Science Spotlight

The Pacific herring – much like squid and anchovy – is an important forage fish that supports a commercial fishery and provides a prey source for all manner of fish and wildlife, including whales, seals, sea lions, sturgeon, salmon, pelicans and numerous other species of birds and invertebrates.

The largest population of Pacific herring in California spawn in San Francisco Bay, and since 1972, CDFW has been responsible for monitoring and managing their numbers. CDFW uses annual vegetation dive surveys and spawn (herring eggs) surveys to calculate a population estimate each year. CDFW also uses commercial fishery and mid-water trawl survey information to look at the composition and general condition of the spawning population.

CDFW has just completed and posted online the 2016-17 San Francisco Bay Season Summary for the Pacific herring fishery. The good news is that the spawning population, estimated at 18,300 tons, is up slightly from the 2014-15 and 2015-16 seasons. But it is still far below the historical average of 49,400 tons. Less than ideal ocean conditions are cited for the below-average numbers.

CDFW closely regulates the commercial Pacific herring fishery in the San Francisco Bay, setting quotas, season dates and using the commercial catch data to help further analyze the size, age and condition of the spawning population. Typically about six inches long, the fish primarily are harvested for their roe, which is prized in Japan. CDFW maintains a blog on the species called the Pacific Herring Management News.

This summer marked the end of an incredible journey for four dozen of California’s designated state freshwater fish, the golden trout, as they returned home after 10 months away. The fish traveled more than 500 miles in tanks and buckets, by hand and by mule, en route to their native waters 9,000 feet up in the Sierra Nevada range.

The journey began last fall after CDFW scientists observed that ongoing drought conditions were severely impacting the rare trout’s mountainous habitat. A decision was made to rescue 52 fish – a representative population that could repopulate the stream and save the species if drought conditions worsened.

Golden trout are one of California’s most iconic trout species. They are native to only two stream systems in the southeast Sierra Nevada – Golden Trout Creek, and the South Fork Kern River in Tulare County. Volcanic Creek, which is home to the rescued fish, connects with Golden Trout Creek during runoff and high-water level years.

The journey began in September 2016, when fisheries biologists made the two-day trek into the mountains to gather the trout. The captured fish were transported to the American River Trout Hatchery near Sacramento, where technicians monitored them, often around the clock. After nine months at the hatchery, the fish were ready to start the long trek back to their home waters. Crew members transferred the fish from the hatchery to a fish tanker truck and hauled them more than seven hours overnight to the trailhead at an elevation of 10,000 feet in the southern Sierra.

The crew met up with a CDFW team that would escort the fish on horseback, 16 miles into the Inyo National Forest. Federal laws forbids motorized vehicles on wilderness land, which left the team no option but to transport the fish by mule train in fish cans.

The operation took tremendous teamwork from multiple divisions in CDFW and the National Forest Service. Ultimately, the CDFW team successfully returned 48 fish to their natural element. Four died in captivity over the winter. CDFW officials consider that a normal mortality rate. Scientists remain optimistic that these iconic fish will continue to thrive and perhaps even be on-track for a brighter future.

See related VIDEO.

California’s coastal waters are home to seven species of abalone, and all but one are endangered or listed as species of special concern. The white abalone in particular has been nearly decimated by overfishing and disease, and scientists can find no evidence that the remaining population is reproducing in the wild. In order to avoid loss of the entire species, CDFW and partner agencies have formed the White Abalone Recovery Consortium, which will employ captive rearing and restoration stocking efforts and extensive public outreach in order to save these animals from extinction. It will be an ongoing, long-term project, but all signs point to future success – already there are more white abalone thriving in the captive breeding program than the entire population living in the wild.

Read more about the efforts to restore California’s white abalone – and learn what you can do to help! – on the CDFW Marine Management News Blog.

The latest issue of California Fish and Game, CDFW’s scientific journal, is now available online. This century-old quarterly journal contains peer-reviewed scientific literature that explores and advances the conservation and understanding of California’s flora and fauna.

The endangered salt marsh harvest mouse (Reithrodontomys raviventris) graces the cover of California Fish and Game, Volume 103, Issue I. Researchers ventured into the pickleweed to study the tiny mouse, which is endemic to the marshes surrounding the San Francisco Estuary Bay and its tributaries. The mice were fitted with tiny radiotelemetry collars and tracked for three years. Researchers documented some curious behavior in the resulting paper, “Potential evidence of communal nesting, mate guarding, or biparental care.” The accompanying photos provide a fascinating glimpse into an active nest.

Another paper, “Documentation of mountain lion occurrence and reproduction in the Sacramento Valley of California,” explores the potential for mountain lions to exist in fragmented habitats if there is adequate connectivity with larger blocks of suitable habitat and sufficient prey. The study used camera traps to document populations of mountain lions in the Sacramento Valley’s Butte Sink, which is made up of relic riparian habitats interspersed with managed wetlands. The photos show healthy mountain lions moving through habitat that has long been considered unsuitable due to extensive agricultural and urban development.

The article, “Mussels of the Upper Klamath River, Oregon and California,” reports on sampling efforts that expand existing baseline population data on freshwater mussels in the Upper Klamath River. The sampling efforts may ultimately assist with protection, mitigation and enhancement efforts for large bi-valve species.

The final paper provides insights into the benefits deer and elk derive from licking mineral rocks. Researchers took samples of “lick sites” that were used by California black-tail deer (Odocoileus hemionus columbianus) and Roosevelt elk (Cervus canadensis roosevelti) in the Klamath Mountains, Siskiyou County. After performing a detailed analysis of the elemental content of each lick site, the researchers concluded that each lick site offers a different smorgasbord of minerals, and in varying concentrations. The study’s objective is to begin identifying, classifying, and analyzing important mineral lick sites to benefit future ungulate management efforts.

As it has for the past 103 years, California Fish and Game continues to publish high-quality, peer-reviewed science that contributes to the understanding and conservation of California’s wildlife. We look forward to witnessing the contributions of the next installment.

Download the entire Winter Issue 103 (PDF) in high resolution, or browse individual articles in low resolution.

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 university’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?”