Herring die off subsiding but cause unknown and may never be known

Published on January 5, 2017

Herring on the beach in Griffin Cove Nov. 25.

©Cindy Graham

DIGBY, N.S. – Those tasked with identifying what was behind a recent massive herring die-off say they may never know the exact cause.

But after exhaustive testing, many officials say it was not due to human-related activity, nor is there any human health concern, although people are still being told, as a precaution, not to eat dead or dying fish found on shorelines.

In a briefing Thursday afternoon, Jan. 5, the Department of Fisheries and Oceans also said the fish mortality is subsiding.

“Our observations are (that) our officers in the field are seeing less and less fish,” said Doug Wentzell, DFO’s regional director of fisheries management.

He said there is only a small swatch of shoreline where they’re still seeing remnants of dead herring. During the die-off the highest concentration of dead herring had been around the mouth of the Sissiboo and on the shoreline near Savory Park in Plympton, Digby County.

But Alain Vézina, Fisheries and Oceans’ regional director of science, doesn’t hold out a lot of hope that they’ll ever be able to pinpoint exactly what was behind this.

“In terms of the likelihood that we will identify the cause of this, I would say it’s pretty low,” he said. The scientist said at present the most probable cause is a natural occurrence, “which remains unknown.”

However, it was suggested that just as important as knowing what caused the die-off is also knowing what didn’t.

In terms of the likelihood that we will identify the cause of this, I would say it’s pretty low. Alain Vézina, Fisheries and Oceans’ regional director of science

EXHUASTIVE TESTING

On this front, much testing over the past month by scientists, toxicologists and chemists has come back negative, meaning there was no evidence of toxins, viral infections, bacterial agents, environmental contaminants or pollutants in the water as causes. In the testing, fish were dissected and tissues and organs were examined, water was tested and underwater surveys were done. Nothing unusual was detected.

“All tests over the last 28 days have been negative,” said Anne-Margaret MacKinnon, DFO’s manager of aquatic health division.

And Jeff van de Riet with the Canadian Food Inspection Agency said all of their testing for the presence of toxins was negative as well.

It was stated during the briefing that meetings have been held with fishing industry representatives, indigenous partners and citizen scientists to also get their input and feedback. DFO says fishermen have told them that the herring is denser and more concentrated than it’s ever been before at this time of year.

DFO monitoring on shorelines for dead herring and sea life.

©DFO

DROP IN TEMPERATURE

There was also talk during the briefing of how the water temperature in the bay experienced a very significant cool-down in mid-December. It was stated this could be related to other sea life washing up dead, like starfish, lobsters and mussels, but it isn’t known for sure. That happened around Boxing Day and DFO said those types of sea creatures washing up was a short-lived occurrence. The change in temperature also happened weeks after herring started washing up back in November.

DFO cautioned that if there are no new cases of herring dying, it will be hard to come up with a conclusion about something that happened in the past since since so much has been ruled out. Nor can they predict if it might happen again.

There were questions about other possibilities, including whether a recent earthquake in the region could have contributed to the die-off. That was discounted by Natural Resources Canada, as there was no evidence of fish mortality on the ocean floor.

There was also a question over tidal turbines located elsewhere in the Bay of Fundy and whether noise could have had an impact or perhaps even displaced a higher concentration of herring to the region. Nothing has been identified to suggest turbine noise was responsible for the fish kill. There was no readily available answer about whether herring populations have been displaced.

Meanwhile, DFO reiterated that the die-off is slowing down. There wasn’t an exact number as to how much herring did die, although DFO says it’s the first time they’ve dealt with an event in the region of this scale.

Chris Sperry, acting area chief of enforcement, conservation and protection for DFO, estimates the amount of dead herring was in the tens of thousands at one point.

“We’re seeing how this has really changed,” he said, noting the day before, during monitoring of an area, the count was down to 10 dead fish.