The advisory recommends that people limit consumption of striped bass caught from Dangling Rope Marina in Utah to Glen Canyon Dam in Arizona.
Regulators say striped bass consumption in the lake's southern portion should be limited by pregnant women and children.
They say it's still safe to consume other fish species in the lake and to eat striped bass in Lake Powell at or below recommended consumption rates.
Authorities recommend, for instance, that pregnant women and children younger than six years old limit their consumption of striped bass to one four-ounce meal per month.
Regulators say mercury is a naturally occurring element that can be transformed into a toxic form.
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