Smooth bay shrimp (Crangon stylirostris)
Commonly used as fish bait, this 2-inch shrimp is found from Alaska to central California, ranging from the intertidal zone to minus 260 feet, where waves and currents leave mainly a sandy bottom.
This adult specimen displays the characteristics of the species: a short, stocky, sand-colored body with the main body part or carapace lacking a dorsal spine (hence the origin of "smooth" in the common name). However, like closely related species, the body coloration can vary with the background. As a result, it sometimes is difficult to recognize Crangon species without closely examining the body parts.
While other types of shrimp defend themselves from predators using body spines, the Crangon group of shrimp uses its cryptic coloration and sand burial to avoid predation. They can swiftly burrow using their legs and pleopods (appendages under the muscular tail). A final sweep of the antennae to smooth out the sand surface leaves only the eyes in view. They feed from this hiding spot, capturing small crustaceans and fish. They also eat small clams.
Like most shrimp and crabs, the young spend a lot of time as small zooplankton, floating about and feeding on smaller creatures. They also serve as food for other small animals as part of the vast marine food chain. Adults occasionally are used locally for human food, but they mainly are eaten by a variety of animals, including anemones, crabs, octopuses, fish and young seals.
David W. Jamison is a marine biologist and Boston Harbor resident