SURVEYING A SCARCE SALMON STOCK

Curtis Brownfield, a U.S. Fish and Wildlife Service fish biologist, pulls a decaying winter king salmon carcass out of the Sacramento River. Summer surveys usually allow biologists to track how many of the threatened fish make it back to spawn. (JAKE SISCO/USFWS)

CARCASS SURVEY TELLS HOW WELL SAC WINTER CHINOOK RUN IS DOING

By Jake Sisco

he feel of the wind in your face, T the sound of a boat motor roaring down a river, the spray of water, the warm sun on your back and the smell of rotting flesh. This is what the U.S. Fish and Wildlife Service biologists on the Sacramento River experience when conducting winter Chinook salmon carcass surveys.

“The carcass survey is a cooperative effort between the Service, the California Department of Fish and Wildlife and the Pacific States Marine Fisheries Commission,” said Kevin Niemela, a USFWS supervisory fish biologist located at the Red Bluff Fish and Wildlife Office. “Typically, two boats are used to survey the river daily, one operated by the Service and the other operated by PSMFC, working under contract through (CDFW). Each boat travels upstream and searches for carcasses, covering opposite shorelines.”

The survey allows USFWS to get an idea of how many fish are returning, and

Brownfield checks the tag number on a salmon carcass pulled from the depths of the Sacramento. (JAKE SISCO/USFWS)

where they came from. Once a salmon carcass is spotted, the boat team will use a gig on a long pole to pull the carcass into the boat, which can be more challenging than it sounds. The boat pilot has to battle river currents and clarity to keep their eye on the carcass while getting into the correct position for their partner to get the fish on board the boat.

“We go out, assess and count the number of carcasses, and we also collect biological data from eyeballs, scales and fin tissue,” said Charlee Cramer, a USFWS fish biologist. “With that, we can see where they’ve been and where they came from, and we also can get a count of how many hatchery fish are out there. There will be some that have their fin clipped, which are hatchery fish, and some that are not clipped. Based on that, we can tell the percentage of hatchery success.”

Hatcheries improve the survival of young salmon (eggs, fry and juveniles). More young salmon survive in the hatchery than would survive in the wild because there are no predators in hatcheries, food is abundant and the environment is relatively constant.

“One important reason that we do the surveys is so that we can evaluate what Livingston Stone National Fish Hatchery is producing and how the fish are doing,” said Curtis Brownfield, another USFWS fish biologist. “We will clip and tag them up there at the hatchery and release them into the river. When they come back, we can pull the coded wire tag out of their snout and find out where they came from.”

“Almost all of the hatchery fish came from Livingston Stone except a few strays, maybe from the Feather River State Hatchery, but all the rest are produced naturally here. This year, quite a bit of the population came from Livingston Stone. It might be half-and-half natural versus hatchery this year.”

A carcass is processed as part of the

JUST BECAUSE THIS YEAR was a successful

run, with the largest number of winter carcasses counted since 2006, it does not mean next year will be. The surviving juveniles from this year’s spawning group will come back in three years. The fish that returned this year were fry or very small fish three years ago, this time of year. After emerging from the gravels, they outmigrated to the Delta, and then to the ocean in March of 2017, and spent two and a half years in the ocean before starting their upstream migration.

The juveniles from this year have a perilous journey between here and the ocean. There are many potential obsta-

Surveying and collecting the carcasses helps evaluate winter Chinook production at USFWS’s Livingston Stone Hatchery and how well those fish are doing.

(LAURA MAHONEY/USFWS) “We go out, assess and count the number of carcasses, and we also collect biological data from eyeballs, scales and fin tissue,” says Charlee Cramer, a federal fish biologist.

(LAURA MAHONEY/USFWS)

cles in their way, including lethal water temperatures, water flow, weather and predators. They also face obstacles to survival in the ocean, as well as the journey back to their spawning grounds.

The number of fish that returned this year was so high that for several days this year the agencies doubled the number of boats from two to four per day.

“In July and early August, we would have been out here until 7 p.m., picking up fish in 100-degree weather, and at the end of August, we have very few fish, and it’s overcast,” said Brownfield. “It’s just always interesting to me how it just takes that plunge from a lot of fish to basically no fish.”

“This year, we had a lot of fish, which might be due to the river’s clarity. With the river being very clear this year, we can see fish at a depth that normally we cannot. This year we’ve been able to cover more of the river and see more

fish, due to that clarity.”

With the need for more boats on the water, partners play a huge role in the survey’s success.

“Our partners are incredible,” said Cramer about CDFW and PSMFC. “The partners actually go out and collect carcasses all year round. They collect fallrun and late fall-run also. We help them mainly in the summer. Without them, we would be out here multiple days on each reach. We have three different stretches of river that we do every single day, so we do one side of the river, and they do the other. If we did not have them, it would be an even longer day out here – very long. They are extremely knowledgeable, and it’s really nice to work with them.” CS

Editor’s note: Jake Sisco is a public affairs specialist with the US Fish and Wildlife Service in Sacramento. For more on the Pacific Southwest Region, go to fws.gov/cno.

USFWS biologists also work with the California Department of Fish and Wildlife and Pacific Fisheries Management Council on this project. “Our partners are incredible,” says

Cramer. (JAKE SISCO/USFWS)