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Preliminary status of Lake Ontario Alewife based on the 2019 spring trawl survey

December 2, 2019

-The 2019 spring prey fish trawl survey was the most extensive fish survey ever conducted on Lake Ontario with 252 bottom trawls collecting 214,569 fish from 39 species, in main-lake and embayment habitats, at depths ranging from 5 to 225 meters (16.5 – 742.5 feet).

-Alewife distribution was similar in U.S. (southern) and Canadian (northern) portions of the lake, which differs from the previous three years of whole-lake surveys when Alewife in April were more abundant in either U.S. (2017) or Canadian (2016, 2018) waters.

-The 2019 lake-wide average biomass index for adult Alewife (Age2+) declined 29% relative to 2018.

-The lake-wide biomass index for Age-1 Alewife in 2019 (2.2 kg/ha) declined relative to 2018 (2.6 kg/ha) and was the lowest Age-1 biomass observed since whole-lake sampling began in 2016.

-The current biomass, size structure, and age structure of the adult Alewife population reflect the lower than-average Alewife reproductive success observed in the 2013- and 2014-year classes. 

-Reproductive success was also lower than average in 2017 and 2018, suggesting the adult Alewife biomass may continue to decline.

Publication Year 2019
Title Preliminary status of Lake Ontario Alewife based on the 2019 spring trawl survey
Authors Brian C. Weidel, Jeremy P. Holden, Michael J. Connerton
Publication Type Report
Publication Subtype Other Report
Series Title Lake Ontario Prey Fish Working Group to the Lake Ontario Committee
Index ID 70204588
Record Source USGS Publications Warehouse
USGS Organization Great Lakes Science Center