Biologists with the Alaska Department of Fish and Game have set the preliminary guideline harvest level for the 2016 Sitka Sound sac roe herring fishery at 15,674 tons, a big leap over the 2015 GHL of 8,719 tons.
The forecast, announced in late November, is based on a 20 percent harvest rate of a forecast mature biomass of 78,372 tons.
The final harvest from this year’s Sitka Sound sac roe fishery, which ran from March 18 to March 25, was 8,756 tons with overall mature roe recovery of 11.8 percent based on fish ticket information.
Faced with low prices for roe and a strong US dollar, which made overseas imports more expensive, processors and permit holders had agreed to harvest their quota in a controlled cooperative style fishery. As of the first week of December 2015, one US dollar was equal to 123.11 Japanese yen.
Just about all of the harvest goes to Japan, to make kazunoko, a delicacy of seasoned herring roe favored by the Japanese as a New Year’s dish. Eating kazunoko on Japanese New Year symbolizes the wish for many children or grandchildren in the year ahead.
To forecast biomass, biologists use an age structured analysis model using a long time series of egg abundance and age composition data from department surveys conducted during and following the spring fishery.
The department mapped 87.9 nautical miles of herring spawn in the Sitka Sound area during the spring of 2015, compared to the recent 10-year average of 60.1 nautical miles. Estimated age composition of spawning herring in 2015 was 46 percent age-3, 5 percent age-4, 21 percent age-5, 3 percent age-6, 4 percent age-7 and 21 percent age-8+.
The hindcast of 2015 mature biomass exceeded the 2015 forecast primarily because of higher than expected numbers of age-3 recruit herring observed in 2015, biologists said.
The continued increase of mature herring biomass forecasted for 2016 is primarily due to the continued maturation and return of a large cohort of age-4 fish, they said.
Estimated maturation rates suggest that 28 percent of age-3 herring mature and spawn, and that 81 percent of age-4 herring mature and spawn.
This large difference in percentage mature between age-3 and age-4, together with the large number of mature age-3 fish in 2015 is why greater numbers of this cohort are anticipated in 2016 as age-4 herring, they said.