Return of the Redfish?

The early 1990s were exciting times for commercial fisheries in the Gulf of St. Lawrence due to an abundance of redfish. But in 1995, the stock collapsed. A moratorium was imposed and fishing of redfish was banned.

Fifteen years later, in 2010, the stock had still not been restored and the primary local population was listed as "endangered" by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). This listing is mainly driven by two factors. First, the quantity of redfish has continued to decline since the collapse of the stock. Second, no significant recruitment has been observed in 30 years, that is, since the strong 1980 year-class.

In 2013, various scientific surveys conducted by Fisheries and Oceans Canada revealed a surprising fact: the Gulf of St. Lawrence has a layer of young, two year old redfish, born in 2011. Surveys conducted in 2014 confirmed these observations and show the presence of an abundant year-class conceived in 2012.

In the past, several promising year classes in the juvenile stage (1985, 1988, 2003) disappeared from the Gulf of St. Lawrence before reaching adult size. Would the year classes of 2011 and 2012 have more success and would they contribute to population recovery in the Gulf of St. Lawrence?

A series of genetic studies based on microsatellite DNA markers offer some hope. These markers not only help distinguish the species, but they also characterize the spatial structure of their populations. The analyses show that juveniles from the year classes 1985, 1988 and 2003, which disappeared from the Gulf, bore the genetic signature of the adult population of Acadian Redfish, distributed at the mouth of the Laurentian Channel, more than 350 km downstream of the Gulf. It can therefore be deduced that this population of Acadian Redfish used the Gulf as a temporary feeding area for its juveniles.

In contrast, the abundant year class of 2011 recently observed in the Gulf of St. Lawrence bears the genetic signature of the local adult population of Atlantic Redfish. This result suggests that the redfish belonging to the 2011 year class should remain in the Gulf and foster the recovery of the population. Analyses are underway on the 2012 year class.

The success of the 2011 year-class should also have an effect on the Saguenay Fjord population. In fact, genetic analyses (combined with other observations) showed that the Saguenay Redfish represent a population for which renewal depends solely on the contribution of juveniles from the St. Lawrence. Over the past three years, the presence of small redfish was reported during winter recreational fisheries in the Fjord. This situation is a sign of an increase in the abundance of the Saguenay Fjord population in the coming years.

Existing scientific knowledge can predict, with greater confidence, the fate of the 2011 cohort in the Gulf of St. Lawrence. However, the reasons for the success of this year class, after more than 30 years of no significant recruitment in the Gulf, are still unknown. Consequently, despite the optimism generated by the 2011 year class, the episodic nature of redfish recruitment remains a significant source of uncertainty when it comes to understanding and managing redfish stock in the long term.

Alexandra E. Valentin, Johanne Gauthier and Claude Brassard
Science