Great Lakes Fishery Commission

Updated 2023-11-08 15:53:22

Lake Michigan -> 2.0 Planktivore (Prey Fish) -> Prey Fish Diversity

2.1.2 Increased diversity and relative abundance of prey fish species in acoustics and bottom trawl surveys

The diversity and relative biomass of preyfish species did not increase in the acoustics or bottom trawl surveys during the reporting period. Whereas species diversity remained generally similar to past years in both surveys, relative preyfish biomass was similar in the acoustics survey and substantially lower in the bottom trawl survey compared to previous reporting periods (Figure 1, Figure 2).

There was an increasing trend in the proportion of preyfish biomass consisting of native species as determined from the annual acoustic survey (Figure 1).  This increase was the result of strong year classes of bloaters in 2015, 2016, and 2021. Unlike the acoustic survey, the bottom trawl did not indicate that there was an increasing trend in proportion of preyfish biomass consisting of native species (Figure 2). 

Figure 1. Relative biomass of species as estimated by annual lakewide acoustic surveys in Lake Michigan. No survey was conducted in 2020.

Figure 2. Relative biomass of species as estimated by annual lakewide bottom trawl surveys in Lake Michigan. Only species with an average contribution to total biomass of 5% or more were included. Data from 2020 were excluded because the survey was partial.