G2 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



except to rub the debris through the outlet screen. Owing to the incli- 

 nation of the trough, the water recedes from the upper end until the 

 lishes lying there are almost wholly out of water, but, although they are 

 left in that position sometimes for 10 or 15 minutes, no harm has ever 

 been known to result. 



TRANSPORTATION AND LIBERATION OF YOUNG SALMON. 



The salmon produced at the station have, with few exceptions, been 

 liberated in the Penobscot Eiver or its tributaries, and more than 90 

 per cent of them in small tributaries within 10 miles of the station. 

 They have been spread about in streams and lakes, at all accessible 

 points. They are transferred in tin cans, holding about 8 gallons, with 

 an extreme height, including neck, of 17 or 18 inches, and a body 15^ 

 inches in diameter and 10 inches deep, making a very broad and low 

 ■can, well adapted to the use to which it is put. Its great width favors 

 aeration at the surface, and a good deal of dashing about of the water 

 when on the road. The cans are filled to within about an inch from the 

 shoulder, giving opportunity for the water to swash about and aerate 

 itself. Into such a can are put from 200 to 400 Atlantic salmon seven 

 months old, more or less, according to the size of the fish, the tempera- 

 ture of the air, and the weather. The ordinary load is about 300 when 

 the temperature of the water is 52° to 54° F.^ making 37 fish per gallon. 

 Such loads are entirely safe for the conditions attending the work. 

 The motion of the wagon in which they are carried keeps up the aera- 

 tion of the water, so that the fish can not exhaust the air. Should the 

 cans stand still a very long time aeration is effected by a force-pump 

 which draws the water from the can and returns it through a tube so 

 that it strikes upon a deflector by which it is broken and scattered in 

 spray. The suction hose is covered with a roomy wire strainer, so that 

 the fish are not drawn in. 



DISEASES. 



Salmon in all their stages of growth are subject to a variety of dis- 

 eases. White spots sometimes occur on the eggs attached to the shell, 

 but have no hold on the embryos, so that when the shell is torn off the 

 white spot is seen as a cluster of globular white masses on its inner 

 surface. These appear to be vegetable parasites, perhaps fungoid in 

 their relations, and are never seriously abundant. Other white spots 

 are connected with the yolk-sac itself. These are more serious, but 

 while they result in the death of many embryos, they are by no means 

 always fatal. In 1896 there were hatched at the station some rainbow 

 trout that were badly spotted on the sac. A portion of the fry were 

 divided into three lots for experiment: (a) Without spots 5 (b) moder- 

 ately spotted: (c) badly spotted. They were kept separate through the 

 season, and a fair percentage survived, as follows: Of lot a, 55 per 

 cent J of lot b, 59 per cent; of lot c, 43 per cent. In the fall they were 



