Dr. Gordon Goldsborough, Department of Biological Sciences, University of Manitoba

Abstract

Delta Marsh, on the south shore of Lake Manitoba in central Manitoba, Canada has become highly turbid over the past four decades. There has also been a near-total loss of submersed macrophytes and emergent plant islands from marsh bays, deteriorating water quality and more frequent phytoplankton blooms, and encroachment of hybrid cattails (Typha X glauca) into shallow inshore areas. These change are due, I believe, to the stabilization of lake water levels in 1961, increases in nutrient loading from the surrounding landscape, and invasion by Common Carp (Cyprinus carpio). A multi-stakeholder restoration project is underway, with the first step, exclusion of large carp, anticipated to begin in 2012. For the past two years (2009-2010), we have been monitoring the size demographics of Common Carp populations moving between Delta Marsh and Lake Manitoba. The purpose is to design barred screens to exclude carp while permitting passage by native species such as Walleye (Sander vitreus), Northern Pike (Esox lucius), and White Sucker (Catostomus commersoni). I will present data on fish passage through experimental screens of varying bar spacing (5 to 8 cm), along with information on the timing of fish movement and the size structure of the large fish community in the marsh. We are also monitoring water quality (turbidity, chemistry) and submersed macrophyte distribution as a baseline for evaluating the relative success of carp exclusion at increasing water clarity and permitting reestablishment of marsh vegetation.