Effect of strain on tolerance of low dissolved oxygen of channel X blue catfish hybrids

Four groups of female channel catfish (Ictalurus punctatus) x male blue catfish (I. furcatus) hybrids were compared for tolerance of critically low dissolved oxygen, 0.6 ppm. Genotype-environment interactions (P < 0.05) occurred based upon temperature. No differences (P < 0.05) in tolerance were observed at 26 °C. However, based on their larger size, hybrids sired by Rio Grande (Texas) strain blue catfish had better low dissolved oxygen tolerance than hybrids sired by Alabama strains of blue catfish. No dam effects were observed. Hybrids sired by Alabama strains had superior tolerance of low oxygen tolerance at lower temperatures, 17 °C and 9 °C. Hybrids of equal size that were intolerant in the pond experiments were tested the following day in tanks and differences among the genetic groups were found at different temperatures, indicating additional genotype-environment interactions. Geographic origin of paternal blue catfish appears to affect low dissolved oxygen tolerance of channel-blue hybrids reflecting the thermal regimes in those localities of origin.