(CNN) A man in Florida could face up to a year in federal prison and a $50,000 fine after witnesses said they saw him kill an endangered smalltooth sawfish by removing the long, flat saw that gives the fish its name.

Chad Ponce pleaded guilty Friday to killing an endangered species, according to a news release from the US Attorney for the Middle District of Florida. Prosecutors said he was seen on a boat off Ponte Vedra last year using a power saw to remove the fish's rostrum -- a long, narrow tooth-lined extension of its head that resembles a saw.

Smalltooth sawfish use that saw to sense and attack prey. Without it, they can't survive.

A sawfish is seen in the waters of the Florida Keys on August 5, 2015.

The numbers of sawfish in the ocean have declined dramatically over the years, according to the National Oceanic and Atmospheric Administration . By some estimates, there may be as many as 5,000 or as few as 500 adult species left in the world, the Natural Resources Defense Council , an environmental advocacy group, reported.

Smalltooth sawfish are typically found in shallow, coastal waters, the NOAA says on its website, and in the United States they are found only off the Florida coast. Though the fish are generally harmless to people, they can do some serious damage with their saws if threatened, according to the Florida Fish and Wildlife Commission

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