1931 



ANNUAL REPORT. 1930 



41 



The analyses indicate (1) that sedimentary rocks contain a higher mineral 

 content than igneous rocks. Mount Pleasant waters being the richest on account 

 of the fact that the artesian wells, from which a certain amount of the water 

 supply is obtained, flow through rocks heavily impregnated with calcium and 

 magnesium salts; (2) that the water supplies are practically free from albuminoid 

 substances and are. therefore, free from pollution; (3) that, although there is a 

 very great difference in the chemical content of the water, speckled trout are 

 able to endure any of these conditions and thrive satisfactorily; (4) that the 

 number of fish produced at each station, per cubic foot of water, may differ 

 widely and should be determined. 



The process of carrying the fish through the complete cycle from the egg 

 to the adult stage is possible at the Normandale trout ponds and is a principle 

 which has received the support of many leading fish culturists. At the 

 Normandale trout ponds, from acclimatized and domesticated trout, the Depart- 

 ment obtains the largest proportion of the trout egg supply for the hatcheries. 

 The Department plans to incorporate this same method in the District 

 Rearing Stations whenever and w'herever practicable, and this will lead to the 

 decentralization of Normandale as the only and major source of fertilized trout 

 eggs from domesticated stock. 



The diagrams and photographs inserted in this report indicate the general 

 principles of rearing-station construction. The raceways are constructed so as 

 to take care of a graded stock, fr\- being retained in the smaller raceways until 

 they are feeding well, when they are transferred to larger raceways. This 

 structure is basic to general hatchery principles, the small raceways simulating 

 the natural running feeders and streams in which trout fry live in a state of nature. 

 The raceways and rearing tanks in general use range in size from 2 to 10 feet in 

 width and from 20 to 100 feet in length. Raceways for fingerlings in general are 

 not over 5 feet in width or 75 feet in length. The raceways are of durable wood 

 construction, and the bottom is covered with sand or gravel. When the water 

 supply warrants, raceways are separately fed and separately drained, and in all 

 cases at our new rearing stations provision is made for a supply of fresh water 

 to those raceways containing running water used previously. The bottoms of 

 the raceways are sloped only slightly, and an effort is made to have the water in 

 the lower end not more than twelve inches or thereabouts, since we have found 

 that this condition allows for the equal distribution of the fish over the bottom, 

 a condition which most fish culturists aim to obtain in order to give the fish a 

 more equal opportunity. 



SPECKLED TROUT 



Appendix No. 4 shows by comparison with previous years and Appendix 

 No. 3 shows in detail the progress that has been made in the culture and distri- 

 bution of trout. 



Comparative Statement of Speckled Trout Distribltion 



