Abstract: Incubation apparatus for use in hatching salmonid eggs in the production of the intermediate stage alevins and the ultimate fish fry is provided. Incubation trays are stacked in a container to which hatchery water is supplied and from which it departs, in the interval passing through the trays and their contents of substrate material and the eggs and/or alevins. The trays are designed to create desirable currents in water flow to facilitate dissipation of gaseous bubbles and, when the time comes, to urge and direct the outward movement of the fry.

Abstract: A rectangular rearing tank is provided with an underflow outlet conduit extending to beneath a tank corner where it couples to a smooth-curved transitional conduit section forming a bottom part of a weir chamber through which both underflow and overflow effluent from the tank may be passed in a stress-relieving manner that avoids injury or death to fry and fingerlings.