Officials say hundreds of dead fish are floating along the tributaries of the Navesink River.

The fish have been showing up around Long Branch and Oceanport. Local residents say the sight and smell of the dead fish is concerning.

"It smells so bad, especially if you live by the water," says Cesar Bonini, of Long Branch. "You can't go outside. You can't do anything outside."

The rotting fish have also attracted more seagulls and other birds to the area. The state Department of Environmental Protection says the fish kills are natural and caused by a lack of oxygen. However, one environmental group thinks other forces may be at work.

"I don't think it's the fishes fault. I think it's the fault of pollution," says Cindy Zipf, executive director of Clean Ocean Action.

Zipf says that while fish kills are natural, they're starting to happen earlier and more often. She says runoff from the Monmouth Park Racetrack may be contributing to the large kills.

Calls by News 12 New Jersey to the racetrack for comment were not immediately returned.