Degree Name

Master of Science (MS)

Semester of Degree Completion

1998

Thesis Director

Robert U. "Bud" Fischer

Abstract

The major challenge to fisheries managers of the 21st century will be to maintain the diversity, not only of fishing opportunity, but also of traditionally non-game and economically unimportant species. With the relatively recent understanding of the importance of ecosystem level management, attention is being focused on native species that were often ignored or eradicated under past management practices. One such fish that has been largely ignored is the bowfin, Amia calva. Ecological data pertaining to bowfin natural history are limited and to date no attempt has been made to integrate bowfin into fisheries management decisions within the species native range. Therefore, I studied the natural history of the bowfin in hopes of determining the role bowfin can play in both the aquatic ecosystem and in fisheries management. A total of 38 bowfin were caught during the summer of 1997 in backwaters of the Illinois and Mississippi Rivers. Each fish was weighed (nearest gram), measured (nearest millimeter) and sexed. Measurements of depth, water temperature, pH, dissolved oxygen levels, secchi disc readings and substrate type were taken at each trap site. The fish were returned to the Illinois Natural History Survey lab where gular plates and stomachs were removed for aging and determination of food habits. The mean lengths and weights for males were 586.3 mm and 1728.1 g and for females were 622.8 mm and 2303.8 g. The averages for habitat parameters were as follows: depth (0.6 m), temperature (22.8 C), pH (8.06), D.O (8.6), secchi disc (22.6 cm). Silt was the substrate type at all sampling locations. Average growth rates for the first six years of life were 324.4 mm, 114.4 mm, 69.4 mm, 46.8 mm, 49.6 mm and 32.9 mm. Crayfish were the most important food items based on the proportion of total weight of all prey items as well as by frequency of occurrence. Crappie, Pomoxis spp., were the most commonly consumed fish genus accounting for 26.5% of the total weight of food items. Aquatic systems incorporating multiple species management plans may benefit from the presence of the bowfin as a top piscivore. The bowfin's feeding habits coupled with its rapid growth rates and hardy nature may make it an ideal species for the control of stunted sunfish populations and for contributing to ecological stability in general.

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