THE BIOLOGICAL SIGNIFICANCE OF THE SMOLT 

 PERIOD IN CERTAIN SALMONOIDS 



By William M. Keil 

 Tuxedo Park, N. Y. 



In a paper read before this Society at the last meeting, the 

 writer made the following statement: "If good results are to be 

 expected from the planting of landlocked salmon and steelhead 

 trout in lakes containing no permanent tributary streams, the fish 

 must not be turned out into such waters until they have passed the 

 parr stage and begun to take on the silvery coloration of the smolt." 

 Such a statement needs substantiation, and the purpose of this 

 paper is to present to the Society the results of over twelve years 

 of experimental investigation of this subject. Preliminary to this 

 it will be necessary to give a brief outline of the stocking oper- 

 ations that were instrumental in bringing about this study. 



There is probably no other angling water in the world where 

 the results from planting salmon and steelhead have been so care- 

 fully recorded as at Tuxedo Lake. For over twenty-five years an 

 accurate record has been kept of not only the number and size of 

 the fish planted, but the number, size and condition of those taken 

 by anglers as well. During the years from 1900 to 1906, both of 

 the above varities were planted either as nineteen-months-old fish 

 in the fall or two-year-olds in the spring, and the fishing registers 

 at the boat houses show that approximately 50 per cent of the 

 numbers turned out were retaken by anglers. This lake also con- 

 tains great quantities of bass, perch and pickerel, and the good 

 results secured by this method of stocking was at that time at- 

 tributed entirely to the size of the fish planted. While thousands 

 of good-sized fish of the two kinds were taken by anglers each 

 season, the salmon especially, were not in the best of condition, 

 and the club fish committee was informed that in all probability 

 these fish were being stunted by being retained too long in the 

 hatchery pools. Several well known authorities advised the plant- 

 ing of fingerlings, and as an experiment, the committee decided to 

 turn out great quantities of these, rather than a smaller number 

 of the older fish. The hatchery was given instructions to put out 



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