Historical movement pattern of juvenile beaked redfish (Sebastes mentella Travin) in the Barents Sea as inferred from long-term research survey series

Abstract

Study of redfish migration by traditional tagging methods is difficult because captured redfish usually prove to be nonviable. The main purpose of the present paper is to determine movement patterns of the beaked redfish (Sebastes mentella) juveniles based on data from Russian and Norwegian scientific trawl surveys conducted during autumn and winter of 1982–1995. The Petersen method was applied to analyse size composition of the beaked redfish catches. The conclusion made from prior researches that the beaked redfish year classes of 1982 and 1988 were strong compared to their neighbouring ones was confirmed. On the assumption that ‘peaks’ in the length distributions of survey catches display strong year classes, the annual corresponding lengths were defined for the 1982 and 1988 year classes of beaked redfish at different ages (from 0 to 7 years). Subsequently, using the database from trawl surveys and knowing the length of the beaked redfish from strong year classes at different ages, the distribution of these year classes by year was mapped. Based on these maps, migration patterns of the beaked redfish juveniles in the Barents and Norwegian Seas were inferred. The present study shows that the duration of the period from spawning to nursery area for one year class of the beaked redfish takes at least 2 years (age 0–1). Seasonal movements within the nursery area seem to last for 3–4 (5) years when the redfish is 2–4 (5) years old. The beaked redfish of the Norwegian–Barents sea population start leaving the nursery areas at age 5–6.