Once released, there is the question, not only of whether stock enhancement will work, but also how to tell if it works. Hatching and growing crabs is just the first, and still theoretical, step in stock enhancement. 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. 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. 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.Īfter seven or eight molts, the zoea become megalopae, which are more shrimp-like in appearance. When fertilized eggs hatch, they become larvae called zoea. Harcke gets sponge crabs - females bearing eggs - from local crabbers and takes the crabs into her lab at the aquarium. And once crabs reach a certain stage of development, they have a nasty habit, in captivity or under crowded conditions, of eating each other.
Mortality is high, especially when the animals molt, or lose their shells - as frequently as every five days in the early stages. 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.īut until now, techniques for growing blue crabs have been elusive. The University of Maryland and the Smithsonian Environmental Research Center report success in growing crabs for the same purpose. Stock enhancement research such as Harcke’s is relatively new with blue crabs.
Some scientists are concerned that a drop in crab harvests in recent years may signal a decline in the species. 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. Ultimately, she hopes to develop procedures for growing blue crabs in hatcheries to help replenish wild stocks. In a project funded by the North Carolina Blue Crab Research Program, Harcke focuses on raising blue crabs from eggs through larval stages. Fortunately, its survival doesn’t depend on its being a beautiful baby.Įqually 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. Before it lives up to its scientific name - Callinectes sapidus or tasty, beautiful swimmer - the blue crab goes through a couple of ugly larval stages.