Observations on siting, dimensions and structure of salmonid redds



Redds of trout, Salmo trutta L., Atlantic salmon, S. salar L., and rainbow trout, S. gairdneri Richardson, were studied at sites in north-east England, south-west Wales and southern England (Dorset). Spawning females preferred gravels of 20–30 mm diameter and water velocities at 0·6 depth of geqslant R: gt-or-equal, slanted 15 cm s-1 and <c. 2·0 body lengths s-1. After logarithmic transformation the major horizontal dimensions of redds could be related to one another by linear regressions, and redd tail length could, similarly, be related to female fish length. Egg burial depth in upland stony streams in north-east England and south-west Wales could be predicted from a linear regression of mean depth upon female length. Information is also given on gravel composition and redd structure.