Genotype-environment interactions for growth of blue, channel and hybrid catfish in ponds and cages at varying densities

Abstract

Channel catfish, Ictalurus punctatus; blue catfish, I. furcatus; and hybrid channel ♀×blue♂ catfish fry were grown in ponds at densities of 7410/ha–2 245 000/ha. Channel catfish fingerlings and hybrid fingerlings were grown in ponds at densities of 7410/ha–22 230/ha, or 7410/ha with the addition of 1000 or 2000 kg/ha of co-stocked larger fish and in cages at 275/m 3. Genotype-environment interactions for growth rate occurred ( P<0.05) between hybrid catfish and channel catfish fry and between blue catfish and channel catfish fry stocked at varying densities. Channel catfish fry grew faster ( P<0.05) than hybrid fry at low densities, but hybrid catfish fry grew faster than channel catfish fry at higher densities. The relative growth advantage of channel catfish fry over blue catfish fry increased with density. The increased growth rate of hybrid catfish fry compared to channel catfish fry at high densities was observed in both communal and separate experiments. Hybrid catfish fingerlings grew faster to market-size than channel catfish fingerlings at all densities in ponds. Their relative advantage to channel catfish increased with density and the addition of larger competing fish in the ponds. The hybrid was also superior to channel catfish in both communal and separate high density experiments when grown from fingerlings to marketsize. Genotype-environment interactions occurred for growth rates in cages or ponds. Hybrid catfish grew faster ( P<0.01) than channel catfish in ponds, but slower ( P<0.01) than channel catfish in cages.