CHAPTER IV. 



GENERAL CONCLUSIONS AS TO THE PROBLEMS CONNECTED WITH THE 

 GROWTH OP SALMON AND TROUT. 



I SHALL now conclude by comparing the growth and manner of growth 

 of the different fish described in the preceding chapters. 



In the accompanying figure (Fig. 81) growth-curves are shown for 

 Salmon, Sea-trout and Mj0sen trout of the same migration age. Included 

 too, in the scheme, are curves representing a slow-growing trout (from 

 Chaigijok) and a rapidly growing mountain trout from Osfjorden in Dagali, 

 Numedal. 



It will be evident at once that the diagram illustrates very different 

 growth and modes of growth. Still more dissimilarity would have appeared, 

 however, if I had depicted several out of the many trout-curves, but I con- 

 sidered it inadvisable to do so, for fear of making the diagram too intricate. 



We see, then, that salmon in their early stages have perhaps the 

 slowest growth of all ; the Mj0sen trout grow relatively better than most of 

 the trout family, and their development after change of growth most nearly 

 resembles that of the salmon. 



The sea-trout after change of environment grows rather less rapidly 

 than the Mj0sen trout. 



Finally, in the curve for mountain-trout from Osfjorden, we meet with 

 a growth which is regular and vigorous throughout the fish's whole existence, 

 and in the burn-trout from Chaigijok we see the representation of a fish 

 that grows regularly but poorly during a great number of years. 



These curves must not, however, be considered as absolute in every 

 case. Indeed they do no more than represent a definite kind of growth in 

 salmon, sea-trout and Mj0sen trout, for every one of which it would be 

 possible to set up a number of subordinates, such as, for instance, curves 

 for the three, four, five, and six-year-old migrants, or curves for their 

 different localities in the case of sea-trout and salmon. 



We see accordingly that in conjunction with each of the type-curves 

 shown there might be put down a number of others, which would still 

 further emphasise the variations in rate of growth shown in the examples 

 here illustrated. 



The diagram shows clearly that the old problems regarding the 

 variability of fish, so far as this is expressed by size, may be reduced to the 



