5o CULTIVATION OF A 



caught in any river (where they have free access to 

 the streams above, from its source to the sea) can, or 

 may have produced the previous year ; and, secondly, 

 the number of years required to produce an average 

 stock offish, varying in weight from 6 Ibs. to 30 Ibs. 

 each. It is difficult to fix the average weight of fish 

 caught in various rivers, but the annual number killed 

 we will take to be 20,000 fish ; experience has enabled 

 me to arrive at the conclusion that it will require at 

 least four years to produce marketable salmon 

 of the average weight. Now we have a migra- 

 tory creature to deal with, which we may hatch and 

 protect for a certain number of months, but at the 

 end of this period it becomes exposed in the river to 

 the same chances of life as millions of others, in going 

 to and returning from the sea. Twice it goes to the 

 sea before, on the average, the fish is fit to be caught ; 

 therefore, out of the forty-eight months of its life, we 

 may protect it only for a few months. I shall assume 

 that the artificial propagation be continued simul- 

 taneously with the natural process of breeding for 

 four years ; consequently, if any reliance is to be 

 placed on artificial propagation it must be fairly tested 

 by comparison with the natural process during a simi- 

 lar period of four years ; or at any rate until the result 

 can be proved by a return of marketable fish from 

 BOTH processes. 



I shall first consider the case of fish artificially 

 hatched and reared for (say) fifteen months. The 

 eggs collected from the fish may be fecundated and 

 incubated artificially in a box, more perfectly and in 

 greater relative numbers than would be the case in 

 the bed of a river by the fish themselves ; and by 

 using spring or filtered water, the destructive insects, 

 as well as trout and larger fish, may be to a greater 

 extent excluded during this period of fifteen months. 



After the age of fifteen months, when the young 



