Grunion run schedule

Once or twice a month through spring and summer, on a handful of Southern California beaches, thousands of small silver fish ride a wave up onto wet sand, spawn in the space of a few seconds, and catch the next wave back out. The California grunion is one of the only fish in the world that leaves the ocean to breed, and it does so on a schedule set almost entirely by the tide.

The tide is the schedule

Grunion runs follow the spring tides, the outsized tidal ranges that arrive when the sun and moon pull in line at every new and full moon. The fish do not run on the night of the peak tide itself. They wait for the nights just after it, typically the second, third, and fourth, when each night’s high tide is a little lower than the one before.

That detail is the whole strategy. A female wriggles tail first into the wet sand at the very top of the wave wash and deposits her eggs several inches down; males curl around her to fertilize them. Because the tide is now falling night over night, every following wave reaches a little lower than the one that carried her in. The nest sits undisturbed above the surf for about ten days, until the next set of spring tides climbs high enough to wash the eggs free. The agitation of that water is the hatching trigger, and the young fish emerge within a minute of it.

To read the tide table that drives all of this, see our guide to how to read a tide chart, and for why the range grows and shrinks across the month, spring vs neap tides.

Season and timing

The spawning season runs roughly from March into August, with the heaviest runs usually falling between late March and early June. California protects the peak of that window by closing the take of grunion for part of the spring; watching remains legal year round. Because the exact closed dates are set by regulation and can change, confirm the current season with the California Department of Fish and Wildlife before planning to take any fish.

Within a run night, the timing is narrow. Expect activity to begin shortly after the night’s high tide and to build over the following hour or two. The first night of a series is often a scattered false start; the second and third nights tend to be the show. Runs happen in darkness, most often between about 9 pm and 3 am.

Where to look

Grunion spawn on wide, gently sloped sandy beaches from roughly Point Conception south into Baja California, with the well known runs concentrated around Los Angeles, Orange, and San Diego county beaches. Steep or cobbled beaches rarely produce a run. Local aquariums and state beaches often host guided grunion programs during the season, which is the easiest way to see one for the first time.

How to watch without wrecking it

A grunion run is fragile in a way that most tidepooling is not, because you are standing in the nursery.

• Keep bright lights off the water. Flashlights and phone torches pointed at the wave wash will turn a building run around. Let your eyes adjust, and use red light if you need any at all.
• Stay back from the wet sand where fish are spawning, and walk on the dry beach. Buried eggs sit inches under the surface for over a week after the adults leave.
• Never dig holes or use buckets, nets, or traps. Where taking is legal, grunion may be taken by hand only, and only in quantities you will actually use.
• Carry a current fishing license if you intend to take any during the open season, and know that year’s closed dates.
• Watch the surf and your footing in the dark, and keep an eye on the incoming set behind you.

Planning a night

Work backward from the moon. Find the next full or new moon, count forward two to four nights, then look up the high tide time for your beach on each of those nights. The window opens shortly after that high tide. Slackwater will show you the tide curve, the exact high tide time, and the moon phase for any California beach, so you can line up a run night without cross referencing three sources.

For the other end of the tidal range, the extreme lows that expose the flats, see minus tides, clamming, and tidepooling.