Science Spotlight

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  • September 11, 2019

Black and white image of a man crouched in front of truck, holding a large fish in one hand and measuring stick in other hand. Man is wearing plaid collared shirt and pants.
Faded black and white photos are all that’s left of the Owens River Gorge’s glory days as a trophy brown trout fishery. Biologists expect the fish to make a comeback following near-annual pulse flows that begin in September to improve habitat.

Sepia colored image of young man and older man sitting behind table covered in nearly 100 fish. A sign in front reads Harry Smith, 23 years 1953 74 browns, from the owens river gorge, limit 25 trout per day.

Two men in waders standing in river. One man has a large machine backpack on and holds a long, yellow stick in the water. Other man holds a net. Rocks and rough river in background.
CDFW crews electrofish the Owens River Gorge two times per year to assess the health of the river’s brown trout.

From boom to bust to decades of angler indifference, few California fisheries have experienced such wild swings of fortune as Mono County’s Owens River Gorge.

The latest chapter in the long saga of the Gorge unfolds this month when the Los Angeles Department of Water and Power (LADWP) sends a relatively brief burst of water known as a “Channel Maintenance Flow” down the 10-mile stretch of river between the Upper Gorge Power Plant and Pleasant Valley Reservoir to benefit fish habitat.

From Sept. 9 to Sept. 17, water flows will rise from the relatively placid 35 to 55 cubic feet per second (cfs) typical in the Gorge to 680 cfs before gradually ramping back down. link opens in new tab or windowAccess to the Gorge will be closed by LADWP during the nine-day “pulse flow” event for public safety.

The temporary boost in water flow represents the successful resolution of decades of legal battles involving LADWP, Mono County and CDFW. The high flows are expected to breathe new life into the Owens River Gorge ecosystem and its once-storied brown trout fishery. Court settlements mandate the pulse flows continue almost annually -- 18 out of every 20 years.

The flows are intended to replicate seasonal scouring that occurred naturally in the Gorge long before dams, power plants and water diversions were constructed in the last century. In fact, these alterations dried up the Owens River Gorge from 1953 to 1991 until years of litigation restored some minimal flows and attempts to restart a once-fabled brown trout fishery.

The Owens River Gorge is paradoxical – so close yet so far away. Just northwest of Bishop and within sight of Highway 395, it is difficult to access with limited and steep trails to reach its waters 500 to 900 feet below the rim. Since water returned to the Owens River Gorge in 1991, it has been more popular with hikers and rock climbers than trout anglers.

It was a much different story prior to the construction of the Long Valley Dam in 1941, which created Crowley Lake, and the subsequent addition of a number of power plants along the stretch of river. Before then, the Owens River Gorge was a destination brown trout fishery with a worldwide reputation. So good was the fishing it was one of the few waters in California with limits based on weight – 25 pounds plus one fish per angler per day.

CDFW Environmental Scientist Nick Buckmaster is based in Bishop and conducts twice-yearly electrofishing surveys in the Gorge along with macroinvertebrate sampling.
“Right now, the fish populations are pretty stunted,” Buckmaster said. “We just don’t have large brown trout in the Gorge anymore.”"

The Gorge is home almost exclusively to wild brown trout and the populations are high. Buckmaster estimates between 1,500 to 5,000 trout per mile, numbers that compare favorably to many blue-ribbon trout fisheries in the state.

“The problem is they are all small. Their growth really slows down around 5 inches, and most of the fish in the Gorge are less than 8-inches long. Their growth really plateaus,” he said. “By the time they get to 8 inches, they are geriatric fish.”

Buckmaster explained that brown trout undergo an important life change once they reach between 8 and 14 inches in size. They mostly stop eating aquatic insects and transition into apex predators, preying on other fish and just about anything else of substance they can eat. The diet change leads to rapid growth and turns them into a prize for any trout angler skilled enough to catch them.

Plateauing at 5 inches, however, most of the brown trout in the Owens River Gorge never reach that important developmental milestone or achieve it only toward the end of their lives.

“If you want big brown trout, they need something to eat,” Buckmaster said. “And they usually need a lot of something to eat.”

CDFW fisheries biologists expect the pulse flows to provide just that by dramatically altering the ecosystem. The big burst of water will scour pools and restore the deep-water holding and ambush habitat needed by large brown trout. The flows will flush out years of accumulated sediment, exposing gravel beds critical for trout breeding while fostering a broader diversity of aquatic life than what’s present in the Gorge today.

Mayflies and stoneflies are largely absent from the ecosystem, and caddisflies – safely encased and underneath rocks in their larval stages – provide a limited food source. Small populations of native Owens suckers exist in the Gorge. Their numbers are expected to grow with an increase in aquatic insect life following the pulse flows, incidentally providing important forage for growing brown trout.

The high waters will inundate and benefit riverside riparian growth, offering shade and cover and additional insect habitat. The flows also are expected to flush out invasive  New Zealand mud snails that have infested the Gorge over time. The snails provide little benefit to fish and are a source of competition for other macroinvertebrate life.

