North America’s Great Lakes make up the world’s largest freshwater ecosystem. The Great Lakes support a $7 billion annual commercial and recreational fishery that is actively managed by the eight US states, numerous tribes, and Canadian provinces that border the lakes. The status and trends of Great Lakes fish stocks are assessed to support management decisions in the face of numerous threats including degraded habitat, changing climate, declining productivity, and invasive species.

To support sustainable fishery management across the binational resource, the US Geological Survey (USGS), in partnership with the US Fish and Wildlife Service (FWS), the Michigan Department of Natural Resources (MDNR), and other agencies use underwater echo sounders to conduct surveys to estimate the abundance of fishes from large research vessels. However, regional fisheries experts suspect the noise produced by those diesel-powered boats may scatter the fish, resulting in inaccurate stock counts.

In Summer 2021, USGS initiated a four-year study of the effects of vessel noise using two Saildrone Explorers equipped with fisheries echo sounders. The Saildrone Explorers were deployed from Holland, Michigan, on the southern end of Lake Michigan and spent some 45 days surveying Lake Michigan and Lake Huron, gathering fish distribution and density data. The Saildrone USVs conducted independent surveys and coordinated comparative surveys with three research vessels to better understand the impact of vessel sound on fish stock assessments. They also assessed fish stock distribution during the day vs. at night, and inshore vs. offshore. USGS scientists are using the data collected to generate more accurate and precise estimates of fish stocks.

A large fisheries dataset from the 2021 mission with Saildrone and agency vessels is currently under analysis for evidence of vessel biases. The saildrones collected data continuously over 3,613 nautical miles during which they were overtaken 61 times by crewed vessels from USGS, FWS, and MDNR. The crewed vessels were also able to collect more than 40 mid-water trawl samples to enable the attribution of species to the echo sounder data. A second mission in the deeper waters of Lake Superior in August 2022 will add further comparative data in this less impacted and much larger lake environment.