202 twelfth annual report of the 



Brook Trout. 



Many of the losses at brook trout stations are caused by imperfect 

 eggs. The hatching stations in New York no longer possess a large stock 

 of brood fish, and most of the eggs developed are obtained from private 

 stock. In some instances, the eggs are taken from young fish. In other 

 cases injuries occur in transportation and disease attacks the egg because 

 of some pollution of the packing material used in shipment. Moss fre- 

 quently carries fungus spores which multiply in the egg trays and jars, 

 causing the destruction of thousands of eggs and embryos. The well known 

 white spot which is observed on the yolk sac of many recently hatched 

 trout is supposed to be due to shock of some kind in egg transportation. 

 There is room for very great improvement in apparatus for carrying fish 

 eggs as well as in the methods of taking and fertilizing eggs. The use of 

 young trout as egg producers should be discouraged, and greater care should 

 be exercised in mingling the eggs and milt, as our experience shows a very 

 large percentage of " ringers " from eggs recently held in some of the hatch- 

 eries. There should be no difficulty on this point, for it is customary to 

 find an excess of males on almost any spawning grounds. 



Among the causes of loss in brook trout is a species of fungus scarcely 

 ever absent from trout waters. Fortunately this cause of disease generally 

 yields to the salt treatment so well known to all fish culturists. Under the 

 chapter descriptive of the State fish ponds at Caledonia reference has 

 been made to a gill parasite of the brook trout, the fish louse introduced 

 from Adirondack waters. So destructive is this parasite and so persistent 

 when once introduced that it has rendered the holding of brood trout 

 of this species practically impossible at Caledonia, at least in hatchery 

 waters. 



Singularly enough, the brown trout and rainbow trout are never affected 

 and appear to be wholly immune from attacks of this copepod. On July 

 1 8, 1906, at Saranac Inn, brook trout fingerlings were dying from no apparent 

 disease. Foreman Winchester stated that they commenced " whirling and 

 boring in a circle, nnallv dropping to the bottom on the side, continuing 

 this for some time until death resulted." The loss in one of the ponds 

 most seriously affected was 250 fingerlings out of 20,000 to 25,000 finger- 

 lings in twenty-four hours. This would seem to indicate a nervous disease 



