Atlantic salmon: the ocean traveller
Atlantic salmon are distributed over large areas in the North Atlantic, and the species is known to undertake long migrations. Salmon are also distributed in the Baltic, but rarely move from there into the Atlantic. More than 100 years ago, with the development of coastal salmon fisheries, detailed information on migration and distribution of the salmon in these waters started to accumulate. The knowledge of salmon movements in oceanic areas was a black box until oceanic fisheries developed in the 1960s at West Greenland and in the northern Norwegian Sea. Since that time, the information about the oceanic life history of Atlantic salmon has improved considerably. At West Greenland, salmon from Canada, the United Kingdom (UK), and Ireland are most abundant, but fish from most salmon-producing countries are probably present there in small numbers and in different proportions. For example, a large proportion of salmon originating from the United States and a small proportion of Norwegian fish are present in this area. In the Norwegian Sea, fish from Norway are most abundant, but there are relatively high proportions of fish from the UK (Scotland) and Russia in this area, and smaller proportions from other areas of Europe. Fish of North American origin have also been observed there. Atlantic salmon home with high precision to the rivers they left as smolts. The homing migration seems to consist of two phases: a first phase with crude navigation from oceanic waters to coastal areas, and a second phase with more precise navigation in coastal and estuarine waters towards the home river. The underlying mechanisms explaining these migrations are still a matter of controversy, but apparently the juvenile fish learn their way (imprint) sequentially and use that information to return home. During the oceanic phase, salmon are thought to use celestial cues, magnetic fields, or a combination of different cues. The olfactory sense plays a major role for the final orientation in tjords, estuaries, and rivers.
Article from Marine Science Symposia Vol. 215 - 100 years of science under ICES. To access the remaining articles please click on the keyword "MSS Vol. 215".