Degree Type


Date of Award


Degree Name

Master of Science


Fisheries Biology


Iowa has more than 30,400 km of fishable streams (Harlan et al. 1987). A 1994 survey oflowa anglers indicated that 26% of the 364,246 licensed anglers preferred to fish inland streams (Lutz et al. 1995) and of the several species of gamefish, the walleye (Stizostedion vitreum) was one of the more popular. Because natural recruitment of walleye is limited or non-existent in most Iowa rivers, populations are maintained by stocking. Walleye were stocked in Iowa waters as early as the 1870s by the Iowa Conservation Commission (now the Department of Natural Resources) (Gengerke et al. 1991). In 1951, fry stocking was expanded to include some of the major rivers (Cleary and Mayhew 1961 ).

Low survival of stocked fry and lack of natural recruitment has been documented in the Cedar, Shell Rock, and Wapsipinicon Rivers (Cleary and Mayhew 1961 , Degan 1978, Kingery 1991 ). However survival of stocked fingerlings in these rivers have made significant contributions to river populations (Kingery 1991, Siegwarth 1996).

The factors contributing to poor survival of stocked larval walleye and limited natural recruitment of walleye in Iowa's interior rivers are not certain. Early mortality of larval walleye in riverine environments has been attributed to lack of food, excessive suspended solid levels, fluctuation in water levels, lack of spawning substrate, fluctuation in water temperature during egg development and first feeding, excessive river discharge in spring, and predation (Cleary and Mayhew 1961 , Priegel 1970, Russell 1973, Busch et al. 1975, Koonce et al. 1977, Corbett and Powles 1986, Paragamian 1987, Fielder 1992, Heidinger and Kohler 1992. Jude 1992, Mion et al. 1998). Mortality attributable to these factors ultimately govern strength of a year class (Colby et al. 1979).


Copyright Owner

Louise Marie Mauldin



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