Document Type



Doctor of Philosophy


Biology, Environmental Studies

Date of Defense


Graduate Advisor

Godfrey R Bourne, PhD


Blake, John


Keevin, Thomas

Loiselle, Bette

Norris, F. Terry


The Middle Mississippi River’s (MMR’s) hydrology and sedimentation patterns have been altered. These activities contribute to loss of backwaters, islands, secondary channels, and reduced biodiversity. The Fish and Wildlife Service included reasonable and prudent alternatives (RPAs) in its Biological Opinion for the Operation and Maintenance of the Nine-Foot Channel Navigation Project. These RPAs mandate dike notching and island building to increase habitat diversity. My first goal was to examine changes in the number and relative location of islands from 1797 to 2003. I found that the total number of islands increased, the number of central islands decreased, and the number of border islands increased. The second goal was to explore island building to increase breeding habitat for the interior least tern (Sterna antillarum). I used UNET to determine island elevations required to allow continuous exposure for 50, 75, and 100 days during 15 May to 31 August. The model resulted in probability tables of overtopping events/successful exposure for the given elevation and time period along the river. The third goal was to investigate the ecological and biological significance to fish assemblages of created islands in a dike field, in relation to dike fields without islands. Species richness was greater at islands (67) than at reference sites (55). For habitat types, species richness was lowest at tips (48), but similar among inside (53), outside (56), and reference (55) locations. Catch per unit effort did not differ among sites or habitat types, but fish assemblages differed significantly among islands and reference sites for total standardized count and for adult standardized count. Fish communities differed significantly among each of the habitat types, with the exception of outside and reference habitat, for total standardized count; and among the habitat types, with the exception of tip and reference sites, for adult standardized count. Created islands increase local habitat diversity by creating shallow backwater-like habitats. Island areas support fish assemblages which are distinct from those found in conventional dike fields.

OCLC Number


Included in

Biology Commons