Homing and Orientation of Cutthroat Trout (Salmo clarki) in Yellowstone Lake, with Special Reference to Olfaction and Vision

Abstract

In-season homing was exhibited by mature cutthroat trout (Salmo clarki) displaced from spawning tributaries to Yellowstone Lake during late May to early August 1964, 1965, and 1966. Of 1908 trout tagged and displaced from Clear and Cub creeks to three release points in the lake (1.55–7.95 km) and to the mouths of the streams, 614 (32.2%) homed, 119 (6.2%) strayed, and 28 (1.5%) were captured by anglers. Only slight differences in homing performance from various release points occurred, but there were differences among years and between streams. Adjusted mean homing times from the various release points ranged from 16 hr to 155 hr, with an inverse relation between homing times and the distance to the release point apparent in one year. Blockage of the olfactory or visual sense did not affect the per cent of trout homing or straying. However, visual clues did increase the speed of homing, since homing times for blinded trout were much longer than for olfactory-occluded, control (anesthetized only), or non-anesthetized trout. A compass-type orientation occurred which was apparently not in response to visual or olfactory stimuli. A general east-northeastward (Clear and Pelican Creek trout) or northward (Cub Creek trout) orientation was exhibited by blind, anosmic, control, and non-anesthetized trout that were float-tracked from an open-water point. Blind and anosmic trout oriented as well as control trout. The directions of orientation were not in the directions of the home-streams, and orientation was not at a constant angle to the current directions or the sun azimuths.