Buckmaster said biologists could see positive changes in the Gorge as quickly as three months after the flows. And bigger brown trout could start turning up in Buckmaster’s electrofishing surveys – and at the end of anglers’ lines – as early as next year.

CDFW Photos. Top Photo: CDFW scientific aids Christi Kruse and Emma Hewitt identify some of the macroinvertebrate life taken from the Owens River Gorge.

Categories: General
  • June 11, 2019

Lake with vegetation in foreground. Snowy mountains and green trees in background.
A long, wet winter has been good for Junction Reservoir and CDFW’s Kamloops rainbow trout that live there.

Dock on lake with small fishing boats. Mountainside with trees in background.
The June Lake Marina graciously offered up its net pens to CDFW’s Kamloops rainbow trout program when the drought forced CDFW to rescue its brood stock from a shrinking Junction Reservoir.

Two men in CDFW uniforms standing in concrete and metal structure in stream. One man is holding a large white net. Trees and patchy snow covered ground in background.
CDFW hatchery staffers Jimmy Sparks, left, and Drew Klingberg prepare to sex and sort Kamloops brood stock for later spawning, separating males from females as well as those females ready to spawn immediately versus those that need more time to ripen. The fish are returned to Junction Reservoir after spawning.

Person wearing blue gloves holding net with fish over metal basin with water.
The offspring from these Kamloops will be raised at CDFW’s Fish Springs Trout Hatchery and stocked by airplane as fingerlings into backcountry waters across the state approved for trout stocking.

Blue-gloved hands holding small fish over metal basin filled with water and fish.
Resplendent in their spring spawning colors, Kamloops rainbow are raised and bred for their hard-fighting ability and wild nature that allows them to thrive in California’s remote backcountry waters and provide a thrill for anglers who catch them.

Junction Reservoir in Mono County is CDFW’s brood lake for the Kamloops rainbow trout, a hard-fighting strain originally from the Kamloops region of British Columbia.

The 20-acre lake sits on a private cattle ranch off-limits to fishing. It provides a secluded setting for the brood stock, whose progeny are used almost exclusively for the aerial stocking of backcountry waters throughout the state.

“We try to keep them raised in a more wild condition so they do better in the wild,” said Hot Creek Trout Hatchery Manager Mike Escallier. “They are a really fun fish to catch. They jump a lot. They will jump 3 feet out of the water when you hook one.”

And Junction Reservoir has never looked better. This spring, the lake was filled to the brim after a long, cold, wet winter. Near the mouth of the lake’s one small inlet, Kamloops were staging for a spawning run, their feisty nature on full display in the clear waters, breaking the surface occasionally and fighting each other over territory.

Kamloops further up the inlet were blocked from moving upstream by a concrete and metal trap. That’s where CDFW’s hatchery staff collect and sort the fish each spring, spawning them manually to produce the offspring that will be deposited as fingerlings this summer by airplane into backcountry waters approved for stocking.

The entire scene is a welcome sight after California’s drought nearly collapsed CDFW’s backcountry fish-stocking program. During the darkest days of the drought, the small inlet feeding into Junction Reservoir dried up. Combined with the years-long shortage of rain and snow, Junction Reservoir withered to about half its size. In 2013, CDFW conducted an emergency fish rescue to save about 2,000 of the brood fish and its backcountry trout stocking program altogether.

The rescued fish were relocated to CDFW trout hatcheries and other nearby waters for safe-keeping. The owners of the June Lake Marina provided a major assist, offering up some of their net pens on June Lake to CDFW and its Kamloops at no charge. The June Lake net pens continue to hold some Kamloops, which CDFW spawns each spring until the program transitions back fully to Junction Reservoir and CDFW’s Fish Springs Trout Hatchery south of Big Pine where the baby Kamloops are raised.

CDFW returned brood fish to Junction Reservoir in the spring of 2017 following a wet winter and heavy snowpack. CDFW is rebuilding production toward its annual goal of collecting and fertilizing 1.4 million eggs. Some of the offspring are put back into Junction Reservoir to add genetic diversity and different age classes to the rebuilding brood population as no natural spawning occurs in the lake.

One benchmark hatchery managers and biologists are striving toward is the return of Kamloops to Crowley Lake, where more anglers will have a chance to enjoy them.

Before the drought wreaked havoc on CDFW’s Kamloops program, a portion of the Kamloops produced each year were allocated to Crowley Lake. While the backcountry trout are sterile – or “triploid” – the fish stocked into Crowley are “diploids” capable of spawning naturally.

“They spawn at different times than other strains of rainbow trout,” explained Escallier. “They give anglers fishing the creeks opportunity. They tend to be running up the creeks from Crowley right around the trout opener.”

CDFW Photos. Top Photo: The inlet to Junction Reservoir is blocked by a fish trap where CDFW hatchery employees catch fish in the spring for spawning.

