Age Determination and Growth of Pacific Ocean Perch (Sebastes alutus) in the Northeast Pacific Ocean

Abstract

Age was determined by means of otoliths of juvenile and adult Pacific ocean perch (Sebastes alutus) collected during 1963–69 in the northeast Pacific Ocean, from Oregon to Unalaska Island, Alaska. Consistency of otolith readings between two readers varied inversely with numbers of translucent (or opaque) zones — from 100% agreement for 0-zone otoliths to 23% for 19-zone otoliths. Variability in zone counts between two readers was not great — 85% ± 1 zone for 3- to 24-zone otoliths — and the dispersion was near-normal about zero. Validity of otolith readings was established by demonstrating the annual formation of the translucent zone for juvenile fish, and by detecting the temporal passage of dominant year-classes among juveniles and adults.Age–length relationship varied inversely with depth off British Columbia, and inversely with latitude (or longitude) in the study region. Off Vancouver Island (48°48′N lat), two partially mixed stocks with near-opposite seasonal availability maxima were delineated, from bathymetric age–length and catch-rate data. Latitudinally, there was a sharp discontinuity in the age–length relationship at Dixon Entrance (54°40′N lat).Ranges of von Bertalanffy growth parameters were as follows: L∞, 37.2–48.2; K, 0.078–0.169; and to, − 0.4 to − 1.8. No geographical trend was evident for any parameter. Values of L∞ were larger for females, while values of K were smaller. Considerable variation in parameter values exists among studies on Pacific ocean perch from the western Gulf of Alaska.Age-weight relationship was generally sigmoid in shape. Values of W∞ ranged from 791 to 1686 g. Annual weight increments were maximal at ages 7–11.