LIHUE — The monitoring team on Lehua Island has collected 45 dead fish and two dead birds from the near-shore waters, after two applications of rodenticide were dropped from a helicopter over the island.
Most of the fish were ama ama, or the striped mullet, and the two birds are juvenile brown boobies.
Samples from the carcasses don’t show any immediate evidence of impact of diphacinone, the restricted-use pesticide being used in the Lehua Island restoration project, according to state officials.
“Mortalities of fish and seabirds occur regularly and there are a many other plausible causes for these deaths,” representatives from the Department of Land and Natural Resources said in a Tuesday news release. “Mortality among wild fish and bird populations is common, so a correlation does not demonstrate causation.”
Samples taken from the carcasses have been turned over to the U.S. Department of Agriculture and will be processed to determine likely cause of death, or presence of diphacinone.
Video taken by a few Kauai residents and posted Sunday on social media is what tipped DLNR, Island Conservation and other Lehua Island Restoration Project partners off to the dead animals.
In the video, carcasses of the two brown boobies can be seen floating alongside green rodenticide pellets and dead fish in tide pools and nearshore environments.
The potential for fish and other animals to eat the bait, laced with the restricted-use-pesticide diphacinone is what has some people concerned.
“We know that the ama ama will eat peas and it stands to reason that they will eat the rat poison pellets that were dropped directly into the tide pools,” said Terry Lilley, marine researcher who is planning a trip to Lehua with a newly acquired research boat.
Lab studies done by the partners involved in the Lehua Island restoration project show that fish reject the diphacinone bait, according to DLNR, and “fish are among the least likely animals to be affected by the rodenticide.”
The bait, according to DLNR, is designed to drift to the bottom of the sea and the diphacinone rodenticide is contained in the pellets. It’s almost insoluble, DLNR representative say.
Once the bait degrades, the rodenticide turns into carbon dioxide and water, according to DLNR.
“What little bait drifts into the water from the over-land application sinks to the sea floor and degrades quickly,” DLNR said in its news release.
The breakdown time is something Kekaha resident Harold Vidinha has questions about because he has a bait sample taken from the first bait drop on the island, Aug. 23.
It has been sitting in a small amount of ocean water since then, and Vidinha has been keeping an eye on it.
“It’s been three weeks and it hasn’t disintegrated,” Vidinha said. “Maybe there’s something to do with it about the motion of the ocean to help disintegrate it, but you can see it’s not dissolving.”
Federal and state permits secured by the partners in the project allow some bait to reach marine waters.
“Project proponents have pursued this project only because they are convinced the small potential for short lived risks to non-targets species is far outweighed by the long-term conservation benefits,” the DLNR release said.
But some are concerned the repercussions won’t be short-lived.
“If something is dying, that could mean that other things will die further down the (food) chain,” said Rep. Dee Morikawa. “I’m worried about that.”
Monitoring teams have been daily making observations to the accessible nearshore environment and tide pools, according to DLNR, and a Division of Boating and Ocean Recreation vessel will be monitoring the crater today.
The third and final aerial application of rodenticide bait pellets onto Lehua Island is planned in the next few weeks, pending weather conditions, according to DLNR, but an exact date has yet to be confirmed.