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US Fish & Wildlife Service FieldNotes

Partnership Produces Needed Data on Key Forage Species in Lake Huron

Region 3, October 10, 2012
Figure 1. 2012 Lake Huron acoustic survey transect locations.
Figure 1. 2012 Lake Huron acoustic survey transect locations. - Photo Credit: n/a
Figure 2. Sample echogram (source www.echoview.com)(a) and trawl operations aboard the M/V Spencer F. Baird (b)
Figure 2. Sample echogram (source www.echoview.com)(a) and trawl operations aboard the M/V Spencer F. Baird (b) - Photo Credit: n/a

By Stephen Lenart


Staff from the Alpena Fish and Wildlife Conservation Office and the crew of the research vessel Spencer F. Baird (M/V Baird) partnered with the United States Geological Survey Great Lakes Science Center to conduct an acoustic forage (prey fish) survey on Lake Huron during September and October 2012, marking the second year of a scientific partnership with USGS. This forage survey has been conducted by USGS on Lake Huron since 2004, the objective of which is to provide information to managers and researchers regarding the status of key prey fish stocks, including exotics such as alewife and rainbow smelt, and native species such as bloater “chubs.”

Utilization of the M/V Baird over the past two years has increased the likelihood that the partners will attain adequate survey coverage in the three distinct areas of Lake Huron: the Main Basin, Georgian Bay, and the North Channel. The survey combines acoustic technology (high-tech “fish finders”) to estimate fish densities (the number of fish within an area) and mid-water trawling to determine species and size composition. The survey design included twenty acoustic transects, distributed across five distinct areas of interest (Figure 1). These transects, each 20 kilometers (12.5 miles) in length, are conducted at night, when prey fish species are suspended in the water column, making them detectable by acoustics. Fish targets are detected when they deflect and return a signal to a transducer, which emits a pulse of mechanical energy, or a “ping.” The strength of the return signal is relative to the size of the target, though numerous physical factors influence the signal as it travels through the water column.These signal returns are logged and mapped as the vessel travels along a transect, creating an “echogram” (figure 2a) that can be analyzed with specialized software to calculate acoustic density estimates.

The M/V Baird completed five such transects, all in the western portion of Lake Huron’s main basin. Seven mid-water trawls (figure 2b) were conducted by the M/V Baird, with rainbow smelt the most numerous species captured. Other species captured included bloater, emerald shiner, and stickleback species. Data collected by the U.S. Fish & Wildlife Service will be combined with those collected by USGS to calculate lakewide biomass estimates for our key forage species. Such information is crucial to understanding the basic predator-prey relationship in Lake Huron, part of the world’s largest freshwater system. This collaboration supports the FWCO’s dedication to improving long-term relationships with partner agencies and using advanced science initiatives in support of native species restoration.

Contact Info: Andrea Ania, 989-356-5102 x1020, Andrea_Ania@fws.gov