Fun Grunion Facts For Kids

Grunions are two different species of fish belonging to the genus Leuresthes. The two species are the California grunion (Leuresthes tenuis) and the Gulf grunion (Leuresthes sardina).

Grunions are native to the North American continent specifically to the coast of the eastern Pacific ocean. They are found near the beaches of California and Baja California.

These fish live in shallow marine waters up to depths of 60 ft (18.3 m). Grunions are non-migratory and are perhaps best known for their spawning behavior. During the spawning months of March-August, grunions push themselves out of the water at the beachy shores, in huge numbers and mate quickly and efficiently.

Female grunions mate with several males and eggs are deposited into the sand, about 4 in (10.2 cm) deep. Mating grunions and hatched larvae are all washed away by the strong waves of the high tides.

For more relatable content, check out these tang fish facts and Siamese fighting fish facts for kids.

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Grunion Interesting Facts

What type of animal is a grunion?

A grunion is a fish.

What class of animal does a grunion belong to?

The grunion fish belongs to the Actinopterygii (ray-finned fish) class of animals.

How many grunions are there in the world?

The exact number of grunions in the world is unknown. This is because it is restricted and moderately common to habitats and waters around California. And its spawning habitat is under threat and when it does spawn it is erratic and happens in great numbers.

Where does a grunion live?

Of the two grunion species, the California grunion is seen along the coast of the eastern Pacific from Punta Abrejos, Baja California Sur to the Point Conception, California. They are not seen that much from San Francisco in their northern habitat towards San Juanico Bay of Baja California, Sur in its southern range.

The Gulf grunion is seen along the Baja California coast inside the Gulf of California. Marking experiments have shown that these grunions are not migratory.

What is a grunion's habitat?

The grunions are known to inhabit coastal waters and for spawning on many a beach. Typically they inhabit the waters near the shore from the surf level to shallow depths of 60 ft (18.3 m).

Who do grunions live with?

Grunions are almost always found together in large numbers in schools. And during the spawning season, they are seen breeding on the beach in huge numbers, too.

How long does a grunion live?

Grunions live for three to four years on average, but may rarely live up to five years too.

How do they reproduce?

Grunions are probably known best for the way in which they reproduce. A 'grunion run' often draws in many spectators on the beaches they spawn in.

Spawning happens on the sandy beaches in the months of March-August, two to six after new or full moons, usually after high tides. Grunions swim as far up the beach as they can.

Females deposit themselves into the ground tail first and up to their pectoral fins, and then lay their eggs. As many as eight males will form a curve around one female and attempt to mate.

They release their milt which runs down the female's body and fertilizes the eggs which are about 4 in (10.2cm) into the ground.

Males return immediately to the ocean after releasing their milt and females follow in the next waves. The entire process takes only half a minute, but there are many fishes that stay for longer.

Mature grunions indulge in successful spawning at 15-day intervals and females spawn six times in a single season. Females produce 1,600-3,600 eggs laid in a single spawning event.

And over a single season, close to 18,000 eggs are laid. And males, who get involved in multiple spawnings in a single run, may release as many as a million sperm in their milt.

The eggs are known to incubate a few inches into the sand, deep enough to not get washed away. They hatch in ten days or they may hatch after four weeks if the tide is not favorable.

The unique feature of Gulf grunions is that they can spawn both during the day and the night. Also, they return to the sea for a short time instead of waiting for the upcoming tide like California grunion fish.

What is their conservation status?

The conservation status of the Gulf grunion species according to the International Union for Conservation of Nature is Near Threatened.

The conservation status of the California grunion species has not been evaluated by the IUCN.

Grunion Fun Facts

What do grunions look like?

Grunions have small and slender bodies. Their backs are bluish-green and their bellies and sides are silver.

The snouts are slippery, blunt, and rounded. Grunions are silversides and they do not have adipose fins like trouts.

The young grunions are known to grow rapidly, as big as 5 in (12.7 cm) after their first year, which is when they reach sexual maturity. Males are 4.3 in (11 cm) long and females are 5 in (12.7 cm) long after one year. The biggest recorded grunion was 8.6 in (22 cm) long.

The rate of growth clearly slows down after the first year, with the adults growing only in winter and fall. Ring-shaped annuli are formed on the scales which can tell their age.

California grunions have tails that are deeply forked. The dorsal fin is divided into two and has 5-7 spines and 9-10 soft rays.

The anal fin originates right beneath the initial dorsal fin and it has 21-24 soft rays. California grunions grow to lengths up to 7.5 in (19 cm). California grunions also have a blue patch on their cheeks and a silver-blue stripe along their sides.

How cute are they?

Grunions are very cute animals. They are small, slender, and are colored bluish-green and silver. Their most novel feature however is their spawning behavior.

During their breeding months, they show up at the shore of the beach in huge numbers and multiply rapidly. Grunion runs in late March or early June are a sight to behold and they naturally draw in crowds at the beach. Also, grunions are greatly edible.

How do they communicate?

Grunions are schooling fish and they communicate via body language. Schooling fish sense the surroundings with precision, are aware of their positions, and respond very quickly to currents of water and movements of other fish. It has been speculated that they do this via the 'lateral line', a sense organ on their bodies.

How big is a grunion?

Fully-grown grunions are 6-7 in (15.2-18 cm), which makes them three to five times smaller than brown trouts.

How fast can a grunion swim?

Grunions are fast swimmers. Two-week-old larvae are able to swim at 35.8 mph (57.6 kph) and 30-day-old larvae can swim at speeds close to 44.8 mph (72 kph).

How much does a grunion weigh?

A grunion weighs less than 2 oz (57 g).

What are the male and female names of the species?

Males and females of the grunion species do not have specific names.

What would you call a baby grunion?

A baby grunion would be called a larva, a juvenile, or a fry.

What do they eat?

Grunions are micro-predators who feed mostly on plankton, crustaceans, copepods, and zooplankton. In captivity, they have been known to accept live brine shrimps.

Grunions have a host of predators who feed on them such as California halibut, white croakers, egrets, herons, sea lions, seagulls, and sand sharks. Their eggs come under threat from isopods, flies, beetles, sandworms, whimbrels, marbled godwits, and ground squirrels.

Are they poisonous?

No, grunions are not poisonous. They are highly edibles fishes.

Would they make a good pet?

No, grunions would not make good pets. They are ocean-dwelling animals with highly entertaining mating behavior. They are taken for food and also as bait for other fish.

Did you know...

Another one of the grunion fish facts is that in the open season, a fishing license is needed for people aged 16+ to catch grunions. They can be caught only by hands and no holes can be dug to catch grunions. There is no limit to how many grunions one may take but is not lawful to waste grunions.

Grunions do not naturally glow but their silver and bluish-green bodies may glisten in the light of full moons.

Can you eat grunion fish?

Yes, grunion makes for a popular eating fish. There are many recipes that can be used to prepare grunions. Grilling and frying are popular methods of preparation.

Do grunions die after spawning?

Grunions come completely out of the ocean to spawn on the shores of a sandy beach. It is not common for grunions to die when outside the water, but some of them may get caught by obstacles or high tide waves may carry them to a dune's back slope meaning they can't get back to the ocean.

Here at Kidadl, we have carefully created lots of interesting family-friendly animal facts for everyone to discover! For more relatable content, check out these swai fish interesting facts and herring surprising facts pages.

You can even occupy yourself at home by coloring in one of our free printable Grunion coloring pages.