Thu. Feb 29th, 2024

While a redfish fishery reopens, scientists are asking the question of the place that the species occupies and will occupy in the longer term in the ecosystem of the Saint-Laurent.

Science recommends massive redfish fishing

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Science recommends significant redfish fishing this year. (Archive photo)

  • Joane Bérubé (View profile)Joane Bérubé

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In order to counter harmful impacts and devastating the overabundance of redfish on certain species in the Gulf, scientists are recommending a massive fishing for redfish this year, i.e. 318,000 tonnes, which is 12 times more than the figure put forward by the Minister of Fisheries, Diane Lebouthillier.

While many fear the impacts of a fishery dominated by deep-sea trawlers, scientists are suggesting an important paradigm shift.

Several reasons favor massive fishing which would be expected to decrease from year to year, indicates Caroline Senay, biologist responsible for the evaluation of redfish stocks at Department of Fisheries and Oceans.

Overpopulation of redfish is seen as a source of imbalance that disrupts and potentially leads to the decline of other species that compete with redfish for food. This is particularly the case for cod or turbot. Redfish is also singled out as one of the reasons for the decline of the northern shrimp which is part of its diet.

This imbalance between the redfish population and other species could also be short-lived and it is not necessarily fishing that will be responsible for this decline.

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One of these causes is the significant natural mortality rate of redfish.

Already, without removal by fishing, clear signs of a major drop in biomass are observed.

In 2019, scientists from the Maurice-Lamontagne Institute estimated the biomass of redfish at 4 million tonnes. Never seen.

In November 2023, it was just under 2.3 million tonnes for both species. Without any fishing, in a short time. That too was unusual.

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A redfish swims in front of a red coral

The population is therefore decreasing at a substantial rate. Roughly speaking, scientists estimate the rate of decline to be between 20% and 30%. It's a bit like we won the lottery in 2011 or 2013. We saw this biomass grow, but at the moment, we are on the downward curve, says the biologist responsible for stock assessment. , Caroline Senay.

To establish a maximum capture rate of 318,000 tonnes, biologists halved the natural mortality rate. The logic being that if humans, industry, fishermen have an effect that is half as small as natural mortality, fishing certainly has an effect, but it will not be the main cause of the decline of redfish.< /p>

With current mortality rates, within 6 to 9 years there could be less than 10% of current biomass, or approximately 200,000 tonnes of redfish remaining.

The redfish population would still be in the healthy zone, meaning that the size of the population would be sufficient to ensure renewal. Fishing will still be possible, but catch rates will then be significantly lower.

The natural causes of the decline in redfish biomass are multiple and some are inevitable.

If the 2011, 2012 and 2013 cohorts surprised scientists , there have been no other surprises since. In recent years, we have not seen the arrival of new babies, new recruitments in the system, notes Caroline Senay.

Before the moratorium, the redfish reproduction cycle was eight to ten years. After the 1980 cohort, we had to wait 30 years before a new generation appeared.

Twelve years later, small rockfish are now very rare and if there are hatching, scientists suspect that the larvae, as big as a grain of rice, serve as food for the largest redfish. The few babies we have seen in recent years do not make it to adulthood, notes Caroline Senay.

Only 2% of the mentella rockfish biomass is below commercial size.

The St. Lawrence mentella redfish population, 2.1 million tonnes, therefore almost essentially includes adult individuals over 22 cm.

These redfish, born more than 10 years ago, have also grown very slowly. The majority of the biomass has reached sexual majority at a size of 24 cm or 25 cm around 2021. These rockfish will no longer grow. According to Caroline Senay, we will not see redfish of 40 cm, as was the case before the moratorium.

To explain this smaller size, Caroline Senay puts forward some hypotheses.

First, the warming of the water in the Gulf could have played a significant role in the growth of the fish.

In fact, preliminary results on redfish raised in ponds at the Maurice-Lamontagne Institute suggest that the fish grows more slowly in waters that are more warm, like those observed in the Gulf in recent years.

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Redfish growth in warmer water pools appears to be slowing. (Archive photos)

Then and above all, the population is too large for the food available. The Gulf of Saint Lawrence is a bit like a pantry that is closed, there is a maximum amount of resources. When there are too many of us, sometimes we don't have enough resources, not enough energy to reach the full growth potential that these species could have had, assesses the biologist.

The biologist points out that most knowledge about redfish often comes from observations of the 1980 cohort. It seems that the new cohorts have different life histories. We would not be surprised if these cohorts live shorter lives than previous cohorts.

Added to this is very significant natural predation. Redfish are so abundant that they are found in the stomachs of almost every other species in the ecosystem, underlines Ms. Senay.

Even if the possibility of massive fishing is there, the industry will have to look at its processing capacity as well as that of fish marketing, to assess what it will be able to collect. Canada is a new player in the global redfish market dominated by countries like Iceland, Norway, Russia and Portugal.

The scientists' findings and recommendations were presented to the industry at a meeting last week.

Minister of Fisheries and Oceans, Diane Lebouthillier, reopened redfish fishing with a total authorized catch of 25,000 tonnes. It's a floor quota, she added.

The total catches granted this year will be discussed in March at industry meetings in an advisory committee.

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