BC farmers tackle algae head-on

BC is experiencing yet another record-breaking year, with extremely high temperatures and drought-like conditions.

These conditions have many people living in the province on water-restrictions, and several forest fires are raging throughout the interior of BC.

For salmon farming companies, these conditions are accompanied by three nasty words: harmful algae blooms. Already this year, Cermaq Canada experienced a severe mortality event associated with a bloom of Chrysochromulina spp.

How can farmers protect their stocks from the effects of HABs?

Marine Harvest Canada (MHC) is taking a three pronged approach: investing in new equipment, pursuing research and development, and changing its operating procedures to protect salmon from potentially lethal plankton.

Plankton blooms occur naturally and have long been accepted as a risk for ocean aquaculture, however MHC believes that with a strategic approach the risk will be lowered significantly.

The company has now fitted a majority of its salmon farms with state-of-the-art air compressor systems which supply a constant flow to diffusers at a depth of 15 to 20 metres. Rising air bubbles push cold, clean, oxygenated water to the surface where plankton generally accumulates. This dispersal of plankton allows salmon to survive and continue to eat during blooms.

As well as capital expenditure on equipment, MHC has employed plankton expert Jay Pudota, who is dedicated to researching harmful algae. Jay has overseen the introduction of daily plankton monitoring using digital microscopes at all sites and capabilities for remote login when sites need assistance, as well as nutrient monitoring and satellite chlorophyll imagery.

The third defense is to integrate plankton mitigation into daily operations. On the west and north coast of Vancouver Island, where more harmful plankton historically occurs, MHC’s daily procedures for salmon farming have evolved to include plankton monitoring and quick responses to blooms.

Daily temperature readings taken at five metre depths at every Marine Harvest farm show an increase in water temperatures of up to 2 degrees Celsius over the last two years. This warming trend creates a favourable environment for plankton and contributes to the physical stress on cold-water loving salmon.

“Wild fish can move away from plankton, but our farm-raised salmon are unable to move out of the way of a plankton bloom so we must be vigilant and proactive at managing this risk,” said Pudota.

“Harmful plankton may poison or become a severe irritant to the gills, causing salmon to suffer or, at worst, die.”