On the basis of the fertilizing and hatching success of naturally
spawned channel catfish at various levels of calcium hardness,
Tucker and Steeby (1993) recommended a minimum of
10 mg/L of calcium hardness for hatching catfish eggs. Recommendations
for other aquaculture species are presented in
Table 1. We hypothesize that the calcium hardness needs of
strip-spawned channel catfish eggs may be higher than those
of the eggs obtained from natural spawning. Strip-spawned
channel catfish eggs are often of a lower egg quality than
naturally pond-spawned channel catfish eggs because of the
hormone treatment, handling stress, younger age of eggs, variations
in maturing stages, and possible mechanical damage suffered
during the stripping process. Poor water hardening is also
known to often reduce egg turgor, increasing the susceptibility
of the egg/embryo to mechanical injury and decreasing survival
(Ketola et al. 1988). Egg-handling procedures such as transportation
to the incubation facility, placement into incubators,
enumeration, and disinfection cause mechanical shocks that lead
to substantial egg mortalities (Krise 2001). All these factors
have prompted us to examine calcium requirements of hybrid
embryos during hatching