LEHUA — Samples taken from 45 mullet-like fish found in Lehua tide pools during the summer 2017 rat-eradication project are too degraded to point to what killed the animals.
And while scientists are still researching the environmental impacts of the project, the state is questioning whether the fish were placed in the island’s northern tide pools on purpose.
“It’s lack of evidence that they would be in that particular location naturally,” said Dan Dennison, spokesman for the state Department of Land and Natural Resources. “The media jumped to the conclusion that the fish were killed by the rodenticide based on social media posts.”
On Sept. 5 an investigation began after dead birds and fish were discovered around the island during the three-wave, aerial application of bait pellets laced with the rodenticide diphacinone over the island.
The first two rounds of bait were dropped Aug. 23 and Aug. 30, and the final was dropped Sept. 12 — a week after photos and video of the dead fish and birds were posted on social media, triggering investigations by both the U.S. Department of Agriculture’s National Wildlife Research Center and state Department of Agriculture.
The entities also collected environmental samples both prior to and following the application of rodenticide to the island and are compiling a full analysis.
Preliminary results of the Lehua mullet-type fish were announced in a press release Monday. It said NWRC and HDOA both showed samples were in a “severely degraded condition,” making it impossible to determine their cause of death.
“Preliminary results from USDA’s visual examination of the specimens show external and internal signs of UV fluorescence from the pyranine biomarker incorporated into the diphacinone bait,” the release said. “However, because the internal organs such as livers and stomachs were decomposed, the results are inconclusive as to whether the fluorescence resulted from consumption of the bait or immersion in the tide pool where bait pellets dissolved.”
Experts say chemical analysis of the degraded tissues won’t give up any information on whether the fish died from ingesting or absorbing diphacinone, either.
Possibilities for causes of death are factors associated with being trapped in tide pools, such as high temperature or limited oxygen.
Kauai researchers, scientists and conservationists say inconclusive results due to decomposition were expected.
“The most important evidence is from the various fish species, crabs, opihi that they collected before and after,” said research scientist Carl Berg. “We have yet to see those results.”
The presence of UV fluorescence, he theorized, is most likely from soaking in tide pools with bait.
Necropsies are a specialty for veterinary anatomic pathologist Jade Fisher, who recently lent a hand with the five pilot whales that died after stranding on Kalapaki Beach in October.
She didn’t take part in any of the Lehua project, but said she’s not surprised with the results, either.
“Fish autolyze (degrade or rot) much quicker than other species, with the degradation process starting almost immediately after death,” Fisher said.
If the organs are so degraded they can’t be identified, it’s nearly impossible to determine the cause of death. Usually fresh samples are taken as soon as possible for toxicologic evaluation, she said.
“Basically, for any aquatic animal, the longer you wait after it dies, the less chance you have of finding a definitive diagnosis and cause of death,” she said.
Gordon LaBedz, of the whale conservation group Kohola Leo, agreed the results were expected.
“To my knowledge, there has never been a case where government agencies or the Navy has said ‘oops, we goofed, sorry,’” LaBedz said.
“The results are always inconclusive.”
He also said he’s not thrilled with the state pointing to the possibility of fishy foul play.
“It is insulting and annoying that they implied that Westside fishermen planted dead fish in the lagoon,” he said. “I think their defensiveness is a little over the top.”