By Antonieta Valenzuela

The Gulf of Santa Clara in Sonora is the spawning habitat of the Gulf grunion, a species endemic to the Sea of ​​Cortez that every year spawns right on the beach. Between March and May, or even June, visitors can admire a unique show where the coast turns silver for a few seconds.

The Gulf grunion (Leuresthes sardina) is a fish similar to sardines; it ranges between 11 and 15 centimeters (4 to 6 inches) in length and has a translucent body with a silver stripe. Males and females ride the waves to get to the beach where the females dig into the sand and deposit eggs (one thousand to three thousand), while the males curve around females to fertilize the eggs.

After this process, which lasts about 30 seconds, females and males return to the sea. In the spring season, the females spawn up to six times, and it usually occurs between one and six days after each full or new moon. The eggs remain buried in the sand for about two weeks, and then hatch and return to the sea helped by the tide.

Just as the Gulf grunion mates every year out of the sea, each year the fate of this species is in danger because its breeding cycle is interrupted: it coincides with the busiest tourist season in the beaches of the Gulf of Santa Clara.

The Gulf grunion depends on the availability of the beaches for spawning; thus, their main threat is tourism since some visitors and locals crush the grunions while reproducing or step on areas of the beaches where the eggs are left, and therefore, no offspring develops.

Since the beaches of the Gulf of Santa Clara are located within the Upper Gulf of California and Colorado River Delta Biosphere Reserve and this fish has no official protection status, the reserve has been working on protecting this species.

For the second consecutive year, the reserve organized the Red Knot and Gulf Grunion Festival in order to inform locals and visitors about the importance of the Gulf grunion and promote recommendations to ensure its reproduction. Read the Terra Story here.

In addition, the Gulf grunion is the main food of the red knot (Calidris canutus), a migratory bird known for flying long distances that rests in the Gulf of Santa Clara before continuing its journey to Alaska, where this species breeds during the summer.

Some of the recommendations for tourists and locals are to avoid disturbing the Gulf grunion during spawning and invite others to do the same by setting an example. It is also recommended not to harvest more fish than necessary, not to use nets or other equipment to catch them and to avoid stepping on the beach areas where the eggs remain. Similarly, it’s recommended not to disturb the red knot while it’s in the area.