Following a pair of incidents last fall in which someone apparently used poison to harvest Tahitian prawns from Hawaii island streams — a dangerous practice that is believed to have killed off other aquatic life and sickened those who ate the shrimp — the Department of Land and Natural Resources Division of Conservation and Resources Enforcement is cautioning the public to know the origin of the prawns they consume.

The alert comes as graduation season arrives with its attendant family gatherings.

In one incident, a container of Ortho Bug B Gon insect killer is believed to have been emptied into a pool fed by Onomea Stream, located within Hawaii Tropical Botanical Garden along the Hamakua Coast.

“We found an empty bottle of the insecticide on the stream bank and found that there were not only no Tahitian prawns in the stream, but it looks like the poison killed everything,” said DOCARE officer Edwin Shishido in a news release. “This was almost eight months ago and now finally with winter rains some life appears to be slowly coming back.”

Farther up the coast last fall, DOCARE officers came upon a group of men carrying 50-pound bags of Tahitian prawns from the stream. It is believed that poison was used to quickly kill and harvest the prawns, also known as giant freshwater shrimp.

DOCARE officials note it is not illegal to remove Tahitian prawns from Hawaii waterways. It is, however, a violation of state and federal law to introduce poison of any kind into a stream or river.

“We heard some people got sick after eating prawns killed in Onomea Stream,” Shishido said. “We also believe that the people doing this sometimes set up alongside roadways to advertise and sell prawns caught in this manner. It’s really important that buyers beware and know for certain where and how the prawns they’re buying were caught.”

In response to the suspected poisoning incidents, DOCARE officers teamed with inspectors from the state Department of Agriculture to tour several streams along the east slope of Mauna Kea. As part of the survey, inspectors took water samples to establish a baseline should further stream poisonings be suspected.

Last fall’s apparent Onomea Stream poisoning led Hawaii Tropical Botanical Garden to add overnight security. “Before the poisonings here, we used to see 10, 20, or 30 prawns in a pool and now we’re lucky to see one,” said gardener Ryan Medeiros in the news release. “We all like to catch and eat these prawns but it’s sad and wrong to harvest them this way.”

Anyone who sees what they believe is suspicious or illegal activity happening near or in a stream should call the statewide DOCARE hotline at 643-DLNR or download the free DLNRtip app on their smartphone.