A genetic project to determine the population structure of Deepwater Redfish across the Northwest Atlantic

Description

Conservation of Deepwater Redfish across Atlantic fishing zones is important to Canada. New information from this study will assist the development and implementation of management and conservation measures for this species.

The geographic distribution of Deepwater Redfish (Sebastes mentella) is essentially continuous across the North Atlantic. Therefore, sustainable management of this resource demands a good understanding of the population structure not only within Canadian waters, but also across the North Atlantic. Indeed, the lack of understanding regarding population dynamics (e.g. no stock recovery since the 1970’s in the Labrador Sea with an accompanying ‘Threatened’ designation by the Committee on the Status of Endangered Wildlife in Canada in 2010) might be explained by the fact that Canadian stocks represent the margin of larger biological units. Using DNA analysis of archived Redfish otoliths (fish ear bones) from fish caught in known areas of the Northwest Atlantic, this three-year project provided:

1. in-depth species and population identification to determine the connectivity of Canadian Redfish stocks from the Labrador Sea and Newfoundland’s Grand Banks with those in the Irminger Sea and western Greenland, as well as with Redfish from Davis Strait and Flemish Cap; and,
2. complemented the genetic description of stock structure with shape analysis of selected otoliths.

Results: Otoliths used for the project were selected from four different collections housed by institutions in Canada, Germany and Spain. These otoliths represent all areas of the Northwest Atlantic. Genetic and shape analyses, followed by rigorous statistical analysis, of several hundred of these ear bones revealed the following:

1. Three distinct genetic groups were detected within the data. One group corresponded to Sebastes fasciatus; the two other groups belonged to S. mentella (called hereafter “S. mentella group I” and “S. mentella group II”). No S. marinus was detected within the data;
2. S. fasciatus was observed in the Labrador Sea and on the Flemish Cap but was not observed in the other regions (i.e. Davis and Hudson Straits, West Greenland, southwest and northeast Irminger Sea;
3. The two genetic groups of S. mentella were present in all regions:
   1. “S.mentella group I” was usually recorded at deeper depth than “S. mentella group II”. However, sampling depth overall was not a good predictor of the expected genetic group of S. mentella; its predictive value varied between regions (e.g., continental shelf/slope regions versus open ocean) and between life stages (i.e., juveniles versus adults).
   2. Except for some genetic indices suggesting the differentiation of the Flemish Cap area, no consistent geographical substructure was observed within the “S. mentella group II”. A possible north-south substructure within the “S. mentella group I” was measured in Canadian waters. Statistical analyses are ongoing for testing the importance of this difference.

Scientific Project Title:

Stock delineation of Redfish (Sebastes mentella) straddling NAFO (Subareas 0, 1, 2+3KLMNO) and NEAFC (ICES Subareas XII and XIV) areas based on genetic analyses of archived otoliths

Program Name

Genomics Research and Development Initiative (GRDI)

Year(s)

2011 - 2014

Principal Investigator(s)

Jean-Marie Sévigny
lead

Don Power
Fisheries and Oceans Canada

Christoph Stransky
Johann Heinrich von Thünen Institute (vTI), Institute of Sea Fisheries, Hamburg, Germany