146 AMERICAN FISH CULTURE. 



only seventy-seven fish fit for the table in three years. To 

 show the advantages to be derived from the artificial pro- 

 pagation of shad, the report alluded to continues : 



" B) the shad, thanks to the admirable experiments of 

 G-reen, we may illustrate the results of natural and artifi- 

 cial propagation side by side. We assume that the male 

 is fecund at one year, that the female carries spawn at two 

 years, and lays from 10,000 to 12,000 eggs to each pound 

 of her weight, and that males and females are in equal 

 numbers. Considering what is known of the hatching of 

 the eggs, by the natural process, and assuming that the 

 young are destroyed in the same proportion as those of the 

 salmon, the following fractions may be deduced : 



A 



| of all eggs laid, get impregnated and escape being 



eaten by other fishes. 

 3^ of these hatch. 



J s of those hatched grow to one year. 

 of the yearlings grow to two years. 

 of the two-year-olds grow to three years. 



" It would hence appear, that of 40,000 eggs of shad 

 laid in the natural way. only one arrives at the age of 

 three years. Now suppose two pairs of adult shad should 

 come to a river each year, for three successive years, and 

 there breed ; what would they and their descendants 

 amount to at the en 1 of that time ? The following table, 

 calculated from tie data foregoing, will answer this 

 question. 



