The Grunion Runs

On Saturday afternoon (3/18/06) we had one of our remarkable Grunion runs. The bay beaches, between the harbor and Punta Estrella are one of the best places to observe this amazing phenomenon. Around an hour after the afternoon high tide, schools of these little six inch long silvery fish beach themselves on the soft sand and wait for females to ambush. The female, bloated with eggs, rears up on her tail and digs a hole in the sand until she is about half buried. Males flock round and wrap themselves around the female to squeeze out her eggs and fertilize them at the same time. The wonderful thing is that here on the west coast of the Sea of Cortez this mating ritual occurs in broad daylight. On the Pacific coast this is a phenomenon that occurs in the middle of the night so very few people see it. Seagulls stand by to seize any fish that are slow getting back into the water. The buried eggs remain a couple of inches below the surface to incubate in the warm sand until the next set of high tides come two weeks later. The hatchlings then emerge into the surf and begin their life in the sea.

The unfortunate part of the event is that the droves of quads that run up and down the beaches take pleasure in trying to run over the grunion and drive them away from the mating grounds. Later on, the quads tear up the sand in the band where the eggs were laid and scatter them to the elements. It is difficult to measure the environmental damage that is done by these uncaring or unsuspecting vehicle drivers but over the past fifteen years I have noticed that the length of the beach that turns silver from the bodies of the mating fish has shrunk from around a mile in length to around 100 yards now.

The Grunion have little value as a fish to eat, though it is considered fair game to scoop up handfuls and deep fry them in hot oil. They are mostly spiny bone and not at all tasty.

For more details on grunion, visit http://www.grunion.org