2014 Assessment of the Greenland Turbot in the Bering Sea and Aleutian Islands
March 05, 2014
Two models are presented for consideration. Model 1 is the model configuration that has been accepted by the SSC for the previous 2 years updated with the most recent data. An error was discovered in the female length at 50% mature used last year and has been corrected in both
models presented this year. Model 2 is similar to the models presented for the past 2 years with a parameter for autocorrelation in recruitment. Model 2 differs from last year’s autocorrelated model in that an additional time block (2010-2014) for the longline fishery selectivity was added
to improve the residual pattern, and catchability was fixed for shelf and survey indices. The stock continues to be modeled using the same software as previous assessments (Stock Synthesis 3).
Greenland turbot (Reinhardtius hippoglossoides) is a Pleuronectidae (right eyed) flatfish that has a circumpolar distribution inhabiting the North Atlantic, Arctic and North Pacific Oceans. The American Fisheries Society uses “Greenland halibut” as the common name for Reinhardtius hippoglossoides instead of Greenland turbot. To avoid confusion with the Pacific halibut, Hippoglossus stenolepis, common name of Greenland turbot which is also the “official” market name in the US and Canada (AFS 1991) is retained.
In the Pacific Ocean, Greenland turbot have been found from the Sea of Japan to the waters off Baja California. Specimens have been found across the Arctic in both the Beaufort (Chiperzak et al. 1995) and Chuchki seas. This species primarily inhabits the deeper slope and shelf waters (between 100 m to 2000 m; Fig. 5.1) in bottom temperatures ranging from -2°C to 5°C. The area of highest density of Greenland turbot in the Pacific Ocean is in the northern Bering Sea, straddling the border between US and Russian exclusive economic zones. Juveniles are believed to spend the first 3 or 4 years of their lives on the continental shelf and then move to the continental slope (Alton et al. 1988; Sohn 2009; Fig. 5.2). Adult Greenland turbot distribution in the Bering Sea appears to be dependent on size and maturity as larger more mature fish migrate to deeper warmer waters. In the annual summer shelf trawl surveys conducted by the Alaska Fisheries Science Center (AFSC) the distribution by size shows a clear preference by the smaller fish for shallower (< 100m) and colder shelf waters (< 0°C). The larger specimens were in higher concentrations in deeper (> 100 m), warmer waters (> 0°C) (Fig. 5.3 and Fig. 5.4).