“Grunion” is a horrible name for a fish. In fact, it’s a horrible name for anything. It sounds like a word that should be used to describe a rotting onion. Still, someone thought it would be a fine name for an animal, much to the grunion’s dismay, I imagine.

Grunion live in coastal waters, off the western coast of the US and Mexico. In the US they are found only in California, and only in Baja California in Mexico. There are two species of grunion, the gulf grunion and the California grunion.

Grunion are fairly small fish, reaching a maximum length of 16 cm. They aren’t very remarkable looking, with green backs and silver sides. They are long and slender, but other than that, there aren’t a whole lot of interesting things to say about a grunion’s looks. It isn’t the appearance of these little fish that makes them remarkable.

Spawning grunion do look pretty silly.
Image by Quinten Questel, CC BY-SA 3.0, via Wikimedia Commons

So what is so strange about the grunion? It all has to do with how grunion mate. They are quiet odd for fish, in that they come to shore to spawn. Grunion spawn at night during high tide, using waves to get themselves as high on a beach as possible. Once a female grunion finds a spot where she feels comfortable, she arches her body to force her tail into the sand. When her tail is firmly buried, she wiggles around to further bury herself, up to her pectoral fins.

At this point, the male grunion arrive. Up to eight of them will surround the female, curling their bodies around her and release their sperm. Once this task is done, the males head back to the safety of the ocean. Back on the beach, the female has laid her eggs below the sand, and she will also return to the ocean once the males’ sperm has flowed onto the eggs.

A female grunion waiting to mate. Image by Eric Wittman from Wichita, Kansas, USA, CC BY 2.0, via Wikimedia Commons

The eggs wait below the sand, delaying hatching until the next high tide. They can wait up to four weeks for a high tide, but usually hatch in ten days. Hatching is triggered when a wave hits the eggs. Once the baby grunion are in the ocean, they grow very quickly, reaching around 13 cm at one year of age. Grunion do not grow during the spawning season, and this arrest of growth leave marks on the fishes’ scales. Thus, the age of a grunion can be calculated by counting the marks on its scales.

Unfortunately for the grunion, their spawning method attracts quite a bit of attention. It’s quite easy to catch a fish out of water, so people often go to grunion spawning sites and catch the poor guys. Laws in California mean that people who want to catch grunion need a license to do so, and that they are only allowed to use their hands to snare the fish. There is also a restricted period during peak spawning season that helps maintain grunion population levels. With these measures, the grunion population seems to be stable, which is definitely good news.

Oh and I should mention – the name grunion comes from the Spanish word for grunter, as grunion tend to make silly noises during spawning. So I guess the name fits, but it’s still a terrible sounding word.

Cover image by Shahan Derkarabetian, CC BY-SA 4.0, via Wikimedia Commons