Age validation of canary rockfish (Sebastes pinniger) using two independent otolith techniques: lead-radium and bomb radiocarbon dating

Abstract

Canary rockfish (Sebastes pinniger) have long been an important part of recreational and commercial rockfish fishing from south-east Alaska to southern California, but localised stock abundances have declined considerably. Based on age estimates from otoliths and other structures, lifespan estimates vary from ~20 years to over 80 years. For the purpose of monitoring stocks, age composition is routinely estimated by counting growth zones in otoliths; however, age estimation procedures and lifespan estimates remain largely unvalidated. Typical age validation techniques have limited application for canary rockfish because they are deep-dwelling and may be long-lived. In this study, the unaged otolith of the pair from fish aged at the Department of Fisheries and Oceans Canada was used in one of two age validation techniques: (1) lead-radium dating and (2) bomb radiocarbon (14C) dating. Age estimate accuracy and the validity of age estimation procedures were validated based on the results from each technique. Lead-radium dating proved successful in determining that a minimum estimate of lifespan was 53 years and provided support for age estimation procedures up to ~50–60 years. These findings were further supported by Δ14C data, which indicated that a minimum estimate of lifespan was 44 ± 3 years. Both techniques validate, to differing degrees, age estimation procedures and provide support for inferring that canary rockfish can live more than 80 years.

Incorporation of bomb-produced14C into fish otoliths. An example of basin-specific rates from the North Pacific Ocean

“…Additionally, this is the first study to compare two radiocarbon reference chronologies representing the same species from adjacent oceanic basins. Prebomb radiocarbon levels estimated for both Pacific halibut reference chronologies are similar to many others reported from the northeast Pacific, for example, yelloweye rockfish (Sebastes ruberrimus; Kerr et al 2004), canary rockfish (Sebastes pinniger; Andrews et al 2007), and Pacific ocean perch (Sebastes alutus; Kastelle et al 2008). However, the EBS reference chronology demonstrates a rapid ascent soon after the first rise, more resembling an intermediary atmospheric signature (Nydal 1993), and peaks much higher than the GOA chronology.…”

“…We consider the comparison of Chesapeake Bay black drum to oceanic North Atlantic reference chronologies analogous to the interpretation of differences between the two basins of the GOA and EBS. Conversely, deeper marine environments have slower mixing rates with surface waters and, thus, may be highly reliant upon downwelling for delivery of surface-absorbed 14 C. The uncertainty surrounding the effect that mixing rate at depth has upon 14 C uptake in the otoliths of deep-marine teleosts presents interpretational difficulties with respect to age validation (Andrews et al 2007(Andrews et al , 2009. The best results are obtained from otolith cores that are derived from specimens that have early life histories that inhabit the surface mixed layer or shallow nearshore areas, and by assuring that age-validation fish are spatially synchronous with the chosen reference chronology.…”

Age determination, bomb-radiocarbon validation and growth of Atlantic halibut (Hippoglossus hippoglossus) from the Northwest Atlantic

“…The close correspondence between the Δ 14 C of the young halibut cores and that of the reference radiocarbon chronology confirmed this assumption. The second assumption is that the water masses representing the reference and halibut chronologies show similar radiocarbon chronologies (Andrews et al 2007;Hamel et al 2008). This assumption is less stringent than the first, since surface marine waters in different regions tend to differ only in the post-bomb radiocarbon content, not in their timing.…”

Bomb radiocarbon dating of three important reef-fish species using Indo-Pacific Δ14C chronologies

“…Bomb radiocarbon dating has since been applied successfully to the otoliths of many species of teleost fishes to validate estimated age (e.g. Andrews et al 2007;Ewing et al 2007;Neilson and Campana 2008) and an important factor for a successful application is assembling a suitable regional D 14 C reference chronology.…”