Toxic algal blooms are a growing problem in the world’s oceans and may be responsible for killing salmon on the West Coast, a federal commission has been told.
Jack Rensel, a U.S. scientist who specializes in researching harmful algae, told the Cohen commission of inquiry that Heterosigma akashiwo is a prime suspect in the disappearance of millions of salmon in British Columbia.
The commission was established by Prime Minister Stephen Harper after sockeye stocks collapsed in 2009, when only about one million of an anticipated 10 million sockeye returned to the Fraser River. Diseases, ocean conditions, climate change and the possible impact of fish farms have all been discussed as possible causes for the collapse.
But Dr. Rensel put forward a new possibility Wednesday, when he testified that there were massive Heterosigma blooms in Georgia Strait in 2006 and 2007.
His research over the past 20 years has shown that when there is a harmful algal bloom, or HAB, in the Strait, “inevitably there would be a correlation with a poor return [of salmon]two years later.”
Dr. Rensel said HABs have been known to wipe out fish-farm stocks and he speculates that wild salmon could also be killed by encountering blooms.
There are no records of major wild salmon kills on the West Coast associated with algae blooms, but he said any fish that did die would likely sink to the ocean floor, and would not be seen.
Dr. Rensel said it isn’t clear how Heterosigma kills fish, but it is thought to work in concert with other factors.
“We don’t know exactly whether it is direct mortality,” he said.
Dr. Rensel said algae could compromise the health of fish by damaging their gills, making them susceptible to diseases.
HAB’s are triggered by a number of factors – including ocean salinity, water temperature, the amount of sunlight available and the level of nutrients in the water.
When a HAB starts, it can spread over a huge area within a few days. In recent years, clouds of Heterosigma have been seen covering more than 30,000 square kilometers of Georgia Strait and Puget Sound.
But the blooms often vanish within a few weeks.
Dr. Rensel said Heterosigma blooms are a growing global problem, affecting Chile, New Zealand, Scotland and China, among other places.
But despite the widespread nature of the problem, the Cohen Commission heard that the Department of Fisheries and Oceans hasn’t done much to study harmful algae on the West Coast.
Don Rosenbloom, a lawyer representing commercial fishing groups (Area D Salmon Gillnet Association and Area B Harvest Committee) filed two DFO internal e-mails that indicated HAB’s were of little interest to the department.
A 2006 e-mail described toxic algal blooms as a “low priority” for research, and a 2009 message, said “toxic algae is a banned (or at least unpopular) topic in DFO.”
Dr. Rensel said he was disappointed by the attitude expressed in the e-mails, but said in fairness to DFO there wasn’t much interest anywhere in HAB’s until relatively recently.
Dr. Rensel said the impact of toxic algae on fisheries began to register as a global concern a few years ago, and recent conferences on the topic have drawn thousands of participants.
“Everybody is considering it now,” he said.