Winter movement, activity and habitat use of Atlantic salmon Salmo salar L. parr in Newfoundland

Robertson, M. J. (2004) Winter movement, activity and habitat use of Atlantic salmon Salmo salar L. parr in Newfoundland. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Knowledge of Atlantic salmon Salmo salar L. parr behaviour in wintering habitat is limited to a few studies suggesting that they are largely sedentary and primarily nocturnal in winter. In a series of field studies, radiotelemetry was used to investigate winter movement, activity and habitat use of Atlantic salmon parr in Newfoundland. In the natural rivers studied, Northeast Brook and Stoney River, Atlantic salmon parr remained active throughout the diel cycle in winter and utilised a variety of mesohabitats, even under stable environmental conditions. Based on the age of parr captured in fluvial habitats in early and mid-winter, young parr (2-3 yrs) appeared to overwinter in fluvial habitat while pre-smolts ( 4-6 yrs) did so in lacustrine habitat. In the regulated river studied, West Salmon River, landlocked Atlantic salmon parr were active throughout the diel cycle in winter. However, there was significantly less daytime than nighttime movement and movement declined significantly with increased fish size. Increases in flow from 1.3 m³ s⁻¹ (low) to 5.2 m³ s⁻¹ (high) for 24 hour periods did not affect fish habitat use, displacement or prey consumption. However, fish activity rates in late winter were lower at high flow than at low flow. The results of these studies supported recent laboratory research indicating that parr are not strictly nocturnal in winter and that individual variation in time spent foraging during the day may result from differences in the benefits of enhanced feeding and growth. The traditional view that Atlantic salmon parr are sedentary stream dwellers in winter, moving only in response to adverse stream conditions, was not supported by the results of the present studies.

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