54 



HOST-PARASITE RELATIONS 



Bait fishes have been reported infected byseveral 

 kinds of parasites: 



Number of parasite species 

 reported from fishes 



Golden shiner — 14 



Common shiner 3 



Blunt-nosed minnow 9 



Pat-headed minnow 2 



Eastern silvery minnow 2 



Common white sucker 20 



Western mud minnow 4 



Most of these diseases and parasites willnot cause 

 loss, and only a few are characteristic enough for the 

 private hatcheryman to recognize. Those likely to cause 

 considerable loss are fungus disease, fin or tail rot, 

 and the black grub. 



CONTROL OF SPECIFIC DISEASES 



Fungus diseose. -Fungus disease of fish is usually 

 attributed to an organism called 5a/)ro/ e^^ina parasitica. 

 At the point of infection the fungus appears as a 

 greyish-white fuzz. This spreads rapidly over the 

 body surface, and the fish is sometimes almost com- 

 pletely enveloped before death occurs. It is a com.mon 

 disease of fish, especially inwarm waters or in tanks. 

 The focus of infection is usually traceable to some 

 injury which permits the entrance of the spores. This 

 disease is controlled in nature by certain bacteria 

 which are found in the mud and ooze of lake and pond 

 bottoms. Infected fish from tanks should be dipped for 

 5 minutes in a concentrated salt solution (p. 57 ). In 

 stubborn cases the treatment can be repeated several 

 days in succession. A lO-second dip in malachite green 

 1:15,000 (1/8 ounce in 15 gallons of water) is very 

 effective. 



Fm rot. — Pin rotmay be caused byseveral bacteria. 

 The disease is characterized by a progressive degenera- 

 tion of a fin or the tail of a fish until the entire 

 appendage is destroyed. The infection starts at the 

 free end of the fin. The diseased tissue is separated 

 from the uninvaded tissue by a white line. Control of 



