BODY MEASUREMENTS IN THE WEAKFISH, CYNOSCION REGAUS. 



143 



curve, it is clear that sex does not influence the relation between weight and length. ° 

 This does not mean that there is no difference in the weight and length of Cynoscion 

 rcgalis of different sexes for the same age; it means that for a given length or weight of 

 fish sex does not affect the correlation. 



The regularity of the curve shown in figure i enables its mathematical equation to 

 be calculated with considerable accuracy. Comparing the abscissas and ordinates of 

 any two points on the curve, we find that the weight varies as the third power of the 

 length. The equation therefore will be of the form y = o x^, in which y represents weight, 

 X length, and a is a constant, the value of which depends on the units used. When length 



WEIGHT-GMS. 



Fig. 2. — Correlation table showing closeness of relation between weight and length of fish represented in figure i. 



is measured in centimeters, and weight in grams, a has the value 0.008771 ± o. 0001 17, 

 and the equation becomes, weight = (0.008771 ±0.0001 17) (length)'. 



From this it is apparent that the weight in grams of a specimen of Cynoscion rcgalis 

 may be obtained by multiplying the cube of its length, in centimeters, by approximately 

 0.009. 



Paton, Fulton, and other investigators * refer to the approximation with which the 

 weight of fishes vary as the cube of their lengths, but they present no comparable evi- 

 dence from which such conclusions can be derived with any degree of accuracy. 



a KeUicott, William E. (The growth of the brain and viscera in the smooth dogfish {Mustelus cants), American Journal 

 of Anatomy, vol. 8. p. 319. 190S), has shown that in the smooth dogfish, the sexes can not be distinguished with respect to either 

 absolute or relative weights of internal parts, except the gonads. 



b Fuiton, T. Wemyss; On the rate of growth of fishes, 24th Annual Report of the Fishery Board for Scotland, 1905. Pt. Ill, 

 and in other reports. Paton. D. Noel: loc. cit.. p. 6. Williamson, Charles H.: On the herrings of the Clyde and other districts, 

 27th Annual Report of tht Fishery Board for Scotland, 1908, Pt. III. 



