A vertical-lift incubator (the "seesaw") designed for channel catfish egg masses.

Abstract Egg masses of channel catfish Ictalurus punctatus are typically incubated in mesh baskets suspended in metal troughs with rotating paddles fitted between the baskets that move the water to agitate the eggs. This system is widely used, but stress caused by low dissolved oxygen resulting from poor water circulation through the egg masses at higher egg loading rates can cause reduced hatch. We designed and tested a vertical-lift incubator to improve hatch with higher egg loading rates. Angle-aluminum racks were placed inside standard hatchery troughs. Three baskets with hinged lids were placed in each rack and the egg masses were placed in the baskets. The racks in a pair of troughs were connected to overhead bars that oscillated at six cycles per minute, raising the rack in one while lowering the rack in the adjacent trough. Egg masses were incubated at a mean ± SE loading rate of 33.4 ± 4.7 lb per trough, which is nearly twice the recommended rate, with no supplemental oxygen. Survival from egg th...