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11/23/2019
ADF&G predicts 'weak' 2020 pink harvest
Annual harvests of pink salmon in Southeast Alaska compared to the actual preseason harvest forecasts, 2004-2020. The error bars represent the 80% confidence or prediction intervals of the forecasts. Courtesy of the Alaska Department of Fish and Game


By SAM ALLEN
Daily News Staff Writer

Earlier this week, the Alaska Department of Fish and Game predicted a 'weak' harvest for pink salmon throughout Southeast Alaska.

The 2020 harvest forecast of 12 million compares to the recent 10-year average of 35 million pink salmon, according to Fish and Game information.

The weak harvest is based on summer catches showing low numbers of young pink salmon.

These catches were carried out by the Fish and Game research vessel Medeia in June and July in the upper Chatham and Icy straits. The harvests showed the third lowest abundance of juvenile pinks in 23 years, according to a Fish and Game press release.

The causes for the decline in juvenile pink salmon are not entirely understood. Water temperatures and weather conditions may play a role.

The press release states, "It is possible that drought conditions present in Southeast Alaska from the parent year 2018 spawn through the spring of 2019 reduced spawning success or negatively impacted overwinter survival of developing juvenile salmon, but the exact reasons for the low juvenile abundance are not know."

It's generally agreed that a large chunk of pink salmon's mortality occurs in fresh water and early marine environments, according to Andy Piston, who works for the Fish and Game as the Southeast Alaska Pink and Chum Salmon project leader.

He said the trawl surveys capture "the survivors that made it through all of that early marine freshwater environment."

If the drought had an impact on juveniles and pink salmon rearing in the streams, it would be reflected in the trawl surveys, according to Piston.

Piston said that, starting off, there was a low parental escapement in 2018 that probably gave way to below-optimal egg disposition.

"There just wasn't that many fish in a lot of areas," Piston said. "We didn't have any huge die-offs anywhere, but just having that extreme low water for a lot of the season, you know, it increases their risk of predation. It probably increases stress on the fish in many ways."

Water temperatures are measured down to 20 meters in the area where the juveniles are caught, and are calculated into the forecast.

"When the temperatures are warmer in Icy Strait, it actually reduces the forecast," said Piston.

However, Icy Strait temperature is positively correlated with pink salmon growth.

"So in these warm years, pink salmon are actually growing very well," said Piston.

Piston said what might be happening is the increase in temperature is affecting the way pink salmon and juveniles are migrating in Southeast Alaska.

The press release states, "the size of juvenile pink salmon was similar to the large size of juveniles observed during the marine heat wave of 2014-2016 and returns from those juvenile years were all below average."

Also stated in the press release was that the "impact of warm sea surface temperatures on the survival of pink salmon that went to sea in 2019 is unknown and adds uncertainty to the forecast."

Piston said that always the big wild card.

"If something happens that greatly affects survival out in the ocean — there's no way we can predict that," said Piston.

If the forecasted 2020 pink salmon run is accurate, it will be more than the 8 million harvested in the parent year 2018.

"It really just reflects the likelihood for continued poor pink salmon returns in even years," said Piston.

The forecast is actually a range between 7 million and 19 million pink salmon for Southeast Alaska. According to Fish and Game calculations, there is about an 80% chance the actual harvest will fall in that range.

The forecasts are helpful to those in the industry.

"It can have a big impact in how fishermen prepare for the season, strategize what they want to do," said Piston, "and, you know, how processors might prepare for the season."

The accuracy of the predictions have increased greatly since the Southeast Coastal Monitoring project started by NOAA in 1997, according to Piston.

Since then, NOAA has had some funding issues.

"And in 2018," said Piston, "we've kind of turned it into more of a joint project between NOAA and Alaska Department of Fish and Game."

The surveys used to be conducted by a NOAA research vessel or a vessel rented out by NOAA.

Piston said this summer they had biologists from Douglas Island Pink and Chum and Southern Southeast Regional Aquaculture Association come out and help with some of the surveys, and he expects that to continue.

"So when we're actually out conducting these surveys," said Piston, "We usually have NOAA, ADF&G and possibly a representative from one of the aquaculture associations on board with us."

Piston said the cost of the surveys are difficult to measure because there's so many moving parts. But he estimated the cost, including NOAA's effort, ranges around $250,000.

While the juvenile abundance index is calculated from catches in northern Southeast Alaska, it is used in forecasting the entire region's harvest.

"And it's kind of interesting because when we use that information for forecasting, it tends to work better forecasting the entire region," said Piston.

He said stock-specific catches of pink salmon can't really be identified.

However, because much of the chum salmon run is marked hatchery fish, those stocks and runs can be identified.

"So based on what we see with chum salmon, it does look like we do pick up a signal of juvenile pink salmon abundance," said Piston. "Or we probably do cause that's what we see with chum salmon."