Radiometric age confirmation and growth of a deep-water marine fish species: The bank rockfish, Sebastes rufus

Abstract

The bank rockfish, Sebastes rufus, is part of a deep-water (31–454 m) rockfish community that is fished commercially off California and has experienced population decline. This species is considered very difficult to age with traditional methods of counting growth increments in otolith cross-sections, creating the need to confirm age estimates with an independent, objective method. We measured the disequilibria of 210Pb/ 226Ra in S. rufus otoliths to compare with ages estimated from traditional methods. Radiometric ages corroborated mean otolith increment counts, with closest agreement for the oldest samples. We conclude that it is appropriate to use traditional cross-section methods to estimate age for S. rufus. Further, our results suggest longevity of 50 years or more for this deep-water rockfish. von Bertalanffy growth parameters calculated from these confirmed ages (with 95% confidence limits) were: L ∞ = 488 mm (46.2) TL, K = 0.0482 (0.019), t o = −8.372 (4.91), n = 81 males; L ∞ = 594 mm (89.5) TL, K = 0.039 (0.018), t o = −6.96 (4.97), n = 86 females. Comparison of age data from our study with length at maturity data from other researchers indicates that S. rufus reach sexual maturity at approximately 15 years of age. Like other deep-water members of this genus, S. rufus is slow growing and matures at an advanced age, important characteristics to consider for management of the species.