470 FISH HAICHKRY MANAGEMENT 



Acute Toxicity Causing death or severe damage to an organism by poi- 

 soning during a brief exposure period, normally 96 hours or less. See 



Chronic. 

 Adaptation The process by which individuals (or parts of individuals), 



populations, or species change in form or function in order to better 



survive under given or changed environmental conditions. Also the 



result of this process. 

 Adipose Fin A small fleshy appendage located posterior to the main 



dorsal fin; present in Salmonidae and Ictaluridae. 

 Adipose Tissue Tissue capable of storing large amounts of neutral fats. 

 Aerated Lagoon A waste treatment pond in which the oxygen required 



for biological oxidation is supplied by mechanical aerators. 

 Aeration The mixing of air and water by wind action or by air forced 



through water; generally refers to a process by which oxygen is added 



to water. 

 Aerobic Referring to a process (for example, respiration) or organism 



(for example, a bacterium) that requires oxygen. 

 Air The gases surrounding the earth; consists of approximately 78"(i 



nitrogen, 21'/o oxygen, 0.9''i) argon, 0.03"ii carbon dioxide, and minute 



quantities of helium, krypton, neon, and xenon, plus water vapor. 

 Air Bladder (Swim bladder). An internal, inflatable gas bladder that 



enables a fish to regulate its buoyancy. 

 Air Stripping Removal of dissolved gases from water to air by agitation 



of the water to increase the area of air-water contact. 

 Alevin A life stage of salmonid fish between hatching and feeding when 



the yolk sac still is present. Equivalent to sac fry in other fishes. 

 Algal Bloom A high density or rapid increase in abundance of algae. 

 Algal Toxicosis A poisoning resulting from the uptake or ingestion of 



toxins or toxin-producing algae; usually associated with blue-green 



algae or dinoflagellate blooms in fresh or marine water. 

 Alimentary Tract The digestive tract, including all organs from the 



mouth to the anal opening. 

 Aliquot An equal part or sample of a larger quantity. 

 Alkalinity The power of a mineral solution to neutralize hydrogen ions; 



usually expressed as equivalents of calcium carbonate. 

 Amino Acid A building block for proteins; an organic acid containing 



one or more amino groups ( — NH7) and at least one carboxylic acid 



group (-COOH). 

 Ammonia The gas NH^; highly soluble in water; toxic to fish in the 



un-ionized form, especially at low oxygen tensions. 

 Ammonia Nitrogen Also called total ammonia. The summed weight of 



nitrogen in both the ionized (ammonium, NHj*") and molecular (NHJ 



forms of dissolved ammonia ( NH4 — N plus NH3 — N). Ammonia 



values are reported as N (the hydrogen being ignored in analyses). 



