The Associated Press

DETROIT (AP) — Crews have dumped 25,000 tons of limestone blocks into the Detroit River as part of a mission to restore lake sturgeon.

The ancient fish can reach 7 feet long, weigh more than 300 pounds and live longer than a century. They once were plentiful in the Great Lakes but fell victim to overfishing and habitat destruction. They’re now threatened or endangered in most of the region.

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