Fergus Falls area Department of Natural Resources fisheries biologists wrapped up their lake survey season last week. This summer, DNR biologists completed twelve lake surveys. Lake surveys (fish population assessments) are the foundation of the DNR’s lake management program. They are essential for collecting biological information concerning habitat, water quality, and fish population characteristics. Data collected from lake surveys allows fisheries biologists to develop lake specific management plans, evaluate management techniques, such as stocking and harvest regulations, and help monitor long term changes or trends in aquatic environments.
Lake surveys are composed of three sampling methods. Water quality, gillnetting and trapnetting. The water quality component consists of a secchi disk reading to measure water clarity, and a dissolved oxygen profile. The gillnetting component uses gill nets to sample fish species that inhabit deeper water away from shoreline areas. Gill nets are important for collecting population data on gamefish species such as walleye, northern pike, and yellow perch. The trapnetting component uses trap nets to sample fish species that use shoreline related habitats such as bass, bluegills, and crappies.
Data are collected from individual fish that are captured during the lake survey. This includes lengths, weights and aging structures. This winter, DNR fisheries biologists will use this data to analyze the fish population characteristics of each species of fish for every lake that a survey was conducted on. Population characteristics that are analyzed include abundance, size structure, reproduction, growth rates, survival, and age distributions. Biologists will use this information to prepare a lake survey report for each lake. These reports contain a detailed analysis for each species sampled during the lake survey. Biologists also use this data to revise the lake management plan for each lake. Management plans include specific fisheries methods that the DNR will utilize to manage each individual lake such as fish stocking (which species, how many, and what size), harvest regulations, habitat enhancement and creel surveys.
Lakes that were surveyed this summer include Donalds, the Leafs (East, Middle, West) Rush, Silver, Swan, East Silent, Lizzie, Jewett, Stalker and Portage. Lake survey reports for these lakes will be available on the Minnesota DNR website next spring.
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