Spatial migration pattern of deep-sea redfish (Sebastes mentella Travin) of the Norwegian-Barents population from survey data

Abstract

Study of redfish migration by traditional tagging-methods faces great difficulties. The redfish taken onboard a vessel usually prove to be nonviable. A sharp hydrostatic pressure differential is lethal for the redfish having a closed swim bladder. The main purpose of the present paper is to determine migration pattern of the deep-sea redfish juveniles. To study the deep-sea redfish migration, data from annual Russian and Norwegian scientific trawl surveys conducted during autumn and winter of 1982-1995 were used. The Petersen method was applied to analyse size composition of the deep-sea redfish catches taken during the above trawl surveys. The conclusion made from prior researches that the deepsea redfish year classes of 1982 and 1988 were strong compared to their neighboring ones was confirmed. On the assumption that "peaks" in the length distributions of survey catches displayed strong yearclasses, the annual corresponding lengths were defined for the 1982 and 1988 year classes of deep-sea redfish at different age (from 0 to 7 years). Subsequently, using the database from trawl surveys and knowing the length of the deep-sea redfish from strong yearclasses at different age, the distribution of these yearclasses by year was mapped. Based on the analysis of these maps, migration patterns of the deep-sea redfish juveniles in the Barents and Norwegian Seas were plotted.