Age determination and confirmation from otoliths of the bank rockfish, Sebastes rufus (Scorpaenidae)

Abstract

Methods for determining and confirming age for Sebastes rufus from otoliths were examined. The periodicity of growth zone formation and of calcium deposition in otoliths was studied to verify ages estimated from counts of otolith growth zones; results were inconclusive. Pb-210/Ra-226 activity ratios were measured in otoliths to confirm ages estimated from counts of otolith growth zones. Radiometric ages agreed well with growth zone counts, giving substantial validity to them and suggesting longevity of 50 years or more Sebastes rufus. Otolith length, width, area, perimeter and weight were evaluated as criteria for determining age. All parameters were highly correlated with growth zone counts, with otolith weight showing the most promise as an age predictor. Von Bertalanfy growth parameters were L ∞ =488, K=0.048, t0=-8.372 for 81 males and L ∞ =594, K=0.039, t0=-6.96 for 86 females. Sebastes rufus are long-lived, slow growing and reach reproductive maturity at 10-15 years of age.