Fish-habitat interactions in a small freshwater lake and the evaluation of a visual census sampling method for the quantification of vertical, littoral zone habitat structure and fish distribution

A visual census method was developed to vertically quantify habitat structure and fish distribution in freshwater lake littoral zones. In the Poorhouse Lake study, several sites were repeatedly sampled to evaluate the fish-habitat interactions when quantified vertically. A temporal gradient explained the most variation in the species data, but a secondary vertical habitat gradient also influenced fish distribution. In the Lake Survey study, several lakes were sampled to test the broader applicability of the vertical visual census method and to compare the observations obtained using it to those obtained using a boat sampling method. Substantial among-observer variability was found using the qualitative boat sampling method. Habitat type influenced among-observer and among-method consistency of habitat characterization. The suitability of the vertical visual census technique can be dependent on the trade-off between the increased sampling effort required and the more detailed, accurate information it can yield.