When the eggs of the Salmo trutta hatch in spring, the fish mature as Brown trout for about three years in the freshwaters of the Tweed River. At maturity, a certain percentage of this population leaves the river for the seas, where their color becomes silver and similar in appearance to salmon. The flesh is paler than that of a salmon, and more delicate in flavor. The wild sea trout return to the river several times in their lifespan to reproduce.
By the mid-2010s, there was just one remaining commercial fishery left on the River Tweed. Using the traditional net and coble method of fishing, which dates to the Tweed Act of 1857, but documented as far back as the 12th century, fishermen release nets from the coble (a small flat-bottomed boat) that are pulled in by fishermen standing on the shore.
Due to recent Scottish Government legislation, the opportunity to purchase wild Scottish sea trout has become very restricted. This sustainable method of catching fish, teamed with the short season of June to mid-September, makes this product very limited. The River Tweed has been give Grade 1 status, which deems that wild stocks are sustainable. Fewer than 1000 fish are caught in an average year, but this number includes both salmon and sea trout. Today, the wild sea trout population is also threatened by disease and parasites originating from caged salmon farming operations.