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What Is a Weir?

Historically, a weir is a kind of fish trap, but in recent times, it's become an aquaculture tool for studying Alaska salmon returns.

by | January 7, 2022

Hidden Lake Weir
The Cook Inlet Aquaculture Association counting weir at Hidden Lake.

The word “weir” means different things to different people. In engineering, it’s a kind of dam that allows water to flow over the top while creating a higher pool of water upstream. In historic terms, a weir is a fish trap made of logs, wooden stakes, or stones that corral salmon into traps. The first Alaska legislature banned these kinds of weirs in was one of its first acts in 1959. The goal was to guarantee public fishery access. Today, fishery groups like the Cook Inlet Aquaculture Association (CIAA) use weirs to help keep track of salmon. These salmon return to the lakes and streams where they were either born or released. Life at a weir is hard work, but it provides valuable data for management and long-range planning.

Weirs Throughout History 

A woman and her children work a traditional fishing weir at Tetlin in the 1920s. UAF Tetlin Photographic Collection.

Fish weirs are some of the earliest-known technology. Ancient cultures all over the world built these circular or wedge-shaped traps to corral and capture fish. Archeologists use radiocarbon dating to establish the age of biological material found in fish weirs. This material includes wooden stakes, fish bones, or charcoal. Using these methods, scientists date the earliest fish weirs to 8,000 years ago in Denmark and the Netherlands. Early sites also include 6,600 years ago in Australia, and as much as 6,000 years ago in southern Africa. 

Scientists believe early Native Americans built the oldest fish weir in North America, at Sebasticook, Maine 6,000 years ago. Scientists have carbon-dated fish weir traps in Southeast Alaska to 3,000 years ago.

When the New State Banned Weirs

A 1907 Case and Draper postcard shows tens of thousands of salmon being pulled out of an Alaskan fish trap. Alaska Historical Society.

In territorial Alaska, canneries could control an entire salmon return by building a weir trap across the entire width of a river. The federal government banned fencing off entire streams in 1889. It also banned the use of fixed fishing gear in rivers and narrow bays. Salmon processors continued to use traps at sea to catch tens of thousands of salmon at a time. 

In the years leading up to World War II in Cook Inlet, canneries on Chisik Island and in Homer, Kenai, Kasilof, and Tyonek used traps. These traps used steel wire fencing anchored to wood pilings to continue trapping salmon. This harvest method, along with drift fishing in the late 40s, packed millions of cans of salmon. Business was booming, but led to overfishing. Salmon runs declined sharply in the late 1940s. During the 1950s, economic disaster in the commercial fisheries led Alaskans to vote for statehood in 1959.

In one of its first acts, the new Alaska Legislature outlawed salmon traps altogether effective in 1960. However, the the federal government closed the fisheries to traps in the summer of 1959. The legislature also founded the Alaska Department of Fish and Game (ADF&G) to manage these valuable fisheries. 

Weirs Take Center Stage in Salmon Management

The first ADF&G commissioner, Andy Anderson, put the recovery of Alaska’s salmon fisheries as his first priority. Recovery ranked above the short-term gain of the fishing industry. 

Andy Anderson
Clarence “Andy” Anderson, the first commissioner of the Alaska Department of FIsh and Game.

“The governor has instructed me to return the salmon runs to their former abundance regardless of the pain that is inflicted on the people,” he reportedly said to his biologists. “I’m charging each one of you to make sure every stream in your district is filled to the maximum spawning capability. Now, if you allow an over-escapement, depriving the fishermen of their livelihood, you can expect to be criticized. But on a personal level, gentlemen, I want you to understand that if you allow an under-escapement, you can expect to be fired.”

Throughout the 1960s, the state restricted fishermen in Cook Inlet to just a few days of fishing a summer. The salmon stocks eventually rebounded. But, how would the state make sure harvest crashes never happened again?

Federal management followed simple formula. Fishermen could catch half of a salmon run and allow the other half to return to the spawning grounds. However, there was no counting nor enforcement. When ADF&G took over the fisheries, biologists implemented harvest rate collection, aerial surveys, and test fisheries. These measures allowed managers make informed decisions about fishery openings and closures. Salmon counting weirs became an important tool in fisheries management. In the 1970s, the state also established regional salmon hatchery programs like Cook Inlet Aquaculture Association (CIAA) to enhance wild stocks.

CIAA’s Counting Weir Program

The Cook Inlet Aquaculture Association (CIAA) maintains weirs at Bear Lake, Hidden Lake, Kasilof River, Paint River, and Shell Lake to monitor smolt on their way out to sea and returning adults. Counting weirs guide salmon into a trap box where weir workers occassionally measure the fish, determine sex and age, and take a small genetic sample. As salmon leave the trap box, weir workers manually count the salmon. Sometimes, a video camera records the salmon’s passage through the weir.

With the information provided by CIAA weirs, the association provides the state crucial information for sustaining salmon harvests in the Cook Inlet region.

CIAA’s weir program also includes a weir at Tutka Bay Lagoon the association uses to help capture pink salmon for spawning. In fact, many aquaculture weirs provide not only valuable information to the state, but also data CIAA uses to evaluate its hatchery programs. With the data it collects, CIAA can work to ensure the hatchery programs are meeting their goals and complying with rigorous state policies.

Habitat and Monitoring

The Cook Inlet Aquaculture Association maintains many other kinds of monitoring methods, as well as habitat restoration projects. Find out all CIAA is doing to help sustain Cook Inlet region salmon fisheries.

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