GLOSSARY 481 



Fixative A chemical agent chosen to penetrate tissues very soon after 

 death and preserve the cellular components in an insoluble state as 

 nearly life-like as possible. 



Flagellum (plural: Flagella) Whip-like locomotion organelle of single 

 (usually free-living) cells. 



Flashing Quick turning movements of fish, especially when fish are 

 annoyed by external parasites, causing a momentary reflection of light 

 from their sides and bellies. When flashing, fish often scrape them- 

 selves against objects to rid themselves of the parasites. 



Flow Index The relationship of fish size to water inflow (flow rate) of a 

 rearing unit; calculated by the formula: 



Flow Index = (fish weight) ^ (fish length X water inflow). 



Flow rate The volume of water moving past a given point in a unit of 

 time, usually expressed as cubic feet per second (cfs) or gallons per 

 minute (gpm). 



Flush A short bath in which the flow of water is not stopped, but a high 

 concentration of chemical is added at the inlet and passed through the 

 system as a pulse. 



Folic Acid (Folacin) A vitamin of the B complex that is necessary for 

 maturation of red blood cells and synthesis of nucleoproteins; defi- 

 ciency results in anemia. 



Fomites Inanimate objects (brushes, or dipnets) that may be contam- 

 inated with and transmit infectious organisms. See Vector. 



Food Conversion A ratio of food intake to body weight gain; more gen- 

 erally, the total weight of all feed given to a lot of fish divided by the 

 total weight gain of the fish lot. The units of weight and the time 

 interval over which they are measured must be the same. The better 

 the conversion, the lower the ratio. 



Fork Length The distance from the tip of the snout to the fork of the 

 caudal fin. 



Formalin Solution of approximately 37% by weight of formaldehyde gas 

 in water. Effective in the control of external parasites and fungal infec- 

 tions on fish and eggs. Also used as a tissue fixative. 



Formulated Feed A combination of ingredients that provides specific 

 amounts of nutrients per weight of feed. 



Fortification Addition of nutrients to foods. 



Free Living Not dependent on a host organism. 



Fresh Water Water containing less than 0.05"o total dissolved salts by 

 weight. 



Fry The stage in a fish's life from the time it hatches until it reaches 1 

 inch in length. 



Fungus Any of a group of primitive plants lacking chlorophyll, includ- 

 ing molds, rusts, mildews, smuts, and mushrooms. Some kinds are 

 parasitic on fishes. 



