Mechanisms of salmon homing migration from molecules to behavior

Abstract

A number of studies have investigated the amazing ability of salmon to migrate long distances from the ocean to their natal river for spawning. For a better understanding of the mechanisms of salmon homing migration, three different analyses have recently been applied using Japanese chum salmon (Oncorhynchus keta). The first is behavioral analysis using electromyogram (EMG) transmitters to monitor chum salmon upstream migration in the Shibetsu River where the restoration of river environments by reconstruction of meanders was carried out in Japan. The second is endocrinological analysis on two molecular types of gonadotropin-releasing hormone (GnRH: salmon GnRH and chicken II GnRH) profiles in the various brain regions of chum salmon during spawning migration using specific time-resolved fluoroimmnoassay systems. The third is olfactory discriminating analysis on upstream selective movement of chum salmon in a two-choice test tank using artificial home stream water that was prepared based on the compositions of amino acids and related substances of their natal river. This paper will provide a new concept for the mechanisms of homing migration in salmon from molecules to behavior.