wes_von_papineäu
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HAMILTON SPECTATOR (Ontario) 19 August 09 Goldfish cull coming to conservation area; Fish dumped in ponds threaten rare salamander (Eric McGuinness)
Tens of thousands of goldfish in two Dundas Valley Conservation Area ponds will be poisoned this fall to protect habitat for the endangered Jefferson salamander.
The Hamilton Conservation Authority says someone is using the ponds as an illegal fish farm, introducing the Asian fish to let them breed, then netting the offspring to be sold as live food for aquarium fish.
Some might also be sold for use in back yard ponds, but authority ecologist Shari Faulkenham says the fish lose their gold colour unless bred in controlled conditions.
Authority board members recently approved a plan to kill the unwanted goldfish with the botanical pesticide rotenone, because the invaders are eating salamander eggs. Dundas Valley is one of only 34 recorded Canadian breeding sites for the Jefferson salamander.
An estimated 50 goldfish were found in the McCormack Pond in 2005. The number has grown to an estimated 40,000, despite the use of traps, nets and electrofishing tools to capture and remove them. Faulkenham says the once-pristine pond has turned into a brown pool of goldfish-churned silt, and new goldfish continue to be dumped.
The number in the other pond, at the site of the former Merrick Field Centre, is put at several hundred.
Faulkenham says the goldfish are a special threat "because they are omnivorous; they eat both plants and animals, whatever they can get into their mouths, potentially even an adult salamander."
She calls poisoning a drastic measure, but says it's been judged to be the most effective and least destructive solution.
Rotenone, derived from tropical plant roots, is federally approved for killing fish, though other uses are being phased out. The authority is seeking provincial permission to use it on the ponds.
The World Health Organization considers the chemical extremely toxic to insects and aquatic life, but only moderately toxic to humans and other mammals. The authority says birds or other mammals consuming water or fish treated with rotenone would have to ingest at least 1,000 times their normal daily intake to be harmed. It says a 160-pound human would have to drink 87,000 litres of treated water in one sitting for the dose to be lethal.
Faulkenham says the only other creatures likely to be affected are green frog tadpoles, though they are not normally susceptible to the dose needed to eradicate goldfish. She says the green frog is common, its populations are strong and any tadpoles showing signs of distress will be removed and put in untreated water until the rotenone breaks down and disappears.
Authority members were told the plan is supported by the Ministry of Natural Resources, the province's Jefferson salamander recovery team and the Hamilton Naturalists' Club.
Asked how the authority can stop illegal re-stocking of the ponds, Faulkenham said more monitoring is planned, along with explanatory signs and efforts to educate visitors not to release pet fish and keep watch for others doing so.
Her message: "Don't even put fish from your fish tank in our ponds. Don't dump your stupid fish in our ponds."
http://www.thespec.com/News/Local/article/620832
Tens of thousands of goldfish in two Dundas Valley Conservation Area ponds will be poisoned this fall to protect habitat for the endangered Jefferson salamander.
The Hamilton Conservation Authority says someone is using the ponds as an illegal fish farm, introducing the Asian fish to let them breed, then netting the offspring to be sold as live food for aquarium fish.
Some might also be sold for use in back yard ponds, but authority ecologist Shari Faulkenham says the fish lose their gold colour unless bred in controlled conditions.
Authority board members recently approved a plan to kill the unwanted goldfish with the botanical pesticide rotenone, because the invaders are eating salamander eggs. Dundas Valley is one of only 34 recorded Canadian breeding sites for the Jefferson salamander.
An estimated 50 goldfish were found in the McCormack Pond in 2005. The number has grown to an estimated 40,000, despite the use of traps, nets and electrofishing tools to capture and remove them. Faulkenham says the once-pristine pond has turned into a brown pool of goldfish-churned silt, and new goldfish continue to be dumped.
The number in the other pond, at the site of the former Merrick Field Centre, is put at several hundred.
Faulkenham says the goldfish are a special threat "because they are omnivorous; they eat both plants and animals, whatever they can get into their mouths, potentially even an adult salamander."
She calls poisoning a drastic measure, but says it's been judged to be the most effective and least destructive solution.
Rotenone, derived from tropical plant roots, is federally approved for killing fish, though other uses are being phased out. The authority is seeking provincial permission to use it on the ponds.
The World Health Organization considers the chemical extremely toxic to insects and aquatic life, but only moderately toxic to humans and other mammals. The authority says birds or other mammals consuming water or fish treated with rotenone would have to ingest at least 1,000 times their normal daily intake to be harmed. It says a 160-pound human would have to drink 87,000 litres of treated water in one sitting for the dose to be lethal.
Faulkenham says the only other creatures likely to be affected are green frog tadpoles, though they are not normally susceptible to the dose needed to eradicate goldfish. She says the green frog is common, its populations are strong and any tadpoles showing signs of distress will be removed and put in untreated water until the rotenone breaks down and disappears.
Authority members were told the plan is supported by the Ministry of Natural Resources, the province's Jefferson salamander recovery team and the Hamilton Naturalists' Club.
Asked how the authority can stop illegal re-stocking of the ponds, Faulkenham said more monitoring is planned, along with explanatory signs and efforts to educate visitors not to release pet fish and keep watch for others doing so.
Her message: "Don't even put fish from your fish tank in our ponds. Don't dump your stupid fish in our ponds."
http://www.thespec.com/News/Local/article/620832