Brown box crab

The brown box crab (Echidnocerus foraminatus) is a king crab that lives from Prince William Sound, Alaska to San Diego, California,^[2] at depths of 0–547 metres (0–1,795 ft).^[3] It reaches a carapace length of 150 millimetres (5.9 in) 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.^[4] 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.^[4] 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.^[2] The gill chamber is also sometimes used by the commensal fish Careproctus to hold its eggs.^[5]

Taxidermied museum specimen prepared in a position to show how the legs and claws form two foramens while folded

Brown box crab
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Malacostraca
Order:	Decapoda
Suborder:	Pleocyemata
Infraorder:	Anomura
Family:	Lithodidae
Genus:	Echidnocerus
Species:	E. foraminatus
Binomial name
Echidnocerus foraminatus Stimpson, 1859[1]

Fisheries

The brown box crab has been fished in California since at least 1984.^[6] Take was minor and largely incidental until the mid 2010s, when landings by mass increased five-fold in 2017 relative to 2016^[7] and remained above 20.5 t (45,000 lb) until 2023.^[6] In 2019, the California Department of Fish and Wildlife launched an experimental fishery for brown box crabs.^[7]