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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The limestone deposit added 4 acres of spawning reef areas for sturgeon near Detroit’s Belle Isle.

The federal government has provided about $10 million for a series of reef construction projects in the St. Clair and Detroit rivers.

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Experts say the reefs are attracting egg-laying females. But because sturgeon mature slowly, it could take decades to determine whether the efforts are boosting the population.


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