CAN TRAINED OBSERVERS ACCURATELY IDENTIFY LAKE TROUT SPAWNING HABITAT

The ability of trained observers to accurately identify potential spaw ning sites of lake trout (Salvelinus namaycush) was tested in a 67-ha lake. Ten-metre sectors of shoreline were first visually assessed and classified by pairs of naive and expert observers. Lake trout were the n displaced from their traditional spawning sites and forced to choose new sites from a 2050-m section of previously classified shoreline. F orty-one sectors from the test area were selected by the displaced fis h for spawning. Egg deposition was restricted to 63 patches (0.25-5.0 m(2)) of substrate (2-30 cm) within the sectors. An estimated 298-551 female lake trout used a total surface area of 53.4 m(2) for egg depos ition. Observers were able to correctly classify 59-76% of the shoreli ne sectors containing egg patches, but their success rate was mainly b ecause of the high number of sites they selected. The study showed tha t traditional assessment methods are useful for large-scale habitat ma pping, but precise predictions of the location of individual spawning sites may not be possible.