Working the 'bugs' 

 out of fish farming 



Disease has been cited as the greatest single 

 technical obstacle to aquaculture. Once a disease 

 infests a tank or pond where organisms of the same 

 species are crowded, the disease can spread with 

 lightning speed. In no time, the entire aquaculture 

 population can be wiped out. 



Dr. Charles Bland, associate professor of biology 

 at East Carolina University, has focused his re- 

 search on the disease organism, Lagenidium calli- 

 nectes, a fungus that attacks blue crab, shrimp and 

 other marine Crustacea. Blue crab, common in 

 North Carolina waters today, is considered a likely 

 candidate for future aquaculture. When Bland be- 

 gan his research five years ago under Sea Grant 

 support, he set out to learn how widespread the 

 fungus is in North Carolina and how destructive it 

 could be in aquaculture situations. Since then, he 

 has shifted his emphasis to finding ways to control 

 parasites of crabs and shrimp. 



Bland's findings have enabled him to assist 

 crustacean aquaculture projects across the nation. 

 He has worked with researchers in Texas, Oregon, 

 California, South and North Carolina on fungal 

 diseases of shrimp, Dungeness crab, lobster, 

 Macrobrachium shrimp and eel. 



In October, Bland traveled to Japan upon the 

 invitation of the aquaculture panel of the U. S.- 

 Japan Natural Resources Program to present his 

 findings at a symposium on "Diseases of Cultured 

 Organisms." 



Before he could begin searching for ways to slow 

 the fungus, Bland had to get to know more about 

 Lagenidium — where and in what numbers it occurs 

 and what happens to it through its life stages. 

 The fungus, which attacks the egg mass, or sponge, 

 of the blue crab, was found to occur in 95 per cent 

 of the sponges examined before June 1. By August, 

 Bland found that the infection rate had dropped 

 to around 30 per cent, with no infected crabs being 

 collected after July 9. Infection rate data over 

 several years will be compared to such environ- 

 mental factors as salinity, water termperature, and 

 oxygen level to determine which factors contribute 

 to increased rates of infection. 



Bland and graduate student Don Ruch have 

 tested a wide variety of chemicals to determine 

 which can best control the development and spread 

 of the fungus. Small doses of malochite green have 

 proven effective. 



The next step in the research, which is now 

 underway, is to determine what ill effects control 

 chemicals may have on the development of crabs 

 and shrimp. Bland's goal is to come up with a 

 chemical that controls the disease without harm- 

 ing the crustacean. 



One exciting development has been Bland's dis- 

 covery that crab eggs may contain a substance 



that effectively resists the fungus. He has learned 

 that an extract from the eggs will cause a resistant 

 cover to form about the spores (the infecting agent) 

 of Lagenidium. Once enclosed, the spores quickly 

 germinate, or begin to develop. But in the absence 

 of a suitable host, they die shortly. After the sub- 

 stance is isolated, tests will be conducted to deter- 

 mine whether pre-treatment of water where shrimp 

 and crab will be grown could stop the infection. 



In another phase of his research, Bland has 

 learned that shrimp are highly susceptible to in- 

 fection by the fungus, Haliphthoros, in confined 

 conditions. Attacking the gills and eyes of shrimp, 

 the fungus is the same as that found causing 

 disease in lobsters in California. 



Aquaculture studies 

 in nearby states 



Sea Grant programs in neighboring South Caro- 

 lina and Virginia are studying improved aquacul- 

 ture of other species. In South Carolina, Sea 

 Grant-supported researchers are devoting much 

 attention to the culture of Macrobrachium shrimp, 

 looking to the possibility of rearing them in South 

 Carolina's abandoned rice fields. Macrobrachium 

 is a big animal, with some species reaching up to 

 nine inches in length. It has been described as 

 being more like a lobster than a brown or white 

 shrimp. 



South Carolina researchers are also studying 

 cultch-free seed oysters from the Wando River. 

 Ultimately, they aim to develop guidelines for 

 successful oyster cultivation in South Carolina. 



Scientists at the Virginia Institute of Marine 

 Science are working to develop superior oysters for 

 mariculture, to identify conditions necessary for 

 increasing the commercial production of the soft 

 stage of the blue crab and determining the poten- 

 tial for commercial use of the rock crab. VIMS 

 researchers with Sea Grant funding are also in- 

 vestigating the feasibility of culturing the hard 

 clam and bay scallop. 



