With natural prey like capelin and shrimp in decline, cod are eating their young: DFO

Ecosystem conditions appear to be the main factor in stalled growth of northern cod, says a Department of Fisheries and Oceans research scientist. (Hans-Petter Fjeld)


That’s how research scientist Karen Dwyer of the Department of Fisheries and Oceans describes the northern cod stock following this year’s assessment.

Ecosystem conditions appear to be the main factor, said Dwyer — especially low stocks of capelin and shrimp.

“Both of those prey are very important in driving the population dynamics for cod,” she said.

While there’s been an increase in different types of zooplankton, Dwyer said, there’s been a decrease in fatty zooplankton.

“There used to be large numbers of large fatty zooplankton, full of fat, which are really good for young fish to eat, young fish such as capelin or even young cod,” she said. “Over time they’ve seen a decline in these large fatty zooplankton.”

As part of the yearly stock assessment, a research vessel surveys an area from southern Labrador to the southern part of the Avalon Peninsula.

Adult cod eating younger cod

Cod are measured, weighed and assessed for age, and their stomach contents are examined.

The fish have been resorting to cannibalism.

“The fact that they are not able to eat their regular prey such as capelin and shrimp and then are eating their own young, that’s a concern,” said Dwyer.

Spawning stock biomass, the weight of mature fish, is still deep in the critical zone, says the Department of Fisheries and Oceans. (Department of Fisheries and Oceans)

Fish harvesters see positive signs

The union representing fish harvesters sees the latest assessment differently.

“It looks like there are some positive signs in there. It didn’t seem to be communicated that way,” said Fish Food & Allied Workers union president Keith Sullivan.

Sullivan says harvesters weren’t consulted before the release of the latest stock assessment.

“It seems like the biomass has grown. It seems like there’s more older fish generally which is good for spawning stock and harvesters have said consistently whether you’re from the Southern Shore right to Labrador, that there was a lot of small fish in particular this year, so that speaks well for recruitment.”

Sullivan says cod cannibalism may be a result of an abundance of small fish, something that was also seen when overall cod numbers were much higher.

Sullivan says even though DFO’s fall trawler survey is just a snapshot, the overall size of the stock has been moving in the right direction.

“Back in around 2012 the biomass in their survey was 100,000 tonnes, and eight years later [it’s] around 500,000 tonnes. I mean this overall is incredible growth.”

DFO didn’t run its full stock assessment model this year, hampered by weather and COVID-19-related issues.

DFO has to show some leadership. – Bob Rangeley

Dwyer, though, feels confident in the latest results.

The spawning biomass, the weight of all adult mature cod, is deep in the critical zone, according to a DFO model used to describe the health of the stock.

The spawning biomass would have to double to reach what is called the “cautious zone.”

DFO needs rebuilding plan for cod: Oceana Canada

Bob Rangeley of Oceana Canada agrees with DFO that the cod stock’s growth is stalled, and is against increasing quotas.

“DFO has to show some leadership. We need a rebuilding plan, we need to do proper monitoring,” said Rangeley, the science director of the non-profit organization dedicated to, according to its website, restoring Canadian oceans “to be as rich, healthy and abundant as they once were.”

“Fishing mortality is not being well monitored in the stewardship fishery and not at all in the recreational fishery,” he said.

Last year a quota of 12,350 tonnes wasn’t fully taken by harvesters, he said. Just over 10,000 tonnes of cod were landed in the commercial and sentinel fisheries and DFO estimates 1,900 tonnes of cod were caught over four years in the recreational fishery.

Rangeley says this year’s quota should be reduced to 9,500 tonnes.

Even if ecosystem conditions aren’t great for cod’s survival, Rangeley said, fishing is one thing we can control.

“The population growth is stalled so we’ve got to roll back the quota, keep some level of fishing activity going. We have recommendations for that. Be patient, let this stock grow — it has great potential.”

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