484 FISH HATCHERY MANAGEMENT 



Hematoma A tumor-like enlargement in the tissue caused by blood 

 escaping the vascular system. 



Hematopoiesis The formation of blood or blood cells in the living 

 body. The major hematopoietic tissue in fish is located in the anterior 

 kidney. Synonym: hemapoiesis. 



Hematopoietic Kidney The anterior portion of the kidney ("head kid- 

 ney") involved in the production of blood cells. 



Hemoglobin The respiratory pigment of red blood cells that takes up 

 oxygen at the gills or lungs and releases it at the tissues. 



Hemorrhage An escape of blood from its vessels, through either intact 

 or ruptured walls. 



Hepatic Pertaining to the liver. 



Hepatitis Inflammation of the liver. 



Hepatoma A tumor with cells resembling those of liver; includes any 

 tumor of the liver. Hepatoma is associated with mold toxins in feed 

 eaten by cultured fishes. The toxin having the greatest affect on fishes 

 is aflatoxin B, , from Aspergillus flavus. 



Heterotrophic Bacteria Bacteria that oxidize organic material (car- 

 bohydrate, protein, fats) to CO2 , NH4 — N, and water for their energy 

 source. 



Histology Microscopic study of cells, tissues, and organs. 



Histopathology The study of microscopically visible changes in 

 diseased tissues. 



Homing Return of fish to their stream or lake of origin to spawn. 



Hormone A chemical product of living cells affecting organs that do not 

 secrete it. 



HRM See Enteric Redmouth Disease. 



Hyamine See Quaternary Ammonium Compounds. 



Hybrid Progeny resulting from a cross between parents that are geneti- 

 cally unlike. 



Hybrid Vigor Condition in which the offspring perform better than the 

 parents. Synonym: heterosis. 



Hydrogen Ion Concentration (Activity) The cause of acidity in water. 

 See pH. 



Hydrogen Sulfide An odorous, soluble gas, H^S, resulting from anaero- 

 bic decomposition of sulfur-containing compounds, especially proteins. 



Hyoid Bones Bones in the floor of the mouth supporting the tongue. 



Hyper- A prefix denoting excessive, above normal, or situated above. 



Hyperemia Increased blood resulting in distension of the blood vessels. 



Hypo- A prefix denoting deficiency, lack, below, beneath. 



Ich A protozoan disease caused by the ciliate Ichthyophtherius multifilis; 

 "white-spot disease." 



