A long-Lived life history for opakapaka (Pristipomoides filamentosus) based on lead-radium and bomb radiocarbon dating

Age estimation for Hawaiian pink snapper or opakapaka (Pristipomoides filamentosus) from the Hawaiian Archipelago has been an ongoing problem because otoliths lack well developed annual growth zones. Early growth was well documented and validation of otolith growth was successful for the first few years of life using daily increments, but determination of age for the largest and oldest adults was still in question. A 1983 paper by Ralston and Miyamoto developed a relationship called numerical integration of daily growth increment widths as a model for age prediction which resulted in a maximum observed age of 18 years; however, the largest fish used in that study were less than the maximum length for this species in the region. This age has been subsequently and uncritically assumed as the maximum age for this species, but the 18 year estimate was based on clearly stated assumptions and the authors cautioned against unjustified estimates of longevity using their findings. Two methods that can provide independent estimates of age using adult otoliths are lead-radium and bomb radiocarbon dating. In this study, the longevity of opakapaka more than doubled using these methods, thus supporting the cautionary statements of the original paper.

This series of otoliths was the first use of bomb radiocarbon dating in the Hawaiian Islands. The mircostructure was sampled with a series of extractions made with a New Wave Research micromilling machine (Elemental Scientific Lasers, Bozeman, MT, USA; http://www.nwrlasers.com/milling/micromill/), which were analyzed for radiocarbon using AMS at WHOI-NOSAMS. 

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Bottomfish News Volume 15