Relative Plumpness of Fish 77 



and weights in pounds and fractions of pounds. As the numerical values 

 derived from condition formulas arc useful for comparisons only, Thomp- 

 son and Bennett ^^ developed a new condition formula in which the total 

 length of a fish was taken in inches and tenths of inches and the weight 

 in pounds and liundredths of pounds. This formula required neither con- 

 versions of centimeters to inches nor grams to pounds, and the entire fish 

 was measured rather than some fraction of the total length. Tenths of 

 inches and hundredths of pounds were used instead of quarters of inches 

 or ounces in order to facilitate rapid calculations. The formula was as 

 follows : 



Index of Condition, C = — 



where W represents weight of the fish to the nearest hundredth of a 

 pound, and L represents total length to the nearest tenth of an inch. 

 When calculations are made using the lengths and weights of largemouth 

 bass between 5 and 15 inches of total length, an Index of Condition of 

 3.5 to 4.5 denotes a fish in poor flesh, 4.6 to 5.5 one of average plumpness, 

 and 5.6 to 6.5 a very fat fish. 



In fish such as the bluegill, which is deep in proportion to length and 

 laterally compressed, the figures for condition are higher. In bluegills 

 from 5 to 8 inches of total length, an Index of Condition figure of 7.0 

 or below denotes a fish in poor flesh, 7.1 to 8.0 one of normal plumpness, 

 and above 8.0 one of unusual plumpness. 



Condition Factor of E. M. Corbett. A system used by the English for 

 figuring condition was the "Condition Factor" invented by E. M. Corbett 

 and issued by the Salmon and Trout Association, Fishmongers Hall, E.C. 

 4, London (date unknown). Corbett used total length in inches and 

 weight in pounds and ounces, but actually converted fractions of inches 

 into tenths and ounces into hundredths of pounds. Using essentially the 

 same formula as that proposed by Thompson and Bennett, Corbett multi- 

 plied his numerator by 100,000 instead of 10,000 to get rid of the decimal 

 point. His formula is as follows: 



o J-.- IT ^ m7 100,000 W 

 Condition Factor, C.F. = — '—- • 



where W = weight in pounds and L = length in inches. This formula 

 gave a condition factor as a whole number. For example, a bluegill having 

 an Index of Condition of 7.22 with the Thompson and Bennett method 

 of calculation was equal to C.F. = 72 with the Corbett system. 



Applying the Corbett system to bass and bluegills in South Africa, 

 A. Cecil Harrison arrived at the same range of condition figures (times 



