If you happen to visit a sandy beach along the Central Coast at night after a full or new moon and immediately after high tide, you may see a spectacle that you’re unlikely to ever forget.
Like sea turtles, California grunion, slender, silvery, turquoise fish about 5 to 7 inches long, come ashore at night in the open air to lay their eggs near the high water mark. Spawning generally occurs during the spring and summer, peaking in May and June.
These fish only spawn three or four nights after each full or new moon and only for a few hours after high tide.
One of the first jobs I had while living in San Luis Obispo was to perform grunion run surveys during dredging operations at Port San Luis Harbor. At the time, I doubted that I would ever see the silvery fish.
Then, on a particularly still and calm night immediately after high tide, I noticed the sound of them flopping on the beach after each successive wave break.
Old Port Beach came alive that night with hundreds of California grunion. A marauding ban of local raccoons took full advantage of this rare bounty.
Female fish swim on the beach with one or more males following closely behind. The females dig a nest into the wet sand vertically with their eyes directed towards the skies.
They can lay between 1,000 and 4,000 eggs about 3 to 4 inches beneath the sand as the males fertilize the eggs.
Nearly two weeks later when the spring tides return, the eggs hatch, completing a remarkable life cycle.
Evidently, the young fish need the wave action to break loose from their shells.
Nobody knows how the grunion can so precisely time the tidal cycle. These fish seem to spend most of their life near the coast in about 15 to 60 feet of water and can live up to four years.
John Steinbeck of Tenera Environmental told me that he has found grunion as far north as San Francisco, but they are most abundant from Morro Bay southward. The grunion found in the Gulf of California spawn during daylight.
The grunion season is closed from April through May. The next expected grunion run along the Central Coast starts on the night of July 1, right after high tide at 10:24 p.m. for about a two-hour period. The second hour is usually better.
The next run will occur at 11:07 p.m. July 2 with another run at 11:58 July 3. The last run is forecast during the early morning hours July 5 at 12:42 a.m.
The best runs normally occur on the second and third nights of the four-night period.
Watching old and young alike trying to catch grunion on a foggy night by hand is always entertaining.
They’re no match for the local raccoons at capturing these slippery fish. Please remember, you can only catch grunion by hand, and you also need a valid California state fishing license if you are older than 16 years of age.
But please remember, the times listed are only predicted grunion run times. They might not always run during those times, because they can be rare events.
This week’s forecast
Marine overcast with a few areas of drizzle along the coast will welcome us this Father Day’s morning.
Temperatures will warm this afternoon as the coastal cloud deck dissipates, leaving behind mostly clear and sunny conditions later today.
Today’s temperatures will range from the high 50s to low 60s along the beaches to the mid-60s in the coastal valleys. The North County is expected to reach high 70s.
The marine layer will redevelop tonight into Monday morning. A warming trend will begin in earnest Monday, with all locations warming several degrees.
The summer solstice will arrive at 10:16 a.m. Tuesday on the West Coast, when Earth’s orbit brings the North Pole to its greatest exposure to the sun.
During this period, if you happen to be north of the Arctic Circle, the sun never sets but remains above the horizon.
At our latitude in San Luis Obispo County, the sun will rise at 5:49 a.m. and set at 8:21 p.m. That gives us about 14 hours and 21 minutes of daylight, the longest day of the year.
The first day of summer will see a classic Central Coast synoptic pattern with a nearly stationary 1,032-millibar Eastern Pacific High about 700 miles to the west of San Luis Obispo and a thermal trough over the Central Valley of California.
Temperatures will warm Tuesday to the 70s near the immediate coast, the 80s and 90s in coast valleys, and the high 90s to low 100s in the interior Tuesday afternoon.
Some cooling could occur Wednesday near the coast as the marine layer surges inland and becomes more persistent, then a gradual cooling trend is expected Thursday and through next weekend as strong to gale force (25- to 38-mph northwesterly (onshore) winds return along the coastline.
Surf and sea report
Moderate gale to fresh gale force (32- to 46-mph) northwesterly winds off Cape Mendocino along the Northern California coastline will produce a 5- to 7-foot northwesterly (315-degree deep-water) swell (with an 8- to 11-second period) along the Central Coast this morning all the way through Monday.
A 3- to 5-foot northwesterly (310-degree deep-water) swell (with an 8- to 11-second period) is forecast along our coastline Tuesday through Wednesday.
Strong to gale force 25- to 38-mph northwesterly (onshore) winds will return along our coastline on Thursday and will generate a 6- to 8-foot northwesterly (320-degree deep-water) sea and swell (with a 5- to 9-second period) Thursday through Saturday.
Arriving from the Southern Hemisphere: A 1-foot Southern Hemisphere (225-degree deep-water) swell (with an 18- to 20-second period) will arrive along our coastline Thursday, increasing to 2 to 3 feet (with a 17- to 19-second period) Friday into Saturday.
Seawater temperatures: The lack of northwesterly winds has decreased the amount of upwelling along the coast. This condition has produced warmer seawater temperatures.
Seawater temperatures range from 53 to 55 degrees through Monday, increasing to 54 to 57 degrees Tuesday through Wednesday.
Decreasing seawater temperatures are forecast Thursday through next weekend.
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John Lindsey is a media relations representative for PG&E and local weather expert. To subscribe to his daily weather forecast, email him at pgeweather@ pge.com.