500 FISH HATCHERY MANAGEMENT 



Urea One of the compounds in which nitrogen is excreted from fish in 

 the urine. Most nitrogen is eliminated as ammonia through the gills. 



Uremia The condition caused by faulty renal function and resulting in 

 excessive nitrogenous compounds in the blood. 



Urinary Bladder The bladder attached caudally to the kidneys; the 

 kidneys drain into it. 



Urogenital Pore External outlet for the urinary and genital ducts. 



Vaccine A preparation of nonvirulent disease organisms (dead or alive) 



that retains the capacity to stimulate production of antibodies against 



it. See Antigen. 

 Vector A living organism that carries an infectious agent from an 



infected individual to another, directly or indirectly. 

 Vein A tubular vessel that carries blood to the heart. 

 Vent The external posterior opening of the alimentary canal; the anus. 

 Ventral Fins Pelvic fins. 

 VHS See Viral Hemorrhagic Septicemia. 

 Viable Alive. 

 Vibriosis An infectious disease caused by the bacterium Vibrio anguil- 



larium. Synonyms: pike pest; eel pest; red sore. 

 Viral Hemorrhagic Septicemia (VHS) A severe disease of trout 



caused by a virus of the Rhabdovirus group. Synonyms: egtved 



disease; infectious kidney swelling and liver degeneration (INUL); 



trout pest. 

 Viremia The presence of virus in the blood stream. 

 Virulence The relative capacity of a pathogen to produce disease. 

 Vitamin An organic compound occurring in minute amounts in foods 



and essential for numerous metabolic reactions. 

 Vitamin D A radiated form of ergosterol that has not been proved 



essential for fish. 

 Vitamin K An essential, fat-soluble vitamin necessary for formation of 



prothrombin; deficiency causes reduced blood clotting. 

 Vitamin Premix A mixture of crystaline vitamins or concentrates used 



to fortify a formulated feed. 

 Viviparous Bringing forth living young; the mother contributes food 



toward the development of the embryos. 

 Vomer Bone of the anterior part of the roof of the mouth, commonly tri- 

 angular and often with teeth. 

 Von Bayer Trough A 12-inch V-shaped trough used to count eggs. 



Warmwater Species Generally, fish that spawn at temperatures above 

 60°F. The chief cultured warmwater species are basses, sunfish, cat- 

 fish, and minnows. See Coldwater Species; Coolwater Species. 



