Agenda Packets - 1988/11/14 - Laserfiche WebLink

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Task _pisheries Analraia The composition of the existing fishery in the wetland will be determined through review of Minnesota DNR records and through further field sampling if necessary. It is our understanding that the Minnesota DNR presently stocks Wetland 893 on an annul] basis as a "put and take fishery." Minimal overwinter survival of stocked fish occurs. Aside from stocked fish, the retaining fish population appears to be comprised mainly of bullheads and minnows. It is particularly important to determine if carp presently inhabit the basin, since this species adversely affects both fish and wildlife habitat value. The methods required to create c viable, reproducing fishery in this wetland are relatively straightforward. To support a healthy game fish population, this wetland must be deepened and have supplementary dissolved oxygen during the winter months. The following fish habitat frprovemant measures will be investigated: t' 1. Deepening of the wetland can only he accoaplished by further dredging. Through coordination with the Minnesota DVR area fisheries manager, a determination will be made as to the ^ptimum maximum depth to be estabIishe•i and the proportion of the wetland that must be d^epened. A conceptual dredging plan will be developed based on theses• determinations and the present characteristics of the basin. Disposal of dredged material is a critical issu- with regard to the feasibility of additional dredging. Thq proposed disposition of dredge spoil may have a major impact on the cost of dredging, the type of equipment that can be used, and the post -construction aesthetics of the pro+ect area. We will investigate potential disnosa) locations, estimate the quantity of material to be deposited, and estimate costs. Based on the foregoing analysis, a recommendation as to the best dredging alternative will be developed. 2. Aeration - 3" !;e necessary to provide a year-round, reproducing fishery since this wetland cannot be dredged Jeepnnl.�nto r en Zh Suai¢litee overwinter survival. During winter, fish depend on dissolved oxygen produced by plant photosynthesis. Much of this oxygen is "pulled" from oxygen surface waters to deeper portions of a lake during the fall ®, "turnover" or stratificatio,i. Even after further dredging, Wetland 893 will be too shallow for turnover to occur. If heavy snow blocks sunlight passing through ice, photosynthetically produced oxygen may decline and, when combined with biological oxygen demand from decomposing