64 KEPORT OF COMMISSIONER OF FISH AND FISHERIES. 



As everywhere civilized man disturbs the bahiuce of nature, and be- 

 comes the great enemy to all forms of life that do not conform to his 

 artificial methods for their protection. Kot only by the hundreds of 

 artifices for the capture of the white-fish, but in the foul drainage from 

 the cities, smelting-works, and manufactories, and in the quantities of 

 sawdust from the mills, they are driven from their favorite haunts and 

 spawning-grounds, and their food destroyed by waters tainted with fatal 

 chemical combinations. 



The white-fish, as far as my observations have extended, is infested 

 with two external and two intestitial parasites. The external ones are 

 a crustacean, a Lcrnea., and an annelid, the Icthyohdella punctata. The 

 Lernean was found only in the Detroit lliver, adhering to the fish on the 

 dorsal region, and with its bell-shaped sucker buried in the epi- 

 dermal sheath of the scales. On the white-fish swimmiiig in schools 

 near the surface around the edge of the pond in Detroit Kiver, it could 

 be detected by close examination lastened to the fish. There were sel- 

 dom more than four on one fish. The lake-herring, confined in the same 

 pond, swam in close contact with the white-fish, but in ho instance, 

 although careful observations were.made repeatedly of the herring while 

 in the water and after capture, was the Lernean found upon them. In 

 Lake Superior they are found to be numerous on the siscowet. 



The Icthyobdellan, a leech of three-fourths of an inch long, grayish 

 white in color, with brown tesselated markings, was seen in great 

 numbers in the month of April, while the fishermen were lifting their 

 nets from about fifty fathoms some fifteen miles out from Kenosha, 

 Wis. 



They covered the nets and fishes of all species, and fell in such 

 numbers on the deck that it became slippery, and an old coat was 

 thrown down for the man who was lifting the gang to stand upon. 



They were very tenacious of life, living for a long time on the deck, 

 and for several days in the bilge-water of the fish-boats. 



They were in such numbers that it was difficult to decide whether 

 they had a preference for any species, and were found filled with blood 

 both in the gills and while attached to the body, though it was difficult 

 to imagine that they could fill themselves with blood from the epider- 

 mal sheath of the scales. They were thought to be most numerous on 

 the white-fishes, as they were in greater numbers on tlieni than on the 

 trout, the lawyer, or the cisco, the only other fishes taken. 



A prevailing but mistaken opinion in the vicinity was that the white- 

 fish fed upon the leech. Dr. Hoj^'s investigations disproved the notion, 

 and all examinations of stomach-contents confirmed this fact. One of 

 the intestinal parasites resembled the leech somewhat in formv The 

 otherwas an Echinorliymlius. They were never found within thestomach, 

 but always in the duodenal portion of the intestine near the mouths of 

 the ciBcal tubes. 



