The sand crab, also known as the Pacific mole crab (Emerita analoga), is common along the sandy beach environment of the U.S. West Coast. They can be found from Alaska down to the Southern Hemisphere. Sand crabs mostly live in the "swash zone" of the beach, but this area varies with each tidal change and affects the exact locations of their colonies.
Sand crabs are small, and they can range from gray to a sandy color. They don't have claws or spines. They do molt during the year, and their empty shells wash up along the beaches. Like all crabs, immediately after molting their new shells are soft, making them a primary target for barred surf perch. Female sand crabs are larger than the males, and at certain times of the year, they also carry a cluster of bright-orange eggs on the undersides of their bodies. When gravid they are most commonly found in the lower section of the tidal zone.
Sand crabs usually occur in large numbers in late spring and early summer. The rippling effect seen on the surface of the sand as the water ebbs identifies their colonies. You will also see a variety of birds feeding on them. Scientists suggest that the sand crab makes up 90 percent of the surf perch's diet, and it's a favorite of the California corbina as well. I have also taken bonefish in Belize and Christmas Island with variations of this fly.
Having fished in the surf zone for three decades, I have tied a variety of surf patterns, including several sand crab flies (visit www.fliesunlimited.com for a listing of my preferred patterns). In my early days, I tied most of my sand crabs with deer hair and coated them with a layer of epoxy to form the shell. I've been using llama hair for four years now, and I prefer it by far. At first, I tied the hair in a linear form but couldn't get the results I wanted, so I tried using a llama hair dubbing brush to make the body. After trial and error, I finally came up with this crab pattern.
I use the sand crab as a dropper fly rather than a point fly. I fish it attached to a three-way swivel with a 3-inch piece of stiff monofilament, which keeps the fly from fouling around the leader.