Be especially careful to avoid any sources having a history
of channel catfish virus disease, since this pathogen is un-
treatable and can spread quickly and destroy an entire
stock. Inbred strains are less desirable than genetically-
superior crossbred strains. Healthy brooders should be
full-bodied and free of sores or hemorrhages on the skin.
Thin or emaciated fish may be old, diseased, or underfed.
 Catfish farmers generally prefer brooders in the 2-10
 pound range; smaller females do not produce as many
 eggs as larger ones, and bigger fish may be difficult to
 handle. Channel catfish reach optimal breeding condi-
 tion in three to four years, when 40-50% of the fish may
 be expected to spawn under good conditions. Scientists
 are currently attempting to breed strains that will mature
 earlier. Proper nutrition of mature fish throughout the
 year is essential to ensure successful spawning, because
 the number and size of eggs produced by a female is
 strongly influenced by diet.
 It is important to select the proper ratio of male and
female brooders. A ratio of two or three females for each
male is ideal. One male can mate with two or more
females in a single spawning season if the eggs are moved
to a hatchery or incubation chamber. Although catfish
normally produce offspring in a 1:1 sex ratio, do not take
this for granted when buying brooders. Males grow faster
than females, so when fish reach 2-3 pounds, up to 80%
of the largest individuals in the population may be males.
It is advisable to determine the sex of each brooder you
buy to ensure a proper ratio of males and females.

Determining Sex
 Both primary and secondary sex characteristics are
useful in distinguishing males and females. Primary sex
characteristics are those features specifically involved in
reproduction, whereas secondary sex characteristics are
not directly involved in spawning. The primary
characteristic used to distinguish the sexes is the urogenital
opening; the secondary characteristics relate to coloration
and body shape.


Male (left), female (right).


Male (right), female (left).

 Secondary characteristics are most prominent during
 the spawning season. Males are usually larger and have
 broader heads than females of the same age. As the
 spawning season approaches, males become lean, develop
 large muscular heads that are wider than their bodies, and
 sometimes become darker, especially on the lower jaw.
 Females' heads are narrower than their bodies when
 viewed from above. They also develop soft, greatly
 distended bellies as the spawning season approaches.
 Preliminary identification of sex should be confirmed
 by examining the urogenital opening. This is particularly
 important with young fish and during the fall or winter
 when secondary sex traits are less pronounced. With prac-
 tice, one can reliably use the following method to deter-
 mine the sex of fish as small as one pound:
 The fish should be turned upside down for examina-
 tion of the genital area, which can be seen as a fleshy area
 about midway between the pelvic and anal fins. Two
 openings should be visible when examined closely: the one
 nearest the head is the anus, and the one nearest the tail
 is the genital pore. In males the genital pore terminates
 on a fleshy, nipple-like structure (the genital papilla),
 which usually becomes swollen and somewhat rigid as
 spawning season nears. The genital area of females is oval
 and flat, with the anus separated from two other open-
 ings by a small flap of skin. The slit or groove toward
 the tail end contains a urinary pore and the genital pore.
 Immediately prior to and during the spawning season,
 the entire genital area of the female becomes red, swollen,
 and may be covered with a thin layer of mucus.
 A probe is useful in determining the sex, especially in
 young or nonbreeding fish. Immobilize the fish by
 holding it belly upward with one hand grasping the head
 and the other hand firmly holding the tail region. With
the fish's head below your chest and the tail held away
from your body, arch the fish's belly upward. This will
allow the male genital papilla or the female slit to become
more visible. Then have an assistant carefully and gently