AbstractChannel catfish Ictalurus punctatus obtained from two spawns were size‐graded into four weight groups: large, mean = 92.4 g ± 0.9 SE; medium = 64.2 ± 0.5; small = 36.1 ± 0.5; and communal = 49.0 ± 2.0 (a combination of large, medium, and small fish). Twelve indoor 643 L rearing units were stocked with the four size‐graded groups at initial densities (but different numbers of fish) of 3.12 g offish per L water and were fed for 66 d at 3% of biomass daily. At harvest the final densities (mean = 9.95 g/L) were equal in all rearing units. Survival and feed conversion were similar among the size‐groups. Initial Coefficients of variation for weight were significantly different among the size‐graded group as large < medium < small < communal. Final coefficients of variations were significantly greater than initial values in the large, medium, and small size‐graded group and were less in the communal group. Gain, survival, and coefficient of variation relationship within the communally stocked rearing units were similar to those for separately reared groups. Final coefficients of variation were greater (210, 204, and 115%) or less (89%) than initial values for large, medium, small, and communal groups, respectively, and indicate a repnrtitioning of variation, perhaps due to altered feeding behavior or social hierarchical order.
