Laserfiche WebLink
1954). Lower harvests reflected a decline in shovelnose sturgeon abundance <br />since the early 1900's (Pflieger 1975). <br />Today, mortality of pallid sturgeon occurs from both sport and commercial <br />fishing activities. In 1990, the head of a pallid sturgeon was found at a <br />sport -fish cleaning station in South Dakota, and in 1992 a pallid sturgeon was <br />found dead in a commercial fisherman's hoop net in Louisiana. <br />The States of North Dakota, South Dakota, and Louisiana require the release of <br />all sturgeon whether taken commercially or for sport. Neither Montana nor <br />Kansas allow commercial harvest of sturgeon. Sturgeon continue to be <br />harvested as a bycatch of commercial fishing operations in Nebraska, Iowa, <br />Missouri, Illinois, Kentucky, Tennessee, Arkansas, and Mississippi. <br />Pollution /Contaminants: Although more information is needed, pollution is a <br />likely threat to the species over much of its range. Pollution of the <br />Missouri River by organic wastes from towns, packing houses, and stockyards <br />was evident by the early 1900's and continued to increase as populations grew <br />and additional industries were established along the river (Whitley and <br />Campbell 1974). Due to the identified presence of a variety of pollutants, <br />numerous fish - harvest and consumption advisories have been issued over the <br />last decade or two from Kansas City, Missouri, to the mouth of the Mississippi <br />River. This represents about 45 percent of the pallid sturgeon's range. <br />Polychlorinated biphenyls (PCB's), cadmium, mercury, and selenium have been <br />detected at elevated concentrations in tissue of three pallid sturgeon <br />collected from the Missouri River in North Dakota and Nebraska. Detectable <br />concentrations of chlordane, DDE, DDT, and dieldrin also were found (Ruelle <br />and Keenlyne 1991). Abandoned landfills, mines, sewage treatment plants, and <br />industries have a high potential to contaminate pallid sturgeon habitats in <br />several States. Some of these sites are currently listed as Superfund sites <br />or are being studied by the Environmental Protection Agency for possible <br />listing under Superfund or Resource Conservation and Recovery Act. <br />The prolonged egg maturation cycle of the pallid sturgeon (Conte et al. 1988), <br />combined with an inclination for certain contaminants to be concentrated in <br />eggs (Ohlendorf et al. 1981; Eisler 1986), could make contaminants a likely <br />agent adversely affecting developing eggs, development of embryos, or survival <br />of fry, and thereby reduce reproductive success (Ruelle and Keenlyne 1991). <br />Further investigations are needed to identify sources of contaminants in the <br />Missouri and Mississippi Rivers and to assess the role of contaminants in the <br />decline of pallid sturgeon populations. <br />Hybridization: Carlson et al. (1985) studied morphological characteristics of <br />4,332 sturgeon from the Missouri and middle Mississippi Rivers. Out of this <br />group he identified 11 pallid sturgeon and 12 pallid / shovelnose hybrids. <br />Suspected hybrids recently have been observed in commercial fish catches on <br />the lower Missouri and the middle and lower Mississippi Rivers (K. Graham, <br />Missouri Department of Conservation, pers. comm. 1992; B. Reed, Louisiana <br />Dept. of Wildlife and Fisheries, pers. comm. 1992) Bailey and Cross (1954) <br />did not report hybrids, which may indicate that hybridization is a recent <br />14 <br />