The oceans are an integral component of the climate system and respond to changes in the system. Natural fluctuations occur in oceanographic conditions -- some are annual while others are less frequent, with cycles that may extend over decades rather than years. Still others are longer-term changes, which might occur over thousands of years. Of current concern are the specific impacts of human activity on climate change, which is expected to result in increases in sea surface temperature, global sea level rise, decreases in sea-ice cover and changes in salinity, wave conditions, and ocean circulation. These changes in turn will have an impact on the biological productivity of marine ecosystems.

The impact on fisheries of changes in the biological productivity of marine ecosystems will vary between fisheries and will depend of the specific environmental changes that occur and the particular biological characteristics of each species. Changes in a particular marine environment may become conducive to a rapid growth of a high-priced species found in that environment, while the reverse may be true in other instances. Climate change will also result in modifications of the area of distribution of marine resources. Most likely they will move towards the North or South pole, whichever is closest. Consequences for the fishing industry could be significant.

An expected characteristic of global climate change is a likely increase in the variability of environmental conditions. Experience already gained in dealing with longer term fluctuations in marine environments, such as those induced by El Niño events, emphasize the need for adaptability. As well, ensuring sustainable economic levels of fishing capacity should be determined with  the variability in mind. The effects of climate change on fisheries will impact a sector that is already characterized by full utilization of resources, large overcapacity and conflicts among fishers, and others, vying for alternative uses of marine ecosystems. Thus, climate change adds a further argument for developing effective and flexible fisheries management system in an ecosystem context.