Fish Hatchery Management - fisheries & aquaculture

196 FISH HATCHERY MANAGEMENTFtcunn 67. Channel catfish trough for egg incubation. Paddles (arrow) gentlycirculate the water in the trough. (FWS photo.)should be larger than the pipe entering the jar to prevent venturi actionfrom sucking air bubbles into the jar.Hatching jars are designed to provide an upward flow of water introducedat the bottom of the jar. When rolling of the eggs is desired, as inthe case of some coolwater species, the bottom of the jar is concave, withthe water introduced at the center. when used for incubating trout or salmoneggs, the jar is modified with a screen-supPorted gravel bottom, andthe water is introduced underneath the gravel. This provides a uniform,upward water flow, and the eggs are stationary. These systems also havebeen used for striped bass and channel catfish egg incubation'Some fry will swim out of the jar and into the waste trough if a coverscreen is not provided. Coolwater species are allowed to swim from the jarsand are collected in holding tanks.MONTANA HATCHING BOXThe Montana Hatching Box operates essentially like a hatching jar. Thebox is constructed of waterproof plywood or fiberglass and is approximatelyI foot square by 2 feet high. A vertical water flow is provided by a