Warmer Oceans Hold Fewer Fish, UN Warns

Most at risk are fishing communities located in the high latitudes and those that rely on ecosystems such as upwelling or coral reefs, that are susceptible to climate change.

Fisheries communities located in deltas, coral atolls and ice dominated coasts will be particularly vulnerable to sea level rise and associated risks of flooding, saline intrusion and coastal erosion.

Fishing boats, Chiloe Island, Chile (Photo by Stefan Wurschinger)

But countries with limited ability to adapt to the changes, even if located in low risk areas, are also vulnerable, UN officials said.

The UN food agency's warning comes at a four day scientific symposium on climate change and marine fisheries being held at its Rome headquarters July 8-11.

The event drew more than 200 experts and policymakers from around the world in an attempt to tackle the challenges that climate change poses to marine fisheries and the millions of people who depend on them for food and income.

Some 42 million people work directly in the fisheries sector, the great majority in developing countries. Adding those who work in associated processing, marketing, distribution and supply industries, the sector supports several hundred million livelihoods, according to the UN Food and Agriculture Organization, FAO.

The ongoing warming of the world's oceans is likely to continue, but with geographical differences and some decadal variability, said the FAO in a statement. "Warming is more intense in surface waters but is not exclusive to these, with the Atlantic showing particularly clear signs of deep warming."

Impacts of climate change on fisheries and aquaculture are already being observed, the FAO says.

Scientists have documented changes in fish distributions in response to climate variations. Warm water species are moving toward the Earth's two poles, and so are the colder water species.

Shifts in ocean salinity are occurring, studies show, with near-surface waters in the more evaporative regions of most of the world's oceans increasing in salinity.

Fishing boats Capetown, South Africa (Photo by Ian Junor)

At the same time, marine areas in high latitudes are showing decreasing salinity due to greater amounts of rain and snow, higher runoff, and melting ice.

The oceans are becoming more acidic, noted the FAO, which predicted "probable negative consequences to many coral reef and calcium-bearing organisms."

In marine waters, climate processes and extreme weather events will increase in frequency and intensity - the best known of these is the El Niño surface water warming phenomenon in the South Pacific.

Wild capture fisheries are uniquely vulnerable to climate change and its effects, the UN agency warned.

"Wild capture fisheries are fundamentally different from other food production systems in their linkages and responses to climate change and in the food security outcomes that result," the FAO said.

The body temperatures of aquatic animal species eaten by humans vary according to the ambient temperatures in their immediate vicinity.

"Any changes in habitat temperatures significantly influence their metabolism, growth rate, productivity, seasonal reproduction, and susceptibility to diseases and toxins," said the UN food agency.

Because fisheries is such a key economic and environmental sector, FAO is increasingly focusing its attention on how climate change will affect fisheries and aquaculture.

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