What the hiyok is happening?

By Dennis B. Chan - Saipan Tribune — Nov 24 2014

Division of Fish and Wildlife's Dr. Todd Miller described at the Asia Pacific Academy of Science conference last week how the CNMI tried to solve the Tinian and Saipan hiyok die-off mystery that happened this year.

He said they are still not sure what exactly caused the deaths of thousands of hiyok. But in toxicological analysis done by the U.S. Geological Survey's National Wildlife Health Center, stomach contents of the fish were blended and injected into rats, with fatal results.

These results became a "smoking gun," according to Miller, pointing at whatever the hiyok was eating as the cause of mortality.

The muscle parts of the fish were blended and injected into rats but the rats turned out OK, Miller said.

Dissection histology tests were also performed on the fish. Miller said the hiyok that were found alive appeared "drunk" and "waddling around."

The tests, however, indicated no tissue damage, no parasites in the tissue, full stomachs, and no presence of parasites in the intestines.

He said the Bureau of Environmental and Coastal quality also did water sampling surveys for bacteria and E. coli, for example, but that "nothing out of the ordinary" was found.

He said the die-offs were not due to a water quality issue. DFW also did "very large surveys" around Tinian where the die-off began, Miller said.

Upwards of 4,000 fish were found in one die-off event, he said.

There has been no indication that hiyok die-offs have occurred on Rota or Guam, according to Miller.

The die-offs began on Tinian and seemed to move northward, according to Miller.

The hiyok is one of the biggest contributors to the CNMI's fish markets, he said.

Will the die-offs happen again? Miller said DFW does not know, but if it does it will probably happen in the same window between July, August, and September.

"The important part is to be prepared for when that happens, that people know and call in so we can quantify this and get the right samples to the lab," he said.

Miller's APASEEM presentation was titled "What the Hiyok is Happening? A report on the hiyok die-offs in the CNMI." Mike Tenorio, Sean Macduff, Trey Dunn, and Frank Villagamoz were listed as those involved in the project.