Belle Isle's Mudpuppies: Monitoring fragile amphibians along Detroit River

(FOX 2) - Hidden beneath the rocky shoreline along Belle Isle are slimy salamanders sporting purple gills and a shy persona.

Mudpuppies are fully aquatic amphibians and one of the best measuring sticks for understanding the health of the nearby environment. They're also the focus of years of monitoring by researchers at the Detroit Zoological Society who hope to better understand both their populations and the water quality of the Detroit River.

Mark Vassallo was among those outside on Belle Isle's southern shoreline looking out for one of these creatures during a late winter morning.

"This is Mudpuppy weather. Mudpuppies prefer colder water, they prefer to come out in the winter and breed. To them, this is a great day out," said Vassallo, who is the curator of the amphibian department at the Detroit Zoo.

Mudpuppies in the Detroit River

For the past several years, Vassallo and his team have laid nets along the island, using bait to trap mudpuppies. After collecting them, their size, gender, and health are assessed.

Based on what they find, researchers can use them as an early warning system for better understanding water quality. 

"Their health is basically indicative of the health of the environment at large. That means their physiology, their skin is very porous, so they're like a sponge," he said. "If there are any contaminants, any toxins in the water, the mudpuppies are going to be the first ones that feel that. That can help us gauge the overall health of the ecosystem here on the Detroit River."

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Up against the challenges that fragile animals can face, mudpuppy numbers are declining around the Great Lakes.

But along the Detroit River, the state of the environment is not so dire. From Vassallo's vantage, the amphibians are coming to Belle Isle.

"They're raising their young here and they seem to be very comfortable. I think it's because there's such a great biodiversity of fish here. There's a lot of food for them. Mudpuppies eat invasive species too, so they're eating round gobies and zebra mussels, so they're ecological warriors in a way," he said.

Monitoring the species

Researchers from the Detroit Zoo monitor the mudpuppy numbers with the help of modified minnow traps. 

In Early March, those teams laid the traps along the shoreline and waited a day. With rope tied to one end and staked along the beach so they don't drift away, the same teams returned 24 hours later and used a tool to scan any trapped mudpuppies for tags.

Those tags track the amphibian's movement, giving researchers vital information about where they have traveled, if they've gained weight, and how they spend their day. 

"It gives us a little peek into the reclusive lives of mudpuppies, which is really what this survey is all about is learning more about them," said Vassallo. "We know so little about them, so coming out here we're able to fill in those gaps."