The Current Status of Research on Geomagnetic Navigation in Pacific Salmon

Abstract Excerpt:
From a human’s perspective, the navigational task of ocean migrants is daunting: the open sea is vast, featureless, and in constant motion. Yet, numerous species transit ocean basins with seeming ease (Gould and Gould 2012). The migratory life-cycle is common and often includes use of spatially-restricted reproductive sites, dispersal of offspring, and eventual homing to the natal site to reproduce (Fig. 1). The life-history strategy is remarkably effective; indeed, many of the world’s most important fisheries take advantage of the large numerical abundance and biomass that results (Secor 2015). The migrations of animals thus require efficient and directed movements between or among distant habitats (Fig. 1). Animal navigation can be likened to a two-step process, the “map step” whereby the animal assesses where it is relative to some goal and the “compass step” whereby the animals maintains a heading in the selected direction (Gould and Gould 2012). It has long been recognized that uncovering the mechanisms of these decisions could provide valuable insight into the movements of fish (and thus species distributions, variability in catch, etc.) (Neave 1964; Royce et al. 1968; Harden-Jones 1968). Determining the sensory basis of marine migrations is obviously challenging (Hays et al. 2016), however studies in species that spend part of their lives in terrestrial habitats have proven quite useful (Putman et al. 2017). Pacific salmon in particular have contributed substantially to what is now known about migration from the animal’s perspective and point to an emerging picture that the use of cues from the Earth’s magnetic field plays a central role (Quinn 2018).