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Monday, January 25 • 2:00pm - 2:20pm
Current Growth, Condition, and Fecundity Trends of Alewives in Lake Michigan

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AUTHORS: Zach Prause*, Ball State University; Thomas Lauer, Ball State University

ABSTRACT: Over the past decade, alewives Alosa pseudoharengus in Lake Michigan have been showing signs of declining overall health and reduced abundance. Because alewives are such an integral part of the Lake Michigan ecosystem, a collapse similar to one seen in a decade ago in Lake Huron is feared. The objective of this study is to identify changes in alewife demographics over time to create possible future trends. Fulton’s condition factor for alewives has declined from an average of 0.83 in the period 1979-1994 to 0.74 in the time period 1994-2012. Recent length-frequency distributions failed to demonstrate a consistent and robust alewife population and are instead showing one or two dominant classes with others being poor or missing. Von Bertalanffy growth curves from the last decade show an overall decrease in growth rate, max length, and max age of fish when compared to growth rates in the 1960s, 1980s, and 1990s. Further, alewife fecundity changes appear to have declined in the most recent years. These composite results identify a scenario In Lake Michigan similar to that shown in Lake Huron in the early part of the 2000s. The shift in alewife abundance and size structure in Lake Michigan in the past two years may alter the predator/prey ratio, ultimately resulting in reduced salmonid abundance.

Monday January 25, 2016 2:00pm - 2:20pm EST
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