CXXVIII REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



ture containing 10 per cent of the waste liquor. A young shad was 

 placed in a solution of 1 per cent strength of acid, which was increased 

 by 1 per cent additions until 10 per cent was reached. The first definite 

 results were obtained with strength of 7 to 8 ])er cent, and consisted 

 in slight distress, especially in progressive enfeeblement of muscular 

 action. At 10 per cent this was more marked, and after one to two 

 hours the fish died from suffocation, as evidenced by paroxysmal efforts 

 to escape and frequent choking gasps at the surface. One fish simi- 

 larly immersed, but removed to pure sea water at the first moment that 

 loss of equilibrium was observed, was easily revived. Young shad 

 were subsequently put directly in strong solutions ranging from 10 to 

 33J per cent of acid, which produced more sudden and acute effects. 



Dr. Gurley concludes from his experiments that fish can support for 

 a long period mixtures into which this refuse does not enter in a 

 greater proportion than 10 per cent; that in greater strengths, even up 

 to 25 per cent, the fish would often have time to make its escape before 

 being overwhelmed ; and that at about 33 per cent the point is reached 

 where the fish is overwhelmed at once, and his escape would usually 

 not be possible. 



In summing up the results. Prof. Evermann remarks that — 

 While it does not seem evident from these tests that the fishes of the Lower Susque- 

 hanna could he affected as seriously as has heen supposed, it should he home in 

 mind that while the contamination may not he great enough to kill fishes, it might 

 be sufficient to drive them from that part of the river where the mill is located. 

 They began using sulphurous acid at the mill about January 14, 1891. According 

 to the fishermen, the herring fishing began a few days earlier than usual in the 

 spring of 1891, and was fairly good until about April 30, when the fish suddenly dis- 

 appeared, this being several days earlier than they generally leave. At the same 

 time numerous such fish were seen upon the surface of the water at various places 

 below the mill. Whether these results were due to contamination from the mill 

 can not be certainly stated. 



DISEASES AND PARASITES OF FISHES. 



Dr. E. R. Gurley has continued his researches respecting the diseases 

 of fishes, a subject which constitutes one of the most important lines 

 of inquiry within the province of this division. While the success- 

 ful determination of the causes of mortality and especially of epidemics 

 among fishes in their wild state will be exceedingly interesting and 

 possibly productive of much good, it is the fish-culturist who will 

 appreciate most highly the solution of any one of the many peri^lexing 

 problems of this nature which are associated with his work. The 

 sudden appearance of some unknown disease or rapidly spreading 

 parasite, for which no remedy has been discovered, affecting breeding 

 stock, the eggs or embryos, or the young fishes held in temporary 

 confinement, is a matter of frequent occurrence, and too often results 

 in great destruction. Scarcely a year passes without receiving com- 

 plaints of serious losses from some such cause, the origin and, in fact, 

 the actual conditions of which have never been accounted for, 



