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The salmon trawl is put out. (Photo: SALSEA-Merge)
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What is happening to the wild salmon in the Atlantic Ocean?

Over the course of three years, NOK 50 million will be spent on finding out why Atlantic salmon are not returning to the rivers where they hatched. This week, 50 experts on wild salmon from ten European countries are meeting for a conference in Bergen to discuss, amongst other things, this summer's scientific expeditions, which together will constitute the most comprehensive survey of Atlantic salmon to date.

By Kjartan Mæstad
“The number of scientific expeditions studying Atlantic salmon in the summer of 2009 will be greater than ever before. This has been made possible by combining the salmon studies with studies of the other major pelagic populations such as herring, mackerel and blue whiting. Expeditions such as these, which focus on whole ecosystems, have the advantage of allowing us to study the various species in relation to the environment and each other in a cost-efficient way,” says researcher Jens Christian Holst of the Institute of Marine Research, which is doing the scientific coordination of the SALSEA-Merge project.


 Two Atlantic salmon swimming through an open trawl. (Photo: SALSEA-Merge)

Rapid retreat

SALSEA stands for Salmon at Sea and Merge is self-explanatory. The project’s objective is to merge and analyse all available information about the life and living conditions of wild salmon at sea. Some of the important elements of the project are to look at where the various river populations migrate, how they migrate in relation to ocean currents, what they eat, how they grow, how they are affected by variations in other fish populations and food sources, and what overlap there is with pelagic fisheries in terms of by-catches,” says Holst.
The background to the project is that salmon populations in rivers around the Atlantic Ocean have declined rapidly over the past 30 years. This is in spite of the fact that the conditions in many salmon rivers have improved greatly over that period.


Examples of catches. (Photo: SALSEA-Merge)

On an expedition

The SALSEA project started on 1 April last year. During the summer, Holst went on a scientific expedition with the fishing vessel “Eros”, to look at the distribution of salmon, whales and herring around Greenland, amongst other things. During 2008, vessels from Ireland, the Faeroe Islands and Norway caught 900 salmon, which now provide the basis for analysing genetic make-up, genetically determined migration patterns, weight patterns, food choices and overlap with pelagic fisheries.
In addition to the data collected on these expeditions, scientists are using previous surveys of hydrography, plankton, wild salmon and other fish in the salmon’s ocean habitats.
At the conference in Bergen, the scientists will discuss the preliminary results from last year, and plan this year’s research activities. The project will end with a salmon summit in 2011, where Holst and the other scientists hope to answer the question of why salmon are not returning to the same degree as in the past.


The Irish research vessels “Celtic Explorer” and “Celtic Voyager” took part in the expeditions last year. (Photo: SALSEA-Merge)

Important genetic component

There is a big and important genetic component to SALSEA-Merge. Genetics will be used to trace the geographic origin of the individual fish out in the ocean. A reference database for salmon liver is currently being built up across the whole of Europe. The reference database describes the genetic make-up of fish in a large number of European salmon rivers.
On account of regional genetic differences, the reference database can be used, in combination with other information such as the river age, catch position and date, to determine the probable origin of fish that are caught in the ocean. The geographic origin will then be used in analyses of geographic mortality rates in order to assess the differences that have been observed in the marine survival of European salmon.


Trawl containing mackerel and herring mixed with salmon, just before the net is opened. (Photo: SALSEA-Merge)