Distribution and habitat use by juvenile Atlantic salmon (Salmo salar) at multiple spatial scales, and implications for habitat modelling and fish-habitat management

• Main Author: Bult, Tammo Peter
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 1999
• Subjects: Atlantic salmon; Salmo salar
• Online Access: https://research.library.mun.ca/9628/; https://research.library.mun.ca/9628/1/Bult_TammoP.pdf

Implicit assumptions of micro-habitat models are that (1) habitat limits population levels and small-scale information on habitat selection behaviours of individuals can be used to manage populations at large spatio-temporal scales (scale-up); (2) the single or few measurement scales used in habitat models are appropriate for identifying important habitats; and (3) better habitats are characterised by a higher density or frequency-of-use, i.e. density can be used as an indicator of habitat quality. -- (1) Based on scope- and rate-diagrams from field-data and theoretical scenarios of movement and mortality, I concluded that salmonid habitat models operate in the context of processes that may not be important to the problems we would like to address. I suggested survey designs that allow problems associated with scale-up to be overcome. -- (2) I evaluated distributions of juvenile Atlantic salmon (Salmo salar) over a range of spatial scales based on a stream-tank study (spatial scales 1 cm to 3 m) and field data (spatial scales 1 cm to 15 m), to determine whether patchiness of fish distributions or associations with depth, water velocity and substrate depended on spatial scale, to determine scales most appropriate to habitat models, and to compare multi-scale versus single-scale habitat modelling approaches. Results indicated associations with conspecifics, substrate, water velocity and depth changed with spatial scale and direction relative to water flow. Associations were most different from random at small spatial scales (ambit radius < 50 cm). Both studies indicated that single- and multi-scale habitat selection models were equally able to describe fish densities at small spatial scales (ambit radius < 4 m). The field-based study indicated that single- and multi-scale models often failed to describe fish densities at scales larger than used in the model (scale-up). -- (3) I studied density-dependent habitat use by Atlantic salmon parr based on experimental riverine enclosures and field data. Results from ...