CHS Fighting... Blue Crabs?

Crabs are a well-known and often popularized part of the coastal ecosystem. Being a CHS graduate, I thought a spotlight on sand crabs would be appropriate. However, while there is, in slang fashion, a "sand crab," it does not occur on the Texas Gulf Coast (though it is sometimes found on Florida's Gulf Coast). It's called the mole crab, or sand flea. There are two types found in North America: Emerita talpoida, the Atlantic mole crab (found from North Carolina to the Florida Gulf Coast), and Emerita analoga, the Pacific mole crab (found from Alaska to Baja California). And they bear almost no resemblance to the CHS mascot. Therefore, in lieu of a native sand crab, we'll take a look at the popular blue crab.

All crabs are members of the:

• Subphylum Crustacea (five fused segments; five pairs of appendages and two antennae; gills; most marine with some in freshwater and few on land; 42,000 species),

• Class Malacostraca (head, thorax, and abdomen; such as lobsters, shrimp, and krill; 18,000 species),

• Order Decapoda (five pairs of legs; such as shrimp, crayfishes, and lobsters; 10,000 species), and the

• Infraorder Brachyura (meaning "short tail"; these are the true crabs and most advanced decapods; body short, wide, and flat; abdomen flap covering reproductive organs; five pairs of walking legs; 5000 species).(1)

The blue crab's scientific name, Callinectes sapidus, is its best description. Literally "savory beautiful swimmer." A fully grown blue crab can be over eight inches wide, from spine tip to spine tip and weigh up to two pounds. The top of the shell is typically green or brownish green, legs are white, and claws are varying shades of blue. Females' claws are tipped in red. We've all had red nails at some point, right girls?(2)

Blue crabs aren't terribly particular about what they partake of during meal time. They'll eat clams, oysters, mussels, almost any vegetable or animal matter, and even young crabs. Despite having nearly 360-degree vision (courtesy of stalked, compound eyes), predators are plentiful and include black drum, red drum, Atlantic croaker, herons, sea turtles, Whooping Cranes, and yours truly. Although they can sometimes be found at the surface swimming along with the currents, blue crabs are bottom-dwellers and can be found in nearly every type of marine habitat from super salty, very deep waters to almost fresh, tide line waters. They live all along the east coasts of North and South America and have also been seen in the coastal waters of France, Holland, and Denmark.(2)

Male blue crabs mate often. However, females mate only once, directly on the heels of their final molt. While the female's shell is still soft, the male deposits his sperm into the female's personal cold storage, so to speak. For most marine species, mating and spawning are synonymous. Not so for the blue crab. The female can, and usually does, hold onto that sperm for up to nine months before fertilizing her eggs.(3) After mating, the male continues to protect the female until her shell hardens. Once this duty is over, the female returns to the higher-salinity areas of the bays, and once her eggs have matured, she migrates to the Gulf to spawn. Males remain in the estuaries, waiting for the next soft female. From this single coupling, females may spawn two or more times before they die. The typical spawning season on the Texas coast peaks in spring and summer, though with warm winters, spawning may occur year round. A single female will lay up to two million eggs, which she carries on her abdomen. An egg-bearing female is often called a "sponge" or "berry" crab. The eggs, which start out orange and darken progressively, hatch in two weeks, turning dark brown or black just before hatching. Of this two million, only one or two will survive to adulthood.(2)

Blue crabs go through three main life stages before reaching adulthood. Newly hatched larvae spend about their first forty days as zoeae, a sort of drifting, surface-dwelling, planktonic form bearing almost no resemblance to the adult form. They start out at 0.25mm, and in four to seven molts, end up at about 1.0mm. Next is the megalops stage. This is a free-swimming, bottom-dwelling stage in which the larvae take on a slightly more crablike appearance, including the all-important claws. The megalops stage lasts anywhere from six to twenty days; no rushing these things, you know. Finally, the juvenile stage. Here the larvae have pretty much reached crabdom. They look like miniature crabs, and they have almost made it to their estuarine homes (if they haven't reached them already) to finish getting bigger, which is really all they have left to do before blossoming as adults. By adults, I of course mean sexually functional which happens at about one year of age. Average lifespan is three years. Average limbspan… not so long. Luckily, crabs can regenerate pinchers or legs lost while fighting or protecting themselves. The lost limb will be replaced after two or more molts.(4)

The blue crab's ecological roles include

• litter cleanup (scavenging a degree of detritus, even when not quite fresh),

• benthic population control (consuming some quite prolific organisms),

• commensalite housing (by allowing barnacles, worms, and leeches to attach on the outer shell; isopods to live in the gills or on the abdomen; and small worms to live in the muscles. Commensalism is a relationship wherein one organism benefits and the other is not affected, positively or negatively),

• "savory" prey for larger interested predators, and

• mass mortalities (the duty of any good indicator species) when pollutant levels reach objectionable levels, oxygen disappears, or a parasite is unusually detestable.(2)

Economically, the blue crab is the most commercially important crab species harvested on the Texas gulf. Recreationally, blue crabs can be enticed by a number of methods. Baited drop lines are often used during the summer months to lure unsuspecting crabs close enough to a boat or dock so that they can be summarily scooped with a net. A popular bait used for drop lines is chicken necks. Thus, a person crabbing with this bait might be dubbed a "chicken necker" by other fishermen.(5) Currently, there is no daily bag or possession when fishing for blue crabs recreationally. However, there are some other rules to follow when harvesting this species including 1) not more than five percent by number of undersized blue crabs may be possessed for bait purposes only and must be placed in a separate container; 2) you may not possess egg-bearing crabs or female crabs with detached abdominal aprons; and 3) minimum length is five inches when measured across the widest point of the body from tip of spine to tip of spine.

And there you have all the basic information of the most tasteful crab on the Texas coast.

Stay crabby!

Footnotes

1) Wesley Rouse, "Crabs," Marine Biology & Oceanography, 31 January 2012 .

2) "Blue Crab (Callinectes sapidus)," Texas Parks & Wildlife Department, 31 January 2012 .

3) Harriet M. Perry and Thomas D. McIlwain, "Species Profiles: Blue Crab," (U. S. Fish & Wildlife Service, 1986).

4) Steven C. Zinski, "Blue Crab Life Cycle," The Blue Crab Archives, 31 January 2012 .

5) "Blue Crab," Texas Gulf Coast Fishing, 31 January 2012 .