The Sea Shepherd Conservation Society is offering a reward for information leading to the arrest and conviction of the person or persons responsible for the illegal slaying of two Steller sea lions and four California sea lions on the Columbia River.

The two species are federally protected by the Marine Mammal Protection Act and Steller sea lions are also additionally protected under the Endangered Species Act.

The six animals found dead Sunday appear to have been shot by somebody on the Washington state side of the Columbia River during the night, according to Brian Gorman, regional spokesman for National Marine Fisheries Service, or NOAA Fisheries, in Seattle.

"We will coordinate this through National Marine Fisheries," said Captain Paul Watson. "This kind of blatant illegal killing must not be tolerated and we need to see that the Marine Mammal Protection Act and the Endangered Species Act are upheld in this country."

The reward of $10,000 will be paid for information leading to a conviction in this case.