Status and Trends in the Lake Superior Fish Community, 2017

Abstract

In 2017, the Lake Superior fish community was sampled with daytime bottom trawls at 76 nearshore and 36 offshore stations. Spring nearshore and summer offshore water temperatures in 2017 were similar to slightly cooler than the 1991-2017 average. In the nearshore zone, a total of 28,902 individual fish from 27 species or morphotypes were collected. The number of species collected at each station ranged from 0 to 13, with a mean of 5.5 and median of 5. Lakewide nearshore mean biomass was 3.8 kg/ha which was below the long-term average of 8.7 kg/ha and the median lakewide biomass was 1.8 kg/ha. which was similar to the long-term average median value of 1.9 kg/ha. Lake Whitefish, Rainbow Smelt, Bloater, Longnose Sucker, and lean Lake Trout were the species with the highest lakewide average biomass. In the offshore zone, a total of 16,674 individuals from 13 species were collected lakewide. The average and median observed species richness at each station was 3.8 and 4 species, respectively, and ranged from 2 to 6 species. Deepwater Sculpin, Kiyi, and siscowet Lake Trout made up 99% of the total number of individuals and biomass collected in offshore waters. Mean and median lakewide biomass for all species in 2017 was 6.8 kg/ha and 6.6 kg/ha, respectively. This was similar to the long-term mean of 6.9 kg/ha and greater than that observed in 2014-2016. Nearshore average larval Coregonus densities in 2017 were greater than observed in any previous year; whereas offshore larval Coregonus densities were much less than observed in previous years.