Age verification, growth and life history of rubyfish Plagiogeneion rubiginosum

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Abstract Age verification of rubyfish ( Plagiogeneion rubiginosum ) was sought using the bomb radiocarbon chronometer procedure. Stable isotopes were investigated for life history characteristics. Radiocarbon ( 14 C) and stable isotope (δ 18 O and δ 13 C) levels were measured in micro‐samples from five otoliths that had been aged using a zone count method. All the core 14 C measurements were ‘pre‐bomb’ indicating ages of at least 45 years, and the 14 C measurements across the otolith sections suggested that the zone‐count ageing method described herein is not biased. Maximum estimated age was 100 years. There was no significant between‐sex difference in the von Bertalanffy growth curves. The δ 18 O values indicated that rubyfish are near‐surface as juveniles, and move deeper with age. Adults appear to reside in 600–1000 m; this is deeper than most trawl‐capture data suggest, but not implausible, and has stock assessment implications. The δ 13 C values reflect fish metabolic rates, trophic feeding levels and oceanographic conditions. The stable isotopes record the environmental life history of each fish, and have value in distinguishing stocks and/or indicating vertical and latitudinal migratory patterns.

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