1977-1979 Assessment of Change in Commercial Size Limit of Channel CatfishChannel catfish harvest and population statistics were described for pools 9, 11, 13, and 18 in the Mississippi River to assess the effectiveness of changing the minimum commercial legal length from 13 inches to 15 inches. The change in minimum length was deemed necessary to prevent overexploitation and reduce fluctuating harvests. The project was terminated when legislation necessary to increase the minimum length of commercially harvested catfish was not enacted. A length limit increase was necessary if project objectives were to be attained. Channel catfish harvest by Iowa commercial fishermen totaled over 538,000 lbs in 1977 and 623,000 lbs in 1978. Eighty-five percent of the catch was marketed by 24% of the fishermen. Length and weight information was obtained from 5,624 channel catfish, of which 4,443 were commercially harvested and 1,181 were experimentally sampled. Age and growth statistics were compiled on 856 fish obtained from the commercial catch and 521 fish obtained from the experimental sample. Eighty-two percent of the commercial harvest was comprised of catfish ages 3-5 and about 12% of the harvest were illegal length fish. Ninety percent of the experimental catch was made up of 1-3 year old fish. Mortality estimates were 61% and 77% for the commercial and experimental samples, respectively. Trawling for 0-age channel catfish was successful, but seining proved unsuccessful, due primarily to small sample size and inconsistent catches.