A recent news release from the Alaska Department of Fish and Game (ADFG) outlines an estimated 2015 pink salmon harvest of 58 million fish.
“An actual harvest of 58 million pink salmon would be well above the recent 10-year average of 41 million pink salmon and a harvest of that magnitude would be in the top ten harvests since 1960,” according to the release.
The release states that the annual forecast was produce in two steps, “1) a forecast of the trend in the harvest, and 2) the forecast trend adjusted using 2014 juvenile pink salmon abundance data provided by the NOAA Fisheries, Alaska Fisheries Science Center, Auke Bay Laboratories.”
Rather than a simple average of past harvests, ADFG uses a technique called exponential smoothing to make its predictions. The technique takes into account all harvests since 1960 but gives more weight to recent harvests.
“Recent harvest observations were given more weight in the analysis while past harvest observations were increasingly down-weighted with time; i.e. the older the datum, the less influence it has on the forecast,” according to the ADFG website.
Though 2013 was a record-breaking year for pink salmon, it was generally on trend with recent odd-year harvests, which have been much higher than even-year harvests. ADFG accounted for the record harvest by making a more conservative harvest projection for 2015, using both even-year and odd-year data in their trend analysis rather than starting with the parent year harvest–in this case 2013– as the organization typically does.
An ADFG forecast discussion states, “Forecasting the 2015 pink salmon harvest was made exceptionally challenging due to the unprecedented harvest of 95 million pink salmon in the parent year of 2013. This harvest was nearly 20 million fish higher than any other pink salmon harvest since commercial fisheries began in Southeast Alaska in the late 1800s.”
ADFG also examines juvenile salmon abundance information, escapements and early marine survival issues. Statistical reports from the NOAA Auke Bay Lab on juvenile pink salmon in 2014 indicate, “very large escapements in 2013 had good spawning success and that there were no major freshwater and early marine survival issues for pink salmon set to return in 2015,” according to an ADFG report.
Also noted in the report were “anomalously warm conditions” in the Gulf of Alaska in the summer of 2014. “The effect of these unusual environmental conditions on the marine survival of pink salmon is not known,” concludes the report.
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