How throwing the big ones back could keep halibut fishery on a roll

You've heard of throwing back the little fish — what about throwing back the big ones?

That's the question researchers are asking in a Canadian study on the survival rate of large Atlantic halibut released after being caught by commercial fishing fleets.

This is not an academic exercise. It could lead to a maximum size limit for halibut, a valuable groundfish in Atlantic Canada.

"It is worth considering whether a maximum size would also be of benefit to make sure that those very large animals that are spawners could continue to contribute to the population," said Nell den Heyer, a research scientist with the Department of Fisheries and Oceans.

Patience pays

The investigation is being undertaken at the request of companies that fish halibut using hook and line from the Grand Banks off Newfoundland to Georges Bank off southern Nova Scotia.

They'd like to see it happen.

"Releasing large halibut is something that fishermen will say, and I will say, that's just logical, because the majority of the large halibut are females. But you really don't know just what goes on after you release a large halibut like that," said Gary Dedrick, a halibut fisherman from Shelburne, N.S., and a founding member of the Atlantic Halibut Council.

"So this is where there is monitoring on the bottom and how long they live."

The science

Large halibut are being fitted with two types of tags that track movements, said den Heyer: pop-up satellite tags that can be retrieved later, and acoustic transmitters that send unique signals that can be picked up by an array of receivers on the ocean floor off Nova Scotia.

By this spring, a total of 150 fish will be tagged and followed for three years.

The information about movement of individual halibut that is stored in the receivers will be uploaded annually by an autonomous glider operated by the Ocean Tracking Network based in Halifax.

It's one of seven science projects in a collaborative, $4.2-million science program between the Department of Fisheries and Oceans and the Atlantic Halibut Council. Industry is putting up a million dollars. The remainder is coming from the federal government's Atlantic Fisheries Fund.

Right now, the fishery has a minimum size only. Discarding halibut over 81 centimetres is prohibited by the Department of Fisheries and Oceans. The research will help decide if the rules should change.

"We would be interested in their survival when being returned because they're such big fish, they might not have the same response to being handled or brought to the surface as the smaller fish," said den Heyer. "So we're interested in their survivability because we are considering changing our management."

The comeback story

The industry focus on conservation started back to the mid-1990s when halibut stocks were at a low point from overfishing. That's when the Atlantic Halibut Council was created.

Small boat fishermen, led by Dedrick, joined forces with big companies and agreed to sustainably manage the fishery.

Halibut has since rebounded as the result of favourable environmental conditions and restraint from the industry which voluntarily capped catches at levels that have ensured the stock keeps on growing.

"What we're seeing is just a really massive increase in the stock," said Dedrick.

The quota has increased six fold since the late 1990s — from 850 tonnes to 5,507 tonnes in 2020.

"The quota could be more. But based on what we do, we're keeping that a low level instead of the higher," said Dedrick. "We started seeing the stock grow, we said, 'We've got something. Let's hold on to it.'"

Abundance at record high

The halibut population has been in the healthy zone for years and is currently at its highest level since DFO started measuring abundance in the 1970s, or "possibly before that," said den Heyer.

The stock assessment is assisted by data provided to DFO by an industry-funded longline survey that gives scientists an idea how many large fish are in the water.

It filled a gap for the fisheries department since its trawl survey only captured smaller fish.

"The investment the industry has made in establishing a science program that feeds into the assessment has greatly helped us provide sound advice for the stock," said den Heyer.

Not all smooth sailing

The halibut comeback has also been marked by tragedy and greed.

In 2013, all five crewmen were lost when the Miss Ally, on a halibut trip, went down in a ferocious nor'easter. The boat was 120 kilometres southeast of Liverpool and en route to Sambro at the time.

DFO also responded to the bonanza of illegal halibut fishing with increased monitoring of catch and landings beginning in 2010.

A major operation resulted in 164 convictions across Atlantic Canada — mostly in Nova Scotia — with fines and forfeitures totalling $1,178,000.

Evidence uncovered collusion between buyers and fishers to illegally process halibut landed in excess of set quotas.

Still, the fishery is thriving, with export sales of fresh halibut alone worth more than $90 million in 2020, according to the Atlantic Halibut Council.

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