The Life of the Blue Claw Crab:

A native to the Hackensack River, but locally dangerous to eat

By Kathy Urffer

The blue claw crab has the scientific name Callinectes (Greek for beautiful swimmer) sapidus (Latin meaning tasty or savory). It lives up to its name, being both an elegant swimmer and when safe to eat and prepared correctly, a delectable feast. It is part of a large group of arthropods called crustaceans (numbering about 38,000 species). The width of the shell is approximately twice the length, and blue claw crabs can grow up to 9 inches in width. They mate after about two years and only live for about three years. They are found south of Cape Cod.

As these crabs grow, they molt from their old, hard shell by swimming out the back. Until a new hard shell develops, their soft shell leaves them vulnerable to predation and injury. Predators claim large numbers of young crabs and soft-shell crabs, and crab populations may vary from year to year according to the abundance of predators.

FORAGING BEHAVIOR

Blue claw crabs are classified either as general scavengers, bottom carnivores, detritivores (eating decaying organic matter called detritus), or omnivores. Adult blue claw crabs prefer mollusks such as oysters and hard clams, but also eat dead and live fish, crabs (including other blue claw crabs), shrimp, benthic macroinvertebrates, organic debris, and aquatic plants.

Food is located by a combination of chemoreception (chemical sense) and taction (touch). The crab uses the tips of its front-most walking legs to probe the bottom for buried bivalves and to manipulate them once caught. Blue claw crabs may play a significant role in the control of benthic populations.

MATING

Blue claw crabs are sexually dimorphic and are primarily distinguished by looking at their abdomen. A male crab has a long, narrow, inverted "T" shaped abdomen, has blue claws and can grow to larger sizes than the female. Females are recognized by the inverted "V" shaped apron of young crabs and an inverted "U" shaped apron of sexually mature female crabs. The females also "paint their fingernails;" i.e., have bright red claw tips.

When a female crab undergoes a pubertal molt (and therefore is soft-shelled), she is sexually mature (called a "sook") and will migrate to shallow areas with marsh-lined banks or beds of submerged vegetation. She will then release a pheromone in her urine that attracts males.

After a male is mature he is ready to mate after his third or fourth intermolt phase, when he will perform a rather elaborate courtship ritual, or "dance." He will stand up high on his walking legs, extend his claws fully outward, and begin slowly waving his swimming legs. Finally, he will snap his body backwards and kick up sand. Should the female fail to respond, he will repeat the process again.

Mating occurs primarily in relatively low-salinity waters in the upper areas of bays and lower portions of rivers. During mating, the female captures and stores the male's sperm in sac-like receptacles so that she can fertilize her eggs at a later time. Once the female's shell has hardened, the male will release her and she will migrate to higher salinity waters to spawn. Extended periods of low temperatures usually shorten the mating season.

Females spawn for the first time two to nine months after mating, usually from May through August the following season. The female extrudes fertilized eggs into a cohesive mass, or "sponge," that remains attached to her abdomen until the larvae emerge. The average sponge contains about two million eggs and is formed in about two hours.

CONSUMPTION ADVISORIES

Eating, selling or taking (harvesting) blue claw crabs from Newark Bay Complex (Newark Bay, Hackensack River, Passaic River, Arthur Kill and Kill Van Kull, and all tributaries to these waterbodies) is prohibited due to contaminant loads of PCBs, dioxin, mercury, and PIHs. The contaminants, which are colorless, odorless and tasteless, accumulate in the fatty tissue and can increase one's chance of developing cancer, neurological impairments and miscarriage. Women of child-bearing age and children under the age of 5 are at particular risk.

The highest levels of chemical contaminants are found in the hepatopancreas, commonly known as the tomalley or green gland. It is the yellowish green gland under the gills. If you buy blue claw crabs in the store or acquire them from water bodies other than the Newark Bay Complex, remove and do not eat the green gland. Also do not use the cooking water or green gland (hepatopancreas) in any juices, sauces or soups.

Again, there is NO safe way to prepare crabs taken from the Newark Bay Complex. It is illegal to take blue claw crabs from anywhere in the Newark Bay Complex, and could result in fines from $100 to $3,000 for the first offense.

FOR MORE INFORMATION ON FISH ADVISORIES
New Jersey health advisories contact:
NJDEP, Division of Science & Research 609-984-6070, (www.state.nj.us/dep/dsr/fishadvpg1.htm)
NJDEP, Division of Fish & Wildlife 609-748-2020
NJ Department of Health & Senior Services Consumer and Environmental Health Services 609-588-3123
NJ Administrative Code 7:25-14, 18A (found at libraries)
Delaware health advisories: 302-739-5617 www.dnrec.state.de.us/fw/fwwel.htm
New York health advisories: 518-457-6178 www.health.state.ny.us/nysdoh/environ/fish.htm
Pennsylvania health advisories: 717-787-9633 www.dep.state.pa.us/dep/deputate/watermgt/Wqp/WQ
Standards/FishAdvis/fishadvisory.htm

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