Movement and habitat use by radio-tagged paddlefish in the upper Mississippi River and tributaries

摘要

We used radio telemetry to evaluate the movement and habitat use of paddlefish Polyodon spathula in the upper Mississippi River and two tributary rivers. Radio transmitters were surgically implanted into 71 paddlefish in Navigation Pools 5A and 8 of the upper Mississippi River, the Chippewa River, and the Wisconsin River during fall 1994 through fall 1996. Radiotagged paddlefish were located through summer 1997. The range of paddlefish movement was typically low during all seasons except spring, but some paddlefish moved throughout the 420-km extent of the study area. Paddlefish tagged in the Chippewa River were closely linked with the upper Mississippi River, as substantial portions of the population inhabited the adjacent Navigation Pool 4 each spring; paddlefish in the Wisconsin River, however, rarely ventured out of that tributary. The use of aquatic area types by paddlefish varied among the study reaches. A cartographic model of paddlefish habitat suitability was developed for Navigation Pool 8 based on geographic information systems (GIS) coverages of bathymetry and current velocity. The value of paddlefish habitat in the cartographic model increased with depth and decreased with current velocity. For example, areas modeled as excellent corresponded to regions classified as having both deep water (greater than or equal to6.0 m) and negligible (<5 cm/s) current velocities. Our study suggests that aquatic area types are an inadequate basis for making sound management decisions regarding the critical habitats of paddlefish in complex riverine systems because such strata rely on gross geomorpological features rather than on the physicochemical variables that fish use to choose habitats. The development of systemic GIS coverages of such variables could improve the understanding of fish habitat selection and management in the upper Mississippi River.