The alternate host, Dero digitata , is controllable by stocking a fish species with a benthic predatory feeding habit and size less than 0.25 lb. Using carp as a model fish in earthen ponds, aquatic oligochaetes, including D. digitata, were reduced in numbers as long as carp of a small size were stocked at 50 or 100 per acre. However, when carp exceeded 0.25 lb, predation of aquatic oligochaete worms was less effective over the 6 week trial periods. Introduction Proliferative gill disease is an important disease of channel catfish involving destruction of the gill lamellae and reduction of respiratory ability leading to catfish death. The parasite involved is a myxosporean protozoan, Aurantiactinomyxon ictaluri n.sp.
Catfish death becomes more acute when pond water dissolved oxygen concentrations are low.
Because the disease can be non-fatal, a far greater number of catfish may be infected by the parasite and suffer reduced growth due to the stress related to the tissue inflammatory response and reduced ability to absorb oxygen across the gill surface. Previous tests in our laboratory showed that chemical treatments were unsuccessful or would be harmful to the catfish or environment. Preliminary to earthen pond trials, several fish species were screened for their effective predation of D. digitata . Practical stocking densities for carp would not exceed 100 carp per acre in companion culture with channel catfish. Preliminary trials in 6 ft diameter pools showed that 1,500 carp per acre could almost eliminate the D. digitata population.