Resident volunteers sought to count silver grunion under the full moon
The grunion are returning to La Jolla’s shores this spring and so are the research assistants who will count them as part of an ongoing study.
Volunteer grunion greeters have been enlisted by Pepperdine University over the last couple years to study the habits, population and health of the five- to six-inch, often-elusive slender fish with bluish green backs and silver sides and bellies.
One of the main objectives of the grunion study, originally requested by City Council President Scott Peters, is to determine whether beach-grooming practices harm grunion eggs incubating under the sand from April to early June.
Early returns indicate the grunion population is running strong and that beach-cleaning activities have not disrupted the fish’s annual mating cycle.
Primarily warm-water fish, grunion are an important part of the ocean ecosystem and an overall indicator of marine environmental health. The species is also an important part of the food chain, being consumed by birds, sharks, squid, seals and larger fish.
Grunion greeters are trained at Birch Aquarium at Scripps Institution of Oceanography, a partner in the grunion project. One such volunteer, Michelle Winter Nowlte, enjoyed greeting grunion with her daughter so much last year at La Jolla Shores she’s back for a return engagement.
“It was pretty great,” said Winter Nowlte. “Some nights we didn’t see hardly any, and some nights we saw so many it was amazing.”
Winter Nowlte said her daughter, who needed community service hours for high school, talked her into participating in the grunion program, which entailed their going out between 11 p.m. and 1 a.m. eight different times at La Jolla Shores to count fish. She said they estimated how many grunion they saw by counting how many there were in a square foot, then estimating the total.
“Some nights there were over 1,000 at north La Jolla Shores toward the pier,” she said, “and then some nights there were very few, just about 100.”
Unlike other fish, grunion come out of the water completely to lay their eggs in the wet beach sand. Grunion is the anglicized version of a Spanish word that means grunter. Grunion are known to make a faint squeaking noise while spawning.
Grunion runs occur late at night, twice a month, after the highest tides under a full or new moon, with the eggs deposited by females burrowing two to three inches below the surface of the sand to lay them. Grunion run in a narrow range along the California coast between San Francisco Bay and Baja California. Highest tides occur about 10 times during the annual grunion spawning period.
Melissa Studer, senior program officer for the Grunion Greeter Project, said very little is known about grunion and their nature.
“They don’t have teeth,” she said, “so you can’t catch them with a hook. We have no way of knowing if the same individuals come back to the exact same beaches.”
Studer explained the grunion spawn with the high tides because the females’ eggs need to be buried in dry sand in order to incubate for 10 days until the next series of high tides.
“Water washing over the egg stimulates the egg to hatch,” she said. “If the water does not reach the eggs, they will not hatch, but wait until the next series of high tides around 10 more days.”
About 150 grunion greeters turned out at a training workshop March 30 at Birch Aquarium. Karen Martin, professor of biology at Pepperdine, is spearheading the grunion program and attended the workshop. She said the research study is designed to get data attempting to answer important ecological questions about the interaction of ocean and land.
“Grunion are very unusual animals,” Martin said, “because they tie together the ocean and the terrestrial environments. They live as adults in the ocean, but their eggs and embryos develop on the sand out of the water.”
The grunion study, which started in San Diego five years ago, is spreading to other parts of Southern California and the rest of the state.
“Just because they spawn on a certain beach does not mean that’s necessarily a good place,” said Martin. “Also, studying grunion is another way of assessing the impact of humans on ecological health.”
Grunion greeter Winter Nowlte feels she’s making a meaningful contribution by participating in the study.
“It’s nice seeing results and helping out,” she said, “and knowing it only happens in this part of the world.”
Grunion research has come full circle as it was a La Jollan, Boyd Walker of Scripps Institution of Oceanography, who pioneered grunion research in the 1940s. Walker determined grunion spawn according to the lunar cycle. Back then, he also used volunteers to monitor beaches and record their observations.
Today, all volunteer grunion greeters receive a certificate of merit modeled after the same certificate used by Walker.
Those interested in participating can call (619) 733-0725, e-mail firstname.lastname@example.org or visit the Web site www.grunion.org.