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Why are some Alaska salmon and halibut getting smaller?

  • Author:
  • Updated: September 28, 2016
  • Published September 17, 2015

With the end of Alaska's biggest fish derby earlier this week, salmon and halibut anglers are hanging up their poles -- waiting for the return of spring -- and with it, another flood of fish into local streams, creeks and rivers. And while many local freezers may brim with fish, chances are, the fillets are a little smaller than in years past.

How small? Well, the 224-pound flatfish that won the Homer Jackpot Halibut Derby this week was the lightest winner in the derby's 30-year history -- and a whopping 134 pounds shy of Chugiak angler Jerry Saunders' derby record, caught in 2007.

Small fish were also gumming up the top of many of the state's silver salmon derby leader boards. And fisheries biologists say that red salmon in Cook Inlet, Bristol Bay and Prince William Sound were noticeably smaller this year, too.

Cook Inlet commercial fisheries biologists are still crunching the numbers from this year's run, but they've already have noticed a trend -- shorter, and thinner sockeye salmon.

"That was the attention-grabbing species during course of summer," said Alaska Department of Fish and Game Cook Inlet Commercial Fisheries Biologist Pat Shields.

Bristol Bay, which hosts the largest wild run of sockeye in the world, saw reds arrive small and late. According to Fish and Game, the average size of red salmon caught commercially in Bristol Bay in 2015 was the smallest on record: 5.12 pounds -- almost 13 percent smaller than the average. By contrast, the average weight for Bristol Bay reds last year was 5.96 pounds.

There were similar stories throughout Alaska.

"The size of sockeye is much smaller than average this year, and we are seeing that around the state," said Jason Pawluk, a sportfishing biologist with Fish and Game's Soldotna office.

Biologists are still trying to determine why some Alaska fish are coming back small. But warmer ocean temperatures -- which have pushed tuna and sunfish as well as Pacific pompano into Alaska's normally cold seas -- may have something to do with it.

"Fish are cold-blooded animals, and when water temperatures are higher, fish use more energy because their metabolic rate has increased," Shields said. "But warmer temperatures don't mean there will be an increase in food for the salmon to eat. So they, sometimes, but not always, come back smaller than average. And they mature a little later so they tend to return later."

Like Bristol Bay, Cook Inlet red salmon returned about a week late, on average, Shields said.

Farther east, Copper River sockeye were the lowest average weight since 1987 and the lowest average length since the late 1960s, according to Cordova-based Fish and Game biologist Stormy Haught.

The one bright spot may be king salmon -- which may have actually gotten bigger than in the past few years -- but biologists said that probably had little to do with water temperatures because, more so than other salmon species, kings return in multiple age classes.

"That may have been associated with more older-aged fish returning on the run," Shields said.

Shields said Fish and Game is still compiling the data on both king and silver salmon sizes in Cook Inlet.

Silver salmon are the second-largest of the five species that call Alaska home. But if not for a last-minute catch of a 16.2-pounder, the 60-year-old Seward Silver Salmon Derby would also have seen its smallest winning fish ever. In fact, many of the top fish in this year's derby weighed 13 pounds or less.

Halibut, among the largest fish to swim in Alaska waters, have been decreasing in size for at least 10 years. And 2015 was no different.

Today's 12-year-old female halibut -- all huge halibut are females -- weighs half as much as it did two decades ago, Scott Meyer, a Homer-based groundfish biologist with Fish and Game, said five years ago.

Why?

"That's the million-dollar question," said Steven Hare, a biologist with the International Pacific Halibut Commission, which manages halibut off Alaska. He has some theories:

• Steady removal of the larger and typically fastest-growing halibut by commercial and sport fishermen reduces those traits in the population over time.

• There are more halibut in the seas than there were in the 1960s or 1970s. At the same time, the rarely fished arrowtooth flounder, which occupies similar areas, has seen a huge growth in its population size. The resulting crowding and competition for food may have driven down halibut size.

• Some unknown problem has harmed the quality or quantity of halibut food.

"They're definitely quite a bit smaller than they were 25-35-years ago," Hare said. "Back then, a 15-year-old female could be 100 pounds. Now it's 30."

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