Spawning habitat of Atlantic salmon and brown trout: general criteria and intragravel factors

Generalized habitat criteria for spawning sites of Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) using depth, water velocity and substrate size were created based on published information. In addition, information on critical intragravel conditions for egg development was summarized. Salmon spawned mostly in relatively deep, swift-velocity habitats (20–50 cm, 35–65 cm s−1), whereas trout selected slightly shallower and slower flowing spawning sites (15–45 cm, 20–55 cm s−1). Salmon and trout preferred pebbles (16–64 mm) for spawning. The minimum oxygen concentration for successful incubation of eggs varies with the developmental stage of eggs, and supply of it may be reduced by deposited fine sediment. Habitat criteria for spawning sites are narrower than those for small juveniles; therefore the use of separate criteria is recommended. In addition to the traditional habitat criteria variables (depth, water velocity, substrate), the critical intragravel factors affecting egg survival should be incorporated in biologically meaningful criteria for spawning habitat modelling. Copyright © 2008 John Wiley & Sons, Ltd.