Variations in abundance of young-of-the-year channel catfish in a navigation pool of the upper Mississippi River

Spatial and temporal variations in the abundance of young-of-the-year channel catfish Ictalurus punctatus were determined over 3 years based on 154 trawls taken from Navigation Pool 7 of the upper Mississippi River. No significant spatial patterns in abundance or length of fish in the catch were found in seven poolwide surveys of the main channel. However, high variation among replicates existed. Temporal patterns in abundance and length-frequency distributions varied among the study years. Seasonal catch curves were similar in 1984 and 1986, although offset due to earlier spawning in 1986. Spawning appeared to have been protracted in both years, based on analyses of back-calculated dates of spawn and length-frequency patterns of young. Sixty to seventy percent more young were produced in 1985, when spawning occurred over a shorter period of time and a more uniformly sized year class was produced.