2013 Assessment of the Deepwater Flatfish Stock in the Gulf of Alaska
April 23, 2013
The "flatfish" species complex previous to 1990 was managed as a unit in the Gulf of Alaska (GOA). It included the major flatfish species inhabiting the region, with the exception of Pacific halibut. The North Pacific Fishery Management Council divided the flatfish assemblage into four categories for management in 1990; "shallow flatfish" and "deep flatfish", flathead sole and arrowtooth flounder. This classification was made because of significant differences in halibut bycatch rates in directed fisheries targeting the shallow-water and deepwater flatfish species. Arrowtooth flounder, because of its present high abundance and low commercial value, was separated from the group and managed under a separate acceptable biological catch (ABC). Flathead sole were likewise assigned a separate ABC since they overlap the depth distributions of the shallow-water and deepwater groups. In 1993, rex sole was split out of the deepwater management category because of concerns regarding the bycatch of Pacific ocean perch in the rex sole target fishery.
The deepwater complex, the subject of this chapter, is composed of three species: Dover sole (Microstomus pacificus), Greenland turbot (Reinhardtius hippoglossoides) and deepsea sole (Embassichthys bathybius). Dover sole is by far the biomass-dominant in research trawl surveys and constitutes the majority of the fishery catch in the deepwater complex (typically over 98%). Little biological information exists for Greenland turbot or deepsea sole in the GOA. Better information exists for Dover sole, which allowed the construction of an age-structured assessment model in 2003 (Turnock, Wilderbuer, & Brown, 2003).