Extensive Sampling and Concomitant Use of Meristic Characteristics and Variation at the MDH-A* Locus Reveal New Information on Redfish Species Distribution and Spatial Pattern of Introgressive Hybridization in the Northwest Atlantic

Abstract

Branton. 2006. Extensive sampling and concomitant use of meristic characteristics and variation at the MDH-A* locus reveal new information on redfish species distribution and spatial pattern of introgressive hybridization in the Northwest Atlantic. J. Northw. Atl. Fish. Sci., 36: 65-80. doi: 10.2960/J.v36.m573 Abstract Variability at the MDH-A* locus, of anal fin ray number and extrinsic gasbladder muscle pattern is used to describe the distribution of Sebastes fasciatus and S. mentella in the Northwest Atlantic and to define the geographical boundaries of the area of introgressive hybridization between the two species. Sebastes mentella distribution extends from the Gulf of St. Lawrence northward while S. fasciatus is distributed from the southern Grand Banks southward as described in earlier studies. Sebastes fasciatus is also found in the southern Labrador Sea where the species appears to reach its northernmost limit. The distribution of the two species overlaps mainly in the Gulf of St. Lawrence and the Laurentian Channel, around the Grand Banks and on Flemish Cap. This area of sympatry comprises a smaller area where heterozygous individuals at the MDH-A* locus are observed and where introgressive hybridization occurs. This area is mostly restricted to the Gulf of St. Lawrence and the Laurentian Channel. The west-east gradient in the abundance of introgressed individuals suggests that the Gulf of St. Lawrence is the centre of introgressive hybridization and that larval dispersion or migration of juveniles and adults takes place from the Gulf of St. Lawrence towards south Newfoundland and the Grand Banks. In contrast, the absence of heterozygous individuals at the MDH-A* locus outside the Gulf of St. Lawrence and the Laurentian Channel indicates that the dispersion of these individuals is limited for all stages of the life cycle.

Image-enhanced burnt otoliths, bomb radiocarbon and the growth dynamics of redfish (Sebastes mentella and S. fasciatus) off the eastern coast of Canada

“…Otoliths were collected as described above, but muscle tissue was not collected for subsequent genetic identification. Rather, it was assumed that most or all of the samples were from S. fasciatus based on previous genetic and meristic surveys of the region (Roques et al 2001;Valentin et al 2006Valentin et al , 2014.…”

Arching effect on fish body shape in geometric morphometric studies

“…The north‐west Atlantic Sebastes species complex consists of three species: Sebastes fasciatus Storer and Sebastes mentella Travin, which undergo introgressive hybridization and support a commercial fishery and Sebastes marinus (L.) [regarded as a synonym of Sebastes scriba (L.) by some authors; Eschmeyer, 2008]. The 1996–1998 multidisciplinary research programme on Sebastes (Gascon, 2003) and related studies (Roques et al , 2001, 2002; Valentin et al , 2002, 2006) gave new insights regarding the Sebastes population structure in the north‐west Atlantic Ocean. Additional investigations, however, were needed to improve the knowledge on the complex question of population structure.…”

Tracking seasonal migrations of redfish (Sebastes spp.) in and around the Gulf of St. Lawrence using otolith elemental fingerprints

“…Virtually all studies on the distribution of adult Sebastes in the Atlantic have been confounded by difficulties in distinguishing among species and thus have been focused on the zoogeography of the congeneric species rather than within-species movements (Misra 1985;Stransky and MacLellan 2005;Valentin et al 2006). Nevertheless, broad categories of deepwater fish migrations have become increasingly well documented.…”

“…The species can be exceedingly difficult to identify, requiring either dissection of the swimbladder musculature or genetic assay or both for confident identification (Ni 1981;Gascon 2003;Valentin et al 2006). Hybridization of the sympatric species has also been reported (Rubec et al 1991;Desrosiers et al 1999;Roques et al 2001).…”