GLOSSARY 477 



Control (Experimental) Similar test specimens subjected to the same 

 conditions as the experimental specimens except for the treatment 

 variable under study. 



Control Fish A group of animals given essentially identical treatment to 

 that of the test group, except for the experimental variable. 



Coolwater Species Generally, fish that spawn in temperatures between 

 40° and 60°F. The main cultured coolwater species are northern pike, 

 muskellunge, walleye, sauger, and yellow perch. See Coldwater Species; 

 Warmwater Species. 



Copper Sulfate (Blue Stone) Blue stone is copper sulfate pentahydrate 

 (CuS04-5H20). Effective in the prevention and control of external 

 protozoan parasites, fungal infections, and external bacterial diseases. 

 Highly toxic to fish. 



Cornea Outer covering of the eye. 



Corynebacterial Kidney Disease See Bacterial Kidney Disease. 



Costiasis An infection of the skin, fins, and gills by flagellated proto- 

 zoans of the genus Costia. 



Cranium The part of the skull enclosing the brain. 



Cyanocobalamin (Vitamin Bi^) One of the B-complex vitamins that is 

 involved with folic acid in blood-cell production in fish. This vitamin 

 enhances growth in many animals. 



Cyst, Host A connective tissue capsule, liquid or semi-solid, produced 

 around a parasite by the host. 



Cyst, of Parasite Origin A noncellular capsule secreted by a parasite. 



Cyst, Protozoa A resistant resting or reproductive stage of protozoa. 



Cytoplasm The contents of a cell, exclusive of the nucleus. 



Daily Temperature Unit (DTU) Equal to one degree Fahrenheit above 



freezing (32°F) for a 24- hour period. 

 Dechlorination Removal of the residual hypochlorite or chloramine 



from water to allow its use in fish culture. Charcoal is used frequently 



because it removes much of the hypochlorite and fluoride. Charcoal is 



inadequate for removing chloramine. 

 Dee's Disease See Bacterial Kidney Disease. 

 Deficiency A shortage of a substance necessary for health. 

 Deficiency Disease A disease resulting from the lack of one or more 



essential constituents of the diet. 

 Denitrification A biochemical reaction in which nitrate (NO3 ) is 



reduced to NO2, N2O, and nitrogen gas. 

 Density Index The relationship of fish size to the water volume of a 



rearing unit; calculated by the formula: 



Density Index = (weight of fish) -^ (fish length x volume of rearing unit). 



