Habitat, distribution and abundance of juvenile lake trout, sculpin and burbot in four small, Precambrian Shield lakes in Ontario

The purpose of this study was to investigate the habitat, spatial distribution and abundance of juvenile lake trout and two closely associated species, sculpin and burbot. Sampling was carried out in four small lakes in Ontario, Canada using a remotely operated, submersible vehicle. Two approaches to sampling were adopted: (1) extensive surveys of the whole lake for estimation of density and abundance, and comparisons of seasonal and between-lake differences in habitat use, and (2) intensive surveys to investigate lake trout usage of headland and embayment habitats features during day and night.

During the extensive surveys, 52 young-of-year (YOY), 69 juvenile, and 1 post-juvenile lake trout, 813 sculpin, and 19 burbot were observed. Whole-lake estimates of density ranged from 7.3 to 40.0 h$\sp{-1}$ for YOY lake trout, 4.0-21.5 ha$\sp{-1}$ for juvenile lake trout, 23.9-459.1 ha$\sp{-1}$ for sculpin and 7.5-11.3 ha$\sp{-1}$ for burbot. Seasonal and between-lake differences in depth distribution of YOY and juvenile lake trout and sculpin were found, but could not be correlated to temperature or dissolved oxygen concentrations alone.

In the intensive surveys, 58 YOY, 82 juvenile, and 9 post-juvenile lake trout, 1060 sculpin, 11 large burbot, and 12 small burbot were observed. Density estimates for lake trout, sculpin, and small burbot were consistently higher during night sampling. Day sampling underestimated density of these fish by 1.3 to 4.7 fold. There were differences in distribution of lake trout, sculpin and burbot with respect to headland and embayment for day and night sampling. All fish species were found in shallower habitat at night than during day.

Structural characteristics of the lake bottom generally did not appear to affect fish densities, with the exception that, sculpin in Victoria Lake were always at higher densities over silt substrates. (Abstract shortened by UMI.)