An Endangered Fish Returns to Muir Beach Lagoon

A tidewater goby from Muir Beach Lagoon. Returning with better gear, the team caught several more and confirmed their identity. NPS/Matt Millado.

In summer 2023, aquatics intern Matt Millado was surveying turtles at Muir Beach Lagoon, in Golden Gate National Recreation Area, when he spotted a small fish he did not recognize. He took it to aquatic ecologist Darren Fong, who could tell it was some kind of goby, and perhaps a federally endangered tidewater goby (Eucyclogobius newberryi). They photographed it and sent the picture to experts for advice.

A surprise in a familiar lagoon

Tidewater gobies live in brackish, slightly salty wetlands, and coastal lagoons suit them perfectly. Yet despite decades of fish surveys, no one had seen them in Muir Beach Lagoon. Fong and Millado went back with a seine net and caught several, and Fong confirmed they were tidewater gobies. The pair took better photographs, kept one as a voucher specimen and released the rest.

Fong hopes genetic analysis of the voucher specimen will show where they came from. Tidewater gobies are no more than two inches long and live in calm water, so they are not strong swimmers, but they can survive being swept out to sea, and some then find their way into nearby lagoons or wetlands. The most likely sources for Muir Beach's newcomers are the populations in Tomales Bay's Giacomini Wetlands and in Rodeo Lagoon.

Why now?

Tidewater gobies are endangered mainly because of habitat lost to development and land use. Muir Beach Lagoon was probably lost to them during the 20th century, when much of the surrounding land was filled and reshaped for cattle grazing.

The part of Muir Beach Lagoon where the new population of tidewater gobies was found. NPS/Darren Fong.

Scientists suspect the gobies returned thanks to the recent restoration at Muir Beach, a major part of which expanded the small tidal lagoon. That created more open water with aquatic plants, benefiting other threatened and endangered species too, such as California red-legged frogs and young coho salmon; improving habitat for some species tends to improve it for many. The gobies found a much healthier lagoon than they would have 10 or 15 years earlier.

Keeping watch

The San Francisco Bay Area Network's coho and steelhead monitoring team will help Fong track the new population as part of its regular work. Regaining any habitat after such widespread loss is a big deal, and a new population also means the species has its eggs in one more basket: if one population suffers a die-off, perhaps from an algae bloom or drought, another nearby can help replenish it.

Sources

• Jessica Weinberg McClosky, San Francisco Bay Area Inventory and Monitoring Network, National Park Service, "Endangered Fish Finds New Habitat at Muir Beach Lagoon" (December 2023). https://www.nps.gov/articles/000/sfanblog_endangered-fish-finds-new-habitat-at-muir-beach-lagoon.htm
• NPS, Pacific Coast Science and Learning Center, "Tidewater Goby": https://www.nps.gov/rlc/pacificcoast/tidewater-goby.htm; U.S. Fish and Wildlife Service species profile: https://ecos.fws.gov/ecp/species/57; Muir Beach restoration: https://www.nps.gov/goga/learn/nature/muir-beach.htm