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Age truncation of alewife in Lake Michigan

July 15, 2019

Empirical evidence has shown increased variability in harvest and recruitment of exploited fish populations, which can result directly from exploitation or indirectly from interactions between external drivers and the internal dynamics of age-structured populations. We investigated whether predation in a freshwater system could affect a prey fish population, in the same way fishing affects targeted populations. Using fishery-independent trawl survey data and a suite of quantitative indicators, we evaluated changes in the alewife population in Lake Michigan. Our results provide evidence for a reduction in the mean spawner age, a reduction in the diversity of age classes and the distribution of biomass across them, and increased variability in the proportion of first time spawners in the spawning stock. We used wavelet analysis and estimates of lifetime egg production to demonstrate how the alewife population displays behaviors of instability as the overall biomass declines. Our results provide evidence that predation pressure can influence prey fish populations in a similar manner to fishing on harvested populations, and that conservation of a broad reproducing age structure is likely to be important for buffering against adverse environmental fluctuations and for sustainable management of fish populations.

Publication Year 2019
Title Age truncation of alewife in Lake Michigan
DOI 10.1016/j.jglr.2019.06.006
Authors T. Vidal, Brian J. Irwin, Charles P. Madenjian, S. J. Wenger
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of Great Lakes Research
Index ID 70222406
Record Source USGS Publications Warehouse
USGS Organization Coop Res Unit Atlanta; Great Lakes Science Center