Research suggests that many countries in Southeast Asia face similar risks. Altogether, 400 million people in Africa and Southeast Asia rely on fish and other marine foods like seaweed to provide half their essential protein and minerals.
Rashid Sumaila, a fisheries economist at the University of British Columbia, said "rough estimates" at modeling the effect of climate change on the world's fisheries suggest catches in the tropics could decline 40 percent by 2055 due to a panoply of factors including warming waters and ocean acidification.
Existing problems like overfishing complicate the picture, making it more difficult to project the effects of climate change.
Like losing 10M bulls every year
"If you have a fishery that is already badly managed, so stocks are not in good shape, and you add another stressor like climate change heating it -- well, then it just goes," said Sumaila.
Eighty-four percent of the world's fish stocks are fully exploited, overexploited or depleted, according to the U.N. Food and Agriculture Organization (FAO).
That overfishing takes an astounding toll on the world economy, ecosystems and food security in areas that rely on fisheries as a cheap and reliable source of food.
When the World Bank recently tried to tally the economic cost of overfishing, poor management and other inefficiencies, it arrived at a princely sum: $50 billion per year, a number that represents both the increased cost of chasing after scarce fish and the price of maintaining an oversupply of fishing vessels.
For the world's poor, many of whom depend on fish as a cheap, reliable source of protein, there is another shocking number: 10 million metric tons. That's the weight of catch lost each year due to overfishing, according to researchers at the University of British Columbia.
"Recently, I tried to convert that estimate to the equivalent in mature bulls," Sumaila said. "They weigh on average 1 ton each. So we are talking about losing 10 million extra bulls every year out of the ocean because of overfishing. When I turned the fish into bulls, that shocked me."
It's also enough food to save at least 20 million malnourished people -- assuming they were fed only fish, he says.
Meanwhile, the global demand for fish is rising. Production of fish and fish products grew from 140 million metric tons in 2007 to 145 million metric tons in 2009, a historic high according to the FAO. Much of that growth has been fueled by aquaculture, which is increasing at a rate of almost 7 percent per year.
Sebastian Troeng, senior vice president for marine conservation at Conservation International, says farming fish is in some ways a more sustainable source of protein than livestock. Producing 1 kilogram of beef (about 2.2 pounds) requires 61.1 kilograms of grain, while producing the equivalent amount of fish protein requires just 13.5 kilograms of grain.
"You can make more with less," Troeng said.
But there are drawbacks to farmed fish that include, in some cases, nutritional trade-offs, said Allison. Farmed fish may not contain all the nutrients their wild cousins do. A fish that is fed grain may not contain as many omega-3 fatty acids as do wild fish or farmed fish that are fed fish meal or smaller fish.
Keeping a reef from 'cement and cockroaches'
In Kenya, McClanahan is hoping that improving the management of the area's fisheries will help gird them against future climate change.
"If you get better management in place, you can buffer these environmental impacts more than if you don't have good management," he said. "If you have already knocked a system back to cement and cockroaches, it doesn't take a lot to make it worse."