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At Nushagak River sonar site, crews monitor sockeye salmon escapement, also low chinook and chum counts

Tyler Hennigan readies the skiff for the next drift.
Jack Darrell
Tyler Hennigan readies the skiff for the next drift.

Every day of the commercial fishing season, westside area management biologist Tim Sands calls from the Fish and Game office in Dillingham to the Nushagak River sonar crew.

“Portage Creek sonar Portage Creek sonar, Dillingham office. Good afternoon,” Sands said.

Hey Tim, How’re ya doing?

On the other side of the two way radio is a member of the sonar crew, with the latest counts for sockeye, chinook, and chum salmon.

“Why don’t you give me the 10:00 numbers please,” Sands said.

For the 10:00 am we got 2,820.

“Okay. How’d session one go, did you get any kings?”

We got 7 chinook, 1 sockeye, and 3 chum.

The Alaska Department of Fish and Game deploys several tools for tracking escapement in the nine rivers of Bristol Bay. Counting towers track most escapement, but there is one sonar site, based on the bank of the Nushagak River. There, a crew of seven techs estimate the number of fish swimming upstream, including sockeye, chum, and king escapement numbers.

But where do these Nushagak River numbers come from, and how can a sonar device tell which species of fish are swimming by? The short answer is: it can’t—on its own.

At the Nushagak River sonar station, Tyler Hennigan drifts a net from a skiff along the bank of the river. He casts a gillnet with 6 inch mesh into the shallow water, while another team member readies the boat for incoming fish. Almost immediately, the corks along the top of the net twitch into action and entangled fish marr the glassy surface of the water.

Together, they haul the net in, pick the fish, and cast the net out again, and again and again.

“We did eight sets just now with our six inch net,” Hennigan said. “And the first one, we got hammered pretty hard. We got maybe a couple, maybe a dozen sockeye and a handful of chums.”

This is Hennigan’s thirteenth season working at the Nushagak River sonar station, where a team of seven intrepid Fish and Game techs monitor the Nushagak river. Each day they set different size gillnets a total of 96 times on the river corridor in front of the camp.

“So we started this morning with a four inch which is pretty small, and then a five and then obviously just hit the six and then we're gonna go into the eight Jonah and I right now,” he said.

The Nushagak sonar crew drifts with an 8-inch mesh gillnet, to apportion species composition to the morning's sonar counts.
Jack Darrell
The Nushagak sonar crew drifts with an 8-inch mesh gillnet, to apportion species composition to the morning's sonar counts.

The site is tucked in along the bank of the Nushagak River and has been in operation every summer during the commercial fishing season since 1984. Each day, these drifts go hand in hand with raw fish counts from two sonar units. The drifts allow the team to apportion species composition to the large number of sonar-counted fish swimming by. That escapement count each day is reported to area managers who determine when and how long to open commercial fishing. Thousands of fishing crews and dollars rely on these counts.

Konrad Mittelstadt is the crew lead at the station and has been counting fish every summer here for the last 26 years.

“We'll find a whole bunch of fish going by, but we don't know what type. So I got my boys out there,” he said. “And 96 times a day, we're floating a net in front of the sonar. You can just see they got a couple of hits right there. So we float in front of two and a half minutes to kind of see what's going by at the time, whether it's kings, or the chum or Sockeye and so we'll take those numbers. And we'll make an estimated apportionment about how many fish went by the sonar during the day.”

The drifts are fast and the fish are picked quickly so they can be returned to the water to continue their upstream journey. While in the boat, fish techs count the number of each species, record sex and length, and take a scale sample to determine fish age.

There are two sonar devices that sit underwater on each side of the river, braced against the current with piles of sandbags. A weir juts out for each, pushing the fish in front of the sonar unit.

Each sonar unit casts 48 beams of light out, creating a shadow behind each fish swimming upstream. These shadows translate to a computer in a canvas tent nearby, appearing as pale, ghostly blue salmon, swimming across the screen.

“We record this 10 minutes of every hour, and we take our famous Bristol Bay tallywackers. And we click away. And then we times that number by six, and that’s how much estimated passage,” Mittelstadt said.

That number is the estimate of how many fish swim up the Nushagak River every hour.

One of our highest counts last year in a 10 minute period was over 7,000 fish. So you take that 7,000 and times that by six. That's 42,000 fish that went by our estimated passage,” he said. “So we get a lot of fish now and then.”

