LIHU'E, Kaua'i — State conservation officers have arrested four men and a boy, all from Kaua'i, for using toxic chemicals to catch fish on the reef off Ni'ihau.

The five, who were not identified, were arrested Sunday and released pending further investigation. They were using a chlorine bleachlike substance, according to a news release from the state Department of Land and Natural Resources.

Chlorine compounds, in either granular or liquid form, kill fish when used on the reef. They also kill corals, marine algae and other living things. The substances are used in caves and holes in the reef, and in areas where there is little water movement. As a result, the living matter in the area is exposed to the chemicals for an extended period of time.

"Every fish, lobster, clam, crab, eel, worm and cowry shell exposed to the chemicals is killed, not just the target species being fished for, but all other living organisms in the vicinity as well," said Peter Young, DLNR chairman.

Fishing with illegal chemicals is a felony with the possibility of a year in jail, $10,000 in fines or both. Boats and fishing gear may also be confiscated.

As evidence in the Ni'ihau case, officers confiscated the boat used by the five people, as well as a truck, boating and fishing gear, and fish and lobster. State Division of Conservation and Resources Enforcement officers and Kaua'i police participated in the bust.

"Using chemicals isn't fishing, it is destruction of marine resources, and could pose a threat to human health and safety," Young said. "The seriousness of the offense becomes apparent when you consider the damaging effects that are associated with chemical fishing."

Residents who witness people using improper substances to fish are urged to report the violations, said Tarey Low, who heads the Division of Conservation and Resources Enforcement office on Kaua'i.

"It is extremely important for anyone knowing of a person or persons using illegal substances to catch fish to report violations immediately," Low said. The state maintains a 24-hour hot line for such reports at 587-0077. Neighbor Island residents can dial 0 and ask the operator for Enterprise 5469.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.