Using cross-dating techniques to validate ages of aurora rockfish (Sebastes aurora): estimates of age, growth and female maturity

Since fishery management regulations have shifted much of the groundfish trawl effort in the northeastern Pacific from the continental shelf to the slope, fishery impacts on unassessed demersal slope rockfish species like the aurora rockfish ( Sebastes aurora ) may have increased. Understanding the life history of these species is a critical first step in developing management strategies to protect them from overharvest. In this study we employ cross-dating methods to validate the annual periodicity of growth increments and investigate the age, growth and maturity of aurora rockfish, a species for which life history information is quite limited. Specimens were collected on an opportunistic basis from Oregon commercial landings and from research cruises, over the years 2003–2006. Age was estimated for 438 individuals using otoliths processed via the break-and-burn method. The maximum estimated age was 118 years for females ( n = 324) and 81 years for males ( n = 114). The von Bertalanffy growth function showed that males grow faster and reach a smaller maximum size than females (males: L inf = 34, K = 0.09, t 0 = −1.9; females: L inf = 37, K = 0.06, t 0 = −5.5), though both sexes demonstrate relatively slow growth. Visual assessment of ovaries showed that the aurora rockfish is a synchronous spawner with parturition occurring in May and June off Oregon. Female age and length at 50% maturity were calculated at 12.6 years and 26 cm, respectively ( n = 307). Maturity and age data provided evidence for a protracted adolescence in this species.