GLOSSARY 483 



Gill Rot See Branchiomycosis. 



Gills The highly vascular, fleshy filaments used in aquatic respiration 



and excretion. 

 Globulin One of a group of proteins insoluble in water, but soluble in 



dilute solutions of neutral salts. 

 Glycogen Animal starch, a carbohydrate storage product of animals. 

 Gonadotrophin Hormone produced by pituitary glands to stimulate 



sexual maturation. 

 Gonads The reproductive organs; testes or ovaries. 

 GPM Gallons per minute. 

 Grading of Fish Sorting of fish by size, usually by some mechanical 



device. 

 Gram-negative Bacteria Bacteria that lose the purple stain of crystal 



violet and retain the counterstain, in the gram staining process. 

 Gram-positive Bacteria Bacteria that retain the purple stain of crystal 



violet in the gram staining process. 

 Gross Pathology Pathology that deals with the naked-eye appearance 



of tissues. 

 Group Immunity Immunity enjoyed by a susceptible individual by vir- 

 tue of membership in a population with enough immune individuals to 



prevent a disease outbreak. 

 Gullet The esophagus. 

 Gyro Infection An infection of any of the monogenetic trematodes or, 



more specifically, of Gyrodactylus sp. 



Habitat Those plants, animals, and physical components of the environ- 

 ment that constitute the natural food, physical-chemical conditions, 

 and cover requirements of an organism. 



Hagerman Redmouth Disease See Enteric Redmouth Disease. 



Haptor Posterior attachment organ of monogenetic trematodes. 



Hardness The power of water to neutralize soap, due to the presence of 

 cations such as calcium and magnesium; usually expressed as parts per 

 million equivalents of calcium carbonate. Refers to the calcium and 

 magnesium ion concentration in water on a scale of very soft (0-20 

 ppm as CaCOy), soft (20-50 ppm), hard (50-500 ppm) and very hard 

 (500+ ppm). 



Hatchery Constant A single value derived by combining the factors in 

 the numerator of the feeding rate formula: Percent body weight fed 

 daily = (3 x food conversion x daily length increase x lOO) ^ 

 length of fish. This value may be used to estimate feeding rates when 

 water temperature, food conversion, and growth rate remain constant. 



Hematocrit Percent of total blood volume that consists of cells; packed 

 cell volume. 



