Understanding recruitment patterns of historically strong juvenile year classes in redfish (Sebastes spp.): the importance of species identity, population structure, and juvenile migration

摘要

Genetic analyses were undertaken on archived otoliths from juveniles representing historically strong year classes of northwest Atlantic redfish (Sebastes spp.) and on tissue samples from adults of known species and population of origin. The results indicated that the species composition of a year class is key information for understanding recruitment dynamics, with redfish species having distinct population-associated patterns of spatial dispersion. In the Gulf of St. Lawrence - Laurentian Channel area (GSL-LCH), the last strong year class (which supported the fishery for more than 30 years) belonged to Sebastes mentella and originated from the area. In contrast, four year classes that appeared abundant at young ages in research surveys in GSL-LCH but contributed only marginally to the adult population and the fishery of the region belonged to Sebastes fasciatus and carried the genetic signature of the adult population from the slope of the Newfoundland Grand Banks. Ocean currents and spatiotemporal trends in abundance-at-length suggest that the latter population uses the Gulf of St. Lawrence as a nursery area, with larvae and early juveniles drifting toward the Gulf of St. Lawrence and older juveniles migrating back to the slope of the Grand Banks after about 5-6 years. It is suggested that juvenile migration behaviour is a postsettlement process that plays an important role in redfish recruitment dynamics and carries both demographic and evolutionary implications.