When the Grunion Run, Citizen Scientists Keep One Step Ahead

Laura Hoberecht
NOAA Fisheries Public Affairs

May 19, 2009 — They observe quietly from the night shadows along the water’s edge, spying on an elaborate age-old mating ritual.

They are the “Grunion Greeters,” a volunteer corps of citizen scientists working with researchers from Pepperdine University and NOAA’s National Marine Fisheries Service to track the secret lives of grunion, the unique marine fish that spawn at night on the beaches of southern California.

With silvery backs glistening in the moonlight, 7-inch-long adult grunion come ashore to reproduce in the spring. During extreme tides, females ride the surf to land high up on the beach and lay eggs in the sand. The males follow, wrapping around females to fertilize eggs, before the aquatic “paramours” return to the water. Grunion eggs incubate onshore for approximately two weeks until the next high tide when they hatch and the baby fish head out to sea.

“We really don’t have a good handle on all the locations that are frequented by grunion or their overall numbers,” said Bob Hoffman, NOAA Fisheries assistant regional administrator for habitat conservation in California. “This volunteer effort gives us a broader understanding about the status of these unusual fish.”

Grunion Greeters grew out of a concern for the effects of beach grooming practices on grunion eggs incubating in the sands of San Diego’s beaches. In 2002, Karen Martin, a professor of biology at Pepperdine University, decided to carry out a scientific study to determine where exactly the grunion were spawning. A large number of observers were needed because spawning can occur on numerous beaches during the same tidal cycle (the period between high and low tides).

Melissa Studer, a marine conservationist and director of the Grunion Greeter program, then organized a workshop to train volunteers in observation and data collection techniques. That first year (2002), the Grunion Greeter program deployed 100 citizen scientists to “run” with the grunion. The program has since expanded along the California coastline as far north as the San Francisco Bay Area. This year, more than 500 Grunion Greeters have been trained.

“The Grunion Greeters program is a great way for citizens interested in their natural surroundings to actively participate in marine research,” said Martin. “It also provides scientists with data necessary to understand this fish that is distinctively associated with Southern California.”

Volunteers stand watch at designated sites to collect data during the peak spawning months of April and May. They primarily assess the strength of the grunion run (which ranges from no fish spawning to thousands of fish spawning for an hour or longer) and record the time the run occurred.

Greeters also note weather conditions and the presence of grunion predators. According to Studer, “Everything feeds on these fish, especially birds and marine mammals. I even had a shark come right up to my feet during one run.”

Although they are not required to do so, Grunion Greeters also act as unofficial wardens to protect the fish. Primarily harvested as bait, grunions cannot be caught during the critical peak spawning months of April and May. If poachers are spotted, the volunteers will often confront offenders. 

“Usually people just don’t know about the law and once the biology behind it is explained, they are eager to comply,” said Studer. “Sometimes, they are even interested in becoming Grunion Greeters themselves.”

The Grunion Greeters project, primarily funded by NOAA Fisheries for the last two years, has had a positive influence on the species. Current grunion runs are stronger than any observed since 2002. Data collected by the Greeters will also contribute to future habitat restoration and beach modification projects.

You can find out when the California grunion will run by visiting California’s Department of Fish and Game at http://www.dfg.ca.gov/marine/gruschd.asp. To learn how to become a Grunion Greeter, check out Pepperdine University’s Grunion.org Web site at http://www.grunion.org.