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Suisun Marsh Study Seeks to Unlock Mysteries of Western Pond Turtles

Suisun Marsh Study Seeks to Unlock Mysteries of Western Pond Turtles

A woman in a marsh holds a turtle
Two men in a marsh, one holds a turtle
Gloved hands hold a pond turtle with long claws
A man throws a trap into a marsh slough
A pond turtle in a marsh pond
Pond turtle's face, close-up
Gloved hands hold a pond turtle as someone neasures its height
Hands hold a six-inch pond turtle with long claws

Does the Western pond turtle (Actinemys marmorata), a freshwater species native to the Pacific Coast, hold secrets to survive climate change and adapt to rising sea levels? CDFW biologists want to know and have partnered with UC Davis and the Department of Water Resources to conduct a long-term study in Solano County’s Suisun Marsh to better understand the aquatic reptiles.

Officially, the Western pond turtle is a Species of Special Concern in California because of declining populations brought about by habitat loss, degradation and competition from that pet store favorite – the non-native, red-eared slider. The pet slider turtles are often released into the environment by their owners after outgrowing or outliving their welcome. They also outgrow and out-compete the medium-sized western pond turtles for food and critical basking spots. Western pond turtle populations are faring even worse in Oregon and Washington.

And yet in the Suisun Marsh, with its brackish water and high salinity, the Western pond turtle appears to be thriving. The Suisun Marsh, ironically, may now be home to one of the strongest populations of Western pond turtles on the West Coast.

“It’s just a really unique population in a place where we didn’t expect to see a freshwater species,” said Mickey Agha, the UC Davis Ph.D. student leading the link opens in new windowuniversity’s turtle research with Dr. Brian Todd, an associate professor in the UC Davis Department of Wildlife, Fish and Conservation Biology.

As if to underscore the point, researchers this summer collected a turtle with a barnacle attached to its shell – a testament to the marine-like environment to which the Suisun Marsh turtles have adapted.

Researchers also have been impressed with the age, health and size of the individual turtles. At 1 ½ to 2 pounds and with an upper shell that stretches up to 8 inches in length, researchers are discovering some of the largest Western pond turtles ever recorded in California.

“Looking at the ones we’ve collected, we’re seeing a lot of healthy turtles in good body condition,” said Environmental Scientist Melissa Riley, who is leading CDFW’s efforts.

The research began in the summer of 2016 with scientists trying to get a basic sense of turtle population numbers. The turtles are trapped in baited, floating hoop nets, their size, weight and age recorded. Before being released, each turtle is marked by filing a unique pattern of small notches along the edges of the upper shell. More than 125 turtles have been recorded in the project’s database.

Turtle trapping is taking place on three sites at the Suisun Marsh in and around the Grizzly Island Wildlife Area. Biologists are particularly interested in turtles at the Hill Slough Wildlife Area along Grizzly Island Road as 500 acres there will soon be restored to tidal marshland. Biologists plan to affix tiny, solar-powered, GPS tracking devices to some of the turtles to study their movements and see how they respond to the increasingly saltwater environment at Hill Slough and other parts of the marsh.

“That’s one of the many questions we have,” Agha said. “If sea level rise occurs, what happens to these turtles?”


New CDFW Research Boat Joins the Fleet

New CDFW Research Boat Joins the Fleet

steel bow and foredeck of a research trawler (boat)
Interior pilot's seat on a 32-foot boat vessel
A winch on the afterdeck of 32-foot boat
skipper's controls in a 32-foot research vessel

Recently at Bay Marine Boatworks in Richmond, CDFW’s Bay Delta Region accepted delivery of a new research boat. Funded by the California Department of Water Resources and the United States Bureau of Reclamation, the 32-foot-long aluminum boat is now part of the fleet dedicated to collecting data for the Interagency Ecological Program (IEP), a consortium of state and federal agencies that have been working together on ecological investigations since the 1970s.

Berthed in Antioch, the boat will be named after a native fish or aquatic invertebrate, and will be christened later this summer. It will be put into service for field work (trawls) mandated for the protection of endangered fishes — especially Delta Smelt and Longfin Smelt — in accordance with state and federal water projects.

The yet-unnamed boat was built and rigged for CDFW specifically to meet the needs of research in the Delta. It features a very sturdy hull and an emphasis on “trawl hydraulics.” Built by Munson in Burlington, Washington, the bright gray boat has a top speed of 25 miles per hour and can carry 4,500 pounds (combined crew and cargo). It has a 10-foot beam (width) that will allow the crew to work safely, and uses two trawl winches for towing nets far behind the boat. The boat’s 473-hp diesel engine uses a special ‘trolling valve’ to tow nets at just one mile per hour. The slow speed is crucial because the nets have very fine mesh designed to catch very small fish.

The vessel is the first new boat that Bay Delta Region's IEP Operations Program has received in 13 years. To avoid increasing the number of boats in the fleet, it replaces a 1995-vintage boat that was far smaller (16 feet) and relegates the Beowulf — a notoriously unreliable 1989-vintage 25-foot trawler with no toilet and very little seating — to the status of back-up boat.

“Water-based science is an essential function for this department, and our biologists put in many long hours on these boats. Their safety is imperative,” said Marty Gingras, IEP program manager. “This new vessel is versatile, cost-efficient, safe and green – and it will play a very important role in our efforts to manage threatened and endangered fish populations in the Delta for years to come.”

Eventually, CDFW hopes to replace other boats in the fleet, including the 50-year-old Striper II, which scientific crews use for striped bass and sturgeon surveys.



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