Production Of Hybrid Catfish

SRAC Publication No. 190

July 1998

PR

VI

Production of Hybrid Catfish
Michael Masser and Rex Dunham*

The mating or crossing of two different species is a process called hybridization,with the offspring known as hybrids. Probably the best recognized animal hybrid is the mule,which is a cross between a female horse and a male donkey. Hybrids can have some characteristics of bothparents. Breeding hybrids with selected or favored characteristics of each parent is one of the goals of animal husbandry. When a hybrid has characteristics superior to both parents it is said to have hybrid vigor or positive heterosis which, of course, is the ultimate breeding goal. Hybrids between different species of North American catfish (ictalurids) have been researched for more than 30 years.Of all these interspecific catfish hybrids (crosses between two distinct species) only one hybrid has characteristics that would favor commercial application. That hybrid is the channel catfish (Ictalurus punctatus) x blue catfish (I. furcatus) hybrid (denoted as the CxB hybrid). More specifically, it is the hybrid produced by crossing the female channel catfish with the male blue catfish. It isimportant
*Extension Fisheries Specialist, The Texas A&M University System; and Professor, Auburn University, Alabama.

to note that the reciprocal cross, crossing the male channel catfish with the female blue catfish, does not have the same superior production characteristics of the CxB hybrid. Research on CxB hybrids has demonstrated that they exhibit many commercially desirablecharacteristics. Compared to most commercially cultured strains of channel catfish, the CxB hybrid exhibits superior characteristics for the following traits: s faster growth; s better feed conversion; s tolerance of low oxygen; s increased resistance to many diseases; s tolerance to crowded growth conditions in ponds; s uniformity in size and shape; s higher dressout percentages; s increased harvestability byseining; and s increased vulnerability to angling. The simultaneous improvement of so many traits in a single line of catfish has not been possible through traditional genetic improvement programs, and there are no other examples of a single mating that has produced

improvement in so many commercially important traits. The problem with commercializing CxB hybrids has been the inconsistency ofseed production. The gametes (sperm and eggs) are compatible but the two species seldom mate with one another because of behavioral incompatibility, preferences in spawning environments, or some other factor(s). However, recent advances in artificial spawning and fertilization techniques have resulted in improved seed production. Another important development has been the use of different strainsof channel catfish and blue catfish to make the hybrid. The crossing of different parental strains has produced genotypically distinct CxB hybrids with even more superior production characteristics. A genotype refers to the actual genes or genetic makeup that produces a trait. Genotype-environment interactions The genotype-environment interaction is defined as the way the value of a genotypechanges relative to other genotypes when the environment changes. In other words, the best genetic type for one set of environmental conditions may not be the best genetic

type for another set of environmental conditions, or the advantage of the particular genotype may increase or decrease in a second environment. In general, the genetic advantage of the CxB hybrid relative to channel catfish orblue catfish can increase or decrease depending on the environment in which they are grown. Appearance of hybrid The channel catfish has a gentle slope from the tip of the snout to the base of the dorsal fin/spine and is spotted. It has high-set eyes; long, thick lateral barbels (whiskers); and a rounded anal fin with 24 to 26 fin rays. The blue catfish has a steep slope from the tip of the snout...