2018 Assessment of the Other Rockfish Stock Complex in the Bering Sea and Aleutian Islands

Dusky rockfish and shortspine thornyheads are distributed in different depths and regions of the Bering Sea and Aleutian Islands. Shortspine thornyheads occur throughout the Aleutian Islands (AI) and eastern Bering Sea (EBS) slope but are most abundant in the western Aleutian Islands, where they are found between 200 m and 500 m depth (Reuter and Spencer 2001). In contrast, dusky rockfish are typically captured between 125-200 m in the Aleutian Islands, and are rarely encountered on the EBS slope in either survey or fishery catches.

There is no data on the genetic stock structure of dusky, harlequin, or redbanded rockfish. Isolation by distance population structure has been identified in rockfish species such as copper, brown, and grass rockfishes along the United States west coast (Sebastes caurinus, S. rastrelliger, and S. auriculatus; Buonaccorsi et al. 2002, 2004, 2005), Pacific ocean perch off Alaska (Sebastes alutus; Palof et al. 2011), and northern rockfish in the Bering Sea and Aleutian Islands region of Alaska (Sebastes polyspinis; Gharrett et al. 2012). Given the similarity in life history among rockfish species, it may be hypothesized that such genetic population structure could exist in the species that comprise the Other Rockfish complex. Genetic data suggests that the genus Sebastolobus, which includes all thornyhead rockfish, are subject to genetic population structure (Stepien et al. 2000).

The two most abundant species for Other Rockfish complex are dusky rockfish (Sebastes variabilis) and shortspine thornyhead (SST, Sebastolobus alascanus); therefore, more information is available on these species than the other species in the complex. The complex also includes all species of Sebastes and Sebastolobus, other than Pacific ocean perch (POP, Sebastes alutus), northern rockfish (Sebastes polyspinis), rougheye rockfish (S. aleutianus), and shortraker rockfish (S. borealis). An analysis was conducted in the 2001 Other Rockfish SAFE report to distinguish species expected to occur in the BSAI Other Rockfish complex from rarely observed and potentially misidentified species. The criteria used for the analysis was occurrence in at least one haul of the BSAI surveys and/or occurrence in at least 1% of observed fishery hauls. Using data from 1999-2001, seven species (shortspine thornyhead, dusky rockfish; Sebastes variabilis, redbanded rockfish; Sebastes babcocki, redstripe rockfish; Sebastes proriger, yelloweye rockfish; Sebastes ruberrimus, harlequin rockfish; Sebastes variegatus, and sharpchin rockfish; Sebastes zacentrus) were identified as meeting these criteria. Dark rockfish (Sebastes ciliatus) also met the criteria, but have since been removed from the Other Rockfish complex and is now managed by the State of Alaska. Species composition of these species in survey.