{Trematodes {Black,Yellow, or White Grub}
Monogenetic trematodes complete their life cycle on fish without involving
other animal hosts. Large numbers may occur on the fish externally,usually
on the gills,and may cause anemia,secondary infections,and irritation which
may be exhibited by rubbing orflashing swimming movements. Common types of monogenetic trematodes include Gyrodactylus,Dactylogyrus,and
Cleidodiscus.They can be controled in ponds with formalin AT 25MG/1.
The host are in snails and fish eating birds ,other than fish and require them to complete their life cycle.The larval stages,commonly known as black,yellow,or white grubs,of certain digenetic flukes may encyst under the
skin and over the entire body of the fish.Severely infected fish may be covered with black or yellow spots. These parasites normally do not kill the fish, but may reduce the growth rate if heavily infested.Proper cleaning and cooking will render the parasite harmless to man. There is no control except
to get rid of the snails and birds. Hope this helps you understand. This info came from the Management Guide for Ponds and Lakes in Ky. Ray
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