The grunion is a weird little fish.
Grunion are perhaps best known for washing up on California beaches — from Baja California all the way up to Monterey Bay — several times a year to spawn en masse for hours, starting on a night with a full or new moon, according to the California Department of Fish and Wildlife.
The creatures travel as far up a beach as waves will carry them, and then females dig nests and lay thousands and thousands of eggs. Males come ashore, too, and fertilize the eggs — and then males and females alike return to the ocean, sometimes in less than a minute, the state fact page on the species says.
But it turns out those fish — bizarre as they might seem — can teach scientists something about sea creatures’ ability to adapt to climate change. That’s according to a new study from scientists at Long Beach State University in Southern California.
Biological sciences professor Darren Johnson and Alexander Tasoff, who was a graduate student during the research, captured more than 300 grunion on Seal Beach to study how well the fish could adapt to ocean acidification, which is one effect of global warming, in addition to sea level rise and more, the university said in a news release on Wednesday.
Researchers found the fishes’ genes mattered a great deal: Grunion eggs from some families were more likely to survive in water with high carbon dioxide levels in the lab — an environment that mirrors a more acidic ocean — which means those families of fish could be better at adapting to changing acidity in the wild.
“Collectively, our estimates … suggest that populations of California Grunion have the capacity to adapt relatively quickly to long-term changes in ocean chemistry,” the authors concluded.
And while more acidic waters meant more larvae died, the acidity didn’t have a major impact on the growth of fish that lived, researchers wrote.
“Understanding whether fish populations can adapt over time and become at least somewhat more tolerant of changes in seawater chemistry will help us anticipate more accurately the long-term effects of ocean acidification,” Johnson said in a statement.
Scientists knew before this study that ocean acidification “can reduce the growth and survival of marine species during their larval stages,” the authors wrote. But the authors also knew that if a species like the grunion had “the genetic capacity to adapt and increase their tolerance” to those conditions, it might offset harmful impacts of ocean acidification.
It turns out the fishes’ unusual on-shore breeding ritual was an advantage for researchers.
“Because of how grunions spawn, it was easier to track the genetic lineages of fish from particular groups of eggs,” according to a university press release on the study.
Despite that peculiar trait, grunion were a good proxy for other fish, in that they “share many life‐history traits with other nearshore fishes” and therefore “may serve as a convenient model species for studying the potential for marine fish larvae to adapt to changes in seawater chemistry,” the study’s abstract said.
The grunion studied were released back into the wild, the researchers said.
Beach-goers often gather on shore to watch the thin fish, which grow up to six inches, as they wash up to mate — and some gather them in buckets to feast on when it’s allowed, the Orange County Register reports.
“Watching old and young alike trying to catch grunion on a foggy night by hand is always enjoyable; however, they’re no match for the local raccoons at capturing these slippery fish,” John Lindsey wrote for the San Luis Obispo Tribune in 2015.
Lindsey said he once watched as a “marauding band of local raccoons took full advantage of this rare bounty. If you happen to visit a sandy beach along the Central Coast at night after a full or new moon and immediately after high tide, you may see these unusual fish. It’s one of those natural spectacles that you’re unlikely to ever forget.”
The study is set to appear in Evolutionary Applications in print in March, the news release said.