Seasonal Occurrence of Paddlefish Following Habitat Rehabilitation in Polander Lake, Upper Mississippi River Pool 5A

The seasonal occurrence of paddlefish (Polyodon spathula) in Polander Lake (MN), a 486-ha impoundment in the lower reach of Upper Mississippi River Navigation Pool 5A, was evaluated before (1995-96) and after (2002) construction of an island complex here (2000) that was intended primarily to improve local conditions for rooted aquatic plant growth.  Results of pre-construction netting surveys suggested: (1) the proposed site of the island complex was unlikely to adversely impact seasonal use of the lake by paddlefish; and (2) the removal of sediments from certain lakebed sites for use in island construction could enhance deep-water habitats preferred by this state-listed species.  Results of post-construction netting surveys found: (1) a marked decline in spring and summer occurrences of paddlefish at a former deep-water site that recently aggraded; and (2) a sharp increase in the summer occurrences of paddlefish at a former shallow-water site dredged to supply fill for island construction.  These findings can help guide the planning and design of future habitat rehabilitation projects that may seek to protect or create paddlefish habitats in other portions of the Upper Mississippi River System.