Brown box crab

The brown box crab is a king crab that lives from Prince William Sound, Alaska to San Diego, California, at depths of. It reaches a carapace length of and feeds on bivalves and detritus. The box crab gets its name from a pair of round tunnel-like openings that form between the claws and adjacent legs when the animal folds its limbs up against its body. Both claws, and their adjacent legs, have matching half-circle notches in them that line up to create a circle-shaped opening when the limbs are tightly pulled against one another. This tubular round opening is called a foramen. The crab often lies buried in the sediment, and the two foramens in the chelipeds allow water into the gill chamber for respiration. The gill chamber is also sometimes used by the commensal fish Careproctus to hold its eggs.

Fisheries

The brown box crab has been fished in California since at least 1984. Take was minor and largely incidental until the mid 2010s, when landings by mass increased five-fold in 2017 relative to 2016 and remained above until 2023. In 2019, the California Department of Fish and Wildlife launched an experimental fishery for brown box crabs.