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Tracking suckers in drought proves to be a tricky task. Spawning data hard to come by in low water
In a last-ditch effort to locate an 1 ˝-inch-long telemetry radio transmitter, Amari Dolan-Caret, a U.S. Geological Survey (USGS) fish technician, rolled up her sleeves, plunged her arms in Clear Lake Reservoir and began tossing rocks behind her.Despite the fact an aluminum antenna and radio receiver picked up a set of coded pulses indicating the transmitter was just inches from her feet, the transmitter never materialized.
“When they are down in the rocks, it’s difficult to find them because the signal bounces around.We’ll come back later when the water is lower,” she said turning to David Hewitt, a USGS fisheries biologist standing on the shore.
Of the eight transmitters the pair hoped to locate that day, only two were recovered. And neither of those provided any clue as to what happened to the suckers they had been surgically implanted in last fall.Stranded transmitters
About two weeks before Hewitt and Dolan-Caret made the 44-mile trek to Clear Lake Reservoir in Modoc County, they toted a small satchel of electronic equipment to Crater Lake-Klamath Regional Airport. There, they met with Uwe Britsch, owner of Pelican Aviation, and attached two receiver antennas to the wing struts of his Cessna 172. For the next two hours, Britsch flew rotations 1,000 feet over Clear Lake, scanning for telemetry tags.“That’s low enough to pick up the data, hopefully, and high enough for us to be safe,” Britsch said.
In October scientists inserted 75 tags in the reservoir’s threatened shortnose and Lost River suckers — both species were listed under the Endangered Species Act (ESA) in 1988 — to monitor how spawning adults are responding to drought. Only 68 have been identified by aerial flight. Of those, the eight Hewitt and Dolan-Caret were after repeatedly identified as stationary near or on the lakeshore.Transmitters can end up stranded in a variety of ways, Hewitt said. Wind and waves might push a dead sucker on shore, or a fish might get gobbled up by a pelican and the transmitter drops out the other end. Sometimes rejected transmitters work out of the body and the fish lives. “Oftentimes, it’s just the transmitter lying on the sand, and you’re not sure how it got there,” Hewitt said. “Obviously if a transmitter ends up on a bird colony, the fish didn’t get there on its own.”
Low-tech sensorsWhile only 75 Clear Lake suckers received telemetry tags, more than 10,000 have been fitted with another type of tag, a passive integrated transponder, or PIT tag.
Unlike the battery-driven telemetry transmitters, which will eventually expire, rice-size PIT tags have a never-ending shelf life because they are nothing more than a copper coil encased in glass.“We have fish that were tagged 20 years ago and we’re still getting remote contacts off them this year,” Dolan-Caret said.
Hewitt explained that PIT tags are useful for monitoring large-scale sucker movements because the receiver sensors are underwater and all fish have to do is pass over or nearby them. Several PIT sensors are installed in Willow Creek, Clear Lake’s primary tributary and the suckers’ main spawning stream, he said.But, if no signal is triggered, no information is collected.
“With the transmitters, the benefit is that you can go find an individual any time you want. With pit tags, you can’t do that. You can set up antenna at certain checkpoints and know when they’ve passed there,” he said. “You typically use telemetry when you need fine-grain information on particular individuals.”In the shallows
Water levels in Clear Lake have nearly zeroed out in the past two years. At its lowest point in 2014, the reservoir’s volume hovered around just 6 percent full.“It’s been so dry the last few years basically no fish were getting contacted on that pit tag array and that was because the water was just too shallow for them to get over to the creek or up the creek,” he said.
Telemetry transmitters are allowing researchers to learn more about how drought impacts spawning behavior because researchers can better monitor sucker movements and how the fish navigate obstacles, such as low water or emerging rock outcroppings.Hewitt said no data has suggested suckers are spawning elsewhere in the lake.
“It doesn’t look like there’s a concentration where they go when they can’t access the creek. That’s kind of bad news. If you have a drought year and those fish cannot get to the creek, and they want to go to spawn, that’s essentially a year class that’s not going to happen,” Hewitt said.Josh Rasmussen, a fish biologist for the U.S. Fish and Wildlife Service, said historically, before 1910 when Clear Lake was created as the first major “improvement” for the Klamath Project, spawning suckers moved from Clear Lake into Lost River, which emptied in Tule Lake. He said fish concentrated in the stretch that passes through Olene and in the Big Springs area in Bonanza.
“Those areas were probably crazy important spawning areas,” he said.Hurdles to spawning
Before Lost River was dammed and Clear Lake was filled, the “lake” was much smaller — its water body mostly consisting of what is now called the “west lobe.” According to Rasmussen, the east lobe was likely a large wetland that filled in the spring with water from Willow Creek and other small tributaries.Now, since Lost River is inaccessible, Willow Creek is the main spawning arm. Hewitt said only 35 suckers have entered Willow Creek this year.
In 2011, when the lake level and creek flows were high, more than 3,000 individuals charged up Willow Creek to spawn, he added.Rasmussen said the U.S. Fish and Wildlife Service — the agency charged with managing the species’ ESA protections — main objectives are to understand what’s going on with the populations and to ensure they remain stable.
He said thanks to efforts from agencies such as the USGS, more and better data is becoming available, but it will still be a couple years before any factual assumptions about the populations or their behaviors can be made.“As far as we can tell from our sampling out here, if the fish can spawn, they do produce young and they survive better than the young in Upper Klamath Lake,” Hewitt said. “It’s just more intermittent because when you have a drought, basically you get nothing.
“Long-term, if drought continues and the reservoir isn’t refilled and the streams don’t flow for spawning, it’s over.“At some point 20 years from now, there’s not going to be any fish in the lake,” Hewitt said. “How many years suckers can do this before it has implications for the spawning runs and water, I don’t know. I think we’re in uncharted territory.”
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U.S. Geological Survey fish biologist Dave Hewitt attaches a receiver antenna to a plane that will survey tagged suckers from the air.
U.S. Geological Survey fish technician Amari Dolan-Caret uses a hand-held antenna to locate signals from suckers tagged with telemetry transmitters. Each transmitter has a unique code that allows scientists to identify individual fish.
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