Atmospheric influence on physical properties of the North Pacific Ocean: consequences for salmon production

Physical properties of seas and oceans are of major importance to marine ecosystems because they induce the nutrient and light environments that shape their primary production. Physical processes act at all scales, from atmospheric temperatures down to molecular salt diffusivity. A selection of such processes has been made and the most important ones for marine ecosystems will be discussed. Moving up the food chain from phytoplankton will lead to marine fish stocks such as salmon populations. Salmon is an economically important species because it is intensively fished throughout the world. It has been found in the North Pacific Ocean that in the period 1925-1989 the salmon production correlated with the Aleutian Low pressure system, which is the dominant meteorological feature in the winter and spring atmosphere in this region. The salmon catches appear to be above normal when the Aleutian Low is more intense than average and vice versa. The trends in salmon production during the period 1925-1989 appeared to be directly related to climate shifts, and were not a result of human activities such as fishing effort, management actions, or artificial rearing. The changes in Northeast Pacific salmon populations are indirectly linked to climate changes through the marine food chain. A new climate shift is expected to occur in the next few years, with probably unfavourable consequences for the abundance of salmon in the North Pacific Ocean.