Tens of thousands of fish have migrated down the Columbia and Snake rivers over the last decade emitting a high-pitched beep every few seconds.
Tiny acoustic tags developed by Pacific Northwest National Laboratory in Richland have become the go-to technology of the Army Corps of Engineers as it manages its eight dams on the lower Columbia and Snake rivers.
The data collected has provided insight into why some fish survive the migration and others do not.
Each tag emits a tone assigned to a specific fish. The sound is picked up by receivers stationed wherever biologists want to know more about fish behavior. They might be placed at dams or along river banks or hung from buoys or carried in boats.
“You get three-dimensional information about the fish so you can get very detailed fish swimming behavior,” said PNNL chief scientist Zhiqun “Daniel” Deng. “With this kind of detailed fish behavior information, you can make management decisions of how you optimize operations of the dam for fish survival and, of course, without loss of power generation.”
Such detailed information was not available to the Corps in 2001, when a federal court biological opinion required an estimate of the survival of juvenile salmon downriver from the Bonneville Dam, the last Columbia River dam before the fish reach the Pacific Ocean, said Brad Eppard, a supervisory fishery biologist in the Corps Portland District..
Acoustic tag technology then on the market was too large for juvenile salmon.
PNNL researchers set to work creating a smaller acoustic tag — weighing less than half a gram and the size of a couple grains of rice — and have been improving the tags and developing more ways to use them since then. Funding has come from both the Corps and Department of Energy.
The results have been used to learn about fish behavior and improve conditions for fish heading to both the Atlantic and Pacific oceans, and to improve fish survival at dams in Australia, Germany and Brazil.
The initial use of the tags to estimate the survival of juvenile salmon downstream of the Bonneville Dam also provided new information about salmon behavior.
Biologists had believed that young salmon take a right at the mouth of the Columbia River and immediately head north toward Canada.
Instead, PNNL ecologists found that, especially in the early spring, the fish scatter in all directions as they reach the ocean.
Its useful information, since the key weeks after salmon enter the ocean seem to set the tone for the strength of the annual class, including the success of the subsequent runs upriver to start the next generation of salmon.
Information on fish behavior in the estuary can be used for decisions on when to release juvenile fish from hatcheries or to adjust plans for barging salmon downstream past dams based on optimal ocean conditions.
Another study using the tags collected data that helped the Corps decide the best place to install a spillway weir at John Day Dam on the Columbia River. The weir acts as a giant fish slide, allowing the fish to pass the dam near the surface of the water, where they prefer to swim.
Data collected at the dam also provided more information on the number of fish that passed the dam only to provide a feast for gulls below it. Wires hung with fluttering ribbons were strung across the river downstream to haze away the gulls.
Not all the studies have involved juvenile salmon.
The Corps has used acoustic tags to learn about the migration and survival of kelts, or steelhead that may spawn and then migrate one or two more times to the ocean before dying. Tagged kelts were monitored from Lower Granite Dam on the Snake River to McNary Dam on the Columbia River near Umatilla.
To date, the Corps has been using acoustic tags that must be surgically implanted into fish in a process that requires fish to be anesthetized and handled for two to three minutes.
A smaller acoustic tag developed by PNNL is “outpatient,” Deng said. It can be injected into the fish, requiring about 20 seconds of handling.
“Fish tagged with this new tag, they have much higher survival rates,” he said.
The result is a truer picture of fish survival, and the Corps plans to start using the injectable tags next year.
They weigh less than .22 grams and are about six-tenths of an inch long.
Researchers have since designed an even smaller tag, this one sized to be used in juvenile lamprey in the West or American eel in the East.
The tag needed to be small enough to fit into a fish about the size and shape of a writing pen.
Much of the research conducted using the tags in the West have been for salmon listed under the Endangered Species Act.
Even though lamprey are not a listed species, they are culturally important to the tribes.
Their migratory behavior does not not completely overlap with salmon, and there is opportunity to manage Northwest dams outside the listed salmon migration season to benefit lamprey, Deng said.
PNNL plans a study — paid for by the Corps and in partnership with the tribes — in late winter that will rely on the new tags to increase understanding of the migrating behavior of juvenile lamprey. A pilot study was conducted this year on the Columbia between the McNary and John Day dams to prove the feasibility of the technology.
The tags weigh just .08 grams and and are just under a half inch long.
They have considerably less power than the injectable acoustic tags that can ping every three seconds for four months before losing battery power.
If the pings are extended to every five seconds, the smaller tags last for 20 to 30 days, just long enough for a lamprey to travel from the Snake River to the Pacific, Deng said.
The size of the tags is keyed to the size of the batteries they carry.
“Once you go smaller you sacrifice tag life,” Deng said. “We used to joke about this. Our ideal scenario is to weigh nothing and last forever.”
PNNL researchers do have an idea on how to make the batteries last forever. They have developed a tag powered by the movement of the fish.
Along with the transmitter, the tag includes a strip of what’s called piezolectric composite, a self-charging material.
Strips 3 to 4 inches long leave the tags much larger than those used in other juvenile fish, but that’s not a problem for studying large fish.
Initially tags were inserted in a rainbow trout and a white sturgeon.
As they swam around tanks at PNNL’s Aquatic Research Laboratory in Richland, microphones picked up the tell-tale beeps, and the tags did not appear to hinder the ability of either fish to swim.
The technology will be tested for the first time outside the lab in a pilot study using white sturgeon in either the Snake or Columbia rivers this year.
“Sturgeon are ancient fish and have been on the planet for millions of years,” Deng said. “This tag can help us mitigate the impacts of human activities, and help these fish survive many more years.”