XLii Kin'OHT OF COMMiSSiONEli OF FISTt AND FiSTTEt?IKS. 



N. Clark was instiucted to visit as many of the stations on Lake Erie 

 as possible, and to report the results of liis iu(]uiry. 



The total number of young fish deposited by the U. S. Fish Commis- 

 sion, and the Ohio and Michigan fish commissions, amounted, from 

 the spring of 1875 to the spring of 1882, to about 82,000,000; half of 

 which were planted in 1881 and 1882, and would not enter into the 

 number of fish taken. 



Mr. Clark found it very difficult to come to any precise conclusion as 

 to the ratio of abundance now and in earlier years, as the constant in- 

 crease from year to year in the number of nets tends to make up for 

 the diminished proportion of capture by each net. As the general re- 

 sult of the inquiry, Mr. Clark is decidedly of opinion that not only has 

 the decrease been arrested, but that there has been a tangible and 

 satisfactory increase, taking all conditions into consideration. 



It is now proposed to collect systematically the statistics of the fish- 

 eries of the Great Lakes in 1885, and to show, by comparison with cor- 

 responding figures made by the census of 1880, more accurately what 

 the change has been, whether for the better or the worse. 



17. — MOJiTALlTY OF FISH. 



The occurrence of extended mortality among the fish, both of the 

 fresh waters and of the sea, has been a subject of much interest, and 

 the attention of the Commission has been specially attracted to the 

 determination at least of the causes, even though they be so general 

 in their action as to be api)arently incai)able of cure. 



Several accounts have been given of the occurrence, at short intervals, 

 of fish pestilences in the Gulf of Mexico, where for weeks at a time, in 

 particular regions, the surface will be found covered with dead or dying 

 fish of all kinds that inhabit the waters. Thousands of tons are esti- 

 mated to be thus destroyed. Nothing satisfactory has yet been indicated 

 as to the origin of this difficulty. The fish themselves do not appear to 

 be diseased in any way. A correspondent of the Commissicm, however, 

 has suggested that, owing to some unusual condition, the cold waters of 

 the deeper parts of the Gulf are brought near to the surface, where they 

 aft'ect these fish, the sudden chill producing such a shock as to cause 

 either death or temporary disturbance of health. The waters in which 

 these occurrences take place are said sometimes to be discolored as if 

 by the presence of microscopic forms of either animals or plants; and 

 it is not impossible that a careful search, prosecuted by an expert on the 

 sjjot, may solve the problem. 



Mr. Philo Dunning, of the Wisconsin fish commission, called the 

 attention of the U. S. Fish Commission to a fish pestilence in the 

 Madison lakes during the summer, the perch especially suffering. It 

 was thought that not less than 200 tons of dead fish came ashore, which 

 were buried by the selectmen for the sake of preventing a jjestilence. 

 Every year there is more or less of this trouble, though not ahvays re- 



