FORT MYERS BEACH (CBSMiami/AP) — Biologists are continuing to perform necropsies on eight pilot whales that died in shallow waters off southwest Florida.

Officials with the National Oceanic and Atmospheric Administration’s Fisheries Services planned an aerial survey Wednesday morning of the waters off Lee County.

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Dozens of pilot whales swam close to shore earlier this week in Lee and Collier counties. Eight whales have died in the waters off Lover’s Key State Park, and officials said six other whales were unaccounted for.

In December, more than 50 pilot whales stranded in Everglades National Park. Several died.

Pilot whales typically live in deep waters far from shore.

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Pilot whales live in deep water and usually make their home at least 20 miles off the coast of Florida, so when they swim inland, that’s often a sign they are suffering from some kind of toxicity or disease, said Blair Mase of the National Oceanic and Atmospheric Administration’s Fisheries Service.

These whales tend to travel in pods of a couple dozen or more and follow one or two leaders, or navigators.

“They have a very tight knit social structure, which helps them survive normally, but if two swim in to shore, the others will follow,” she said.

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