The search for 'chirping' signals part of pilot project to learn if captive-raised endangered suckers are surviving in Upper Klamath Lake
by Susan Sawyer,
Klamath Basin Public Affairs Officer. Klamath Basin National Wildlife Refuge Complex.
Chris Derrickson tilts his head slightly, listening to the faint bird-like ‘chirping’ sound through his earphones while standing in a slowly moving boat. He concentrates on a digital scanner as the chirp grows stronger, closing in on his target. But rather than look to the sky for a bird, Derrickson leans over, peering into the murky waters of Upper Klamath Lake.
His target is a fish, more precisely a juvenile endangered sucker fish with an implanted radio transmitter.
Derrickson and Jordan Ortega, both interns at Oregon State University, are spending the summer tracking two-year-old Lost River and shortnose suckers. As part of a pilot project, their mission is to determine where the young fish hang out, and more importantly, if they are surviving.
The radio-tagged fish are the latest phase of the endangered sucker captive rearing program managed by the U.S. Fish and Wildlife Service's Klamath Falls Fish and Wildlife Office, whose goal is to boost sucker populations since juvenile fish are not making it beyond their first year in the lake.
“This study will allow us to gather real-time information on sucker survival and location that we can’t get from other tags,” said Mike Senn, Deputy Assistant Regional Director for Ecological Services in Sacramento. “It’s pretty cool and more involved, but yields much better science and critical information on where these transplanted fish spend their time.”
Two years ago, these suckers were collected from the river as tiny larvae and raised at a facility south of Klamath Falls, Oregon. All but 200 were released in March; the remaining fish were held back to grow slightly larger before undergoing the radio implant surgery.
“We don’t know a lot about the early life stage of these suckers, because no juveniles have survived to reach adulthood since the late 1990s,” said Dr. Evan Childress, a senior fish biologist for the Service. “We’re doing this study because we don’t know how suckers do after we release them. It’s critical to understand the variables that influence their survival such as size, when and where we release them. Those are things we can tweak and improve as we move forward.”
Lisa Gee, a private consultant, and one of several partners involved with the sucker rearing program, performed the surgeries, which is a tightly coordinated effort with many moving parts.
The procedure starts with the fish being anesthetized and a tissue sample collected for genetic study. A stopwatch monitors ‘air time,’ how long a fish is out of water, as they are weighed, measured and prepped for surgery. A small rubber tube is inserted in the suckers’ mouth to provide running water during the surgery. A small incision is made in the belly and a fine needle is pushed through the side of the fish. Gee tucks the radio capsule snugly inside the fish and pulls the thin 12 inch long antenna wire through the needle hole. She quickly closes the incision with three sutures and places the fish in a recovery tank. The whole process takes slightly more than two minutes.
Since these fish were released in April, every Tuesday and Thursday the interns hop aboard the research boat which is equipped with a tall mast-like antenna, and patrol near the lakeshore searching for signals. The transmitters are set to turn on for eight hours on these days, which extends battery life up to eight months.
The tags are tuned to two VHF frequencies that have a range of about 1,500 feet. Each tag is programmed with a unique code specific to a particular fish. The interns take turns listening for the ‘chirps’ of the tags and recording data as they cruise the lake each survey day.
At the same time, a contract pilot flies a small plane with antennas attached to each wing over the lake in a grid pattern. Sucker signals travel out of the water through the air to the receiver, with the strongest signal directly above a tagged fish. A digital recorder collects the data, allowing for hands free tracking while flying.
Although a plane can cover more area faster than a boat, the disadvantage is that signals are missed because the plane, as well as the fish, moves out of range quickly. The boat is better for finding individual fish when they are schooled together because it can float over them longer.
While results of the project won’t be determined until this fall, Childress already feels it is worthwhile. "Without this study, we would have no idea what happens to these fish," he said. "This will help us evaluate sucker survival in the wild and aid in recovering their populations so they can become self-sustaining."
About the writer...
Susan Sawyer is the Klamath Basin public affairs officer, covering the Klamath Basin National Wildlife Refuge Complex, Klamath Falls and Yreka Fish and Wildlife Offices. She was raised in the California desert gaining a deep appreciation of the outdoors on family vacations to the Pacific coast,Sierras and Redwood forests.
She has worked in Arizona, Nevada, Montana, Idaho and now Oregon, where she spends her free time landscaping for wildlife, continuing to learn from and about nature and spoiling her animals.