Science Spotlight

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  • December 19, 2017

A woman wearing a blue top stands next to three white, plastic, chest-high vats.
Kerstin Wasson is leading the Olympia oyster restoration at Elkhorn Slough. Kerstin Wasson photo.

shallow water and bare mudflats of an estuary
Scientists are working hard so that a new generation of Olympia oysters may one day line the mudflats at the Elkhorn Slough Reserve.

Two women and a man wearing mud boots, carry 18-inch stakes with clam shells attached, in an ecological reserve
Volunteers Ken Pollak and Celeste Stanik join Dr. Chela Zabin to improve the native oyster habitat at Elkhorn Slough. Kerstin Wasson photo.

suspended clam shells hang in plastic laboratory tanks
Suspended gaper clam shells hang in aerated laboratory tanks, home to what scientists hope will be a new generation of Olympia oysters at the Elkhorn Slough Reserve.

In a marine laboratory, a man wearing a red T-shirt holds what looks like a clam shell mobile.
Graduate student Dan Gossard, at CSU’s Moss Landing Marine Laboratories, shows off one of the clam shell “mobiles” on which the Olympia oyster larvae will attach when suspended in aerated tanks.

A woman wearing camouflage waders stands in shallow water and points to a clam shell embedded in the muddy bank of a slough
Kerstin Wasson points out Olympia oysters along the banks of the Elkhorn Slough Ecological Reserve in Monterey County.

For the first time in California history, scientists are turning to shellfish farming techniques to restore native oyster populations.

The groundbreaking research is taking place with Olympia oysters at CDFW’s Elkhorn Slough National Estuarine Research Reserve in Monterey County, in partnership with the California State University’s nearby Moss Landing Marine Laboratories and its new Center for Aquaculture.

Olympia oysters and other shellfish were once so abundant at Elkhorn Slough that Native Americans living there had multiple processing centers along the estuary’s banks to handle their harvest. Olympia oysters have disappeared altogether from many places along the California coast and their numbers at Elkhorn Slough have dwindled so low – estimated today at just a few thousand oysters – that scientists fear they may no longer be able to reproduce in the wild. Not since 2012, they say, have Elkhorn Slough’s wild oysters produced any offspring.

A combination of factors is believed to have caused the population drop over time, including poor water quality because of agricultural runoff from nearby farms and alterations to the landscape and tidal flow from generations of farming and other human activity prior to the area becoming protected in a series of conservation purchases beginning in 1971. An infusion of freshwater from last year’s rainy winter caused a severe oyster die-off and spurred biologists into action.

“This is an iconic species in our estuary in danger of disappearing,” said Kerstin Wasson, Research Coordinator at Elkhorn Slough, where she has worked for 17 years with funding from the National Oceanic and Atmospheric Administration (NOAA), the federal partner in the Elkhorn Slough Reserve. “These oysters fed native people here for 7,000 years.”

In late August, dozens of Olympia oysters were gathered and brought to the Moss Landing Marine Laboratories, where 20 spawned successfully. A few hundred thousand of their microscopic offspring are now swimming in large, circular laboratory tanks and attaching themselves to gaper clam shells suspended on fishing line from the top of the tanks. The clam shells bearing young oysters will be bound together into makeshift reefs and returned to Elkhorn Slough early in 2018 to bolster the native population.

The research is being led by a small group of scientists, including Wasson and graduate student Dan Gossard with funding provided by the Palo Alto-based Anthropocene Institute. These are uncharted waters for California scientists, however, and a major assist is coming from the aquaculture industry itself. Peter Hain of the Monterey Abalone Company has worked closely with the two researchers to set up the laboratory facility for the Olympia oysters and help with their care and feeding.

Due partly to their small size – an individual Olympia oyster is about the size of a 50-cent coin – and slow growth, Olympia oysters hold little appeal and little potential profit for most commercial oyster farmers who focus on larger Pacific varieties, many native to Japan. Taylor Shellfish Farms in Washington State is the only known commercial producer of Olympia oysters.

Wasson welcomes interest and support from aquaculture and hopes growers might one day add the native oyster to their operations. She believes even a niche commercial market for Olympia oysters could have positive implications for wild populations, enhancing recruitment, broadening scientific knowledge and a general appreciation for the native mollusk by the public.

