Kieran McCarthy of Alliance said the decline of salmon was not fully understood and that rising sea surface temperatures may have had a role to play.

BBC: Sustainability of indigenous fish stocks

Both surface temperatures and sea levels have been rising for some time.

ECONOMIST: Blowing hot and cold

One theory is that an initial warming changed the distribution of heat in the oceans so that deposits of gas hydrates on the sea floor were released, with carbon dioxide and methane rising to the surface and entering the atmosphere, causing further greenhouse warming.

BBC: NEWS | Science/Nature | Past gives clue to climate impact

And now the Arctic's upper layers are getting less dense, for several reasons: melting Arctic glaciers, rising surface-water temperatures, increased precipitation and an absence of salt concentrations resulting from sea-ice formation.

ECONOMIST: The science