Status of pelagic prey fishes in Lake Michigan, 2017
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Abstract
Acoustic surveys were conducted in late summer/early fall during the years 1992-1996 and 2001-2017 to estimate pelagic prey fish biomass in Lake Michigan. Midwater trawling during the surveys as well as target strength provided a measure of species and size composition of the fish community for use in scaling acoustic data and providing species-specific abundance estimates. The 2017 survey consisted of 34 acoustic transects [711 km total (442 miles)] and 40 midwater trawl tows. Mean prey fish biomass was 7.99 kg/ha [38.9 kilotonnes (kt = 1,000 metric tons)], which was 46% higher than in 2016 and 35% of the long-term (22 years) mean. The numeric density of the 2017 alewife year-class was 27% of the time series average and 0.6 times the 2016 density. This year-class contributed 15% of total alewife biomass (4.4 kg/ha). In 2017, alewife comprised 55% of total prey fish biomass, while rainbow smelt and bloater were 32% and 14 % of total biomass, respectively. Rainbow smelt biomass in 2017 (1.0 kg/ha) was 29% of the long-term mean and increased for the second time since 2008. Bloater biomass in 2017 was 2.5 kg/ha and 32% of the long-term mean. Mean density of small bloater in 2017 (120 fish/ha) was 80% of the long-term mean. Biomass density of large bloater increased to 2.2 kg/ha in 2017. This remains much lower than in the 1990s but likely shows evidence of recruitment of small fish observed in the past 5 years. Although prey fish biomass remains low relative to the 1990s, it did increase in 2017. This increase, along with higher-than-average survival of two recent alewife year classes, are likely a response to reduced predation pressure stemming from a reduction in the abundance of Chinook salmon.
Suggested Citation
Warner, D.M., Turscah, B., Hanson, D., Desorcie, T.J., O’Brien, T.P., Dieter, P.M., Smith, J., 2018, Status of pelagic prey fishes in Lake Michigan, 2017, chap. of Complied reports to the Great Lakes Fishery Commission of the annual bottom trawl and acoustics surveys, 2017, p. 29-38.
Study Area
| Publication type | Book chapter |
|---|---|
| Publication Subtype | Book Chapter |
| Title | Status of pelagic prey fishes in Lake Michigan, 2017 |
| Year Published | 2018 |
| Language | English |
| Publisher | Great Lakes Fishery Commission |
| Contributing office(s) | Great Lakes Science Center |
| Description | 10 p. |
| Larger Work Type | Report |
| Larger Work Subtype | Other Government Series |
| Larger Work Title | Complied reports to the Great Lakes Fishery Commission of the annual bottom trawl and acoustics surveys, 2017 |
| First page | 29 |
| Last page | 38 |
| Country | United States |
| State | Michigan, Wisconsin |
| Other Geospatial | Lake Michigan |