Grunion shrimp. An isopod, two species of flies, sandworms, and a beetle have been found preying on the eggs. Some shorebirds such as egrets and herons prey on grunion when the fish are on shore during spawning. Seagulls, sea lions, and larger fish such as sand sharks have also been observed feeding on grunion during a grunion run. The reduction of spawning habitat due to beach erosion, harbor construction, and pollution is believed to be the most critical problem facing the grunion species. Despite local concentrations, the grunion is not an abundant species. While the population size is not known, all
Grunion regulations, the resource seems to be maintaining itself at a fairly constant level. The coastal Indians in California harvested grunion during spawning runs. Archeologists have found fossil grunion otoliths (tiny, bonelike particles or stony platelike structures in the internal ear of lower vertebrates) at various Indian campsites. Grunion were mentioned by Spanish explorer Juan Rodríguez Cabrillo in his ship's log dated around 1542. Scientists first identified grunion in San Francisco Bay in 1860. Frank Zappa wrote a song named "Grunion Run" (originally released as a single by The Hollywood Persuaders), as has Jonathan Richman ("Grunion Run" on his album "I,