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Media Contact:
Peter Tira, CDFW Communications, (916) 322-8908

Categories: General
  • May 9, 2019

Closeup of man holding up fishLahontan cutthroat trout are a Crowley prize. In addition to natural spawning that occurs in the lake, CDFW plants the fish as fingerlings in the fall. By the spring opener, many like this fish are resplendent in their spawning colors.

Man in brown and beige CDFW uniform on boat bent over cooler with fish while holding a ruler in cooler. Jim Erdman conducts creel surveys to see how many trout CDFW planted last fall turn up on opening day. Fish 15 inches or longer are determined to be from last fall's stocking when they were planted as fingerlings.

Man in white t shirt, sunglasses and ball cap on beach in front of body of water holding up a fish with spots. Mark Risco from Temecula shows off the 20-inch brown trout he caught opening day at Crowley Lake. In addition to natural spawning, CDFW's Hot Creek Hatchery stocks thousands of brown trout each year, which are very popular with Crowley anglers.

Man wearing CDFW uniform, sunglasses, and green ball cap standing in dirt parking lot holding clipboard.CDFW volunteer Carl Ronk conducted opening day creel surveys at Crowley Lake along with CDFW Environmental Scientist Jim Erdman.

Mono County’s Crowley Lake is a destination fishery that attracts trout anglers of all kinds – bait fishermen, lure casters, trollers and fly anglers – throughout the state during its open season.

The sprawling lake, situated at 6,700 feet and covering some 5,300 surface acres in the Eastern Sierra, also represents a huge investment for CDFW. The nearby Hot Creek Trout Hatchery raises hundreds of thousands of rainbow, brown and Lahontan cutthroat trout for Crowley each year that provide the backbone of the quality angling experience. Many of the fish are stocked as fingerlings in the late summer or fall and grow rapidly in the invertebrate-rich environment. Some go on to spawn in the lake’s many feeder creeks and supply wild progeny to the population.

All of which helps explain why CDFW Environmental Scientist Jim Erdman has been out conducting creel surveys at Crowley every opening day since joining CDFW in 2005. Based in Bishop, Erdman’s goal is to contact at least 300 anglers and see which hatchery fish are turning up in their catch, in what numbers, in what proportion of species, and in what condition. The report is an annual check to see whether CDFW’s management plan for Crowley remains on point or whether adjustments need to be considered. The opening day creel surveys have been taking place since 1997 when CDFW biologist Curtis Milliron wrote the Crowley Lake Management Plan.

CDFW volunteer Carl Ronk assisted Erdman this past opener April 27. The two split up at times – one checking anglers along the shoreline, the other awaiting returning boats to the Crowley Lake Fish Camp marina, the only formal boat launch at the lake.

Their tools for the day included a clipboard for note-taking and a 15-inch wooden “Crowley Stick” for measuring fish. CDFW biologists have determined that a fingerling trout stocked in the fall should be 15 inches or greater by opening day in the nutrient-rich waters. Erdman typically completes and submits his report by the afternoon of the opener and shares it with anyone interested. Local papers have been known to reprint it in its entirety.

For the 2019 Crowley opener, the creel survey found shoreline angler success was greatly improved from the previous year with an average catch per angler of 3.66 trout compared to last year’s average of just 0.71 trout. Overall, however, catch rates and total catch per angler were lower than 2018. Fish size was also down. Approximately 41.4 percent of the rainbow trout measured were greater than 15 inches, well below the annual average of around 70 percent. The catch rate fell below CDFW’s management goal of one fish per angler for each hour of effort.

A long, cold winter and late ice-out were cited as factors in a slower-than usual Crowley opener and smaller fish with less time to fatten up post ice-out.

“Crowley Lake did not ice-out until April 10, 2019, and this kept fish in deeper water than usual,” Erdman wrote. “No fish were seen in the McGee, Crooked or Whiskey Creek inlets and few to no fish were seen staging for a spawning run. Water temperatures in the inlets remained below 40 degrees.”

Rainbow trout made up the majority of the catch followed by brown trout. Lahontan cutthroats were scarce. CDFW annually stocks 100,000 Lahontan cutthroat fingerlings in the fall. Cutthroats represented just 0.9 percent of the shoreline catch and 1.6 percent of the boating catch compared to 2018 findings of 11.3 percent of the shoreline catch and 2.2 percent of the boating catch.

Opening day on Crowley Lake, with its big crowds and festive atmosphere, has always been about more than bag limits as reflected in Erdman’s creel survey report.

“Returning boat anglers were a bit slower than usual coming in off the lake probably due to the pleasant conditions on the lake. Relaxing in the sun and drifting in the slight breeze. A grand day to be on the water.”

CDFW Photos. Top Photo: CDFW's creel surveys play an important role in evaluating the lake's management and stocking allocations.

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Media Contact:
Peter Tira, CDFW Communications, (916) 322-8908

 

Categories: Wildlife Research