Behaviour and Microhabitat of Young Atlantic Salmon (Salmo salar) during Winter

Abstract

Underwater observations at two sites along a small Nova Scotian river were carried out between December and April (water temperature range = 0.5–7.0 °C) to describe the winter microhabitat of young Atlantic salmon (Salmo salar). Salmon (5–15 cm fork length) were consistently found hiding beneath rocks (mean diameter = 16.8–23.0 cm) in riffle-run habitats where mean water depths were 40.9–48.9 cm and mean water velocities were 38.7–45.7 cm∙s−1. Many of the salmon were found overwintering within redd excavations. "Home stones" were distributed closer to midstream than to river banks and where sediment compaction was minimal. Monthly collections of fish (ages 1 and 2) indicated that feeding continued over winter. The data suggest a nocturnal activity pattern and photonegative response by young salmon during winter.