Students measure and count Pismo clams during the survey. The Marine Conservation Lab | Courtesy

When Cal Poly alum Carolyn DeRosa was 10 years old, she would spend her summer days digging up clams in Pismo beach. Her grandparents would get her up early in the morning to head to the coast and dig through the sand to find the massive Pismo clams. 

She remembers sitting on the beach with her family and watching her friend dive down in the ocean. She said he would find so many clams, but because they were so heavy, he wouldn’t be able to bring them all back up to the surface. He had to leave them on the ocean floor to swim up for air. 

After a day of clamming, they would take them all home and cook a feast of clams. She remembers making soups and big clam patties. Her grandfather even ate raw clams right on the beach.    

The Pismo clam used to be a staple of Pismo Beach life, but then they disappeared. The population of clams rapidly declined in the 1980s and according to the Marine Conservation Lab, the last legal sized clam was found in 1993. 

The Pismo clam is not only an important organism to the California coast, but also to the culture of Pismo Beach. When the clams disappeared, the city of Pismo lost a significant aspect of its identity.  

The Cal Poly Pismo clam research project was started by Director of the Center for Coastal Marine Sciences Ben Ruttenberg as a part of his larger Marine Conservation Lab. The Marine Conservation Lab has several projects, but started focusing on the conservation of Pismo clams in 2014. 

Gabrielle Downey | Mustang News

The city of Pismo Beach approached the Marine Conservation Lab and asked if there was a way to bring the clams back in order to allow people to start fishing them again. 

Despite the popularity of the Pismo clams and importance of them, the Marine Conservation lab researchers said that not much research has been done on why they disappeared. So, they set out to learn what exactly happened to these clams. 

“The epicenter of [the clam] population used to be Pismo Beach, so that’s just right in our backyard here from Cal Poly,” Cal Poly biological science graduate student Marissa Bills said. “They’re also an important part of the sandy beach ecosystem, so they’re a neat clam just on their own.” 

Bills runs the day-to-day operations of the Pismo clam lab along with several other graduate students. 

The lab focuses on three areas of research surrounding the clams. 

First, the lab has to understand the changes in population and size. To track these changes, the lab takes surveys every month. They go to the beach, dig up the clams and then count and measure the ones they find. 

“By doing that every month, we get comparative estimates of how the population is doing,” research assistant and Cal Poly marine sciences alum Robert Moon said. “And that’s been really helpful to sort of track how the numbers have progressed from year to year.”

Bills said the surveys have revealed how pismo clam populations have exploded. But, they still haven’t found a clam big enough to fish. 

According to Bills, the surveys are key to understanding the growth of the clams. As of right now, there is no concrete data as to why exactly the clams disappeared or how their population came back. 

“It’s going to be kind of one of those things, where this is why long term monitoring can be so important and so exciting,” Bills said. “We can then look back retrospectively and try to understand where there’s similarities in things that happened in those years because with just a data point of one it’s really hard to say what’s going on.” 

Students dig transects to find the clams. Gabrielle Downey | Mustang News

The second research aspect of the project focuses on learning how the clams grow. The researchers keep captive clams at the Cal Poly pier in order to study their growth and how they reproduce. 

The third study is called the “mark and recapture” study. This study involves going out and tagging the clams in order to gather more information about the clams as they grow in the wild.

“There’s two methods that we use to get the tag back,” Moon said. “We basically have QR codes, so if a member of the public finds a tagged clam, they can submit some information back to us, and then we are also going out and looking ourselves in very specific areas with very active clams.” 

Tagging the clams helps the team understand their growth, their movement and potentially their mortality rate. But, the QR code aspect of the study allows the public to be involved in the research. It also helps the researchers gather a larger amount of data. Bills said they want the public to be involved in order to gain awareness on what is happening with the clams. 

“We’ve kind of turned it into a community science project,” Bills said. “[It] has actually been really successful. We have about 600 clams that we’ve tagged thus far and we have over 50 submissions from the community of people who have found the clams.”

