Tainted fish in Nevada lake linked to mercury in loons

Tuesday, June 22, 1999 | 9:32 a.m.

The loons gained elevated levels of mercury by eating tui chub at Walker Lake, said Dave Evers, director of the Biodiversity Research Institute in Freeport, Maine.

Tui chub is the bird's primary food source during their spring and fall stops at the lake.

"For wildlife health issues, the fish there are extremely high (in mercury)," Evers said. "They have mercury levels that do put wildlife at risk."

In April, researchers took blood samples from 20 loons at the lake. The results show seven loons had blood mercury levels above 3 parts per million and four had levels above 4 ppm.

Levels between 3 ppm and 4 ppm are risky to the loons' health and reproductive systems. Levels above 4 ppm pose high risks.

Evers theorizes that the longer the birds stay at the lake, the higher their blood mercury levels are.

The source of the tui chub's mercury contamination is unknown and more research needs to be done on it, said Mike Yates, a University of Maryland research center biologist.

"(The loons) are a sentinel for what's happening in the environment," he said. "Maybe a half a part per million of mercury doesn't hold any threat to human beings, but human beings aren't the only thing on the planet."

Nevada Wildlife Division officials have said the loons are picking up the contamination elsewhere, possibly their summering or wintering grounds.

But Evers said he doubts the birds are exposed to significant mercury levels at their wintering grounds, which are believed to be along the Baja California coast.

Ocean environments typically have much less mercury contamination than inland lakes, he said.