PNNL

Efforts to support and restore declining native North American fish species rely on accurate data to inform conservation and management decisions, from setting fishing regulations to guiding hydropower operations. Monitoring fish with a variety of specialized fish tag technologies can assist in answering important questions about fish movements, habitat use, and the outcomes of their interactions with infrastructure like hydropower dams and fish passageways. However, if a small species or juvenile fish is too sensitive to be handled or tagged, it limits the data available to inform these important decisions. One such sensitive species is American shad (Alosa sapidissima), an economically and culturally important fish in the eastern United States whose populations are in decline.

To address this challenge, researchers at Pacific Northwest National Laboratory (PNNL) developed a new mini-acoustic transmitter and tagging procedure that is designed to enable valuable in-water monitoring and data collection for highly sensitive species and young life stages of fish.

“Populations of small, fragile fish like American shad were considered essentially untaggable because they have high rates of mortality after being tagged,” explained Daniel Deng, Laboratory Fellow and principal investigator at PNNL. “Our new approach makes it possible to gather much-needed data on these species to inform management decisions and fish passage through hydropower facilities.”

For example, tracking juvenile American shad could shed light on exactly how they migrate through hydropower facilities—information that could help improve fishways and bypass facilities to better support shad populations.

Tagging American shad

Fish tags and tagging procedures are designed to be painless, non-traumatic experiences for fish, but some fish are inherently more sensitive to handling and tagging than others—including the American shad.

“Shad are so sensitive that there’s a saying among fish biologists that just looking at them wrong could cause them to die—but the reality is that shad are biologically adapted to be extremely sensitive to sound and movement in the water to avoid predators,” explained Kate Deters, Earth scientist at PNNL and lead author on the peer-reviewed publication detailing the new tagging protocol for juvenile shad.

Native to the east coast of North America, shad are a type of anadromous fish that migrates from rivers to the ocean and back again to spawn, sometimes multiple times in their lives. American shad are a species of concern because they are declining in some parts of their current native range. Unfortunately, detailed life history information to better support management decisions is not available for juvenile shad because their sensitivity to standard tagging procedures leads to high mortality.

“Our goal was to develop a protocol to successfully tag shad and maximize their post-operative survival,” said Robert Mueller, Earth scientist at PNNL and co-author of the published study. “This will provide more detailed information about shad populations and movement to managers and decisionmakers.”

The team developed a tiny tag to track shad that weighs only one-twentieth of a gram. To put that in perspective, a paperclip weighs about 20 times more than this tag. Equally important is the modified tagging procedure developed to minimize impact on sensitive shad, which shortens handling time and calls for using brackish water. Combined, the new tag and procedure led to similar survival rates between tagged and untagged shad in laboratory testing.

Shad, smelt, and more

Now, the team is focused on moving the tag from the laboratory to the real world. Preliminary results of field tests using the new tag to track American shad promise to shed valuable light on shad behavior and survival through hydropower facilities.

Although originally designed for shad, the new tag and procedure can be widely applicable to other small, sensitive fish species and young life stages of fish. It is already being used to track Delta smelt (Hypomesus transpacificus) in California—a small fish endemic to California that is listed as threatened under the Endangered Species Act.

“This is much more than just a shad tag—it’s really a tag for any small fish that we haven’t been able to adequately study,” said Deng. “The ability to tag these fish for in-river studies will inform management and hydropower operations to support fish passage overall.”

This work was funded by the Department of Energy Water Power Technologies Office. The results are published in Reviews in Fish Biology and Fisheries, entitled “Development of optimal methods for collection, transportation, holding, handling, and tagging of juvenile American shad.” The techniques are published in JoVE, entitled “Handling and Tagging Techniques for Implanting Juvenile American Shad with a New Acoustic Microtransmitter.”