AN EVALUATION OF SAMPLING TECHNIQUES AND LIFE HISTORY INFORMATION ON BIGUEAD CARP IN THE MISSOURI RIVER, BELOW GAVlNS POINT DAM, SOUTH DAKOTA AND NEBRASKA

Bighead carp Hypopthmichtys nobilis were introduced into the United States from south and central China (Robins et al. 1991) in 1972 (Henderson 1979). It is an efficient planktivore (Henderson 1978) that was imported into Arkansas by an aquaculturist to improve water quality in catfish ponds (Henderson 1976). In 1974, the Arkansas Game and Fish Commission began looking at potential impacts of bighead and other Asian carp as well as their beneficial effects on the environment. Regulations were also imposed to prevent these fish from entering public waters from private sources (Henderson 1975). In 1981, nevertheless, the first bighead carp was found by a commercial fisherman from the Ohio River below Smithland Dam at Mile Marker 919 (Freeze and Henderson 1982). Currently, Fuller et al. (1999) report that bighead carp are present in 19 states; however, specimens have been captured as far north as Gavins Point Dam on the Missouri River, South Dakota (Figure 1). Life History. Bighead carp can weigh 18-23 kg (40-50 lbs) by their fourth year (Henderson 1978) (Figure 2) and have been documented as large as 40 kg (90 lbs) in their native range (Pflieger 1997). Henderson (1979) noted it can vary with climate and enviromental conditions. Spawning is limited to free-flowing streams (Henderson 1979). Bighead carp migrate upstream to spawning grounds (Jennings 1988) which are characterized by rapid currents with a mixing of water, such as at a confluence of rivers or behind sandbars, stonebeds, or islands (Huet 1970)