Bomb Radiocarbon - Parrotfishes
FIRST VALIDATED LIFE HISTORIES — Hawaiian parrotfishes
Published with Canadian Journal of Fisheries and Aquatic Sciences 2018
Fig. S2. Measured radiocarbon values from sagittal otolith cores plotted at the calculated birth years from age estimation for Scarus rubroviolaceus and Chlorurus perspicillatus — with parrotfish (Labridae) otolith references (juveniles = + and x symbols)—relative to the regional bomb radiocarbon reference chronology (Kona, Big Island hermatypic coral and otoliths = grey circles). Overall decline (dotted line for MHI otoliths & coral, 1982-2015) with subset regression (solid line, 1990-2015) for comparison with specimen birth year regressions. Each birth year regression was in agreement with the rate and expected variability of the bomb radiocarbon decline over time as recorded in the reference records for region (see Andrews et al. 2016 and Tables S1-3). Regression relationships for S. rubroviolaceus and C. perspicillatus were Y = 5396.2 – 2.6618X (r2 = 0.87, P<0.0001, n=19) and Y = 6185.7 – 3.0555X (r2 = 0.86, P < 0.0001, n = 18), respectively. The regression for the 1990 and more recent portion of the coral and otolith reference chronology was Y = 6410.7 – 3.1665 X (r2 = 0.98, P < 0.0001, n = 30).
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Published Article: https://doi.org/10.1139/cjfas-2016-0523
Both spectacled and redlip parrotfishes we validate in an innovative manner — use of the bomb radiocarbon decline period. The consistent decline in the regional 14C signal provides a basis for validating short-lived species. In addition, the older age scenario — a confounding factor for measurements that cross the 14C peak — was eliminated using 14C measurements from whole lapillus otoliths.
Mature male spectacled parrotfish (C. perspicillatus) at Hanauma Bay.
Growth rates and longevities were estimated for five major fishery species of parrotfishes (“uhu”) at Oahu, Hawai’i. All species grew rapidly with von Bertalanffy growth formula k values ≥0.4·year−1. Longevities were found to range broadly among the three small species, 4 years in Calotomus carolinus and 6 and 11 years in Scarus psittacus and Chlorurus spilurus, and to 15–20 years in Scarus rubroviolaceus and Chlorurus perspicillatus for the two large species. Age reading and growth curves for the latter two large species were validated using bomb radiocarbon dating. Median ages at sexual maturity as females (AM50) and at sex change (from female to terminal phase male, A50) were estimated using logistic models. Sexual maturation occurred at 1–2 years for the small species and at 3–3.5 years in the large species. A 50 estimates ranged from 2 to 4 years in the small species and were about 5 and 7 years in S. rubroviolaceus and C. perspicillatus, respectively. Estimated milestones poorly corresponded to the current minimum legal size for uhu in Hawai’i (12 in. or 30.5 cm fork length). Pooling these parrotfishes for management seems generally inappropriate, especially for the two large species. Age-based metrics are more informative than size-based metrics for these fishes.
Comparative growth, age at maturity and sex change, and longevity of Hawaiian parrotfishes, with bomb radiocarbon validation
Picture of me with a spectacled parrotfish (C. perspicilatus) at old Aiea Lab.