Despite the success of the research, there is not much explanation as to why or how the clams disappeared in the first place. 

There are several theories as to why the clams disappeared. Moon said that “the likely cause is probably sort of a perfect storm of a number of different things.” 

One possible cause of the population decrease is a few large storms that took place in the 1980s. Moon said that strong storms could decimate populations because when the waves get too big, they can dig up the clams and kill them. 

Another possible factor is that the sea otter population increased around this time. Sea otters were almost hunted out of the area due to the fur trade, but when their populations returned, they hunted clams for food.

A third theory is that the amount of humans fishing for the largest clams really hurt their populations. Moon said that the bigger clams are the most successful reproducers, but those bigger clams are the ones that humans can fish.

Similarly, the researchers do not know exactly why the clam population is booming again. It’s possible that the lack of fishing for these clams and that ideal environmental conditions play a role in why the clams are back, but the researchers need more data to come up with any conclusive answers. 

“It’s an interesting sort of ecological problem of how this species essentially just sort of vanished [and] is now making this comeback,” Moon said.  

The research has stirred a lot of excitement from the Pismo community, but the increase in numbers of clams has also caused a rise in poaching. 

Researchers finding undersized Pismo clams. Gabrielle Downey | Mustang News

The legal size of a clam that can be fished is 4 ½ inches. If the clam is less than that in size, it is illegal to fish. Poaching the clams can result in a citation and a minimum fine of $100. Despite the growth in population, no one has found a legal sized clam yet. 

In 2020, law enforcement officers seized over 25,000 clams and issued 225 citations. Department of Fish and Wildlife patrol lieutenant Matthew Gil said that while poaching decreased in 2021, they are starting to see another increase in poaching this year.  

“We definitely know that some of the poaching is people who do know better and who are just disregarding the law,” Bills said. “But then probably a lot of these people probably just don’t know because we haven’t seen this many clams on the beach for a really long time.” 

In order to legally fish the clams, you also have to have a fishing license and you can only take 10 clams per day. The lab is working with the Department of Fish and Wildlife as well as California State Parks to spread awareness about the fishing regulations surrounding the clams. 

While there are many people who go out to the beaches with the intention of poaching these clams, the team is finding that not many people know about the clams and know the laws surrounding the clams. 

“We’re just trying to get the word out as much as we can about the Pismo clam and the resurgence and reemergence of it and how awesome that is, but that they’re still undersized,” Gil said.

Marine Sciences senior Gillian Ippoliti works with the Department of Fish and Wildlife and California State Parks on outreach in the community for her senior project. She is researching how much people know about Pismo clams and how it relates to the amount of poaching. 

The project involves researching the signs on beaches around the San Luis Obispo area. While there are a couple beaches that have signs detailing the clam regulations, most don’t. Ippoliti believes this could potentially be a reason why people are accidentally poaching clams–they just aren’t aware of the rules.

“I do notice a lot of people picking up clams and I’m assuming that most of them just don’t know that you can’t take them, but I have seen a lot of people who do take them or just are taking a handful of them,” Ippoliti said. “It does seem that there’s a lot of, I guess, small scale poaching occurring.”  

Ippoliti’s research is in its early stages, but she said she hopes that she can make a real change in the conservation of these animals.  

“I think having more signs at the beach is probably going to be the most likely [way to inform people] because when everyone goes to the beach that’s kind of the main way that they can get information,” Ippoliti said. “Hopefully, this project can inform state parks and [California Department of Fish and Wildlife] about creating more signage.”

Even with all of the progress in research, outreach and communication about the Pismo clams, the clams still aren’t quite to the size where people can start legally fishing them again. 

“A really great outcome would be that people could eat Pismo clams again, that there would be a recreational fishery for them and that people would kind of know the regulations and be following those regulations,” Bills said. “Normally in conservation, you don’t think about eating the animal that you’re trying to conserve, but for us, that would be the best end goal.”

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