Federal scientists are testing water samples and scanning images of the bottom of St. Marys Bay, hoping to determine what caused thousands of herring and sea creatures to wash ashore near Digby, N.S.
Staff aboard a vessel gathered samples Thursday and used an underwater camera to film and photograph the ocean floor.
Kent Smedbol, manager of population ecology for the Department of Fisheries and Oceans (DFO) in the Maritimes, said the data will be examined to try to figure out whether an environmental factor caused the fish to die.
“It could be an intrusion of very cold water very rapidly, it could be related to a rapid change in salinity with the storms that have gone through … due to the sudden influx of fresh water, rain or runoff from the land,” he said.
“Depending on what we find, then hopefully that will allow us to discount a number of possibilities and focus our efforts on some possible explanations.”
Trying to rule out contamination, weather
Smedbol said if photos and video are clear enough, staff will examine the benthic invertebrates, the small creatures that live in or on the bottom sediments of the bay.
The organisms are sensitive to changes in the environment and wouldn’t be able to get out of the way if there were a contamination issue, a drop in oxygen in the water or a spike in cold temperatures, Smedbol said.
“If we have a broad-scale die off, multiple species, that would lead us to think, or at least suggest it may be an environmental stressor.”
Could be separate events
If the scientists determine the benthic invertebrates are healthy, they’ll then try to pinpoint what killed the herring and consider that the other sea creatures could have died from something else.
The crabs, mussels, lobsters and shellfish could have been “affected by the recent storm front that went through, wrong place at the wrong time, if you will,” said Smedbol.
They’ve already looked at water patterns over the past few weeks and found nothing “that indicates anything really strange going on in that location,” he told CBC Halifax’s Information Morning.
No evidence of disease so far
So far, they have found no evidence of disease, parasites or toxins.
Work by the Canadian Food Inspection Agency, and Environment and Climate Change Canada to look for contaminants and by the fish health lab in Moncton has come back negative, Smedbol said.
“It’s a bit frustrating that we haven’t been able to identify a cause yet, but it is good to know that some of the items that we would have more concern about have been negative thus far … it’s not a bad outcome,” he said.
No problems found at fish farms
As for next steps, a fish health lab in Moncton is still running tests on viral causes, but it could take up to a month to get the results.
If it is determined that an environmental issue caused the die-off, Smedbol said monitoring or sampling could be set up in the area in the long term.
DFO is leading the investigation into the fish kills. Nova Scotia’s Department of Fisheries and Aquaculture said provincial veterinarians have been keeping a close eye on farmed fish in the area, with the most recent visit last week.
They haven’t found any signs the herrings deaths have affected the farmed fish, said Heather Fairbairn, a spokeswoman for the department.
Province, municipality don’t see unusual activities
The province also has not received any “recent reports from aquaculture operators in the St. Marys Bay area regarding fish escapes, accidental discharges of chemicals, or aquatic animal health issues,” Fairbairn said in a statement.
The Municipality of the District of Digby said there are no municipal sewer or water systems in the area where the fish have been found.
The town of Digby isn’t involved in any investigation, and said it has not had any issues with wastewater collection or treatment facilities.
Chief administrative officer Tom Ossinger said there’s no reason to believe the town’s operations contributed to the fish kill.
Article source: http://www.cbc.ca/news/canada/nova-scotia/department-fisheries-oceans-1.3916013?cmp=rss