Climate change is already impacting the world’s oceans and will have serious consequences for the hundreds of millions of people who depend on fishing for their livelihoods, according to the United Nations Food and Agriculture Organization (FAO). Changes in sea temperatures alter the body temperature of aquatic species used for human consumption and therefore impact their metabolism, growth rate, reproduction and susceptibility to diseases and toxins, FAO said at the start of a four-day scientific seminar in Rome on climate change and marine fisheries.

Impacts on fisheries that have already been observed include an increase in the frequency and intensity of extreme weather events, such as the El Niño phenomenon in the South Pacific; the warming of the world’s oceans, with the Atlantic in particular showing signs of warming deep below the surface; and warmer-water species increasing toward the South and North Poles.

There has also been an increase in salinity in near-surface waters in hotter regions, while the opposite is occurring in colder areas because of greater precipitation, melting ice and other processes.In addition, the oceans are becoming more acidic with probable negative consequences for coral-reef and calcium-bearing organisms.

Fishing communities in the world’s high-latitudes, as well as those that rely on coral reef systems, will be most exposed to the impact of climate change. Fisheries located in deltas, coral atolls and ice-dominated coasts will be vulnerable to flooding and coastal erosion because of rises in sea level.

FAO says that some 42 million people work directly in the fishing sector, the great majority in developing countries. Counting in those who work in processing, supply, marketing and distribution, the fishing industry supports several hundred million jobs.

Aquatic foods have high nutritional quality, contributing 20 per cent or more of average per capita animal protein intake for more than 2.8 billion people, again mostly in developing countries.

Fish is also the world’s most widely traded foodstuff and a key source of export earnings for many poorer countries.The sector has particular significance for small island States.