For Tim McClanahan, a zoologist studying fisheries, what happened in Kenya during the spring of 1998 was a wake-up call.
Between March and July of that year, a rare climatological double whammy sent ocean temperatures spiking 1 to 2 degrees Celsius above the normal range for spring and summer. An unusually intense El Niño weather pattern coincided with the warm phase of another cyclical area weather event.
This turned out to be a slow-motion disaster. Half the corals in the region bleached and died that year. Some had a 90 percent loss. "The bleaching and mortality event took about six months to fully unfold, but many of the reefs have not recovered even today -- 14 years after the event," said McClanahan, an employee of the Wildlife Conservation Society. He has spent more than 20 years working along Kenya's southeastern coast.
It took four years before scientists could definitively show dramatic declines in three commonly caught species of food fish. The lag and the devastating results got McClanahan thinking about climate change's potential to damage the economies of communities that traditionally rely on fish to eat and fish to sell.
He's not alone in pondering the fate of the world's fisheries in a changing climate, and how the fortunes of fish will affect the lives and livelihoods of more than 1.5 billion people who depend on seafood for at least a fifth of the animal protein they consume.
"This is an area that is pretty seriously underresearched, I think," said Edward Allison, a senior fellow at the University of East Anglia's School of International Development. "The rest of agriculture sometimes forgets fisheries, and the fisheries sector has been a little slower than others to realize the potential seriousness of climate change impacts."
Already, there is evidence that as the ocean warms, many commercial fish stocks are moving poleward in search of cooler waters. Rising ocean temperatures have triggered coral bleaching events that have caused widespread damage to the world's reefs, which serve as a habitat for many species.
A case of 'double jeopardy' for Africa and Asia
Researchers are also concerned about the effects that shifting ocean chemistry will have on marine ecosystems. As the world's carbon dioxide output has risen, oceans have absorbed more and more of the heat-trapping gas, leaving seawater 30 percent more acidic than it was before the Industrial Revolution began.
Eventually, ocean acidification could scramble ocean ecosystems by making it harder for sea creatures like oysters, coral and plankton to grow the hard, chalky shells that protect them from predators.
But experts say the consequences of those changes for fisheries are uncertain, though many believe that climate change will ultimately separate fish species, fisheries and the human communities that depend on them into winners and losers.
A crop of recent studies is just beginning to figure out who those winners and losers might be.
When researchers at the Malaysia-based WorldFish Center tried to rank countries by the vulnerability of their fisheries to climate change, Gambia topped the list -- and all but two of the top 10 nations were African, hailing from a continent where fish accounts for half the animal protein consumed each day and often provides significant income.
For many countries in Africa, climate change amounts to "double jeopardy," threatening food supplied by land and sea, said Allison, who led the WorldFish Center analysis.
Countries like Sierra Leone, Niger and the Democratic Republic of the Congo already face "extremely alarming" levels of hunger, according to the International Food Policy Research Institute. With climate change expected to decrease yields of staple crops like rain-fed maize and irrigated rice up to 20 percent by 2050, loss of fisheries catch as well could prove devastating.