2018 Assessment of the Demersal Shelf Rockfish Stock Complex in the Southeast Outside Subdistrict of the Gulf of Alaska
The demersal shelf rockfish (DSR) complex (yelloweye, quillback, copper, rosethorn, China, canary, and tiger rockfish) is assessed on a triennial cycle, with a full stock assessment typically conducted every third year. Historically, the stock assessment was based on relative abundance estimates from a manned submersible (Delta) and transitioned to a remote operated vehicle (ROV) in 2012. The recommended acceptable biological catch (ABC) and overfishing level (OFL) for this year’s assessment are based on the
most recent ROV density estimates of yelloweye rockfish in each management area using the methodology described in Brylinsky et al. (2009). The results of a preliminary statistical age-structured assessment model (ASA) that incorporates submersible, and ROV yelloweye rockfish density estimates, commercial, sport, and subsistence fishery data, and International Pacific Halibut Commission (IPHC) survey data are not presented this year due to personnel changes.
The yelloweye rockfish biomass estimate increased from 11,508 t to 12,029 t from 2018 to 2019. The increase in abundance is driven by an increase in average weight of yelloweye sampled in the CSEO management area.
Yelloweye rockfish comprise the largest component of the DSR complex and are managed using the Tier 4 harvest rule. The maximum allowable ABC for DSR in 2018 is 333 t (313 t yelloweye + 20 t nonyelloweye). The ABC and OFL for non-yelloweye DSR are calculated based on the Tier 6 rules harvest rule, species and these are added to the Tier 4 values for yelloweye. The Tier 6 values for non-yelloweye DSR utilizes catch data from 2010–2014 as this is the only time period with data available from the commercial, sport, and subsistence. This time period was the only range when all three catch data sets (commercial, sport, and subsistence) overlapped (Table 14.1). The maximum allowable ABC for DSR for 2019 is 333 t (313 t yelloweye + 20 t non-yelloweye), which is 14 tons higher than the maximum allowable ABC for 2018. This increase can be attributed to our increase in average weight for yelloweye rockfish in NSEO and CSEO. The DSR complex is particularly vulnerable to overfishing given their longevity, late maturation, and habitat-specific residency. Therefore, as in previous years, we recommend a harvest rate lower than the maximum allowed under Tier 4; F=M=0.02. This results in an author’s recommended ABC of 261 t (241 t yelloweye + 20 t non-yelloweye DSR Tier 6) for 2019. The OFL is set using F35%=0.032; which is 411 t for 2019.