CULTURE OF THE SHAD. 

 Natural Breeding. 



147 



"Even at this rate, and allowing that all shad die at 

 three years old, the number of three-year-old fish in a 

 river, derived from a single pair, would double in about 

 eight years, although, for several years, there would be, of 

 course, no three-yea^blds at all in the river, the original 

 pair having died. But, since the number of the largest 

 fish is always small, compared with those of less size, and 

 as these large ones are most liable to get caught, it may 

 well be understood that the river fishermen think that both 

 shad and salmon have ' decreased in size,' and that they 

 are obliged to make their net-meshes smaller. The gain 

 by artificial propagation of shad, lies at the very outset, 

 and consists in the increased percentage of spawn that may 

 thus be hatched ; the ratio of the artificial to the natural 

 being at the most moderate estimate, as seventy -two to one. 

 Starting with this difference, and taking the other propor- 

 tions just as in the above table, we should have the follow- 

 ing results from the artificially hatched spawn of two pairs 

 of large shad, taken three years in succession, added to 

 the spawn of their mature progeny within that period : 



