Tuesday, February 20 , 2018, 2:35 am | Fair 39º

 
 
 
 

Local News

Tiny Sand Crabs Lead to Big Discovery

If you look closely while walking on the beach, you, too, can observe one of nature's phenomena.

I have spent most of my spare time in, on or near the ocean environs of Southern California, most frequently of Santa Barbara County. I consider myself somewhat of an expert — or more of an enthusiast — in that area of topography.

I have speared fish, surf-fished, beachcombed, been a lifeguard, body surfed (no board surfing please; I never could stand up on one of them), snorkeled, dived, dug clams, launched dories, got dumped, swam with sharks (basking — no teeth), stepped on sting rays, split kelp roots (revealing many animals), grabbed grunion and stepped on embers, among other dumb things.

At age 78, I sometimes think I’ve seen or experienced it all. But everyone knows the old adage: “You learn something new every day.”

That “every day” was Wednesday. I witnessed one of nature’s phenomena, something I had never seen. Although beachcombers, walkers and surf-fishermen have probably seen it many times.

On that day, my friend, Bud Bottoms, and I walked from Coast Village Road through the Biltmore grounds to the beach, turned left and headed for the point below the Coral Casino. On the way back, we noticed a large patch of sand — and it was moving. The patch of sand was actually thousands of tiny — about a quarter-inch — sand crabs.

They were piled on top of one another, making it easy to pick up a handful of them without getting any sand. They followed the tide, stopping as the water percolated and moving out on the next surge, never burrowing.

We started hunting sand crabs. There were suspect patches along the stretch of beach from Hammonds to the steps at Butterfly Beach. The patches, measuring 4 feet by 10 feet, were moving, keeping up with the edge of the receding water. We dug deeper thinking there were adults shepherding them, but none showed.

One of the strangest factors was that there wasn’t one bird in the water or on the length of the beach. It was phenomenal. I had never witnessed nor heard of such activity. I kept thinking we wouldn’t have a shortage of crabs for a while and that predators were probably waiting for them to grow up.

To satisfy our curiosity, we drove to Summerland and walked to the sand to verify and duplicate what we had seen the day before. They were there, but not in the same abundance. We missed it by about 30 minutes. The tiny crabs had burrowed. We could see their telltale marks on the surface and dug a verifying handful sand and all. They were probably waiting for the tidal flow to return.

That piqued my interest. I scoured the Internet and found information about the Emerita analoga, or Pacific mole crab. Enough of that. Of more interest is that sand crabs make up 90 percent of the diet of the barred surf perch and corbina, commonly hunted fish by surf-fishermen. I knew that, but then I learned about the crab’s contribution to science. They are bioindicators. The Monterey Bay Online Field Guide says that “their tails have the largest sensory neurons found in any animal.”

Mussels have always been studied for contaminants in their environment, but science has learned that sand crabs, because of their sensitivity and capacity to store fluorocarbons, toxins and other contaminants, might be better indicators of water quality. A study prepared for the Central Coast Regional Water Quality Control Board by Jennifer Dugan, among others, is an excellent source for more information.

Thus, my admonition not to eat sand crabs. Of course, no one eats them. If you’ve ever held a 2-inch specimen in your hand, you would know why.

We looked at only two beaches and thought we saw what might amount to hundreds of thousands. But where are the birds?

If you go to a beach at low tide, you’re certain to see the sand crabs at work. For Bud and me, it was an amazing walk.

Noozhawk contributor Mike Moropoulos is a longtime outdoors writer in Santa Barbara.

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