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2016 Assessment of the Arrowtooth Flounder Stock in the Eastern Bering Sea and Aleutian Islands

February 13, 2016

Arrowtooth flounder (Atheresthes stomias) are relatively large flatfish that range from central California to the eastern Bering Sea and are currently the most abundant  groundfish  species  in  the  Gulf  of  Alaska.  Arrowtooth flounder occur from central California to the Bering Sea, in waters from about 20m to 800m, although  catch  per  unit  effort  (CPUE)  from  survey  data  is  highest  between  100m  and  300m.  Spawningoccurs in deep water in the Gulf of Alaska and along the shelf break in the eastern Bering Sea. Migration patterns  are  not  well  known  for  arrowtooth  flounder;  however,  there  is  some  indication  that  arrowtooth  flounder move into deeper water as they grow, similar to other flatfish (Zimmerman and Goddard 1996).  Fisheries  data  off  Washington  suggest  that  larger  fish  may  migrate  to  deeper  water  in  winter  and  shallower water in summer (Rickey 1995). 

In  the  Bering  Sea  and  Aleutian  Islands  management  area,  their abundance  is  approximately  six  times  higher in the eastern Bering Sea than in the Aleutian Islands region. The distribution of ages appears to vary by region and sex; male arrowtooth as old as 36 years have been observed in the Aleutian Islands are not  commonly  observed  older  than  age  10  on  the  Bering  Sea  shelf,  while  the  female  length  and  weight  relationships  do  not  vary  significantly  between  the  two  regions.  Arrowtooth  flounder  begin  to  recruit  to  the  eastern  Bering  Sea  slope  at  about  age  4.    Based  on  age data  from  the  1982  U.S.-Japan  cooperative  survey,  recruitment  to  the  slope  gradually  increases  at  older  ages  and  reaches  a  maximum  at  age  9.    However,  greater  than  50%  of  age  groups  9  and  older  continue  to  occupy  continental  shelf  waters.  The  low  proportion  of  the  overall  biomass  on  the  slope  during  the  1988,  1991,  and  2016  surveys,  relative  to  that  of  earlier  surveys,  indicates  that  the  proportion  of  the  population  occupying  slope  waters  may  vary  considerably from year to year depending on the age structure of the population.

Arrowtooth flounder spawn in deep waters (>400m) along the continental shelf break in winter (Blood et al. 2007). They are batch spawners, spawning from fall to winter off Washington State at depths greater than 366m (Rickey 1995).  Spawning females have been found at 400m and males at ≥450m in the Gulf of Alaska, and larvae have been found at depths greater than 200 m (Blood et al. 2007; De Forest et al. 2014). The age composition of the species shows fewer males relative to females as fish increase in age, which suggests higher  natural  mortality  (M)  for  males  (Wilderbuer  and  Turnock  2009).    To  account  for  this process, natural mortality was fixed at 0.2 for females and 0.35 for males in the model.

The arrowtooth flounder resource in the EBS and the Aleutians is managed as a single stock although little is known about stock structure. There has been no research on this topic for this species.

Last updated by Alaska Fisheries Science Center on 02/13/2019

Research in Alaska North Pacific Groundfish Stock Assessments Arrowtooth Flounder