GLOSSARY OF TERMS 



Annual mark or winter zone .- -The concen- 

 tration or interruption of the growth pattern 

 of circuli, which indicates the reduced scale 

 growth of the late fall, winter, and early spring. 

 These marks are formed each year and can be 

 counted to determine the age of the fish. See 

 figure 1. (Annual marks on all the figures are 

 indicated by arrows: Broad arrows in the 

 ocean zone, narrow arrows in the fresh-water 

 zone.) 



Anterior field (sculptured area) . --The part 

 of the scale that is nearest the head of the fish, 

 lies in a dermal pocket, and has most of the 

 circuli. See figure 1. 



Bases of the circuli .- - The ends of the circuli 

 where they adjoin the posterior field of the 

 scale. 



Circular striations .- -Continuation of circuli 

 around the posterior field. Circular striations 

 are weak but usually present on the scales of 

 Chinook and masu salmon and steelhead trout; 

 they are strong and often resemble enlarged 

 circuli on scales of coho salmon. See figure 2. 



Circuli .-- The ridges on the upper surface 

 of the anterior field of the scale. Visually these 

 ridges and interspaces appear as light and 

 dark rings around the scale. They are formed 

 on the margin as the scale grows. Additional 

 information on the growth and structure of 

 scales can be found in Neave (1936), Welander 

 (1940),'' Wallin (1957), and Koo and Finn (1964). 

 The first few circuli of most species com- 

 pletely encircle the focus; the number that do 

 is a character in species identification. After 

 the complete circuli, the others are arcs that 

 tend to end abruptly at the junction with the 

 posterior field. In some species of salmon and 

 trout, the bases of the circuli may not end 

 abruptly, but may extend into the posterior 

 field for varying distances, or the circuli may 

 be broken or enlarged in this area. 



Posterior field (clear area) . --The portion 

 of the scale toward the tail of the fish that 

 protruded from the scale pocket. This area of 

 the scale is important in identification of 

 species. Sockeye and most pink salmon scales 

 have only faint, irregular markings in this 

 area. Chum, chinook, and coho salmon scales 

 have strong radial striations that radiate from 

 the center of the scale. These striations often 

 produce a scalloped edge of the posterior field. 

 Sonne of the circuli on the chinook and masu 

 salmon and steelhead trout and on some pink 

 salmon extend into or around the posterior 

 field as faint irregular circular striations. On 

 the coho salmon scale these extentions are 

 strong and appear as enlarged circuli or seg- 

 ments of circuli. In the area of these circuli, 

 radial striations may be obscured on the coho 

 salmon scale. This part of the scale is often 

 difficult to examine. Because it is uniformly 

 translucent, the features are often obscured 

 by too much light. Thus it is usually necessary 

 to vary the angle and intensity of the lighting 

 on the scale to reveal the features of this 

 area. See figure 2. 



Radial striations . --Markings on the pos- 

 terior field that tend to radiate from the focus 

 as ridges and troughs. They are usually strong 

 on the scales of chum, chinook, and coho sal- 

 mon, but on the coho salmon they may be 

 obscured in the area of the circular striations 

 or enlarged circuli. See figure 2. 



Regenerated scale . --A scale that replaces 

 one that has been lost. The new scale grows 

 without the formation of circuli until it reaches 

 the approximate size of the scale that was lost. 

 See Mosher (1968). 



R eticulations .- - The network of lines or dots 

 that occurs along the bases of the circuli of 

 some scales. Reticulations may be either net- 

 like (a series of interconnecting lines between 

 circuli) or granular-appearing (a series of 

 dots or little o's). See figures 1 and 2. 



Focus (central platelet) .-- The center of 

 scale growth, the area enclosed by the first 

 circulus. See figure 1. 



Arthur D. Welander. 1940. A study of the develop- 

 ment of the scale of the chinook salmon, ( Oncorhynchus 

 tschawytscha) . M.S. thesis, Univ. Wash., Seattle, 59 pp. 

 (typescript). 



Shoulders of the scale .-- The wide portion of 

 the anterior field of the scale on both sides of 

 the longest axis. See figure 1. 



Winter zones, winter marks . --The concen- 

 tration of circuli that indicates the reduced 

 scale growth of the late fall, winter, and early 

 spring. See annual mark and figure 1. 



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