River and Sky: A fish biologist’s perspective on counting salmon from the air

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On a cool morning, I’m awake and alert as I can be. I’m strapped into a helicopter seat, flight helmet on, doors closed, security checks done, GPS in one hand, radio in the other, and a spec sheet strapped to my thigh. The excitement builds as the rotor blades pick up momentum and begin to hum loudly. We take off from the ground and begin our journey into the backcountry. As I gaze out at the wild mountains, my heart races, I feel like a fish out of water and I think, “How did I get here? I’m a fish biologist!

As fisheries biologists, we are used to walking along a stream bed looking down to see what fish we can find. However, each September, in the middle fork of the tributaries of the Salmon River, we shake things up a bit and take a totally different perspective on fishing: flying.

For more than 70 years, biologists have been counting chinook salmon nests, called spawning grounds, in the middle fork of the Salmon River to estimate the number of chinook salmon returning from the ocean to these tributaries to spawn. Spring and summer chinook salmon, which refer to their upstream migration period as adults, are listed as threatened under the federal Endangered Species Act.

As with other regional salmon species, these fish have very important ecological, cultural, and economic roles in Idaho, so Fish and Game biologists are working hard to monitor their populations to better protect and protect them. manage them. A key part of management is to continuously assess reproduction and population abundance to monitor trends over time and this is where spawning ground numbers come into play.

Wild Spring/Summer Chinook salmon are born in tributaries of the Middle Fork Salmon River, then swim about 900 miles from central Idaho to live and grow in the ocean. After a few years, they swim to their natal stream to dig a nest and spawn before dying, usually arriving August through September. As the females turn on their side and beat their tails in the gravel to dig a nest, a few males begin to gather around her and wait. The males chase each other and fight for the best position to fertilize her eggs once she has laid them. A female typically digs a spawning ground, so counting spawning grounds year after year is a good method for estimating female abundance to understand sex ratios and calculate total abundance over time.

Many of these spawn count surveys are done on foot, but some of the more distant tributaries are difficult or dangerous to walk, so it makes more sense to do aerial surveys from a helicopter. But how can we see a redd from up there?

Biologists spend a lot of time studying the characteristics of spawning grounds and the typical surrounding aquatic habitat so we know what to look for. Luckily for us, female chinook salmon turn over a lot of the pebbles when they dig the nest, so the algae comes off and the newly exposed rocks are clean and contrast well with the surrounding river bottom, creating a bright patch that can be spotted from the air. Sometimes, if we are lucky, we can even see a female salmon and several males around the spawning ground.

Backcountry flying at low altitudes can be difficult and potentially dangerous. Helicopter pilots and biologists encounter several challenges during these surveys. Bad weather, especially high winds, is a major player when flying in remote canyons and should be monitored very closely before and during flights. The pilot remains in close communication with the regional flight followers to monitor the weather conditions on approach.

For the biologist, the angle of sunlight on the water and the associated cloud cover can make spawning grounds difficult to spot. Wildfires are another big challenge: smoke from wildfires creates poor visibility and dangerous flying conditions. The pilot and the biologists must therefore quickly adapt their flight plans to avoid dangerous zones.

In 2021, two large wildfires in the Frank Church River of No Return Wilderness delayed and prohibited surveys in some areas. While we’re happy to get the data, safety is the number one concern, and sometimes the best decision is to leave early in order to get home safely.

The purpose of the ongoing ground and aerial spawning count surveys is to contribute to the data set that illuminates trends in adult chinook abundance and reproductive parameters. This long-term dataset provides relative comparisons of abundance between spawning years and is essential for Chinook salmon status assessments under the Endangered Species Act.

Datasets like the Middle Fork Salmon River spawning counts are crucial because they improve our understanding of the life history and population trends of an important endangered species, which in turn helps improve our management and conservation efforts. Looking at these beautiful waterways from a helicopter is definitely a different perspective and reminds us of the big picture we are working towards.

Check out the Wild Salmon and Rainbow Trout page for more information on the science behind the conservation of Idaho’s wild salmon and rainbow trout.

Carli Baum is a fisheries biologist with the Idaho Department of Fish and Game.

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