Grunion run has fascinated scientists and locals for decades, but their future is threatened by the climate crisis
CaliforniaKnown as the “grunion run”, the spectacle is one of the lesser known natural wonders of the US west coast. Grunion are a rare fish species that come ashore to spawn, and during the months of April to August they cover beaches from Baja California to Santa Barbara like a glittering carpet, wriggling in the sand to lay and fertilize eggs just after the highest tide of a full or new moon.
Students use night-vision goggles to spot their wiggling bodies flipping around, avoiding using light sources. The air is thick with anticipation – how much fish sex will there be? Beach spawning fish are rare – just a handful of fish around the world come out of water to lay eggs on the sand. And beach spawning fish near major cities are even more unusual. 90% of the grunion population lives off the coast of three densely-populated counties: San Diego, Orange county and Los Angeles. Even so, grunion weren not really studied until 1927, when the state created the first rules to protect them.Photograph: G. Martin/ Grunion.
There is no way to know if the fish return to the same beach where they were born, says Martin, because so many of them get eaten by birds or larger fish. She has plans for a tagging program that could help answer that question, but funding to study the humble, six-inch long fish has not been easy. This year, the state has prohibited people from taking any fish in April, May and June, the peak time of the grunion run – adding June to the prohibition for the first time since 1949.
Darren Johnson, a biologist at California State University at Long Beach, has been doing studies on climate crisis’ impact on the species. He has found the effects of changing ocean chemistry – more carbon dioxide in the water makes it more acidic – are having an impact on the larval fish.The fact that grunion spawn on land makes them a good species for understanding such effects, he says.