2015 sockeye run produced underweight fish across state
With the bulk of the sockeye season over, biologists and fishermen have continued to notice smaller than average weight for one of Alaska’s most valuable exports.
Workers statewide from offices of the Alaska Department of Fish and Game, or ADFG, noticed an early in-season trend of smaller-than-average fish. Throughout the state’s early season salmon fisheries, particularly sockeye and chum, fish were coming in shorter and lighter for their age
At the time in late June, ADFG lead fisheries scientist Eric Volk said the run was early and couldn’t yet be called a pattern. Now that the run’s peak has come and gone, along with a statewide commercial harvest of 52 million sockeye, biologists said the trend continued throughout the season, though salmon processor fish tickets won’t be able to verify the exact weights and trends until sometime in October.
Steve Moffitt was the Cordova ADFG management biologist who first noted the early season trend, and predicted that it would continue through the season.
While acknowledging wide margin of sampling error, Moffitt said the average weight for a Cordova sockeye in 2015 is 5.07 pounds. The historical average, he said, is closer to 6 pounds.
Kenai area commercial management biologist Pat Shields said he expects this year’s sockeye size to be smaller than average as well.
Geoff Spalinger, the Kodiak area commercial fishery biologist, said the average weight for Kodiak sockeye is a half-pound below the historical average at 4.7 pounds.
Bristol Bay, home to the largest and most valuable sockeye run in the state, has also maintained a below average size, according to commercial fishery biologist Tim Sands.
The average baywide sockeye weight was 5.12 pounds, smaller than the historical average and the 2014 average of 5.92 pounds.
From a management perspective, the smaller average weight carries little import to Sands.
“It is what it is,” said Sands. “From my point of view as a manager, it’s more just something we note instead of plan around.”
In other areas, ADFG managers said the small size of the fish could have possibly impacted the harvest. The mesh size of gillnets is specifically engineered to entangle certain-sized fish.
Smaller average size could have allowed some to slip through the mesh, said Moffitt, which could help explain the escapement for Copper River sockeye being slightly greater than average at 1.34 million as of July 27.
Escapements measured at the same date in 2014, 2013, and 2012 were 1.18 million, 1.27 million, and 1.27 million, respectively.
Managers all have their own theories about the cause of the decline in size at age. Some insist the warm blob of water in the Gulf of Alaska, 2 degrees centigrade warmer than average, is the root.
Moffitt thinks the warm water simply created more food competition, as the plankton sockeye eat prefers cooler temperatures. Beyond that, the warmer water simply has a calorie-burning effect.
“It’s not just food competition, it’s also warm water itself,” said Moffitt. “Their base metabolism is higher. As the water gets warmer, they’re using more energy without doing anything additional, and no additional food to replenish the energy.”
Sands notes that the correlation between large run sizes and small fish is well established, and that 2015 could simply be another example of the principle.
“The biggest reason would be lots of fish equals small fish,” Sands said. “The catch last year (in Bristol Bay) was 28 million versus 35 million this year. Ocean conditions are always an important factor. The entire idea of ocean carry capacity is what we look at.”
DJ Summers can be reached at [email protected].