A preliminary guideline harvest level for Alaska’s 2015 Sitka Sound sac roe herring fishery is down dramatically from the preliminary GHL posted for 2014, with very low numbers of age-3 recruit herring cited as a factor.
The preliminary GHL announced in late November was 8,712 tons, based on a 19.7 percent harvest rate of a forecast mature biomass of 44,237 tons. A year ago, the preliminary GHL announced for the 2014 season was 17,592 tons, based on a 20 percent harvest rate of a forecast biomass of 87,958 tons.
The forecast and GHL for the 2015 fishery are to be finalized using average weight-at-age from samples obtained in the winter test fishery, to be conducted in late January or early February 2015. The final forecast is to be announced in late February or early March.
ASF&G uses an age structured analysis model that uses a long time series of abundance and age composition data from department surveys conducted during and following the spring fishery. Herring abundance is estimated using aerial surveys designed to map the length of shoreline receiving spawn and dive surveys that estimate the density of eggs and the average width of the spawn. The department mapped 50 nautical miles of herring spawn in the Sitka Sound area during the spring of 2014, compared to the recent 10-year average of 60 nautical miles.
The estimated post-fishery spawning biomass in 2014 was 51,321 tons and the total sac roe harvest was 16,957 tons. An additional 121 tons were harvested in personal use and test fisheries for a total mature population biomass of 68,399 tons, which was below the 81,663 tons forecast. Samples of the spawning herring in 2014 resulted in an age composition of 1 percent ag-3; 39 percent age-4; 10 percent age -5; 5 percent age-6; 6 percent age-7 and 34 percent age-8 and older herring.