Age and growth of Greenland Halibut (Reinhardtius hippoglossoides) in the Northwest Atlantic: A changing perception based on bomb radiocarbon analyses

Greenland Halibut (Reinhardtius hippoglossoides) is a large circumpolar, right-eyed flounder that supports several international fisheries. Age estimates for this stock have customarily been obtained by counting annuli on the surface of whole otoliths but a matched pair comparison indicated that ages estimated from whole and thin-sectioned otoliths were the same up until age 9 (∼60 cm), after which whole otoliths underestimated the true age of the fish by up to 60% and 18 years. Bomb radiocarbon analyses on otolith cores from thin sections were similar to expectations based on the Greenland Halibut reference chronology, indicating that on average, thin sections gave an accurate age for fish in the 57-108 cm TL range. Growth curves estimated using thin-sectioned otoliths indicated that Greenland Halibut in this region are slower growing and longer lived than was previously thought. A comparison of growth parameters with other populations of Greenland Halibut showed that although the Pacific and Arctic are faster-growing, the stock off the East Coast of Canada is longer lived. This study represents the first age validation study for this stock in the Northwest Atlantic. Since the fishable portion of the population is largely <60 cm, it is possible that these results may not change the current perception of stock status. However, the increased longevity and reduced growth rates will undoubtedly affect other biological parameters and further work should be done to incorporate the new ageing knowledge into the Management Strategy Evaluation for this stock.