Distribution and Abundance of Larval Burbot and Deepwater Sculpin in Lake Michigan

Abstract

Samples from seven locations at depths to 21 m, collected over periods of up to 8 years, were used to describe the nearshore distribution and abundance of burbot Lota lota and deepwater sculpin Myoxocephalus thompsoni larvae in Lake Michigan. Based upon power-plant-entrainment samples and field collections, burbot larvae (3.0–7.5 mm) occurred from late March to mid-June, most abundantly in April and May, and most often at water temperatures of 6–12 C. Larvae were collected from the 0.5- to 13.5-m depth strata as far lakeward as the 21-m bottom contour, the limit of offshore sampling. In eastern Lake Michigan, highest densities (up to 843 larvae/1,000 m3) were at the 1-m contour; in Green Bay, up to 24,000 larvae/1,000 m3 were detected near the Bark River. High densities of burbot larvae at bottom depths 3 m and less indicated inshore spawning and river spawning at some sites. Deepwater sculpin larvae first occurred in early February and were common in March and April entrainment samples. Larvae (8.0–22.0 mm) were in nearshore waters usually through May at depth strata of 0.5 to 17 m as far lakeward as the 18-m bottom contour. Most larvae occurred at water temperatures below 6 C. Field densities were low, 5 to 78 larvae/1,000 m3. Deepwater sculpin larvae were pelagic and were dispersed over great distances by currents.