Updated 2021-10-07 13:32:06
Lake Erie -> 4.0 Prey Fish -> Prey Fish
Reporting Interval
2016 - 2020
Area
Lake Erie
Meeting Target?
Does Not Meet
Indicator Trend
Downward trend
Confidence?
Medium
Prey-fish populations support predator condition and growth rates near the long-term average
Dominant prey-fish species vary between basins with spiny-rayed prey fishes (young-of-year (YOY) white perch and yellow perch) and YOY gizzard shad being more prevalent in the west basin, and rainbow smelt, round goby, and emerald shiners being dominant in the central and east basins. Determination of critical levels of prey-fish is based on growth and condition of walleye and lake trout with the goal of keeping predator growth and condition at or near the long-term average.
During the 2016-2020 reporting period, the lakewide prey-fish index declined across Lake Erie and was well below the long-term average (2,620 fish/ha; average = 3,503 fish/ha; Figure 1). Prey-fish indices in 2019 and 2020 were the lowest in the 29-year time series. Emerald shiner and adult rainbow smelt catches have been particularly low in recent years. Lake trout and walleye both exhibited declining trends in condition during the reporting period with average condition indices falling well below the long-term average for both species (Figure 2). However, condition increased to near average levels for both species in 2020.
Figure 1. Annual lakewide prey-fish abundance (fish/ha) in Lake Erie, 1992-2020.
Figure 2. Annual condition (Relative Weight; Wege and Anderson 1978) and time-series average of lake trout (age-5) and walleye (ages 3-6) in Lake Erie, 1983-2020.
Methodology
The prey fish community is assessed through long-term trawl surveys that occur in each of the basins. Four bottom trawl surveys are conducted annually by three agencies in late summer through fall across the three lake basins: West (OMNDMNRF and ODNR), Central (ODNR), and East (NYSDEC and OMNDMNRF). The lakewide index is an average of basin-specific abundance indices. Generally, all small fishes that can be eaten by an average-size walleye are considered prey fish; the most important prey fishes in Lake Erie include rainbow smelt, emerald shiner, gizzard shad, and round goby.
Condition metrics (i.e., how heavy a fish is at a given length) are obtained from length and weights on individual fish taken in assessment surveys. Lake trout condition data for age-5 fish are collected during August by a multi-jurisdictional coldwater assessment survey conducted in the east basin; walleye condition data for ages 3-6 are collected during October and November from ODNR gillnet surveys in the west and central basins.
Other Resources
- Forage Task Group. 2021. Report of the Lake Erie Forage Task Group 2021. Lake Erie Committee, Great Lakes Fishery Commission. Ann Arbor, Michigan. Available at: http://www.glfc.org/pubs/lake_committees/erie/FTG_docs/annual_reports/FTG_report_2021.pdf
- Francis, J., T. Hartman, K. Kuhn, B. Locke, and J. Robinson. 2020. Fish community objectives for the Lake Erie basin [online]. Available at: www.glfc.org/pubs/FisheryMgmtDocs/Fmd20-01.pdf
- Wege, G. W. and R. O. Anderson. 1978. Relative weight (Wr): A new index of condition for largemouth bass. In G. D. Novinger and J. G. Dillard (editors), New Approaches to the Management of Small Impoundments, Special Publication, volume 5, pp. 79–91, American Fisheries Society.
Contributing Author(s)
- Zak Slagle - ODNR
- John Deller - ODNR
- Tom MacDougall - OMNDMNRF
- James Markham - NYSDEC
- Mike Hosack - PFBC