Pixel Tracker

Saturday, December 15 , 2018, 10:07 pm | Fair 49º


Outdoors Q&A: Can You Tell a Clam’s Age by Counting Its Rings?

The largest Pismo clam in California was 7.37 inches across and estimated to be 26 years old. Click to view larger
The largest Pismo clam in California was 7.37 inches across and estimated to be 26 years old. (Michael Wilson)

Question: Although the population of Pismo clams is seriously depleted in the Ventura/Oxnard area, I was blessed to dig this guy during the recent low tides. He is bulky and has many (growth) rings. Most are dark in color, but there are lighter ones as well.

To determine the age of the clam, do you only count the dark rings or do you count all the rings? The rings indicate this guy is between 25 and 50 years old. (Michael)

Answer: California Department of Fish and Wildlife (CDFW) marine biologist Christy Juhasz tells us CDFW staff who conduct fisheries-independent Pismo clam surveys count and measure clams encountered and do not utilize an aging method.

That said, Juhasz was able to find references to aging Pismo clams using their annual rings in CDFW’s 2006 Status of the Fisheries report, as well as in an article in the California Fish Bulletin No. 7.

The article, titled The Life-History and Growth of the Pismo Clam, was published in 1923 and examines this method in detail.

According to these reports, the age of Pismo clams can be determined by the darker rings that are laid during the fall/winter, perhaps due to prolonged periods of exposure to colder water, reduced food abundance or spawning.

These would be the annual rings that can be counted to age individual clams. The yearly rate of shell growth varies from individual to individual, and considerably slows down as the clam ages.

You can observe this rate of growth when you compare the greater distance found between adjacent annual rings toward the older part of shell (closer to the hinge) than the closer rings nearer to the newer section of the shell, near the growing margin.

More information concerning the growth rate can be found in the Status of the Fisheries report:

“The Pismo clam grows continuously throughout its life. As it grows the shell not only becomes thicker but increases in diameter. Growth varies considerably from month to month, with the greatest increase taking place in the spring, summer, and early fall months.

"The Pismo clam is about 0.009-inches (0.23-millimeters) at metamorphosis, and grows at an average rate of 0.84-inches (21.4-millimeters) for the first three years.

"Growth slows considerably as the clam ages, with the increase in shell length not more than 0.2-inches (5-millimeters) per year at age 10. Growth rates are dependent on water temperature and vary among beaches.

"A 4.5-inch (11.4-centimeter) clam could be from 5 to 9 years old. Along the central coast of California, clams are estimated to reach 4.5-inches (11.4-centimeters) between ages 7 and 8.”

As for unofficial records, the oldest Pismo clam was collected from Zuma Beach and was estimated to be 53 years old, measuring only 5.25 inches (13.3 centimeters) across.

The largest Pismo clam in California came from Pismo Beach and was 7.37 inches across and estimated to be 26 years old.

CDFW’s official sport caught records don’t reflect sizes quite this large. It appears that 6.75 inches is the current record.

What’s new in turkey hunting?

Q: It has been a few years since I have been hunting, but I hunted turkeys this past weekend with a friend and I’m glad he was with me because he told me there were new regulation changes for turkey hunting.

Most important one was the need to use nonlead ammunition. Am I missing anything else? (Anonymous)

A: First of all, we’re happy you’re back. It is incumbent upon all hunters to review the laws and regulations any time before they return to the field, but especially if it is after a few years absence.

Consulting with a friend can help, but going to the source is the best way to bring yourself up to date. The 2017-2018 Waterfowl and Upland Game Hunting regulations book is the place to start (see page 20) or go online.

There have been two significant changes over the past few years that should be highlighted:

First, shooting hours for spring turkeys are now from one-half hour before sunrise to 5 p.m. Second, nonlead shot is required when taking wild turkeys with a shotgun anywhere in the state except when hunting on licensed game bird clubs.

These regulations apply to both public and private land, including all national forests, Bureau of Land Management properties and CDFW properties.

For more information on nonlead ammunition regulations, please visit wildlife.ca.gov/Hunting/Nonlead-Ammunition.

— Carrie Wilson is a marine biologist with the California Department of Fish & Wildlife. She can be reached at [email protected].

Support Noozhawk Today

You are an important ally in our mission to deliver clear, objective, high-quality professional news reporting for Santa Barbara, Goleta and the rest of Santa Barbara County. Join the Hawks Club today to help keep Noozhawk soaring.

We offer four membership levels: $5 a month, $10 a month, $25 a month or $1 a week. Payments can be made using a credit card, Apple Pay or Google Pay, or click here for information on recurring credit-card payments and a mailing address for checks.

Thank you for your vital support.

Become a Noozhawk Supporter

First name
Last name
Select your monthly membership
Or choose an annual membership

Payment Information

Membership Subscription

You are enrolling in . Thank you for joining the Hawks Club.

Payment Method

Pay by Credit Card:

Mastercard, Visa, American Express, Discover
One click only, please!

Pay with Apple Pay or Google Pay:

Noozhawk partners with Stripe to provide secure invoicing and payments processing.
You may cancel your membership at any time by sending an email to .(JavaScript must be enabled to view this email address).

  • Ask
  • Vote
  • Investigate
  • Answer

Noozhawk Asks: What’s Your Question?

Welcome to Noozhawk Asks, a new feature in which you ask the questions, you help decide what Noozhawk investigates, and you work with us to find the answers.

Here’s how it works: You share your questions with us in the nearby box. In some cases, we may work with you to find the answers. In others, we may ask you to vote on your top choices to help us narrow the scope. And we’ll be regularly asking you for your feedback on a specific issue or topic.

We also expect to work together with the reader who asked the winning questions to find the answer together. Noozhawk’s objective is to come at questions from a place of curiosity and openness, and we believe a transparent collaboration is the key to achieve it.

The results of our investigation will be published here in this Noozhawk Asks section. Once or twice a month, we plan to do a review of what was asked and answered.

Thanks for asking!

Click Here to Get Started >

Reader Comments

Noozhawk is no longer accepting reader comments on our articles. Click here for the announcement. Readers are instead invited to submit letters to the editor by emailing them to [email protected]. Please provide your full name and community, as well as contact information for verification purposes only.