GLOSSARY 495 



bicarbonate, carbonate, sulfate, and halides (chloride, fluoride, 

 bromide) in water. See Dissolved Solids. 



Sample A part, piece, item, or observation taken or shown as representa- 

 tive of a total population. 



Sample Count A method of estimating fish population weight from 

 individual weights of a small portion of the population. 



Sanitizer A chemical that reduces microbial contamination on equip- 

 ment. 



Saprolegniasis An infection by fungi of the genus Saprolegnia, usually 

 on the external surfaces of a fish body or on dead or dying fish eggs. 



Saturation In solutions, the maximum amount of a substance that can 

 be dissolved in a liquid without it being precipitated or released into 

 the air. 



Scale Formula A conventional formula used in identifying fishes. 

 "Scales 7 + 65 + 12," for example, indicates 7 scales above the lateral 

 line, 6.5 along the lateral line, and 12 below it. 



Scales Above the Lateral Line Usually, the number of scales counted 

 along an oblique row beginning with the first scale above the lateral 

 line and running anteriorly to the base of the dorsal fin. 



Scales Below the Lateral Line The number of scales counted along a 

 row beginning at the origin of the anal fin and running obliquely dor- 

 sally either forward or backward, to the lateral line. For certain species 

 this count is made from the base of the pelvic fin. 



Sea Water Water containing from 3.0 to 3.5"o total salts. 



Secchi Disk A circular metal plate with the upper surface divided into 

 four quadrants, two painted white and two painted black. It is lowered 

 into the water on a graduated line, and the depth at which it disap- 

 pears is noted as the limit of visibility. 



Second Dorsal Fin The posterior of two dorsal fins, usually the soft- 

 rayed dorsal fin of spiny-rayed fishes. 



Secondary Invader An opportunist pathogen that obtains entrance to a 

 host following breakdown of the first line of defense. 



Sediment Settleable solids that form bottom deposits. 



Sedimentation Pond (Settling Basin) A wastewater treatment facility in 

 which settleable solids are removed from the hatchery effluent. 



Selective Breeding Selection of mates in a breeding program to pro- 

 duce offspring possessing certain defined characteristics. 



Sensitive, Drug Said of a microorganism, usually a bacterium, that can 

 be controlled (inhibited) or killed by use of a drug. See Resistant, 

 Drug. 



Septicemia A clinical sign characterized by a severe bacteremic infec- 

 tion, generally involving the significant invasion of the blood stream 

 by microorganisms. 



