So serious is the destruction of the spawn and fry of salmon, both by sea and fresh-water trout, that the Duke of Sutherland's manager would willingly, were it possible, extirpate the entire breed of these fish. "They commence," he informs us, in a letter of 15th May 1843, "the moment the salmon begin to deposit their spawn, and in the course of the spawning season they devour an immense quantity of ova. Indeed, at all other times of the year, they feed on the fry of salmon, and continue their destruction till the day the smolts leave the rivers. I have often cut up trout, and got smolts in their stomach; and last week a trout was opened in Mr Buist's fish-yard with four full-grown smolts in its belly. From these and other similar occurrences, you may judge to what extent this destruction is carried on, in the course of a single year, in such a river as our Oykel, where I have killed seven hundred trout at a single hawl." We understand that, some years ago, when Mr Trap, (a most appropriate name,) the fishmonger in Perth, had the Dupplin cruives, he got about 400 whitlings (or sea-trout) in one day, all of them gorged to the throat with salmon fry. The sea-trout of Sutherlandshire, like those of the Nith and the Annan, almost all belong to the species named _Salmo trutta_ by naturalists. They scarcely ever exceed, indeed rarely attain to, a weight of five pounds; and such as go beyond that weight, and range upwards from eight to twelve pounds, are generally found to pertain to _Salmo eriox_, the noted _bull-trout_ of the Tweed. The great grey sea-trout of the river Ness, which sometimes reaches the weight of eighteen pounds, we doubt not, also belongs to the species last named. It is rare in the waters of the Tay. In regard to the seaward migration of salmon fry, Mr Scrope is of opinion that some are continually going down to the salt water in every month of the year, not with their silver scales on, but in the parr state.