Review of the population structure and ecology of S. mentella in the Irminger sea and adjacent waters

Abstract

page 455 Introduction 455 Redfish spawning areas and time 458 Larvae and fry (0-group) distribution and drift patterns 459 Juvenile distribution, nursery areas, and migration pattern 463 Adult distribution 463 Genetic differentiation 471 Conclusions 474 Acknowledgements 475 References 475 AbstractSignificant controversies exist over the three types of Sebastes mentella found in the Irminger Sea and adjacent waters. Preliminary genetic studies have given evidence for the existence of three distinct groups, characterized using several molecular genetic markers. The biological or ecological significance of these between-group differences has, however, not been evaluated. In the present paper, we review the life cycle of S. mentella in this area, based on published data. Spawning of S. mentella in the Irminger Sea takes place in a single area above Reykjanes Ridge. The larvae drift towards East Greenland from where they are carried to West Greenland (NAFO Subareas 0+1). Later they return to East Greenland where the main nursery area has been identified. There is evidence for a migration of juvenile fish from the nursery area into the open Irminger Sea, where many different cohorts spawn. We also compare these ecological data with the genetic results and we conclude that the observed genetic differences can be derived from possible genetic drift, selection or mostly from temporal variation (age dependency) which has also been reported for other species with as high longevity as S. mentella. We conclude that S. mentella in the Irminger Sea and adjacent waters comprises one single population.

Geographic variation of golden redfish (Sebastes marinus) and deep-sea redfish (S. mentella) in the North Atlantic based on otolith shape analysis

“…The relatively high discrimination of the Barents Sea samples from the other areas, however, suggests separation of the Northeast Arctic stock from S. mentella in the central and western areas. Some previous studies pointed to uniformity of S. mentella within the Irminger Sea and close relations with the demersal occurrences on the Greenland and Iceland shelves (Saborido-Rey et al, 2004). The existence of two pelagic stock units of S. mentella in the Irminger Sea, as suggested by differences in haemoglobin and enzyme patterns between ''oceanic'' and (pelagic) ''deepsea'' S. mentella (Johansen et al, 2000a), has also been supported by nuclear DNA methods (microsatellites and AFLP; Daníelsdóttir et al, in press).…”

“…Among the four species found in the North Atlantic, golden redfish (S. marinus) and deep-sea redfish (S. mentella) are the most widely distributed and commercially exploited representatives, while Acadian redfish (S. fasciatus) are generally limited to the Northwest Atlantic, and Norway redfish (Norway haddock; S. viviparus) are only found in the Northeast Atlantic (Whitehead et al, 1986). S. marinus grows larger than S. mentella and inhabits continental shelves off eastern Canada, Greenland, Iceland, and the Faroe Islands, Norwegian waters, the Barents Sea, and Svalbard, mainly in depths between 100 m and 300 m. S. mentella is generally distributed deeper than S. marinus and found in the pelagic zone of the Labrador and Irminger Sea down to 1000-m, in addition to the areas where S. marinus occurs (ICES, 1998;Saborido-Rey et al, 2004).…”

“…Past efforts to clarify the complex stock structures of redfish, however, all demonstrated high variation within geographic areas or stock units, and relatively weak differentiation between these (ICES, 1998). The existence of separate stocks of S. mentella in the Irminger Sea and adjacent waters has been controversially discussed and raised unsolved problems in the assessment and management of this important fishery resource (Saborido-Rey et al, 2004). In a multidisciplinary approach, species and population structure of redfish was investigated using extensive material from all important distribution areas in the North Atlantic.…”

Female reproductive biology of the bluemouth Helicolenus dactylopterus dactylopterus: spawning and fecundity

“…Another explanation could be related to the bathymetric distribution of the species, where the largest specimens of H. d. dactylopterus are found in progressively deeper waters (Massutí et al , 2000), together with the so‐called Mediterranean reproductive fish refuge paradigm (Caddy, 1993). For the genus Sebastes , for instance, a clear migratory movement of mature fishes from the recruitment area to the spawning area has been observed (Saborido‐Rey et al , 2004). So, larger and actively reproductive H. d. dactylopterus females could have migrated to submarine canyons and abrupt bottoms that are not usually reached by longliners, making their capture more difficult.…”

Resolving species identification problems in the genus Sebastes using nuclear genetic markers

“…For example, most of the individual of the sample MeOc96 were typed as oceanic, but clearly defined the deep-sea group in the Bayesian analysis together with the defined deep-sea individuals (MeDs01). Significant controversies exist around the oceanic and deep-sea type of S. mentella within the Irminger Sea (Johansen et al, 2000a;Saborido-Rey et al, 2004;Stransky, 2005), and although there are evidence for the existence of these two types (Johansen et al, 2000a; this study), we recommended further genetic analyses combined to biological information to assess the biological significance of the observed genetic differences.…”