Status and trends of pelagic prey fish in Lake Huron, 2013

The USGS Great Lakes Science Center (GLSC) conducted acoustic and midwater trawl surveys
of Lake Huron during 1997 and annually during 2004-2013. The 2013 survey was conducted
during September and October and included transects in Lake Huron’s main basin, Georgian
Bay, and North Channel. Pelagic fish density was 1,033 fish/ha in 2013 and increased 62% over
the 2012 estimate. Total biomass in 2013 (6.07 kg/ha) was similar to the 2012 estimate (6.97
kg/ha). Mean numeric density of alewife Alosa pseudoharengus was substantially greater in
2013 than in 2012, but the 2013 estimate has low precision. Age-0 rainbow smelt Osmerus
mordax abundance increased from 2012, whereas age-1+ rainbow smelt decreased. Age-0
bloater Coregonus hoyi abundance increased over 2012 estimates. Density and biomass of large
bloater in 2013 was similar to 2012 levels. Emerald shiner Notropis atherinoides density and
biomass increased during 2013. Two adult cisco Coregonus artedi were captured in Georgian
Bay. Based on comparable biomass estimates during 2012 and 2013, prey fish availability during
2014 will likely be similar to 2013. Lake Huron has pelagic fish biomass similar to that observed
in recent lake-wide acoustic surveys of Lake Michigan and Lake Superior, but species
composition differs in the three lakes. There is an increasing gradient of diversity and native
species occurrence from Lake Michigan to Lake Superior, with Lake Huron being intermediate
in the prevalence of native fish species like coregonines and emerald shiner.