EFFECTS OF DYNAMITE EXPLOSIONS ON FISH LIFE 



25 



SESSIONAL PAPER No. 22a 



placed under water and the swim bladder compressed. The smaller animals generally 

 floated; the larger ones sank. 



These results were, however, not satisfactory. In shallow water, explosions always 

 stirred up the mud, and our crude telescope was useless. We determined, therefore, to 

 make a tremendous ' slaughter of the innocents,' and with this end in view selected a 

 small bay, nearly west of Grassy island, and there, set off the largest blast of dynamite 

 which was used during the season — ^ten cartridges. The noise was loud enough to have 

 awakened the spectral inhabitants of the old French island. There was a tremendous 

 upheaval of water and mud, and in ten minutes wind and tide had spread the dirty 

 water all over the little bay. Twenty-eight dead came to the surface. On returning 

 next morning, we could find only three dead fish lying on the bottom, near where this 

 explosion had occurred; that is, less than ten per cent had sunk in this experiment; in 

 the previous one about thirty per cent. 



The next attempt that was made to throw fresh light on this important point was 

 in St. John harbour. New Brunswick. As a preliminary to the real test, a visit was 

 made to one of the salmon weirs at low water. In one compartment of the weir were 

 found two full-grown salmon, one 'fiddler' (small salmon), and ten or twelve adult 

 gaspereau. The time was noon of August 10th. That evening, of course, there was a full 

 tide, and next morning another, sa that there were these two chances for additional fish 

 to join their fellows in the weir. At 8.30 next morning, the weir was visited in com- 

 pany with the two fishermen who owned it, and one cartridge was exploded in the 

 compartment which we had previously examined. The two salmon at once floated to 

 the top, also six or eight gaspereau. But the deadly effect of the explosive was brought 

 out in another, and rather unexpected way. Almost simultaneously with the occur- 

 rence of the explosion, an immense number of young gaspereau leaped from the water, 

 and then fell back almost motionless upon the surface. They varied in size from 2^ 

 to 5 inches in length. They came partly from inside the weir, but chiefly outside the 

 inclosure, stretching away up towards the city. Evidently a school of these young fish 

 was making its way up into the harbour, or they were leaving it. We counted over 800 

 of them being driven away by the wind and tide, and estimated that as many of them 

 sank as floated; but this was, of course, mere guess-work. 



After rowing along the path of these floating fish for half an hour, we returned to 

 the weir, and awaited the falling of the tide. The tide in this harbour goes out so far 

 that the floors of many of the weirs are left almost dry. We had no difliculty, there- 

 fore, in determining the exact number of fish which sank. There they were, 2Y gas- 

 pereau varying from T to 12 inches in length, lying dead on the bottom; 7 others some- 

 what larger on the average were swimming around in the scanty water remaining in 

 the weir, and in company with these, 2 lively dog-fish which seemed to know perfectly 

 well that they were in a trap. Here were the results which we had been looking for — 

 8 or 10 killed and floating, 27 killed and sunk, and 9 alive. If the dynamite killed the 

 young gaspereau in the same proportions outside the weir, as inside, then 2,500 of them 

 lay dead at the bottom of the harbour in addition to the 800 which we had counted at 

 the surface. 



CAUSE OF FLOATING. 



Nearly all the fish floated belly up ; the sunfish lay more upon their side ; lake 

 trout on their back, but with the tail end deep in the water and head above it. Enp- 

 ture of the swim bladder and escape of its gas ventrally so as to displace the centre 

 of gravity, was probably the cause of the fish floating on their back. But a physio- 

 logist can scarcely escape the conviction that the nervous mechanism for the main- 

 tenance of equilibrium must have been paralyzed in all of them. Fish which die in 

 water from other causes than concussion, say, from suffocation or from poison, lose 

 their power of maintaining the vertical position, and in these cases they lie on their 

 back because of muscular (i.e., nervous) inability to balance themselves. 