Other efforts to save wild oyster populations in California and elsewhere have focused on building jetty-like artificial reefs constructed from oyster shell contained in plastic mesh.

Wasson prefers that more natural materials be used as part of the oyster restoration efforts underway at Elkhorn Slough, creating small clusters of oysters rising above the mudflats.

“I want this place to look like it did 200 or even 2,000 years ago,” she said.

Top photo: A huge influx of fresh water during winter 2017 resulted in an Olympia oyster die-off and spurred biologists into action.

Categories: General
  • December 12, 2017

a brown frog looks up from green water and grass at the endge of a pond
A California red-legged frog sits motionless at the edge of McClure pond at the Sparling Ranch Conservation Bank. Photo by Ashley Spratt/USFWS

a small stand of oak trees is reflected in the green water of a pond, surrounded by dead, yellow grassy hillsides
McClure pond is one of the most productive California red-legged frog ponds at the Sparling Ranch Conservation Bank. Like many of those on Sparling Ranch, it was named after the family who homesteaded in site in the late 1800s. Photo by Ashley Spratt/USFWS

Since the mid-1980s, California has been using a system of conservation and mitigation banking to protect valuable natural resources and critical habitat for fish, wildlife and plants. These banks are generally large, connected, ecologically meaningful areas of preserved, restored, enhanced or constructed habitat (for example, wetlands) that are set aside for the express purpose of providing mitigation for project impacts. Conservation banks provide mitigation for impacts to listed species and habitats, while wetland mitigation banks primarily provide mitigation for wetland impacts. Together, they serve to prevent inadequate, fragmented reserves that can result when mitigation projects are carried out individually.

Banks work by establishing credits for sensitive species or habitats found on a given site. These credits can then be sold to developers or other project proponents who need to meet permitting requirements or are otherwise required to compensate for environmental impacts. For those parties needing to mitigate for project impacts, banks serve to streamline the regulatory process by providing a pre-established mitigation site that the regulating state and federal agencies have already confirmed will provide adequate and appropriate mitigation for certain habitats or species. By mitigating at a bank, project proponents can avoid the time and cost of searching for a suitable mitigation site and protecting it in perpetuity themselves.

In order for the banking system to be effective, state and federal agencies must work closely together to align processes and practices. Since 1993, CDFW has been participating in the planning, review, approval, establishment, monitoring and oversight of 81 banks statewide. Other agencies that typically participate in the regulation and approval of conservation banks include the U.S. Army Corps of Engineers (USACE), U.S. Environmental Protection Agency (USEPA), Natural Resources Conservation Service (NRCS), U.S. Fish and Wildlife Service (USFWS) and the National Oceanic and Atmospheric Administration National Marine Fisheries Service (NOAA NMFS).

To read more about one of these successful partnerships, link opens in new windowplease visit USFWS’ newsroom.

Learn more about CDFW’s Conservation and Mitigation Banking program, on our website.

All photos courtesy of U.S. Fish and Wildlife Service.

Top photo: A herd of cattle graze atop a hillside at Sparling Ranch near Hollister, Calif. Photo by Ashley Spratt/USFWS.

Categories: General
  • December 6, 2017

a woman wearing a California Fish and Wildlife uniform, standing in waist-high grasses, connects cables in a 1-foot-square, plastic box.
CDFW Scientific Aide Aimee Taylor prepares electrofisher to harmlessly catch Paiute cutthroat trout in North Fork Cottonwood Creek.

an irridescent gray, purple, pink and white cutthroat trout hovers in the sunlit water of a shallow creek
The extremely rare Paiute cutthroat trout (PCT). Photo by William Somer for CDFW.

Two people wearing Fish and Wildlife uniforms stand in a shallow mountain stream, surrounded by lush Alpine vegetation
Aimee Taylor and Senior Environmental Scientist Jeff Weaver electrofish PCT in North Fork Cottonwood Creek.

Four people kneel in green grass next to a stream, huddled around something on the ground
Jeff Weaver, USFWS Biologist Chad Mellison and others take genetic samples from the fish.

