Editor’s note: This story is the second in a three-part series about the operations of Alaska’s salmon hatcheries and their impact on the North Pacific. Check our July 15 edition for the first part about the process of otolith marking.

Among the millions of wild salmon swimming in the high seas of the North Pacific are hatchery fish with marks embedded on their bones, readable like a bar code.

Before they’re born, most hatchery-origin salmon are subjected to a series of water temperature cycles that leave a mark on their inner ear bone, called an otolith. To an experienced eye, the marks are readable under a microscope, sourcing the fish back to its birthplace. Around the Pacific rim, there are about 480 different readable otolith marks.

From the Alaska Department of Fish and Game in Juneau, Dion Oxman coordinates those different marks. They all have to be different enough for readers to make out on a microscope when the bones are ground down, and for the most part, they are.

“To coordinate throughout the Pacific Rim, essentially, countries own a specific suite of marks, and other countries won’t use it,” he said. “For this year’s proposed mark plan, there was a proposed 482 different mark patterns. Of those 482 marks that were submitted to me, only 3 were duplications.”

The U.S isn’t the only place that releases hatchery salmon. Canada, Japan, Russia and South Korea all run hatcheries, participating alongside the U.S. in the North Pacific Anadromous Fish Commission, an international body intended to preserve anadromous fish stocks across the North Pacific Ocean. Like the U.S., the other countries also have hatchery management programs and otolith marking coordinators. In 2017, altogether, more than 5.1 billion hatchery salmon were released, according to the North Pacific Anadromous Fish Commission.

Of those, though, only 2.2 billion or so were marked. Oxman said Alaska tends to be fairly consistent with marking its pink, sockeye and chum salmon, though other countries may have reasons for not doing so.

Fish tracking

Otolith marking isn’t the only way to track hatchery fish, though. Some hatcheries use coded wire tags, particularly in coho and king salmon, Oxman said.

Coded wire tagging certainly isn’t new — managers began marking hatchery fish with them in the 1960s as an alternative to just clipping fins or using external tags. Essentially, a tag with a number is embedded in the tough nasal tissue of juvenile salmon, where it won’t come loose. It’s invisible from the outside.

In the earliest days of use, a fish with a coded wire tag could be spotted by a clipped adipose fin, but now that fin-clipping is a mass-marking method, people looking for tags have to get a little more inventive, according to the Regional Mark Processing Center, which coordinates hatchery fish marking for the Pacific States Marine Fisheries Commission.

That’s how people like U.S. Coast Guard officers end up swinging a metal detector over the head of a dead fish in the Bering Sea occasionally. Oxman said using metal detectors to find a coded wire tag is fairly effective, and if someone finds a fish with a coded wire tag, Fish and Game asks that the heads be sent in. They remove the tag and read it, and the code sources the fish.

Otolith marking works effectively for pink, sockeye and chum salmon, but not as much for king and coho salmon, where the otoliths are bigger and take much more time to read.

“We do thermal mark recoveries to manage the fish in real time,” Oxman said. “They get to us and we turn it over in real time … it’s high production. When you’re dealing with a sockeye otolith, which is what we deal with mostly here in Southeast, (those are quick). With a Chinook otolith, those are big. Your handling time goes from a few minutes may be to an hour … there’s a lot more preparation that goes into recovering a thermal mark from a Chinook than from a sockeye.”

The coded wire tagging makes reading it faster and very accurate. However, it has its drawbacks — it’s expensive, and not an entire release group is tagged, Oxman said.

International relations

Coded wire tagging and otolith marking are key parts of the information that goes into negotiation of the Pacific Salmon Treaty, a major piece of international salmon policy that affects how many salmon Alaska fishermen can harvest. Originally signed in 1985, e U.S. is currently re-negotiating the treaty to extend it for another 10 years.

The parts of the treaty that affect Alaska primarily deal with Canada, though the section on king salmon stretches from Yakutat to Oregon. Fish and Game Deputy Commissioner Charlie Swanton, one of the Pacific Salmon Treaty negotiators for the U.S., told the Board of Fisheries members in a March meeting that Alaska is obliged to meet certain escapement goals in Southeast rivers as part of the treaty. Tied to that is information about where the salmon are being harvested and when, but once the salmon are away from their home rivers, it’s hard to tell where they’re from.

Using the information from marks, managers want to try to shift harvest onto hatchery stocks as much as possible and away from wild stocks, called a mark-select fishery, Swanton said.

“But if they’re not 100 percent marked, therein lies part of the problem,” he said. “We’ve attempted in two years, 2016 and 2017, in a limited fashion, to implement a mark-select fishery on a very, very limited fishery… in most cases, we’ve received a fair amount of criticism because of the mark rate.”

He said Fish and Game is looking to Washington, D.C. for extra funds to require better marking. That doesn’t obligate Canada to do it, though, he said.

One of the things fishery managers are looking for is information from the hatchery fish in commercial harvests to see where the fish are coming from in order to track movement patterns, Oxman said. The North Pacific Anadromous Fish Commission is also engaged in a multi-year effort called the International Year of The Salmon, part of which is an attempt to get funding to answer some of the outstanding research questions about salmon.

“The mark recoveries are really helpful … there’s interest now as things are kind of gearing up to try to dedicate more time and effort to finding out with the fish when they’re in the Gulf,” he said. “Do the stocks mix? Do they interact with each other at all? (The International Year of the Salmon initiative) is over multiple years, and it’s an initiative they’re trying to get off the ground to look at these very problems. How are salmon being affected, and how are the people who rely on salmon being affected? They’re trying to get funding to answer some of those questions.”

Straying and carrying capacity

On Tuesday, the Board of Fisheries will hear an emergency petition from a group of Alaska sportfishing groups with concern about hatchery production. The group, led by the Kenai River Sportfishing Association, is asking the Board of Fisheries to halt a request from the Valdez Fisheries Development Association, a hatchery nonprofit, to increase its egg take by 20 million fish.

The petition argues that increasing hatchery production places more fish into an ecosystem that may not be able to account for them and runs the risk of more fish straying into other streams. The groups cite the data from Fish and Game that in 2017, pink salmon from Prince William Sound hatchery fish strayed into streams across Lower Cook Inlet in high proportions.

Hatchery nonprofits and commercial fishermen object to the petition, saying the hatchery production helps stabilize commercial fisheries in years of poor wild runs and that straying is a natural survival mechanism.

Tied up in the debate is the question of what the ocean’s carrying capacity for salmon is and whether hatchery salmon have an impact on the integrity of wild stocks. Fish and Game is about six years into a long-term effort to study the fitness of wild stocks and their interaction with hatchery fish, though there are no definitive results yet.

The meeting will take place at the Egan Center in Anchorage on Tuesday beginning at 1 p.m.

Reach Elizabeth Earl at eearl@peninsulaclarion.com.