Redfish rebound in Gulf of St. Lawrence show no signs of slowdown

The rebound of redfish in the Gulf of St. Lawrence continues to amaze the region's fishery and marine biologists.

Redfish biomass surged by 20 per cent last year and is now estimated at a staggering three million tonnes, according to Canada's Department of Fisheries and Oceans.

"The biomass that we're seeing right now is something that we have never seen before," said DFO biologist Caroline Senay of the redfish, also known as ocean perch.

The massive population is primarily made of of fish live born — not hatched from eggs — from 2011, 2012 and 2013.

The region's fishing industry has been licking its chops for several years over the prospect of a redfish bonanza.

The average size within the population reached 22 centimetres, the minimum for harvest, in 2018, Senay said.

Nova Scotia fishing companies are urging the federal government to wait until the fish are larger, and able to produce larger filets, before approving bigger harvests.

The numbers of redfish did not grow, but their combined mass increased because the individual fish are thriving and heavier.

"It's just that they're getting bigger, Senay said. "They're longer. They're getting some weight on. Obviously, some of those guys are dying every year, are getting eaten by birds and seals and big cod and halibut. But the biomass is still increasing."

80 per cent of what's down there

It continues to be a remarkable run for redfish, which now now dominate deepwater in the Gulf of St Lawrence.

In surveys last summer, they accounted for the overwhelming majority of all fish captured in DFO's bottom trawls, ranging from tiny individual shrimp to sharks several metres long.

"If we look at all those species combined, 80 per cent of the biomass was composed of redfish, which is pretty impressive," Senay said.

Eating down northern shrimp

But the sheer size of the population is likely affecting other species.

For example, the increased numbers and size of redfish is playing a role in the decline of northern shrimp, which is a redfish staple.

Redfish are also a potential threat to turbot, which also eats shrimp.

The Gulf of St.Lawrence has experienced environmental changes in recent years, including the warming of its deep waters.

Redfish rarely survive being brought up from deep water, leaving scientists uncertain as to what effect, if any, warming temperatures and hypoxia — the depletion of oxygen at the ocean bottom — has on the population explosion.

"There is a lot of unknowns in terms of their tolerance to different environmental conditions," Senay said. "And it's not that we don't want to study them. It's really a challenge to bring them back alive up to the surface given that there's so deep."