Date of this Version
The average size of Missouri River channel catfish has declined. The percentage 10 years old or older is 4.8% compared with an unexploited population in which 32% are 10 years and older. From 1944 through 1988 commercial harvest declined as much as 64%. Total mortality was 37% at age 4 and 79% at age 5. The increased mortality occurred as they reached 13 inches and became fully recruited to the commercial fishery. Harvest statistics are not wholly reliable because reports are not verifiable and commercial fishers do not return fish tags. Harvest exceeded a reasonable limit for maximum sustained yield. Commercial minimum-size limits have been ineffective due to their design and because they are not easily enforced. Commercial catfishing was closed in action taken by the Nebraska Game and Parks Commission in November 1990 to take effect 1 January 1992. Since then the mean size has increased from 286 mm total length (TL) to 324 mm TL in 25.4-mm mesh net samples from the channelized section of the Missouri River, and the percentage of fish longer than 330 mm TL increased from 8% in 1987 to 44% in 1993.