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Sockeye shortfall forecast

the Fish Site Editor
25 April 2017, at 1:00am

This years commercial sockeye harvest in Upper Cook Inlet (UCI) is projected to be 1.2 million fish less than the 10-year average, according to the Alaska Department of Fish and Game.

The department expects the commercial harvest to be approximately 1.7 million fish, out of the 4 million sockeye expected to return. The run forecast for the Kenai River is approximately 2.2 million, which is 1.4 million less than the 20-year average run of 3.6 million.

In 2017, the predominant age classes are projected to be age 1.3 (60%), age 1.2 (16%), age 2.2 (7%) and age 2.3 (15%). The 10-year mean absolute percent error (MAPE) for the set of models used for the 2017 Kenai River sockeye salmon forecast is 20%. The department uses the European salmon aging system. One digit is placed to the left of the decimal point to indicate freshwater age (not including the year spent in the gravel during egg incubation and hatching – referred to as the gravel year), and another digit is placed to the right of the decimal point to indicate ocean age. For example, an age 1.3 sockeye salmon spent two years in freshwater and three years rearing in the ocean. A salmon of this age is referred to as a five-year-old fish, with the total age starting from the year of egg deposition.

The Kasilof River sockeye salmon run forecast for 2017 is 825,000 fish, which is 16% less than the 20-year average annual run of 987,000. The predominant age classes in the run forecast are age 1.2 (34%), age 1.3 (28%), age 2.2 (25%), and age 2.3 (10%). The 10-year MAPE for the set of models used for the 2017 Kasilof River sockeye salmon run forecast is 12%. The Susitna River sockeye salmon run forecast is 366,000, which is 5% less than the 10-year average of 387,000.

This forecast was derived using mean return per spawner by age class and mark–recapture estimates of spawner abundance for brood years 2006–2012. Sonar estimates of spawner abundance were not used, because mark–recapture studies have shown that the Yentna River sonar project underestimated sockeye salmon escapement, causing estimates of adult returns to also be underestimated.

The 4-year MAPE for this forecast method is 17%. The predominant age classes in the 2017 Susitna River sockeye salmon run forecast are age 1.2 (20%), age 1.3 (53%) and age 2.3 (12%). The Fish Creek sockeye salmon run forecast is 75,000, which is 11% less than the 20-year average of 84,000. The predominant age classes in the 2017 Fish Creek run forecast are age 1.2 (64%) and age 1.3 (23%). The 10-year MAPE for the Fish Creek sockeye salmon run forecast is 70%.