At a pack station with horses in the background, two men transfer fish by net, into an old-fashioned milk can.
The project’s lead biologist, Bill Somer, and Chad Mellison transfer the trout from CDFW’s tank truck to cans for the ride to Silver King Creek, by pack mule.

A pack train of seven loaded mules and three riders on horseback traverse a high mountain plain under a partly cloudy sky
The CDFW-FWS-USFS team packs pure PCT in milk cans through the Silver King drainage.

A man wearing hip waders and a California Fish and Wildlife uniform stands knee-deep in a stream that runs through a green meadow, where he lowers a white bucket into the water to release two small fish.
Bill Somer releases Paiute cutthroat trout into Silver King Creek, above Llewellyn Falls.

A trout lies in an elongated net with measuring marks, held next to a white bucket with water and other live fish in it.
Team members measured each Paiute cutthroat trout caught at White Mountain.

The California Department of Fish and Wildlife (CDFW), U.S. Fish and Wildlife Service (FWS), and U.S. Forest Service (USFS) have returned a rare trout species to its home water after a 71-year absence.

In 1946, poachers were decimating the Paiute Cutthroat Trout (PCT), a species whose native range was limited to a nine-mile section of Silver King Creek (Alpine County). To ensure the species’ survival, the USFS and Eastern Packers Association translocated 401 of these fish to North Fork Cottonwood Creek in Inyo County’s White Mountains. This population has persisted in isolation from other forms of trout and has recently provided important restoration options for resource managers. None of this would have been possible without the foresight of concerned biologists seven decades ago.

The conservation history of this rare trout is complex. The initial “conservation” measure was entirely inadvertent. In the early 1900s, Basque sheepherders in the area caught and transported PCT into the previously fishless portion of Silver King Creek above Llewellyn Falls. This early within-basin transfer was the salvation of the PCT, since non-native species were later introduced below the falls. The falls prevented non-natives from reaching the habitat above and protected PCT from hybridization and competition.

The FWS listed PCT as endangered under the Endangered Species Preservation Act of 1966 – the precursor to the federal Endangered Species Act (1973). The species was down-listed to threatened status in 1975, in order to facilitate management and restoration and to allow regulated angling. In 1994, CDFW, FWS and USFS began developing a restoration plan to remove non-native fishes from Silver King Creek and return the PCT to its native waters. From 2013 to 2015, the partner agencies treated 11 stream miles of Silver King Creek and three tributaries below Llewellyn Falls with a fish toxicant, rotenone, to remove all non-native fish species.

The PCT population in Upper Fish Valley, an area of Silver King Creek above the falls, has been considered a primary source for restocking the recovery area. Unfortunately, that population was heavily impacted by the extreme 2012-2016 drought. During this extended drought, lack of snow cover resulted in the stream freezing almost solid during cold snaps. In order to offset the resulting population decline, the partner agencies caught 86 pure PCT in North Fork Cottonwood Creek. On August 23, 2017, the fish were planted back into Silver King Creek above Llewellyn Falls.

Agency staff met in the White Mountain Wilderness (Inyo National Forest) and, along with volunteers and pack mules, hiked from their campsite to North Fork Cottonwood Creek. There, the team used electrofishers to retrieve descendants of the fish moved back in 1946. The fish were hauled out by mule, put in a specialized transport truck, and driven approximately 100 miles to the Carson Iceberg Wilderness. Another mule team then hauled them back to Silver King Creek. Thanks to careful handling by the collection and transport teams, every fish survived the trip home.

Due to its limited habitat, the Paiute Cutthroat Trout has been called the rarest, but most recoverable, form of trout in the United States. With the most recent success of this partnership, and due in large part to the foresight of conservationists in the past, the future looks bright for this beautiful native salmonid.

Learn more on the Paiute cutthroat trout web page.

Photos by Joe Barker, courtesy of U.S. Fish and Wildlife Service, except as noted.

Top photo:
Liz Vandentoorn, from the Inyo National Forest Region 5 Center of Excellence, leads a pack mule team and state and federal scientists to North Fork Cottonwood Creek to capture Paiute cutthroat trout and return them to Silver King Creek.

Categories: General