246 EEPOET OF COMMISSIONER OF FISH AND FISHERIES. 



July the mean temperature of the water at the bottom was only a frac 

 tion of a degree lower than the air, the figures being, air, G60.37 ; bottom, 

 650,39*; surface, 72°.45, In x4Lugust the bottom temperature is higher 

 than that of the air, the means being, air, 67°.01 ; bottom, G90.48 ; surface, 

 730.04. Owing to a misunderstanding the observations were omitted 

 during the first half of September, and after that they were only made 

 once a day on the water., . The mean was now only 59° at the bottom, 

 620.92 at the surface. The last of October the daily observation showed 

 450. 



On some days in August the bottom temperature was at midday as 

 high as 740. Yet the salmon did not appear to suffer in the least. Dur- 

 ing the hottest weather a dead one was rarely found, and their coudi' 

 tion in the fall was unexpectedly fine. 



Observations made on the temperature of several small rivers in the 

 State in August and the early part of September exhibit averages quite 

 as high as those in the pond,* and I think it altogether probable that in 

 the pools where, in a state of nature, they lie during the summer, thej" 

 are, in this State, often subjected to a temi)erature of above 70° F., and 

 always without injury. 



Of the salmon turned into the pond, none were found dead until the 

 12th of June. On the loth fifteen salmon were found dead in a net 

 that had been hung on the inside of the brush hedge to make it doubly 

 secure. It was a common menhaden net, hung on loosely with the ex- 

 pectation that the salmon would see and avoid it. But the fish exhib- 

 ited remarkable dimness of vision, and probably became entangled in 

 the net before seeing it. It was therefore removed, and, the brush 

 not proving an efficient barrier, the salmon passed out into the main 

 pond in large numbers. The hedge being then useless, it was taken up. 

 The deaths among the salmon continued, and during June counted, 

 from all causes, fiity-six. Thirty three died during July, all before the 

 23d day. In August there were only three deaths, and in September 

 none. As the water was warmest in August, and lowest in September, 

 I think the mortality among the salmon was not owing either to excess- 

 ive heat or stagnation in the water, nor yet to any incapacity of the 

 water to sustain the life of fish so lately from the sea, but whollj' to the 

 mechanical injuries received. 



A good many of the salmon, after being placed in the pond, exhibited 

 strong symptoms of uneasiness, swimming slowly to and fro along the 

 shores, as if searching for a way of escape. Occasionally they swam about 

 in compact schools, of perhaps ten to thirty each, near the surface, often 

 with the tail or dorsal fin projecting. Others were continifally leaping into 

 the air, now to the height of a foot only, and again six feet high, or higher. 

 While the hedge was standing a salmon was seen to jump clear over it 

 at a point where it was five feet and a half above the water. This salmon 

 jumped out of the enclosure, and it might be thought that the leap 



* See tables 3, 4, .5, and 6. 



