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Amphibians threatened by non-native fish and climate change

  • May 19, 2014
  • 441 words
  • 2 minutes
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It ain’t easy being green, particularly if you’re a frog in western North America.

Non-native fish are eating up amphibians in the mountainous areas of the western United States, and the few frogs or salamanders that manage to survive are being taken out by climate change.

But a new study, co-authored by Simon Fraser University ecologist Wendy Palen, suggests that removing non-native fish and using new climate adaptation tools could keep amphibians alive.

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A Cascades frog perched on moss at Olympic National Park, Wash. (Photo: Robin Munshaw, Simon Fraser University)

Non-native fish were largely introduced after the Second World War for recreational purposes. Military aircrafts carpet-bombed large lakes with hundreds of thousands of fingerling trout. Now, in 95 per cent of these lakes, the non-native fish have already devoured entire populations of amphibians.

“The amphibians don’t even try to use the large lakes anymore because they can sense the chemical cues given off by fish,” Palen says.

But they’re still surviving in shallow ponds and wetlands, some scattered around the lakes, which are the main areas of focus for Palen and her colleagues. Amphibians need these areas to remain predator-free so they can breed and feed.

There are two ways to remove non-native fish, and both have their downsides.

The first is using piscicide, a fish poison, which quickly travels through the lakes and kills the fish. Palen says this is the method of last resort because it hurts other things, including amphibians.

The second option would be physical removal, which would require field technicians to put up and take down nets every day for a minimum of four to five years before they can be sure every last fish is caught. Even though this is environmentally safer, it’s also more arduous and expensive.

“We have to figure out which lakes will give us the biggest bang for our buck, so to speak,” Palen says.

The report also raises the issue of these ponds and wetlands drying up as a result of climate change.

In response, Palen and her colleagues developed new maps and hydrological models, adapted from climate forecast models, to predict how water is going to exist in these high-elevation areas over the next 40 to 80 years.

“We can link that with a survey of where amphibians and fish occur in these ecosystems and figure out where fish could be removed to allow a climate refuge for amphibians.”

While these threats also exist for British Columbia’s amphibians, there’s poor documentation of the areas where non-native fish have been stocked in comparison to the United States’ records.


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