As near shore shelf fisheries in the Pacific Ocean have become depleted, commercial exploitation has moved to deeper continental slope fisheries for which there is very little information. One such fishery developed in the late 1980’s for the blackgill rockfish, a deep-dwelling (600-800m) species that congregates over rocky pinnacles mainly from southern California to southern Oregon. Preliminary age estimates of blackgill rockfish suggest they may live up to 90 years, yet this age has not been validated. Age estimates in this study utilizing the quantification of growth increments in thin otolith thin sections will be validated using the radioactive disequilibria of 210Pb and 226Ra in otolith cores from juvenile through adult blackgill rockfish collected off the Pacific coast in 1985 and 1998-2000. It is hoped that radiometric ages will closely agree with known age estimates and confirm the annual periodicity of growth increments for this species.
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| Larval blackgill otolith…how many days old? | Adult blackgill otolith under reflected light… |