2015 Assessment of the Shallow-water Flatfish Stock Complex in the Gulf of Alaska
The "flatfish" species complex previous to 1990 was managed as a group in the Gulf of Alaska and included the major flatfish species inhabiting the region with the exception of Pacific halibut (Hippoglossus stenolepis). The North Pacific Fishery Management Council divided the flatfish assemblage into four categories for management in 1990; "shallow flatfish" and "deep flatfish" (Table 4.1), flathead sole (Hippoglossoides elassodon) and arrowtooth flounder (Atheresthes stomias). This classification was made because of the significant difference in halibut bycatch rates in directed fisheries targeting on shallow-water and deep-water 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 deep-water groups. In 1993 rex sole (Glyptocephalus zachirus) was split out of the deep-water management category because of concerns regarding the Pacific ocean perch bycatch in the rex sole target fishery.
The major species, which account for the majority of the current biomass for shallow-water flatfish are: northern rock sole (Lepidopsetta polyxystra), southern rock sole (Pleuronectes bilineata), butter sole (Pleuronectes isolepis), yellowfin sole (Pleuronectes asper), and starry flounder (Platichthys stellatus). For this assessment, biomass, fishing mortality rates, and ABC estimates are presented for each species and management category.
Beginning with the 1996 triennial trawl survey, rock sole was split into two species, a northern rock sole and a southern rock sole. Due to overlapping distributions, differential harvesting of the two species may occur, requiring separate management in the future.
This report describes flatfish catches taken from 1978 through October 27, 2015 and presents information on the status of flatfish stocks and their potential yield based on Gulf of Alaska demersal trawl survey data through 2015.