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1. Identity of stock of redfish Sebastes mentella in the pelagic Irminger Sea and adjacent waters (from results of Russian investigations) by V.N. Shibanov, S.P. Melnikov, Yu.I. Bakay Knipovich Polar Research Institute of Marine Fisheries and Oceanography (PINRO), Murmansk, Russia Stroganov A.N. and G.G.Novikov Moscow State University, Moscow, Russia

2. slide 1 • Single-stock hypothesis: All S. mentella in the Irminger Sea and adjacent waters is one stock and is segregated according to age/size/maturation. • The extruded larvae are found over one big area. • Main nursery area on the shelf of West- and East-Greenland. . • That all the morphological and biological characters used to phenotype the redfish, incl. parasite infestation, are related to growth, age and/or the environment. • The overall genetic distances are small among locations and depths • Morphometric data/results did not reveal any clear stock structure in the area (except Flemish Cap) • Otolith shape and trace element analyses did not reveal any stock structure in the area • Parasitological data did not reveal any clear stock structure in the area • Consider to keep it a single stock until better (improved) sampling has been conducted and more conclusive evidences have been put forward

3. slide 1 continue • Three-stocks hypothesis: The three described components are biologically different stocks. • Microsatellite test on material from shelf deep-sea S. mentella at Iceland shows significant difference to pelagic deep-sea S. mentella in deeper pelagic waters of the northern Irminger Sea. • If distribution of females and males in maturity stage 3 is representative for showing the area of larvae extrusion and mating, respectively, then the distribution maps of this maturity stage show separate larvae extrusion and mating areas for oceanic phenotyped S. mentella, pelagic deep-sea phenotyped S. mentella, and Icelandic shelf deep-sea phenotyped S. mentella (in the latter case, to a lesser extent). • Deviations from Hardy-Weinberg law, statistical tests of microsatelite genetic data (those data sets containing samples from all areas and depths), AFLP genetic data and fatty acid data show up to three different, and statistically significant, groups. Fatty acid results also group the fish significantly into three groups in this area.

4. slide 2 • The principal criteria to distinguish a population/stock/management unit are as follows: • stability in time; • full range of age groups/ life cycle stages; • self-reproduction; • spatial and/or temporal isolation from analogous groups of the same species. • For the majority of widespread fish species, which population habitat area has a complex functionally divided structure, an extra criterion is: • functionally divided population habitat area with all subareas (reproduction, feeding, wintering and nursery areas).

5. slide 3 Scheme of functional structure of the habitat and ontogenetic migration of S. mentella in the North Atlantic: 1 – direction of larvae and fry drift; 2 – direction of immature individuals migration; 3 – direction of return migration of maturing and mature individuals; 4 – area of reproduction; 5 – distribution area of immature individuals; 6 - feeding area.

6. slide 4 Scheme of the North Atlantic Currents: Warm currents (1): NaC - North Atlantic; IC - Irminger; Cold currents (2): EgC - East Greenland; WgC - West Greenland; LC - Labrador; boundary of subpolar cyclonic gyre (3); isobathes (4). Distribution and mean length (cm) of larvae, fry and juveniles of S. mentella in the North Atlantic.

7. slide 5Length composition of redfish in the layers 0-500 m (A), 500-1000 m (B) in the Irminger Sea in 1995-2003. Age composition of redfish in the layers 0-500 m (A), 500-1000 m (B) in the Irminger Sea in 1995-2003.

8. slide 6 Linear growth of redfish males and females in the layers 0-500 m (1), 500-1000 m (2). Weight growth of redfish males and females in the layers 0-500 m (1), 500-1000 m (2)

9. slide 7 Maturation of redfish by length groups in the layers 0-500 m (A), 500-1000 m (B) Redfish maturation by age groups in the layers 0-500 m (A), 500-1000 m (B).

10. slide 8 Frequency of dominant allele in polymorphic loci of Sebastes mentella (1999-2002).

11. slide 9 Maturation of males and females of redfish by age groups in the layers 0-500 m (A), 500-1000 m (B)

12. slide 10 S. mentella infestation with Sphyrion lumpi and occurrence of fish with pigment patches on the skinin different areas of the Irminger Sea and adjacent waters in 2001 * - prevalence (%) and abundance index taking into account the remains of the copepod parasitizing (alive S. lumpi + old cephalothoraxes of S. lumpi).

13. Conclusions • During the study of the intra-species structure in the North Atlantic it was ascertained that there exists a single population of S. mentella. • The habitat is subdivided into two functional areas. The area of reproduction and feeding is in the oceanic pelagic waters of the Irminger and Labrador seas and is inhabited with mature individuals. The main reproduction area is above the slopes of the Reykjanes Ridge. Immature and maturing individuals are distributed in the margins of the population habitat on the slopes of Greenland and Canada, in the nursery area. • The population habitat of S. mentella is contained within the sub-polar cyclonic gyre. • The fishable stock of S. mentella in the pelagic waters of the Irminger and Labrador seas is the spawning stock of the S. mentella population. • When working out management measures for S. mentella fisheries in the Irminger Sea and adjacent waters it is biologically grounded to keep the current regime of the stock exploitation and two practical management units, in the pelagic waters and on the shelf.