Grass Carp Larvae in the Lower Missouri River and Its Tributaries

Abstract

Abstract We surveyed the lower Missouri River over its entire length in Missouri and 23 tributaries for larval grass carp Ctenopharyngodon idella in 1987 and 1988. Grass carp larvae appeared as early as 23 May and as late as 15 July in 1987. We captured larvae in four tributaries and at three Missouri River stations, all in central Missouri; densities ranged from 0.9 to 67.3 larvae/100 m3. Larvae ranged in total length from 6.1 to 7.9 mm, and there was no relationship between fish length and date of capture. Larval grass carp occurred at three stations, 8, 4, and 2 km from the mouth, on each of two intensively sampled tributaries, Moreau River and Aux Vasse Creek. The greatest densities occurred at the most downstream station in each stream. Whether these larvae were produced in the Missouri River or in the tributaries is not certain; however, their presence at stations 8 km from the mouth in these tributaries suggests that grass carp may be capable of spawning in smaller streams than previously reported....