Homing Instinct in Salmon

Abstract

K NOWLEDGE of the migrations of fishes is of considerable economic importance and biological interest. Most fisheries depend on the congregation of certain species for feeding or spawning in definite regions; a knowledge of the movements of the fishes to and from these regions has aided the prosecution of the fishing operations and has been of value in attempts at regulation of these operations with a view to conservation. Russell (1937) states that most fish migrations consist (i) of a dispersal of eggs, larvae, or young fishes by passive drifting with the current or by active seeking of the normal habitat, then (z) of an active movement, usually against the current, to the spawning grounds, and finally (3) of a dispersal of the spent fishes, either by movement with a current or an active feeding migration. Salmon migrations are in general accord with this plan. The young fishes go down-stream to the sea after a stay in fresh water which varies in length with the species and with conditions in the stream. There follows a period of feeding and growth in the sea which also varies in length, but rarely, if ever, exceeds five or six years. The mature fishes now enter streams and proceed to spawning grounds; after spawning, the Pacific species of salmon die, while the steelhead trout and the Atlantic salmon may return to the sea, subsequently to enter a stream and spawn again. The suggestion was made many years ago that the salmon invariably returns for spawning to the stream in which it was hatched. Many biologists looked upon this view with skepticism. Jordan (igz5) opposed the idea, and Rutter (I903) said,