Bomb Radiocarbon - Hapu
Hapu’upu’u - A long-lived deep-water grouper of the Hawaiian Islands
Canadian Journal of Fisheries and Aquatic Sciences 2019
Growth and longevity of Hawaiian grouper (Hyporthodus quernus) — input for management and conservation of a large,
slow-growing grouper
Allen H. Andrews, Edward E. DeMartini, Jon Brodziak,
Ryan S. Nichols, Robert L. Humphreys Jr.
Abstract: Hawaiian grouper (Hyporthodus quernus) is endemic to the Hawaiian Islands and is regionally important, yet little is known about its life history. This large species is managed within the Deep 7 bottomfish complex, 6 snapper that are assumed to have similar life histories. Previous age estimates were not validated and suggested a maximum age of 34 years. To evaluate the preliminary study and provide a valid basis for life history parameters, otoliths were aged using bomb radiocarbon (14C) dating. Measured 14C values provided ages for smallest to largest fish that differed from the original study. The fundamental information provided here when evaluating Hawaiian grouper conservation status is longevity(valid to 50 years and estimated to 76 years) — no male sampled was <80 cm TL and younger than 34 years — and age-at-sexual maturity and age-at-sex change, which were indirectly estimated and compared to prior published estimates for this and other groupers. Updated life-history parameters (k = 0.078, Linf = 95.8 cm TL) should be used to improve future management and conservation assessments.
Update: Published - https://doi.org/10.1139/cjfas-2018-0170
The longevity of this endemic Hawaiian fish is not known, but recent evidence from use of bomb radiocarbon dating has revealed this species can live more than 50 years with a longevity estimate approaching 80 years.
Above is a mounted hapu’upu’u otolith on the micromilling machine (lower right). The spindle is a chuck used to hold the micromilling bit (called a bur) which is actually a dentist’s drill bit. The very tip of the bur is 300 microns in diameter and it is guided across the otolith surface by the computer (screen in background). Careful guidance of the bur leads to an extracted pile of powder (see on top of the mounted otolith) that represented the earliest growth of this fish. That small pile is approximately 0.003 g (3 mg) of material. This material is analyzed for radiocarbon to later provide a measure of fish age. The mircostructure of the otoliths were 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/).
Popular Article I wrote for the fishers of Hawaii:
“One of these fishes is not like the others”
The hapu’upu’u is a member of a group of Hawaiian fishes called the Deep 7. This complex of species is currently managed as a unit for a number of logistical reasons, including a lack of life history information. This species needs to be managed separately because of its relative scarcity and what is now known to be a very different life history fro the snappers of this management group. The findings of the study have validated the age, growth, and longevity to assist with making decisions about proper assessments and management of this endemic species of the Hawaiian Islands.
For more information on the Deep 7 please visit the following links:
