Very cool. If I'm not mistaken, that's a pretty rare thing to see them during the day, but could be due to the tide. They usually mass the beach at night in the light of the full moon.
cool video. I watched them go up the beach in las conchas over easter weekend. took a ultra lite ride & they were thick between the new public beach & the estuary.
We used to go Grunion hunting at Huntington beach at the cliffs, usually it's on a full moon. They look very much the same, but the way they act once they get to the beach looks very different. You'll see the female dig herself tail first into the sand on the Pacific side, and then the males wiggle around her fertilizing the eggs, and of course they ride waves in and out instead of the small surge's we have in our big bathtub; the Sea of Cortez.
Some people still think it's like a Snipe hunt, and that you're pulling their leg when told about them.
That sounds exactly like how they spawn- the female digs the hole by spiraling in, lays the eggs, spirals out, then the male fertilizes the eggs. I've seen Miramar beach full of the silver fish- usually at full tide or a day or two later.