most of the experimentation was done with 

 \- stick charges. In the relatively shallow 

 water depths tested, it was found that 

 much of the energy of a full-stick charge 

 was lost in creating a large water geyser 

 and produced but little increase in the 

 lethal range of the pressure wave (fig. 3). 

 At depths of less than 3 feet a y~ stick 

 charge was also excessive as evidenced 

 by the large geyser produced. Experi- 

 ments conducted at depths of 4 and 6 

 feet indicated that increasing the charge 

 from one-half stick to one full stick re- 

 sulted in roughly a 15 percent increase 

 in the killing range. 



Figure 3.--An explosion of lj sticks of dynamite in 6 feet of 

 water. 



Effect of reflectors and deflectors 



Sandbags filled with gravel and sand 

 were used in these experiments to deter- 

 mine the possible effect on the pressure 

 wage of a rock or irregular bottom contour 

 as might be encountered in tag recovery 

 work. 



At the 4-foot depth, as previously 

 shown, a -|-stick charge had a lethal 

 range of 13 feet. A sandbag placed 1 foot 

 from the charge directly between the 

 charge and the fish reduced the range in 

 that direction to the extent that a fish 



11 feet away was unharmed. A 6-inch 

 hole was blown in the burlap material of 

 the sandbag. No other depths or distances 

 were tested with this arrangement. 



In another experiment a platform 

 made from concrete reinforcing rods and 

 wire screen was used to support a sandbag 



12 inches directly above the charge; the 

 purpose being to direct the pressure wave 

 in a horizontal direction and increase its 

 lethal range. A fish placed at a distance 

 of 17 feet from the charge in 4 feet of 

 water was unharmed by the blast. The 

 sandbag was blown apart and the supporting 

 stand was tipped over, indicating that the 

 reflective qualities of this setup were poor 

 since much energy was absorbed in lifting 

 and tearing the sandbag. This experiment 

 was terminated since no materials were 

 available for construction of a suitable 

 reflector. 



FISH RECOVERY WITH DYNAMITE 

 AT COUNTING TOWER SITE 



After the initial experiments were 

 completed an electric blasting circuit 

 was installed at counting tower No. 2 

 on the left bank of the main Kvichak River. 

 Preliminary observations of the salmon 

 migration paths during peak and slack 

 periods were used to establish the correct 

 placement of charges. The migration past 

 tower No. 2 occurred over a width of 40 

 feet and in depths ranging from 3 to 6 

 feet. This area was adequately covered by 

 3 one -half stick charges placed at 10 -foot 

 intervals. The charges, as shown in figure 

 4, were placed about 10 feet upstream 

 from the counting panels In order to be 

 visible under the smooth water behind 

 the ripple -dampener. This distance was 

 found to be important since it allowed 

 the observer time to make a more positive 

 identification of a tagged salmon while it 

 crossed the panels. 



The circuit wires were run up to the 

 tower platform and connected to either a 

 4-volt dry-cell battery or a plunger-type 

 detonator. The battery, when connected 

 into the circuit by a knife switch, was 

 found to be the best method for detonating 

 the charges since it is both easy to operate 

 and safe against accidental discharge. The 

 detonator was an excellent source of 

 current but its operation required more 

 attention by the operator. 



