2016 Assessment of Blackspotted and Rougheye Rockfish Stock Complex in the Bering Sea and Aleutian Islands
Rougheye rockfish (Sebastes aleutianus) have historically been managed within various stock complexes in the Bering Sea/Aleutian Islands (BSAI) region. For example, from 1991 to 2000 rougheye rockfish in the eastern Bering Sea (EBS) area were managed under the “other red rockfish” species complex, which consisted of shortraker (Sebastes borealis), rougheye (S. aleutianus), sharpchin (S. zacentrus), and northern rockfish (S. polyspinis), whereas in the Aleutian Islands (AI) area during this time rougheye rockfish were managed within the rougheye/shortraker complex. In 2001, the other red rockfish complex in the EBS was split into two groups, rougheye/shortraker and sharpchin/northern, matching the complexes used in the Aleutian Islands. Additionally, separate TACs were established for the EBS and AI management areas, but the overfishing level (OFL) pertained to the entire BSAI area. By 2004, rougheye, shortraker, and northern rockfish were managed with species-specific OFLs applied to the BSAI management area.
Fish historically referred to as “rougheye” rockfish are now recognized as consisting of two separate species (Orr and Hawkins 2008), with rougheye rockfish retaining the name Sebastes aleutianus and resurrection of a new species, blackspotted rockfish (S. melanostictus). Both species are distributed widely throughout the north Pacific. S. aleutianus is distributed from the eastern AI near Unalaska Island along the continental slope to southern Oregon, where S. melanostictus is distributed along the continental slope from Japan to California (Orr and Hawkins 2008). Several studies (Hawkins et al. 2005; Gharrett et al. 2005; Orr and Hawkins 2008) have used genetic and morphometric analyses to document the scarcity of rougheye rockfish west of the eastern AI and the occurrence of blackspotted rockfish throughout the BSAI area, thus establishing differences in species composition between areas in the BSAI. This distribution pattern has also been observed in recent AI trawl surveys, where rougheye rockfish are rarely found in the central and western AI. Some differences in species composition may be due to errors in field identifications, particularly in areas where both species are common, as blackspotted and rougheye rockfish are similar in appearance. This issue appears to be particularly problematic in the Gulf of Alaska (GOA), where a field test in the 2009 GOA trawl survey reported high misidentification rates. However, the distribution pattern in the AI survey biomass estimates is consistent with information obtained from the previously cited genetic and morphometric analyses, which did not rely on field identification. The title of this assessment was changed to “blackspotted and rougheye rockfish” in 2008 upon recognition of blackspotted rockfish and its high abundance in the BSAI relative to rougheye rockfish. Data for the two species are combined in the assessment, as species-specific catch records do not exist and identification by species has occurred in the AI trawl survey only since 2006.