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KETCHIKAN (KDN) — A joint state-federal forecast for pink salmon harvests during 2019 in Southeast Alaska estimates a harvest of about 18 million pinks — about half the recent 10-year average harvest of 36 million pink salmon.
The Alaska Department of Fish and Game published the annual pink salmon harvest forecast on Thursday.
The 18-million fish estimate is near the upper end of the “weak” harvest range of 11 million to 19 million fish, according to the department.
An actual harvest “near this forecast would be the lowest odd-year harvest since 1987,” according to the forecast report.
Fish and Game notes that the agency combined efforts with the federal NOAA Fisheries agency to produce the joint forecast, which is primarily based on the National Oceanic and Atmospheric Administration’s long-running Southeast Coastal Monitoring Project that measures the abundance of juvenile pink salmon in northern Southeast Alaska waters during the months of June and July.
“These data were obtained from systematic surveys conducted annually in upper Chatham and Icy straits and are highly correlated with the harvest of adult pink salmon in the following year,” according to the forecast document.
The 2018 surveys resulted in an “extremely low” abundance index for juvenile pink salmon, according to the agencies, which added that the index was the third lowest in 22 years of such surveys.
This result was unexpected, because the 2017 escapements of pink salmon into spawning streams was “generally good,” — and escapement goals had been met throughout Southeast Alaska.
“This indicates that brood year 2017 pink salmon likely experienced poor freshwater and/or early marine survival,” states the forecast report.
In addition, the juvenile pink salmon caught in the 2018 surveys were the smallest in length of any of the 22 survey years.
The forecast announcement cites “anomalously warm” sea surface temperatures in the Gulf of Alaska as a potential source of uncertainty regarding the 2019 return of pink salmon.
“The warm temperatures that persisted throughout the Gulf of Alaska from fall 2013 through much of 2016 ... have returned in 2018,” the announcement states. “Pink salmon that went to sea from 2014 to 2016 returned in numbers below expectation and below recent odd- and even-year averages. Although sea surface temperatures moderated in the Gulf of Alaska in 2017, effects on the Gulf ecosystem likely persisted and pink salmon that went to sea in 2017 and returned in 2018 also experienced reduced survival.
The current return of anomalously warm sea surface temperatures in the Gulf of Alaska might have a negative impact on pink salmon survival, according to the announcement.
“Although the weak harvest forecast in 2019 is consistent with poor survival, the impact of Gulf of Alaska temperatures is unknown and adds uncertainty to the forecast,” states the announcement.
Data included with the forecast materials indicate that actual harvests of pink salmon during the 2015-2017 fishing seasons were below the forecast estimates. In two of those years — 2016 and 2017 — the actual harvests were within the “80 percent confidence intervals” cited in the forecasts.
In layman’s terms, a confidence interval is a “range of values we are fairly sure our true value lies in,” according to the website “Math is Fun” website (www.mathis fun.com).
The 80 percent confidence interval for the 2019 pink salmon harvest forecast is 15 million to 26 million fish, according to the announcement.
Fish and Game plans on managing the commercial purse seine fisheries in 2019 inseason, using information available about the strength of pink salmon returns as the runs materialize.
“Aerial escapement surveys and fishery performance data will continue, as always, to be essential in making inseason management decisions,” states the forecast announcement.