Pismo clam population has been in decline for nearly a century. What happened?
Clams have been associated with Pismo Beach since the beginning.
Giant concrete bivalves are scattered through town and decorated for holidays.
Pismo Beach will celebrate its 75th Clam Festival in October after canceling festivities in 2020 due to COVID-19.
Despite the prevalence of clam iconography, the health of the local clam population has long been in question.
According to the 1961 booklet “The Pismo Clam,” published by the California Department of Fish and Wildlife, Pismo clams were consumed by humans from the earliest days.
Shells have been found in middens, or, refuse heaps, dating back over 2,000 years. In addition to providing food, clams came with shells that were used as tools and ornaments.
From the late 1800s, clams were treated as an infinite resource.
Farmers could pop bushels of clams out of the sand with hay rakes and horses. Often the shellfish were loaded onto a wagon and used to feed hogs and chickens.
The greatest commercial harvest was in 1918, when 666,000 pounds were gathered by commercial diggers.
Commercial clammers worked in shoulder-deep water, chained to their hand rakes and clam sacks.
Danger lurked, as a sneaker wave or riptide could drown the unwary. In fact, a husband and wife drowned while clamming in the Hazard Canyon area at what is now Montana de Oro State Park, the Telegram-Tribune reported on Sept. 15, 1958.
During the Great Depression, clamshells marked with India ink were used as novelty currency in Pismo Beach.
According to Fish Bulletin No. 18, a 69-page report published in 1929 by William Herrington, commercial shipping of clams was banned in 1927. Until then, a yearly average of over 370,000 pounds of clams were taken from beaches from Monterey to Oceano and shipped to the cities.
The most productive sands for clamming were in Pismo Beach and Oceano. Even Morro Bay sent clams to market.
Restrictions began in 1911 with a limit of 200 clams per person, but as clam populations fell more restrictions were made.
By 1927, each person was allowed to take 15 clams per day, provided they were at least 5 inches in diameter.
But clam populations were still falling at the end of the 1920s.
Herrington’s report recommended limiting the take and increasing study with an annual clam census. It was hoped that clams could one day be farmed like oysters are.
Another suggestion was to educate clammers and reduce oil pollution from the expanding oil port at Avila Beach.
Herrington’s report concluded with a warning: “The number of people who now are able to come to the beaches during the summer is so great that with the present bag limit of 15 a day, they are able to deplete in two or three years even such a numerous year class as was that spawned in 1919.
“Then follows a period of scarcity or, if the strain is too great, practical extermination. With the increasing automobile traffic this condition is, under present regulations, bound to become worse each year.”
When I moved to the area to attend Cal Poly, my grandparents had a clam fork with a gauge on the handle to measure legal-sized clams but it hadn’t been used for decades.
Today it’s almost impossible to find a legal-to-harvest clam. The last 4.5-inch clam was seen in 1993.
The current legal limit for recreational clamming is 10 clams per day, with a minimum size of 5 inches north of the border between San Luis Obispo and Monterey counties and 4.5 inches south of that county line. Anything smaller must be reburied immediately.
Here’s one reason that it is important to leave small clams in the sand: It takes several years for the mollusks to hit reproductive viablilty.
In his 1929 report, Herrington explained that spawning begins in the third or fourth summer and that the number of eggs is related to the weight of the clam.
He also said in Fish Bulletin No. 18 that cyclical fluctuations influence the population size, with a big spawn every five to seven years.
Cal Poly researchers have begun a new study to track the Pismo clam population. They’re tagging Pismo clams with QR codes; if somebody finds a tagged clam, they can scan the code and send information about it to the research team.
By tracking the mollusks, the researchers hope to learn more about their life cycle, mortality and growth rate.
“We’re hopeful that someday in the future there might be a recreational fishery for Pismo clams on Pismo beach again,” Cal Poly graduate student Marissa Bills told KSBY-TV. “That would mean a lot to the local community.”
