2021 Climate-enhanced multi-species Stock Assessment for walleye pollock, Pacifc cod, and arrowtooth founder in the South Eastern Bering Sea Kirstin K. Holsman, Jim Ianelli, Kerim Aydin, Grant Adams, Kelly Kearney, Kalei Shotwell, Grant Thompson, and Ingrid Spies kirstin.holsman@noaa.gov November 2021 Alaska Fisheries Science Center, National Marine Fisheries Service, NOAA, 7600 Sand Point Way N.E., Seattle, Washington 98115 Summary of assessment results for 2021: Biomass • At 3.3 million tons, the 2021 SEBS pollock spawning biomass from the multispecies model is below the long-term (1979-2015) average of 4.7 million tons and represents a -15% change from 2020 and -33% change from 2019 spawning biomass levels. Similarly, the downward trend in total biomass observed in the past few years has continued through 2021, with recent declines placing the total 2021 biomass (10.5 million t) below the 1979-2015 average of 14.7 million tons. However it is important to note that because there was no Alaska Fisheries Science Center summer bottom trawl survey in 2020, estimates of, and diferences relative to the 2020 biomass should be interpreted cautiously. • The 2021 SEBS Pacifc cod female spawning biomass has declined -24% since 2020 and -38% since 2019. 2021 estimates are approximately -32% below the 1979-2015 average. Total biomass in the SEBS has declined -48% since 2016, and at approximately 685 thousand tons, is 36% below the long-term 1979- 2015 average of 1.1 million tons. These patterns are driven in part by continued low survey indices in 2020 and warm bottom temperatures that have induced northward redistribution of the P. cod stock (Spies et al. 2020, Stevenson et al. 2019). This assessment does not include Northern Bering Sea survey data collected in 2017, 2018, and 2019. • Arrowtooth total and spawning biomass estimates are 44% and 58% greater than the long-term 1979- 2015 average (respectively), and trends suggest relatively stable biomass since 2012. • The multispecies model estimates of a -15% and -24% change in spawning biomass (SSB) between 2020 and 2021 for pollock and Pacifc cod ( respectively) agree with CEATTLE single species model patterns of decline ( -16% and -23%, respectively). Both models predict an increase (slightly) in spawning biomass for arrowtooth founder relative to 2020. Recruitment • While pollock age 1 recruitment estimates for this year are -12% below the 1979-2015 average, estimated recruitment has increased in 2021 relative to 2020( note that the most recent estimates have the highest uncertainty). • Pacifc cod age 1 recruitment in the SEBS remains -66% lower than the 1979-2015 average, and is similar in 2021 to the record low recruitment estimated for 2017. 1 December 2021 Multi-species supplement NPFMC Bering Sea and Aleutian Islands SAFE