How is the age of a sea trout determined?

Age determination of sea trout is usually carried out by scale-reading.  This can be trickier than scale reading for salmon, mainly because of the extensive variation that can occur in feeding activity. Temporary visits to fresh water may be interpreted wrongly as winters until the scale reader gains a wider picture of stock movements and associated local growth patterns.  Where possible, scale reading should be validated by tagging and recapture studies.  Spawning is inferred from single or repeated patterns of loss of the scale edges, followed by further growth rings. [ Scale erosion is part of the recovery process of the body from depleted physiological reserves.]