Three dolphins have been found dead from puncture wounds off the Florida coast since May.

Last week, biologists with the Florida Fish and Wildlife Conservation Commission found a dead dolphin off the coast of Naples with what appeared to be a bullet wound or a puncture from some kind of sharp object.

The Miami Herald reported that the same week, experts from the Emerald Coast Wildlife Refuge found another dolphin with a bullet in its left side near Pensacola beach.

In May, a dolphin was found off Captiva Island with a puncture wound in its head.

The National Oceanic and Atmosphere Administration is offering $20,000 for information leading to the civil penalty or criminal convictions for anyone responsible.

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Biologists believe that humans feeding dolphins have made the marine mammals more comfortable around people, which has opened them up to dangerous situations.

Nearly 30 dolphins have been shot by bullets and arrows or have been impaled since 2002. Hurting or harassing dolphins is illegal and people caught doing so may face up to $100,000 in fines and a year in jail, according to the NOAA.

In addition to the attacks on dolphins, there have been a growing number of incidents in which dolphins are stranded on land and die.