Late at night during the spring and summer, when the moon and tides are just right, the grunion come ashore to perform their arcane mating rituals, lay their eggs in the damp sand and head for sea again, leaving their fry to fend for themselves.
The runs usually occur on the first through the fourth nights after the highest tides of a full or new moon. And tonight's the night--or at least one of them.
Tonight, the Cabrillo Marine Museum in San Pedro will present this year's final "Meet the Grunion" program--a chance to learn more about the intriguing reproductive habits of this native Southland fish.
First, there will be a short film on the life cycle of the grunion. Then, between 11 p.m. and midnight when the tide is highest, there will be an encounter guided by museum staff with the grunion themselves.
Indigenous to Pacific Coast
Grunion, known to scientists as Leuresthes tenuis, are indigenous to the Pacific Coast, where they can be found in the waters from Point Conception near Morro Bay to Punta Abreojos in Baja California. The adults are 6 to 8 inches long.
Scientists are at a loss to explain the reproductive habits of the grunion, and, while most runs can be predicted, grunion sometimes fail to appear on any given beach. Runs occur from March into August, with spawning diminishing from the spring to the summer.
About 30 minutes after the peak tide, with the waters beginning to ebb, a few scouts swim ashore. At this point it is imperative to remain quiet; the slightest sound will frighten the scouts and the school will head for another beach to spawn.
George Van Doran, a program assistant at the Cabrillo Marine Museum, cautions: "You must provide the ideal conditions or you'll spook them off." Observers are encouraged to bring flashlights, but because light also can frighten the scout fish, observers must follow the direction of the program leaders.
If all is well, a horde of writhing fish will hit the beach to perform a compelling mating dance above the waterline--grunion can live out of the water for as long as 20 minutes--and give off a luminous, silvery glow that makes the beach seem alive.
As the females bury their tails several inches into the wet sand, two or three males wrap themselves around her to fertilize the eggs. A single female can produce 1,000 to 3,000 eggs.
The egg-laying frenzy lasts less than a minute. Then the fish swim back to the sea. The fertilized eggs will incubate for about 10 days, and when the next high tides create sufficient agitation, they will hatch and swim to the ocean.
Unlike salmon, which die after spawning, the female grunion return to the ocean and come back to repeat the mating dance.
Hands-On for Kids
The museum's educational program includes a hands-on experiment designed to delight the youngsters.
After a short film, children are allowed to hatch small jars of grunion eggs the size of pin heads. The children shake the jars to approximate the agitation of the ocean's waves, and the tiny eggs metamorphose into twisting fish. Then the silvery babies are returned to the ocean. Cub and Boy Scout troops use the program to earn high-adventure merit badges.
From June through August, children younger than 16 and adults with valid California fishing licenses may catch grunion, but rules are enforced by the California Department of Fish and Game. Van Doran cautions the assembled group: "No fondling of grunion without a license." It is against the law to use pails, Frisbees, pans, shovels, nets or trenches to catch the fish. You may not catch more than you can eat. During the runs, Fish and Game wardens may visit beaches to enforce the rules. Violations carry a fine of up to $500. Fishing licenses may be obtained at sporting goods stores.
Because tonight is the museum's last presentation of the year, a large crowd is expected. Starting at 8 p.m., the program will be repeated as often as necessary. The grunion are expected to run between 10:50 p.m. and 12:50 a.m., but Cabrillo Beach closes at midnight.
Participants are urged to bring a flashlight and sweater. Parking is available in a lighted lot at $4 per vehicle. The program is free.
Grunion may also be viewed on many other Southland beaches. Other scheduled runs this summer:
Sunday: 11:40 p.m.-1:40 a.m.
Monday: 12:40 a.m.-2:40 a.m.
Tuesday: 1:40 a.m.-3:40 a.m.
Aug. 14: 10:50 p.m.-12:50 a.m.
Aug. 15: 11:30 p.m.-1:30 a.m.
Aug. 16: midnight-2 a.m.
Aug. 17: 12:40 a.m.-2:40 a.m.
To reach Cabrillo Marine Museum, take the Harbor Freeway to San Pedro. Go south 1 1/2 miles on Gaffey Street to 22nd Street. Turn left. Go two blocks to Pacific Avenue. Turn right 1 mile to Stephen M. White Drive. The museum is at 3720 Stephen M. White Drive.
Information: (213) 548-7563.