tilapia have now established themselves here and there along the US Gulf coast. The same characteristics that make them useful for aquaculture – tolerant of low oxygen levels, feed at low trophic levels, fecund- also enable them to colonize new waters readily. Even if carefully confined to aquaculture facilities they will eventually escape – just wait for a hurricane. Their effect on the ecology of Gulf Coast rivers and bayous is as yet little understood, but we shouldn’t be surprised if things go awry.

All of which should not be taken as blanket condemnation of aquaculture or biocontrol of mosquitoes, for both of which there is a compelling need, particularly in poor countries. We should however address fish introductions with the utmost circumspection.

But, cfrost, if the fish get out of control, they can bring in Australian mud snakes to eat them. If the snakes get out of control, they can bring in Tasmanian mongooses to eat them. If the mongooses get out of control, they can bring in gorillas to eat them. So, no biggie.

Some variety of Tilapia have been used in the ponds in the area of India where I lived for mosquito control for quite a long time now.

I put the Gambusia in a free-standing swimming pool (from which water is pumped to a larger pool, for nursery irrigation) to eat mosquito larvae, and they've traveled through the pump & up 50' of garden hose to the "big pool". They're tough- & I'd hate to see them in a "wild" setting, locally. I don't wanna use poisons (& don't)- but will probably have to drain both pools to really eliminate them here. The grass carp that were introduced into the Columbia R system decades ago are everywhere in the river basin- in irrigation canals, reservoirs, larger tributaries, etc. cfrost is right- spreading fish around- for whatever reasons- is an ecological nightmare, in most cases (maybe in All cases, eventually). Mosquito larvae (mini-shrimp) are important food for most native fish here... and that's probably true wherever there are fish & mosquitoes sharing a habitat. chow ^..^

herbert browne, - the E.P.A. currently permits four piscicides, of which two are for lampreys, leaving antimycin and rotenone for anyone wanting to poison fish in a situation such as yours. Both are relatively benign when used properly. Antimycin and rotenone are very toxic to fish and you’ll also lose any frogs or newts using the water. They break down rapidly however, and if used responsibly do not threaten people or pets and have no lasting effects other than killing your fish. Read up on them thoroughly before making any decisions.
If they sound familiar, it's because antimycin is also used as an antibiotic and rotenone as a pesticide.

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