Movements and Homing of Cutthroat Trout (Salmo clarki) from Open-Water Areas of Yellowstone Lake

Abstract

Cutthroat trout (Salmo clarki) showed in-season homing after displacement from their spawning tributaries to Yellowstone Lake during June–August 1966 and 1967. Of 300 nonanesthetized trout tagged and displaced from Clear and Cub creeks to three release points (0.5–22.0 km) in the lake and to the mouth of Clear Creek, 38.3% homed, 10.0% strayed, 2.7% were caught by anglers, and the remainder were unaccounted for. Anosmic (olfactory chambers plugged) and blind-anosmic fish homed in significantly lower percentages than nonanesthetized and control groups. Fish released just outside the mouth of the homestream had the shortest average homing time, but the average homing time for fish displaced 22.0 km from the homestream was shorter than for those displaced 5.0 km away. Homing percentages for trout tagged after being tracked individually in the open lake were similar to those for trout in the group tagging experiments, but the former had longer average homing times than the latter.The directions of orientation of fish tracked in open water were generally toward the homestream, the directions usually coinciding with those of the sun azimuth. However, fish taken from the east side of the lake went west-northwest when tracked late in the afternoon and fish taken from the west side of the lake went east-southeast when tracked in the morning, these directions being away from those of the homestreams. Orientation was affected by current. Mean directions for males and females were generally not significantly different. Average swimming speeds and vector lengths for males and females were about the same. Immature cutthroat trout were trained to use a light source as a reference point for orientation.