Grunion Fun

An adventurous crowd of kids and adults stayed up well past their bed times April 7 in hopes of witnessing a late-night ocean wonder – the mysterious grunion run.

The night marked the 2008 season launch of Birch Aquarium at Scripps’s naturalist-guided grunion runs, and the small fishes – and humans – were out in full force. The participants were there to learn more about their unusual mating habits and to try to catch a first-hand glimpse of a grunion run in action.

During this remarkable mating ritual, female grunion bury themselves in the sand and deposit up to 3,000 eggs each, while males protectively wrap themselves around the females to fertilize their eggs. When the dance is complete, both flip and flop their way back to the water where they can ride a wave to sea.

The grunion can be picky about where they spawn, and sometimes choose not to appear on nights that would otherwise seem perfect for the fish, said naturalist Chelsea Rochman. The most probable nights for grunion runs occur following the highest tide after new and full moons along dark, sandy beaches along Northern Baja California and Southern California.

Birch Aquarium’s program began with a presentation about grunion spawning behavior, during which participants watched grunion eggs in tiny cups of sand and saltwater hatch right before their eyes.

Following the presentation, dozens of hopeful, flashlight-clad grunion watchers anxiously wound their way through the darkened Scripps Institution of Oceanography campus to the beach below to experience the run. The nocturnal spawners didn’t disappoint; the observers arrived just after 11 p.m. to a shoreline glittering with hundreds of tiny fish.

It was an incredibly exciting and beautiful natural phenomenon well worth a little lost beauty sleep.