Seasonal Bathymetric Distribution of 16 Fishes in Lake Superior 1958-75
NATIONAL BIOLOGICAL SERVICE ASHLAND WIGREAT LAKES SCIENCE CENTER
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The bathymetric distributions of fishes in Lake Superior has not been studied on a lakewide scale. Knowledge about the bathymetric distributions will aid in designing fish sampling programs, estimating absolute abundances, and modeling energy flow in the lake. Seasonal bathymetric distributions were determined, by 10m depth intervals, for 16 fishes collected with bottom trawls and bottom-set gill nets within the upper 150m of Lake Superior during 1958-75. Bathymetric distributions in spring gill nets were similar to those in trawls, with some exceptions. Lake herring and kiyi were rarely caught in trawls. In summer, pygmy whitefish, shortjaw cisco, lake herring, kiyi, longnose sucker, burbot, ninespine stickleback, trout-perch, slimy sculpin, and spoonhead sculpin were at shallower depths than in spring, whereas rainbow smelt were found in deeper water there was no change for the other species. In fall, shortjaw cisco was at shallower depths than in summer, whereas the remaining species were found deeper, except for lake whitefish and lake trout whose modal depths did not change. Distributions of lake trout and lake whitefish were also analyzed by age group. The shallow-water species exhibited little seasonal changes in bathymetric distributions, whereas the species that inhabited the middepths and deeper water generally moved shallower as the seasons progressed. Most of the more pronounced seasonal changes in bathymetric distribution were associated with spawning movements.