SEA 



SCIENCE 



MALE BLUE CRABS: 



ROOM TO GROW? 



Shortly after molting and rehardening, 

 blue crabs — especially males — have little 

 muscle tissue and are called "white bellies" 

 because of their clean, white abdomens. 



But harvesting these crabs can create 

 waste within the blue crab fishery, says Marc 

 Turano, the blue crab specialist for North 

 Carolina Sea Grant. 



"Crabbers earn little money for white 

 bellies," he explains, referring to a white belly's 

 lack of tissue, or meat. "And picking houses 

 lose money attempting to get a few pounds of 

 meat from many pounds of crabs." 



For the last few years, research funded 

 by the North Carolina Blue Crab Research 

 Program (BCRP) and Fishery Resource Grant 

 Program (FRG) has focused on reducing waste 

 in the fishery and maximizing blue crab harvests. 

 The programs are funded by the N.C. General 

 Assembly and administered by North Carolina Sea 

 Grant. 



One solution would be a release and re- 

 capture program that culls white bellies from the 

 catch and returns them to the water. Simple as it 

 sounds, culling would be difficult to implement, 

 says Turano. 



Legally, a culling program would need dis- 

 tinct criteria for harvest. Economically, crab deal- 

 ers would have to accept only the meatiest crabs, 

 and crabbers would have to forgo larger daily 

 catches for the long-term benefit of the fishery. 



Another option is to hold white bellies in 

 shedding systems until they develop into more 

 profitable crabs. Three BCRP studies examined 

 this "growout" technique and found it might be 

 profitable for crabbers with existing shedding 

 systems. 



But growout entrepreneurs beware: the way 

 white bellies are handled may affect their survival. 



Because white bellies are still relatively soft, 

 their shells are easily punctured. A 2001 FRG 

 study by David Eggleston and Juan Chaves, both 

 of NC State, found that survival rates of peeler 

 crabs — which experience molting stressors similar 

 to white bellies — were much higher if the crabs 

 were carefully handled, stored on ice and covered 

 with wet burlap during transport. □ — K.A. 



CLOCKWISE FROM TOP LEFT: Barry Nash and CregBolton of the NCState University Seafood 

 Lab examine a crab catch. • Dell Newman of Swan Quarter conducts research at his blue crab shedding 

 operation. • A moltingcrab backs out of its shell. • A mature female, or "sook" displayingthe telltale 

 U-shape on her abdomen. 



And that's a shame; especially 

 considering the process has all the 

 elements of a compelling drama 

 — a dangerous task, lurking enemies, 

 suspense and yes, even deception. 



SEABED STRUGGLES 



As an invertebrate, a blue crab 

 literally bears a burden on its back. Lack- 

 ing a spinal column, its skeleton forms 

 as a hard shell outside the body. As its 

 internal tissue grows, a crab is periodi- 

 cally forced to shed its exoskeleton — 

 a process known as molting. 



Before molting, a blue crab under- 

 goes a premolt, or "peeler" stage. The 

 crab releases a hormone that prompts 

 a layer of cells underneath the shell to 

 separate. These cells produce enzymes 

 to dissolve the existing shell, as a softer 

 shell develops beneath. 



As the chemicals in the old shell 

 dissolve, the crab reabsorbs and stores 

 the inorganic salts. Once the develop- 

 ing shell is complete, the crab faces a 

 difficult and — especially if it's an older 



crab — potentially life-threatening task: 

 removing its muscle mass from its own 

 exoskeleton. 



As the molting or "busting" stage 

 begins, the crab looks for a hiding 

 place. Shedding will ravage the crab's 

 energy, making it weak and vulnerable 

 to a variety of predators, including fish, 

 sharks, turtles and other blue crabs. 



After hunkering down in the 

 sandy bottom, the crab absorbs water 

 and swells its tissues. Soon, like a 

 slow-motion crustacean version of the 

 Incredible Hulk, the old shell begins to 

 fracture and bust open as a larger and 

 seemingly more imposing crab backs 

 out. 



Although its new shell is about 

 one-third larger, the crab's size is 

 deceptive. Instead of bulging muscles 

 that expand within the shell, the crab 

 continues pumping water into its 

 tissues. For the next six hours, the crab 

 will inflate its new exoskeleton with 

 nothing more than sea water. 



The immediate postmolt, or 



24 M'Tl'MN 2004 



