Unit 1 Stock up 20 Per Cent in One Year
Redfish are making a comeback in the Gulf of St. Lawrence, with estimates the stock has reached three million tonnes in Unit 1, an increase of 20 per cent in one year.
“It’s a very impressive situation. It’s not something we see often,” said DFO biologist Caroline Senay. “It’s maybe not a good story for Northern shrimp, but overall you cannot be unhappy a fish that was almost gone is coming back.”
Under moratorium since the 1990s, surprisingly in 2011, 2012 and 2013, scientists started seeing very large year classes of redfish coming in, said Senay. “Actually, the largest we’ve ever seen in our surveys” which DFO has been doing since 1984.
“What is impressive is the redfish biomass was accounting for 80 per cent of everything that we captured” in the most recent survey, said Senay. “Redfish are really dominating the bottom ecosystem of the Gulf.”
What impact this is having on other species is something scientists are looking at, said Senay.
“We know they’re eating Northern shrimp. We know that Northern shrimp is going down. We also need to realize Northern shrimp started going down before this redfish increase. We’ve seen shrimp going down for multiple years but obviously the presence of redfish eating a bunch of them can just exacerbate their decline. We’re also seeing slower growth with turbot who have a similar diet so we’re looking at what could be the competition interaction between those two species.”
The warming waters of the Gulf could be one reason redfish are making a return, said Senay.
“We know it’s bad for Northern shrimp (but) it may be one of the reasons why redfish is coming on strong,” noting the last big increase in redfish stocks was in the 1980s “when we also had a bit of warmer waters in the Gulf, then in the 1990s the water temperature went down a little at the bottom and redfish recruitment was not super strong so there may be a link with temperatures. It is one of the hypotheses we would like to test.”
As Senay explained, there are actually two species of redfish in Unit 1, Sebastes mentella and Sebastes fasciatus. Mentella is the species that is most abundant, she said, with a biomass about 10 times larger than the other one. The two species are genetically different but morphologically similar, said Senay. “We need to preserve that biodiversity.”
Extremely hard to tell apart, Senay said work began last year collecting information that will give scientists an idea of which species are being harvested.
“We know from surveys that mentella is located deeper than fasciatus so maybe there’s a way to fish deeper water and maybe that would target the most abundant species,” said Senay. “The depth profile is something we know from our surveys in August, but we don’t know if it’s the same in spring, fall and winter. With the information we started collecting in the commercial fishery we will be able to see if that holds true.”
Since the moratorium has been in place in Unit 1, a yearly index fishery of 2,000 tonnes has been conducted “to keep the fishery a bit alive and to make sure we get some data,” said Senay. With the strong year classes coming in, DFO added an experimental fishery with 2,500 tonnes in 2018/19, which has been increased to 3,950 tonnes for the 2019/20 fishing season.
The experimental fishery was put in place so fishermen can test different gear and mesh sizes and find some strategies to avoid bycatch, said Senay.
“We don’t want this redfish fishery to start and be bad for cod or halibut or white hake or so on. We want to try to find some strategies to minimize bycatch. Another objective of this experimental quota was to find gear or fishing strategies to avoid small fish. We know there’s a lot of recruitment right now. Those small under 22 cm we want to leave in the water.”
In the 2018 survey, the length of redfish most abundant was 22 cm, which is the minimum commercial size. Redfish are a slow growing species that can live up to 75 years old, said Senay adding it takes a long time for them to reach commercial size.
As it is, a 22 cm redfish “doesn’t give a very huge fillet. Fishermen would argue it’s a bit small for the market,” said Senay.
During the 2018/19 season, only 558 tonnes of redfish were landed in the experimental and index fisheries and so far in 2019/20, 707 tonnes has been landed.
“I think things will come in place when fish get to a more decent size,” said Senay.
