Day 15: Climate change could find Nemo

Adult orange clownfish Amphiprion percula form breeding pairs. Photo courtesy of the National Academy of Sciences, PNAS.

The news about oceans was pretty grim last week, but there is hope. Most of the world’s fishing countries are reneging on their agreements to fish responsibly and sustainably. Despite harvest restrictions in the Delaware Bay, plummeting horseshoe crab populations are leaving their migratory bird predators high and dry. In a climate change scenario, the poorest fishing countries will be the hardest hit, and are likely to face “unprecedented hardship.”

And global warming could rob Nemo of his sense of smell.

Seriously.

But each of the findings spells out an opportunity to avert the worst.

 

First, the greed:
Tony Pitcher, a fisheries ecologist at the University of British Columbia in Vancouver, and several co-authors wrote a scathing editorial in the journal Nature this past week in which they call out the global fishing community for failing to comply with voluntary limits set forth 13 years ago in the Code of Conduct for Responsible Fisheries.

A study of 53 countries landing 96 percent of the global marine catch “reveals dismayingly poor compliance,” the authors wrote. No country demonstrated much better than 60 percent compliance with the sustainable catch guidelines. Norway is ranked top, followed by the United States, Canada, Australia and Iceland. The authors fouond a strong link between code compliance and parameters such as political stability, as measured by the World Bank governance index. But some developing countries, including Malaysia, South Africa and Namibia, outperformed many developed European countries, “signifying that some elements of good fishery management can be achieved with limited resources,” the authors wrote.

In the end, the study authors say it’s time to put some teeth behind worldwide fishing regulations: “Although the voluntary nature of the code was crucial to getting all-nation agreement,” they wrote, “the time has come for an integrated international legal instrument covering all aspects of fisheries management.”

The crabs:
Beloved long-legged shorebirds called New World red knots stop in the Delaware Bay each year on an annual, 18,000-mile migration that takes them from Arctic breeding grounds to the southern tip of South America and back. At the bay, they feast on the eggs of spawning horseshoe crabs, to fatten up for the rest of their trip. In recent years, though, there haven’t been enough crabs to lay the eggs. The birds are taking off underweight, and they aren’t making it. Lawrence Niles, chief biologist with the Conserve Wildlife Foundation of New Jersey in Bordentown, and his co-authors wrote a paper in last week’s issue of the journal BioScience urging tighter crab harvest regulations until both populations — the crabs and the birds — can be stabilized.

The vulnerable:
A study in the February issue of the journal Fish and Fisheries has pointed out individual countries that are most vulnerable to the impact of climate change on fisheries. The at-risk nations include Malawi, Guinea, Senegal and Uganda in Africa, Bangladesh, Cambodia, Pakistan and Yemen in the Asian tropics and two South American countries: Colombia and Peru.

“From a strictly environmental perspective, countries in the higher latitudes will see the most pronounced impact from climate change on fishing,” said lead author Edward Allison, director of policy, economics and social science at WorldFish. “But economically, people in the tropics and subtropics likely will suffer most, because fish are so important in their diets and because they have limited capacity to develop other sources of income and food.”

The researchers urge teaching vulnerable countries to adapt to climate change possibilities such as loss of coral reefs and drought-hammered lakes.

And, finally, Nemo:
Clownfish, popularized by the indisputably lovable Nemo, select their habitats as larvae based partly on their sense of smell. They prefer to live on ocean reefs that surround vegetated islands, in partnership with anemones, and not too close to their parents (to avoid inbreeding). So in a healthy scenario, larval clownfish are drawn toward the smell of a reef near island vegetation, and away from the scents of their parents and of swampy vegetation, like Melaleuca.

But ecologist Philip Munday of James Cook University and the  Australian Research Council, along with his co-authors, found that the level of acidification expected with global warming disrupts the clownfish larvae’s sense of smell, rendering them unable to make appropriate habitat choices. The study authors say their findings hold “significant consequences for marine biodiversity.”  Larvae of many marine species seem to navigate and orient by their sense of smell, and disrupting those cues could have dramatic consequences for entire marine populations. The study appeared in this week’s issue of the Proceedings of the National Academy of Sciences. The solution? You guessed it: reduce worldwide carbon emissions, so that ocean acidification never reaches the danger zone.