Conservation Commission. 205 



opment takes place in certain water birds which eat the fish. 

 Unfortunately we have no effective means of checking this para- 

 site except to keep water birds off the premises. An account of 

 this cataract caused by worm larvae is given by Dr. Hofer in his 

 Handbuch der Fischkrankheiten, 1904, pp. 293-295. 



On April 15, 1911, many of the breeding black bass in Pond 

 INo. 3, the oldest bass pond at the Oneida station, were dead or 

 dying. Bass had been kept in that pond during three winters 

 preceding the last winter without serious loss. The pond was 

 one of the tannery vat locations, and it was suspected that the 

 nemlock bark liquor had something to do with the loss of the fish, 

 but this has not affected the bass heretofore and probably has 

 nothing to do with the losses referred to. 



An examination of some of the recently dead fish showed para- 

 sitism of several forms. A larval worm encysted under the epi- 

 dermis causing black specks resembling fly specks, immature 

 jointed worms, perhaps related to tapeworms, in the mouth and 

 gills, and fish lice (copepods) in the roof of the mouth and other 

 parts of the head were all observed simultaneously. This unfor- 

 tunate combination of parasites no doubt reduced the vitality of 

 the bass to such an extent that they could not take the live min- 

 nows provided for their use in winter quarters, and they starved 

 to death. There is no other way of accounting for the large 

 mortality among the fish. This is the first time in the history 

 of the ponds that such winter losses have occurred, and this con- 

 dition demonstrates the necessity of liberating the bass at Oneida 

 station after they have protected their young up to the time of 

 " breaking the swarm." Thus far, it has been easy to net in 

 Oneida lake all the gravid bass needed for the season's work, and 

 the transfer of the fish to breeding ponds almost immediately be- 

 fore spawning begins has involved no interruption of the nest 

 building. 



A specimen of the parasitized bass was forwarded to Prof. 

 Edwin Linton, Washington and Jefferson College, Washington, 

 Pa., and from him was received the following report: 



" Length of the fish, 12 inches. 



" The following parasites were found : 



