VALUE OF NORWEGIAN LAKES FOR FISH CULTURE. 577 



The two first-named kinds have been previously so far mentioned that 

 I shall in this place merely add a few remarks. Both are born in fresh 

 runnings water, both remain therein during their earlier youth, and go 

 therefrom to the sea, where they quickly develop, after which they again, 

 driven by the instinct of reproduction, return to the places where they 

 were born. Some have thought that this returning, at all events so far 

 as the salmon are concerned, is also caused by the instinct of freeing 

 themselves in fresh cold water from certain parasites which infest them 

 in the sea in summer ; but this appears scarcely probable, since the lake 

 and river trout are also attacked in summer by similar animals. The re- 

 turn to fresh water takes place earlier in the case of the salmon than 

 with the sea-trout, which last, as a rule, first enters the mouths of the 

 rivers towards autumn. Owing to this circumstance, one has a longer 

 fishing season for the first than for the last. 



It is thought that the salmon and the trout do not agree well, but 

 conflict with each other about the spawning-places, so that where the 

 trout appears in any great abundance, particularly the large form, erioae, 

 there the salmon decreases, and vice versa. It may, however, be some- 

 what doubtful how far this observation is founded upon any mutual an- 

 tipathy between the races. It may possibly be based upon other cir- 

 cumstances; for instance, conditions accidentally more favorable for the 

 propagation of one species or the other in different years, which plainly 

 will cause one or the other species to occur in greater comparative 

 abundance some years after than was the case earlier. 



With regard to flavor, the salmon must generally be preferred to the 

 trout, particularly salmon of the better kinds. It has already been 

 stated that salmon, like the fresh-water trout, vary considerably in 

 quality from one place to another ; this is, however, true in a less degree 

 with the ocean-trout. In the salmon this may be the case even in a 

 very high degree with fish from adjacent rivers, a phenomenon which 

 can be explained only by race differences, since fish from the different 

 rivers get their development in the sea, where both find equal conditions 

 for thriving and fatness. At Christiansand we have a striking example 

 of this. While the salmon in Torisdal Eiver is plump and beautiful in 

 form, bright in color, and must be called excellent in fatness and flavor, 

 the salmon of Topdal Eiver is thin, dark in color, and can be styled noth- 

 ing but indifferent or even bad in plumpness and taste. 



In regular culture one has it in his power, among fish as \\'ell cattle, to 

 select the best races which are known, and it seems to be beyond ques- 

 tion that these, transplanted to a new locality, will retain their pecul- 

 iarities ; because, as remarked, the wealth of the sea is everywhere free 

 for all, and supplies all a like abundance of food. What can produce the 

 existing great difference in adjacent places is not easy to perceive. 

 The only mode of explanation seems to be this, that the rivers possess 

 very different nourishing capacity for the tender young, so that they in 

 one in a manner are checked, while in the other they thrive greatly. 

 37 F 



