Fish Hatchery Management - fisheries & aquaculture

t4 FISH HATCHERY MANAGEMENTfish. Most of the desirable crustacean species will repopulate the pond intwo or three days.Most members of the aquatic insect groups Coleoptera (beetles) andHemiptera (b"gs) prey on other insects and small fish. In some cases,members of the order Odonata (dragonflies) cause similar problems. Mostof these insects breath air, and can be controlled by applying a mixture ofone quart motor oil and two to four gallons diesel fuel per surface acreover the pond. As insects surface, their breathing apertures become cloggedwith oil and they may get caught in the surface film. The treatment isharmless to fish but supplemental feeding should be discontinued until thefilm has dissipated. Nonsurfacing insects can be killed by 0.25 part per millionmasoten.Large numbers of crayfish in rearing ponds may consume feed intendedfor the fish, inhibit feeding activity, cause increased turbidity, and interferewith seining, harvesting, and sorting of fish. Baytex is an effective control;0.1-0.25 part per million Baytex will kill most crayfish species in 48 hoursor less without harming the fish.Vertebrates that prey on fish may cause serious problems for the pondfishculturist. Birds, otters, alligators, and turtles, to name a few, are implicatedannually. Some can be shot, although killing of furbearing mammalsgenerally requires a special license or permit issued by the states. Fencescan keep out some potential predators, but nonlethal bird control (severalforms of scaring them a*ay) do not produce long-lasting results.Adult and immature frogs have long plagued the warmwater culturist.The adults are predaceous and may transmit fish diseases; the immaturefrogs consume feed intended for fish and must be removed by hand fromfish lots awaiting transport. Adults usually are controlled with firearms,whereas attempts to control the young are limited to physical removal ofegg masses from ponds or by treating individual masses with copper sulfateor pon's green. Although some laboratory success has been achieved withformalin, there still is no good chemical control available for frog tadpoles.RecordkeepingFactors to be ConsideredRecordkeeping, in any business or organization, is an integral part of thesystem. It is the means by which we measure and balance the input andoutput, evaluate efficiency, and plan future operations.Listed below are factors that should be considered in efficient recordkeeping.These factors are particularly applicable to trout and salmonhatcheries, but many of them pertain to warmwater hatcheries as well.