THE EFFECTS OF POLLUTED WATERS ON FISH LIFE 



11 



'SESSIONAL PAPER No. 22a 



days afterwards it had a kink in its tail. This experiment showed that unit mass of 

 fish had lived in unit volume of aerated water for 130 minutes. 



In another experiment of a similar kind a small rock bass lived for 74 hours in 

 700 c. c. of aerated water. 



RATE OF RESPIRATION. 



A few observations were made upon the rate of respiration in fish confined in an 

 aquarium. Four rock bass breathed at the rate of 44, 48, 52, and 56 per minute in 

 water at 22°C, Rate of respirat'on here means the rate at which the gill covers were 

 raised and lowered. When the water was cooled down to 5°C. the rate in one of these 

 animals fell to 16 per minute, and when warmed to 32°C, the rate increased to 112 per 

 minute. 



Warm water (32°C.) had another peculiar effect on rock bass. It caused the pig- 

 ment cells of the skin to spr ad out and give a decidedly darker hue to the whole fish. 

 This became particularly marked when the animal was returned to the aquarium where 

 it could be compared with the other fish. I had often observed that sunlight and dark- 

 ness produced a similar effect upon the chromatophores of fish embryos, but I had 

 never observed this marked effect of warm water. 



Muscular exertion also increased the rate of respiration. 



EXPERIMENTS WITH SAWDUST. 



About two miles up James' brook, from where it empties into Chamcook harbor, 

 near St. Andrews, N.B., was the site chosen for this experiment. The water was clear 

 and cool, and runs over a gravelly and stony bottom — a typical trout stream containing 

 a fair number of Salvelinus fontinalis. Primitive forest or second growth elder, balsam, 

 cedar and various kinds of hardwood covers the district through which the stream 

 runs. 



A box 3 feet long, 2 feet wide, and 14 inches deep, lined with zinc, was used as a tank 

 in which to confine the sawdust and the living fish. The box was covered with mosquito 

 nettin,^ and over this wire gauze. A pailful of old, that is water-soaked, sawdust and 

 about a quart of fresh sawdust was placed in the tank. A trough 12 feet long conveyed 

 water from a dam on the stream down to the tank. The tank itself was immersed in a 

 small pool, the water in which came up the sides of the vessel to within three inches of 

 the top. The temperature of the water in this pool was 17-3°C. in the sun, and 16-9°C. 

 in the shade. 



An hour's fishing in the brook furnished four speckled trout and a post- 

 larval eel for the experiment. Two of the trout had been badly injured in the eye by 

 the fish-hook. All five animals, along with a frog, were placed in the tank about 5.30 

 p.m. of July 6, and the water turned on. The flow was abundant and con- 

 tinuous, the descent from the dam being sufficient to stir up the saw-dust into a gruel- 

 like mixture as thick as in any mill stream no matter how much sawdust may have been 

 thrown into it. All the conditions were therefore, as much as possible like those pre- 

 vailing in a sawdust polluted stream. 



The tank was not visited until July 11, when all the animals were found active 

 and apparently healthy. The frog was lying at the bottom as he could get no air at 

 the top, on account of the cover. About half-a-pail more sawdust, some sand, and 

 gravel were added, and the tank again closed. 



On July 14 the tank was again visited. All four trout were alive, active and 

 apparently well. The eel escaped as the cover was removed. The frog was dead. 

 About a dozen earthworms were thrown into the tank, but the trout did not touch them 

 so long as they were under observation. More sawdust was added and the tank closed. 



On July 21, three-fourths of the water in the tank was emptied out, and the 

 tank containing the four trout was brought to the laboratory, St. Andrews, a distance 

 of about three miles in a wagon, and part of the journey over a very rough road. On 

 examination the four trout were found to be very active, so active indeed, that they 

 were only captured after emptying out nearly all the water. 



