See a Grunion Run, Coronado, California

Add to My List Check Off

Grunion are are sardine-sized teleost fishes of the Atherinopsidae family of New World silversides, found only off the coast of California, USA, and Baja California, Mexico, where the species are found on both the Pacific Ocean and Gulf of California coasts. Many people enjoy catching grunion at events called "grunion runs." Grunion runs in San Diego typically occur from March through August, with peak activity in April, May, and June, usually taking place 2–3 hours after high tide during new or full moons. Prime viewing spots include La Jolla Shores, Coronado Beach, Imperial Beach, and Silver Strand State Beach. Grunion Fishing Tips: Anyone aged 16 or older must have a valid California Department of Fish and Wildlife (CDFW) fishing license to catch grunion. The best — and only legal — way to catch grunion is with your bare hands. When take is permitted, the bag limit is 30 fish per person (see the list of open months below). Avoid using headlamps or flashlights. Grunion spook easily, so stay quiet and keep a low profile until the run is well underway. Watch for the early “scouts” — allow the first few fish to come ashore undisturbed, and the rest of the shoal is more likely to follow. The third and fourth nights of a run are typically the most reliable for sightings. If you don’t see any activity, keep your lights off and walk along the beach. Runs are often concentrated in a specific stretch, sometimes toward one end of the shoreline. Grunion are known for their unusual mating ritual wherein at very high tides, the females come up on to sandy beaches where they dig their tails into the sand to lay their eggs. The male then wraps himself around the female to deposit his sperm and for the next 10 days the grunion eggs remain hidden in the sand. At the next set of high tides, the eggs hatch and the young grunion are washed out to sea. Average body lengths for males and females are 4.5 and 5 in (11 and 13 cm), respectively, at the end of one year; 5.5 and 5.8 in (14 and 15 cm) at the end of two years; and 5.9 and 6.3 in (15 and 16 cm) at the end of three years. The normal lifespan of the grunion is three to four years, although individuals up to five years old have been found. Their growth rate slows after the first spawning and stops completely during the spawning season. Consequently, adult fish grow only during the fall and winter. This growth rate variation causes annuli to form on the scales, which have been used for determining ages. The Gulf grunion, with its smaller eggs, is unique in that it may spawn during daytime. California grunion spawn on beaches from two to six nights after the full and new moon beginning soon after high tide and continuing for several hours. As a wave breaks on the beach, the grunion swim as far up the slope as possible. The female arches her body while keeping her head up and excavates the semifluid sand with her tail. As her tail sinks, the female twists her body and digs tail first until she is buried up to her pectoral fins. After the female is in the nest, up to eight males attempt to mate with her by curving around the female and releasing their milt as she deposits her eggs about four inches below the surface. After spawning, the males immediately retreat toward the ocean. The milt flows down the female’s body until it reaches the eggs and fertilizes them. The female twists free and returns to the sea with the next wave. The whole event can happen in 30 seconds, but some fish remain on the beach for several minutes. Spawning may continue from March through August, with occasional extensions into February and September. However, peak spawning is from late March through early June. Once mature, an individual may spawn during successive spawning periods at about 15-day intervals. Most females spawn about six times during the season. Counts of maturing ova to be laid at one spawning ranged from about 1,600 to about 3,600, with the larger females producing more eggs.[citation needed] A female might lay as many as 18,000 eggs over an entire season. The milt from the male might contain as many as one million sperm. Males may participate in several spawnings per run. The eggs incubate a few inches deep in the sand above the level of subsequent waves. They are not immersed in seawater, but are kept moist by the residual water in the sand. While incubating, they are subject to predation by shore birds and sand-dwelling invertebrates. Under normal conditions, they do not have an opportunity to hatch until the next tide series high enough reaches them 10 or more days later. Grunion eggs can extend incubation and delay hatching if tides do not reach them for an additional four weeks after this initial hatching time. Most of the eggs will hatch in 10 days if provided with seawater and the agitation of the rising surf. The mechanical action of the waves is the environmental trigger for hatching. The rapidity of hatching, which occurs in less than one minute, indicates it is probably not an enzymatic function of a softening of the chorion as in some other fishes.

5.0 out of 5 Write a Review

No Ratings Yet

Flag as inappropriate ›