Mittelstadt says, over his 26 years on the river, the technology has changed quite a bit. Through the 90s, the Alaska Department of Fish and Game used what’s called a Bendix sonar.

“All you could see of the fish—You hooked an oscilloscope up to it, and so you'd be sitting there, it'd be a flat line, all of a sudden a fish would go by, and there'd be a little *bleep*. Now that could be a downstream fish that could be there could be a stick. That could be… you know, so we thought those were fish. That's the bestest technology we had,” said Mittelstadt.

Thankfully, the sonar station’s technology has advanced since the mid 1990s. Today, the sonar records digital imaging that can be played back and studied. Phil Stacey is a commercial fisheries biologist with the Alaska Department of Fish and Game, and oversees counting towers and sonar operations in the district.

“So we have one here on right bank that is tied directly into our computer system here in the tent. And then on left bank, we have it all set up in a boat. So the sonar unit is still underwater, but all of our electronics are in the boat,” Stacey said. “And then we have a radio device that transmits the signal over here so that we can just check everything on the computer.”

The buoys bobbing in the river mark distinct inshore and offshore portions of the river for each sonar device. The sonar team drifts in both portions of the river to get a more accurate representation of the species swimming upstream.

Kings swim a little further offshore, chum as well,” said Stacey. “Sockeye are more oriented to the bank. So we drift inshore and offshore to get a representative sample of everything.”

Stacey says when the fish are running strong, the drifting is action packed.

A week or so ago when we were hitting a lot more fish the numbers were a lot higher. They'd set that net and those quarks would just explode with fish right off the bat,” he said.

Konrad Mittelstadt says which fish show up in which strata depends on the time of year.

“The kings in the beginning of the year seem to go along the bank because that's where less friction is because it's shallower, and it's less current in front of their face,” he said. “But as the sockeye and chum move in, I think the kings move out a little bit more.”

A canvas tent on site houses computers that the sonar units transmit data to, as well as a two-way radio for relaying data to the Dillingham Fish and Game Office.
Jack Darrell
A canvas tent on site houses computers that the sonar units transmit data to, as well as a two-way radio for relaying data to the Dillingham Fish and Game Office.

This year, two of the three monitored species along the Nushagak River are still far below their escapement goals; those are sockeye, king and chum salmon. So far, the sonar crew has estimated that only 30,399 King salmon have made it up the river as of July 13th, well below the minimum escapement goal of 55,000. Kings were declared a stock of concern for the first time this year, and commercial fishing was delayed to allow for more to escape upriver in the Nushagak. For chum salmon, an estimated 82,107 have passed the sonar station, less than halfway to the minimum escapement goal of 200,000.

And according to crew lead, Konrad Mittelstadt, a few other things are different around the camp this year. Snow patches still can be seen along the banks of the river, and water levels are high.

“This is the most water I've ever seen this late in the season,” Mittelstadt said. “Usually we have 330 feet 40 feet of gravel. You could walk all the way out.”

Also for the first time, the camp is equipped with Starlink satellite internet. This morning, technical difficulties with the tracfone required booting up the internet to get the day’s data out.

“I just started the generator, got the Starlink going and I could give him a picture of the data so he can get into his nine o'clock report,” he said.

Mittelstadt says, many of the neighboring guide camps along the river have Starlink this year too. He says while handy for sending out the day’s numbers in a pinch and keeping in touch with family, he prefers to be off-line.

I'd rather have it just, you know, maybe Morse code, but I'm an old guy,” said Mittelstadt, laughing.

On the water, Tyler Hennigan begins the next round of drifts, this time with an 8-inch net. Phil Stacey has brought the camp’s next week of supplies, and loads the boat up with trash to bring back to town.

The fish keep pushing up the river, the blue shadows keep swimming cross the sonar screen, and the Nushagak sonar team resumes their 96 daily drifts, a routine yet essential part of monitoring Nushagak River escapement, and maintaining one of the most abundant salmon runs in the world.

Get in touch with the author at or 907-842-2200.

Jessie Sheldon is a fisheries reporter for KDLG. She has spent several summers working in Alaska, both on the water and in the recording studio. Jessie is passionate about marine ecosystems, connection through storytelling, and all things fishy.