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By Cynthia Henderson 



A RECIPE FOR SURVIVAL 



• Photographs by Michael Halminski 



ABOVE: Murray Bridges of Endurance 

 Seafood is a veteran crabber who supplies 

 sponge crabs for the hatchery project. Here, 

 he is gearing up for the soft-shell season. 



LEFT: Here is "Number 59" from the 2002 

 batch of blue crabs grown at the N.C. 

 Aquarium on Roanoke Island as part of the 

 N.C. Blue Crab Research Program. 



efore it lives 

 up to its scientific name — 

 Callinectes sapidus or tasty, 

 beautiful swimmer — the 

 blue crab goes through a 

 couple of ugly larval stages. 

 Fortunately, its survival 

 doesn't depend on its being 

 a beautiful baby. 



Equally fortunate is 

 the fact that Joanne Harcke, 

 conservation and research 

 coordinator for the North 

 Carolina Aquarium on 

 Roanoke Island, finds the 

 ugly stages fascinating if 

 not, in their own way, 

 beautiful. 



In a project funded by 

 the North Carolina Blue 

 Crab Research Program, 

 Harcke focuses on raising 

 blue crabs from eggs 

 through larval stages. 

 Ultimately, she hopes to 

 develop procedures for 

 growing blue crabs in 

 hatcheries to help replenish wild stocks. 



The Blue Crab Research Program is 

 funded by the General Assembly and 

 administered by North Carolina Sea Grant to 

 address problems facing the blue crab 

 industry — the largest of the state's commercial 

 fisheries. Some scientists are concerned that 

 a drop in crab harvests in recent years may 

 signal a decline in the species. 



Stock enhancement research such as 

 Harcke' s is relatively new with blue crabs. 

 The University of Maryland and the 



Smithsonian Environmental Research Center 

 report success in growing crabs for the same 

 purpose. And, Harcke says, stock enhancement 

 has been tried in Japan with another species of 

 crab, Portunis trituberculatus, which is a 

 swimming crab like Callinectes sapidus. 



But until now, techniques for growing 

 blue crabs have been elusive. Mortality is high, 

 especially when the animals molt, or lose their 

 shells — as frequently as every five days in the 

 early stages. And once crabs reach a certain 

 stage of development, they have a nasty habit, 

 in captivity or under crowded conditions, of 

 eating each other. 



Harcke gets sponge crabs — females 

 bearing eggs — from local crabbers and takes 

 the crabs into her lab at the aquarium. When 

 fertilized eggs hatch, they become larvae 

 called zoea. Viewed under a microscope, they 

 look like something that might be controlled 

 by spraying, with sharp thorn-like structures 

 between their eyes and on their backs. 



After seven or eight molts, the zoea 

 become megalopae, which are more shrimp- 

 like in appearance. 



Harcke' s goal is to find replicable ways to 

 grow crabs to the megalops stage — just 

 before they turn cannibalistic — so they could 

 be released to the wild. However, in the lab, 

 she has made tiny isolation chambers from 

 short lengths of PVC pipe with screen mesh 

 bottoms to protect juvenile crabs from each 

 other until they reach adulthood. 



Hatching and growing crabs is just the 

 first, and still theoretical, step in stock 

 enhancement. Once released, there is the 

 question, not only of whether stock enhance- 

 ment will work, but also how to tell if it works. 



Continued 



COASTWATCH 13 



