Species Status, Clapper Rails, Invasive Mussels Years of efforts to help endangered wildlife recover and keep exotics out are paying off, according to speakers at Tuesday afternoon’s session on the status of native and invasive species. Pipe-clogging mussels have made incursions but are being held in check. Weed warriors have made progress in clearing San Francisco Bay’s mudflats of invasive spartina. On the endangered species front, California clapper rail populations appear to be holding their own. And the audience was reminded that nature’s surprises aren’t always unpleasant: after decades of absence, a highly visible marine mammal has returned on its own to the Bay.
Harbor porpoises (Phocoena phocoena) were once common here, explained William Keener of Golden Gate Cetacean Research. Their bones were found in Emeryville’s ancient shellmound. But these cetaceans abandoned the Bay about 65 years ago, after the construction of the bridges and Treasure Island and the installation of a wartime anti-submarine net. Only in 2008 did boaters began sighting the five-foot-long marine mammals again. The National Marine Fisheries Service estimates a local population of 3,000.
Keener and his team have been able to identify 600 individuals by their markings (one is all white, a miniature Moby Dick) and scars. The porpoises gather where high-energy tidal rips concentrate fish, making the Golden Gate Bridge’s pedestrian walkway a prime place to observe them at high tide. “If you spend too much time there watching porpoises, you’ll get the bridge patrol coming over to ask how you’re feeling,” Keener said. Porpoise mating in the Bay also has been documented for the first time. (The gonads of a breeding male outweigh his brain, and his courtship is unsubtle.) Observers haven’t yet witnessed a local birth, although females have been accompanied by calves. Keener has also documented previously unsuspected commensal associations between dolphins and seabirds. Bottle-nosed dolphins (Tursiops truncatus), historically unrecorded in the Bay, have also moved in, feeding on salmon. They stay closer to shore than the porpoises; last year a couple briefly got stuck in the mud near San Francisco International Airport. One dolphin with distinctive fin notches spotted in the Bay was resighted off Ensenada. Keener sees the return of the porpoise and the dolphin colonization as signs of success in cleaning up the Bay: “The fish population in the Central Bay is doing pretty well. A healthy Bay will get predators coming in.”
Although they abandoned the Bay, harbor porpoises were never at risk of extinction. The California clapper rail (Rallus longirostris obsoletus) was less fortunate. Habitat loss, hunting, and non-native predators reduced its San Francisco Bay population to a perilously low level and extirpated it from other Central Coast marshes. Since its listing as endangered, the rail’s progress toward recovery has been uneven. Yet Julian Wood of Point Blue Conservation Science (formerly PRBO) expressed optimism about the bird’s future. “The clapper rail is continuing to rebound,” he said. “There was a drop in 2008. We don’t know exactly what caused it, but it was a Bay-wide effect.” By then, rails had begun using invasive hybrid cordgrass (Spartina alterniflora x foliosa) as habitat: “Part of the decline could be explained by the removal of spartina, but not the whole thing. There was no significant removal in the North Bay.” The apparent decrease in rails documented in 2013 may be an artifact of reduced survey coverage in the North Bay. The best current population estimate is under 2,000. The birds still face daunting threats: predation by feral and domestic cats, native raptors, and others; habitat degradation by invasive plants; contaminants and toxic spills; and a future likely to bring rising sea levels and extreme weather events. “Marsh restoration is critical for their survival and the best hope for recovery,” Wood continued. The birds will colonize restored tidal marshes, as they’ve done at Faber Marsh in Palo Alto and Carl’s Marsh in Sonoma County. Surveys from 2005 through 2013 indicate the rails do best in large marshes of at least 150 hectares that are compact rather than narrow or fragmented and have good structural diversity. He cautioned that the welfare of clapper rails was only one factor in formulating restoration strategies: “We should be making decisions that consider multiple species. It’s not always easy.” Point Blue’s conservation priority map addresses a whole suite of marsh bird species under a range of sea level and sediment scenarios.
Reporting for the California Coastal Conservancy’s Invasive Spartina Project, Drew Kerr recapped the campaign to eradicate the hybrid superweed. The hybrid can exploit more ecological niches than either parent species, and its enhanced pollen and seed production help it swamp competitors. As of 2012, the infestation had been reduced from a maximum of 809 acres in 2005 to just 39 acres as of 2012. Native plants like perennial pickleweed (Sarcocornia pacifica) have resurged on their own where the hybrid has been removed, mudflat has been reclaimed for foraging shorebirds, and waterfowl and fish spawning habitats have been preserved. But it’s too soon to declare victory. “Restoration programs are at great risk of invasion,” Kerr warned. “Every tidal marsh project over the last 25 years has been invaded and/or dominated by hybrid spartina.” Ten East Bay sites occupied by clapper rails remain off-limits for treatment under the current Biological Opinion, which Kerr said has resulted in a slowdown in acreage reduction. Hybrids in untreated marshes have the potential to export seed to areas that are currently spartina-free. Regarding the rail population swings Wood described, Kerr said, “Those impacts are in the past at this point. Things have stabilized out over four years of rail monitoring.” ISP is now emphasizing the propagation and planting of native spartina (S. foliosa), Pacific gumplant (Grindelia stricta), and other indigenous marsh plants adjacent to hybrid infestations where future treatment is anticipated: “The goal is to enhance marshes around the treatment sites to provide a safety valve for the clapper rails.” Seed suppression with a dilute herbicide solution is also being field-tested at a Bair Island site. “Managing the risk of proceeding with tidal marsh restoration will allow us to move forward,” Kerr concluded.
Feared invasions by shellfish appear to have been nipped in the bud, reported Martha Volkoff of the California Department of Fish and Wildlife. The 2007 discovery of quagga mussels (Dreissena bugensis) in California waters tripped the alarm. Its relative the zebra mussel (D. polymorpha) showed up the following year. Native to the Black Sea, these tiny but prolific mollusks crossed the Atlantic in ship ballast water and colonized the Great Lakes. They can also hitchhike cross-country on boat hulls. That’s likely how they reached Lake Mead, their jumping-off point for the lower Colorado River. Zebras and quaggas clog underwater pipes and screens, consume food that native species need, and impair water quality. Their presence could have a major impact on the state’s water conveyance system. “We were acutely aware they were bad news,” Volkoff recalled. “But it was hard to plan for a potential threat while already dealing with existing threats.” Fish and Wildlife’s Incident Command System, partnering with the state Water Resources and Food and Agriculture agencies, swung into action, surveying potentially infested water bodies and developing regulations to contain and control the mussels. “It was clear early on that state agencies couldn’t shoulder the entire responsibility,” she added. “They would have to play an advisory role to local agencies.” All but one of the state’s 25 infested reservoirs now have control plans in place. Boat inspections at the state line are a key piece of the strategy; so far, 499 vessels with mussels attached have been intercepted and quarantined. Outreach to the fishing and boating communities has included fliers, a web site, and a YouTube video. “Our biggest claim of accomplishment is that there’s been no known overland spread as the result of boats,” Volkoff said. “We feel our work with the public has been effective.” But challenges remain. Funding is tight, and California has much vulnerable freshwater habitat to protect.