OPERATING THE HATCHERY 



Figure 25. — Floating turtle trap. Tur- 

 tles seeking a sunning spot are tipped 

 into the net or wire bag. 



should be treated with rotenone 

 before minnows are introduced and 

 whenever there is an indication 

 tliat predatory fish have become 

 established. 



The best procedure is to apply 

 1.5 to 3 pounds of 5-percent rote- 

 none powder to an acre- foot of 

 water, depending: on the hardness 

 of the water. Ponds with hard 

 water, very cold water, or contain- 

 ing bullheads require a heavier 

 dosage. Emulsifiable rotenone can 

 be used at the rate of 1 gallon for 

 each 3 acre-feet of water. The 

 emulsifiable rotenone can be ap- 

 plied as it comes from the can but 

 the powder must be mixed with 

 water to form a thin batter. The 

 poison is usually spread evenly 

 over the pond with a boat and out- 

 b o a r d motor. The rotenone is 

 poured over the edge of the boat 

 into the propeller wash at a steady 

 rate. The pond should be criss- 

 crossed in a good pattern with 



lines about 50 feet apart for good 

 distribution of the poison. 



SALAMANDERS 



The tiger salamander (fig. 26) 

 is abundant in many minnow 

 ponds and is often considered an 

 important predator of minnows. 

 Salamanders grow fast enough to 

 keep ahead of most minnows and 

 could be fish predators during the 

 entire period of pond life. Stud- 

 ies on Minnesota sucker ponds 

 show that the salamander is more 

 important as a competitor of the 

 sucker, than as a predator. The 

 stomach contents of 133 salaman- 

 ders of all sizes from 8 sucker 

 ponds was only 2.3 percent min- 

 n o w s . Copepods and cladocera 

 which are important sucker foods 

 made up 29.6 percent of the total 

 food of the salamander. Corixid 

 water bugs which are little used by 

 suckers made up 28.9 percent of 

 the salamander diet. 



Figure 26. — The tiger salamander is 

 abundant in many streams and is 

 considered an important predator of 

 bait fishes. (Photograph courtesy of 

 the Minnesota Department of Conser- 

 vation.) 



64 



