Fisheries managers in Alaska have set the guideline harvest level for the 2021 Sitka Sound sac roe herring at 33,304 tons of mature herring, but say based on input from processors the commercial harvest is not expected to exceed 20,000 tons. The size of this year’s forecast of mature herring biomass is 210,453 tons of mature herring.
It is the second largest for Sitka Sound herring and is 16 percent smaller than the 2020 mature biomass estimate of 250,468 tons.
Because there was no commercial harvest in 2019 or 2020, the forecast used an average of the spring commercial purse seine weights at age from the 2017 and 2018 fisheries harvest: age-3, 79 grams; age-4, 92 grams; age-5, 109 grams; age-6, 126 grams; age-7, 144 grams; and age-8+, 165 grams. The forecasted average weight across all age classes is 112 grams.
According to the Alaska Department of Fish and Game the size of the forecasted age-5 herring cohort is unusually large. Still it is more uncertain than other year classes due in part to the magnitude of estimated abundance and the impact of uncertainty is estimated maturity and survival. Because the department has observed the 2016-year class of herring as age-3 fish in 2019 and as age-4 fish in 2020, the overall uncertainty with the 2021 forecast is less than that of the 2020 forecast. This same extremely large year class has been observed in other herring populations throughout the Gulf of Alaska in 2019 and 2020.