Schools of dead herring keep washing ashore along the rocky beaches of western Nova Scotia, prompting a retired scientist to enlist the help of local naturalists and bird watchers as he continues to gather data about the mysterious phenomenon.

Ted Leighton, an adjunct biology professor at Nova Scotia's University of Sainte-Anne, said Friday he has compiled more than 40 sightings since tens of thousands of dead and dying fish started appearing in St. Marys Bay in late November.

Leighton, who has an extensive background in wild animal disease investigations, said the latest sightings were reported Thursday in the Tusket River area, which is southeast of Yarmouth — and he says more dead fish were spotted in St. Marys Bay and in the Annapolis Basin earlier this week.

'Event does not appear to be over'

"The event does not appear to be over," he said in an interview. "Whether it's diminishing or not is really hard to say."

On Wednesday, federal scientists said they had yet to determine what is causing the die-off, despite a battery of tests.

Negative results have been reported for physical damage and several types of bacterial infections and viruses.

Fisheries and Oceans Canada says more tests are expected, including a check by the Canadian Food Inspection Agency for toxins caused by algae, and the possible presence of domoic acid — a toxin sometimes found in shellfish.

Meanwhile, Leighton has posted a message on his Facebook page calling on all naturalists to report sightings of dead herring to him.

'Citizen scientists' make observations

"It wasn't clear to me that there were enough people in the field to really determine the extent of the problem," he said, adding that nature groups and bird watchers are at the water's edge every day, keeping watch.

"They're in a good position to make these observations. I thought they would be quite willing to act as citizen scientists."

Leighton said any observations should include details about the approximate number of fish, their specific location, the length of shoreline affected and the presence of other dead fish, birds or mammals.

He also wants to know what proportion of the herring are still alive.

Information forwarded to feds

All the information he collects is being forwarded to federal officials and the Canadian Wildlife Health Co-operative, which Leighton led for 12 years.

Federal officials are warning people not to handle any dead or dying fish, mainly as a precaution.

On Nov. 30 Leighton was stunned to find roughly 5,000 herring spread across 100 metres along the pebble beach in front of his home in Smiths Cove, which is part of the Annapolis Basin, near Digby.

Nothing amiss after herring dissection

He dissected some of the herring at the university, but couldn't find anything amiss.

"The laboratory side is being covered as good as it can be," he said. "They're going at it hammer and tongs. They're not being passive. So, we have to have some patience."

Earlier speculation had suggested the herring could have been driven ashore by whales or other predators, but federal surveillance flights have failed to spot any large mammals along that section of the coastline.