A manatee has been spotted in the Delaware River north of Philadelphia.

New Jersey's Department of Environmental Protection said the marine herbivore, sometimes called a sea cow, was sighted by a fishermen in the river near Crosswick Creek in Bordentown, Burlington County, Tuesday evening.

It was about 7 feet long, the department said.

Bob Considine, a DEP spokesman, said there have been no reported sightings since then.

The manatee's appearance in Bordentown came less than a week after Delaware wildlife officials reported a manatee was in the Chesapeake and Delaware Canal, some 60 nautical miles to the south.

While manatees are mostly concentrated in the waters of Florida, they can be found as far north as Massachusetts in the summer when ocean waters are warmer.

The greatest threat to the slow-moving, docile creatures' are boat propellers and sailors in the Delaware are being urged to be on the watch to avoid hitting a manatee.

Manatees are endangered and it is against federal law to harass, hunt, capture, or kill them.