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Master's Project: TRAWL AND ERROR: DESIGNING A FORAGE FISH BOTTOM TRAWLING SURVEY ON LAKE CHAMPLAIN
Scarfo, Shelby
Scarfo, Shelby
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Abstract
A dynamic equilibrium generally exists between predator and prey fish populations within a system. Fluctuations in predator or prey populations due to changes in predator abundance, or factors that affect reproductive success, can drastically affect the ecosystem as a whole. Long-term monitoring surveys are frequently used to track metrics associated with forage fish communities, resulting in a better understanding of the drivers of predator population changes. Lake Champlain’s offshore fishery is dominated by two coldwater predators, stocked and wild native lake trout (Salvelinus namaycush) and stocked Atlantic salmon (Salmo salar), while predominant prey species consist of non-native alewife (Alosa pseudoharengus), native rainbow smelt (Osmerus mordax), slimy sculpin (Cottus cognatus), and trout-perch (Percopsis omiscomaycus). Significant changes in the coldwater community in the past two decades, including the invasion of alewife and substantial natural recruitment of lake trout, have highlighted the importance of understanding predator-prey dynamics in Lake Champlain through a long-term survey of the coldwater prey community. The primary objectives of this study were to design and implement a comprehensive coldwater forage fish bottom trawling survey throughout Lake Champlain and standardize the analysis of data to produce a potential foundation for a long-term monitoring survey. To achieve these objectives, I developed a standard operating procedure and relevant data analysis scripts and implemented the survey for two years. During these two years, I surveyed and analyzed prey populations in the three basins of Lake Champlain where coldwater predators are common. The data collected through this study is the beginning of a potentially long-term survey dataset that can enable managers and researchers to identify trends in the forage base, better understand the drivers of predator population changes, and make informed stocking decisions to maintain the coldwater fish community and fishery.
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2026-04-10
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Natural Resources