“Big run, small fish,” is a Cordova fishermen’s rule of thumb that seems to be holding true for salmon in 2015, particularly in the areas adjacent to the Gulf of Alaska.
Workers statewide from offices of the Alaska Department of Fish and Game are just beginning to notice an early in-season trend of smaller-than-average fish. Throughout the state’s early season salmon fisheries, particularly sockeye and chum, fish are coming in shorter and lighter for their age.
“It’s still pretty early in the game,” said Fish and Game fisheries scientist Eric Volk. “That being said, fish are a little bit smaller than they usually are. It may not be a pattern this early, but we have seen declines in size-at-age.”
Even seasoned fishermen are puzzled.
“We’ve seen small fish before,” said Jerry McCune, president of both Cordova District Fishermen United and United Fishermen of Alaska. “But nothing like this.”
State workers and fishermen have been noticing drops between a half-pound and a pound in the size-at-age, which is the fish’s size relative to how many years it has spent growing in the ocean before returning to the river.
Biologist Steve Moffitt was first to notice the trend in his Fish and Game management district of Copper River.
“Copper River sockeye are the smallest we’ve ever measured,” Moffitt said. “This size-at-age is the smallest we’ve ever measured, and the overall size is the smallest we’ve ever measured.”
Though early in the season, Moffitt said the trend is deep enough for him to predict that it will continue the rest of the year. If the run was going to get larger, he said, they would have seen a sign by now.
“For the Copper River, we’re past the peak of the early run,” said Moffitt. “That’s just the way it’s going to be for the early stocks in the Copper. Sometimes we do see an increase in size later. But just the fact that we see sockeyes are smaller, Wally Noerenberg hatchery chums are smaller, Main Bay hatchery chums are smaller … I suspect it will hold for most of the Copper River run most of this year.”
According to biologist Jeremy Botz, the average size for a Copper River sockeye over the last five years is 6.2 pounds, with a max of 6.6 pounds in 2012. What fishermen are pulling out of the water now is closer to an average of 5.5 pounds, though he cautions that the imprecision of inseason processor counts might make the actual average drop another fraction of a pound when Fish and Game makes its own size counts later in the season.
Pat Shields, the area biologist for Upper Cook Inlet, also said that this year’s returning reds are the smallest on department record for this time of year.
“We took a look on the Kasilof,” said Shields. “We looked at the five-year-olds, meaning they’ve spent three years in salt water, one winter in fresh water, and one in egg that doesn’t really count. They’re the dominant age class in the early part of the run. The lengths were the smallest we’ve ever seen. We are early in the run, but it’s consistent with what other areas have told us.”
In the Kasilof, Shields said, early-run sockeyes typically have a fork length, the distance from the fish’s snout to the fork in its tail, of 540 millimeters. This year, most of the fish they’re measuring clock in the low 500s, which translates to about a half-pound difference on average.
In Kodiak, assistant area biologist Geoff Spalinger said the early reds are coming in roughly one pound less than the average size.
“The averages are about 4.4 pounds. Usually early reds are about 5 to 5.5 pounds,” said Spalinger.
In Bristol Bay, home of the state’s most abundant and valuable sockeye fishery, biologist Tim Sands said he’d been hearing about the small sockeye sizes statewide, but did not have enough information to make the call about Bristol Bay’s fish.
“We don’t have a good handle on that just yet,” Sands said. “Some of our fishermen said they fished normal sized salmon.”
Reds are also coming in younger than usual. In Copper River, which typically has a mix of four- and five-year-old fish, more of the younger year class is showing up. Under normal circumstances, this could mean that the average size is showing decreases because of younger, smaller fish coming into the river in higher volume. Botz, however, said the decrease is a true size-at-age shrinkage; both four year fish and five-year fish are coming into the Copper River smaller than average.
Smaller fish can be an issue for harvesters as processors pay by the pound, not by the fish. Even with healthy projections for the number of sockeyes, pinks, and chums around the state, there’s no guarantee that fishermen won’t be working for more fish and less pay.
Wholesalers could face problems as well. Processing equipment that is set up for 5 ½-pound fish is no longer optimized for efficiency, and fresh and frozen fillets from smaller fish are less marketable than larger fillets, even if they make up for the size with quantity.
Fish and Game has no official theories concerning the decline in size-at-age at this early stage, but several biologists had their own ideas related to food supply.
The fish aren’t getting big because they aren’t eating big, with too many salmon sharing a supply of food that could be smaller due to environmental factors. “It depends on a couple different factors,” said Moffitt. “If you have poor feeding conditions, you can have lots of fish but they’ll be much smaller.”
In light of record projections for both Prince Williams Sound pinks and Bristol Bay reds, Botz agrees that food competition is the likely culprit for puny fish.
“Seems like they definitely must’ve had a lot of competition for forage in the Gulf of Alaska,” said Botz. “We’ve got small chum, small sockeye across the board. I would just say that there was a lot of fish and not enough food.”
Food competition, some biologists said, could be exacerbated by a patch of warm water on the surface of the Gulf of Alaska, reported in 2014 by the National Oceanic and Atmospheric Administration as being up to five degrees warmer than average. Certain organisms thrive in warmer water, but the plankton salmon eat needs cold water to survive.
“One of the correlations is sea surface temps in the Gulf of Alaska in the year before return,” said Shields. “In 2014, it was pretty consistent that fish returned smaller on average. When temperatures are warmer, their metabolism increases but there’s not as much to eat.”
DJ Summers can be reached at firstname.lastname@example.org.