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The Porsche of the Sea

Together, we can steer it clear of a collision course with extinction!

By Jean-Michel Couteau

Photo: Carrie Vonderhaar, Ocean Futures Society


Through my regular column I am pleased to share with you vital information on the state of the oceans – waves of hope coupled  with much work that needs to be done to ensure future generations have the same privileges as we have enjoyed.  This month I must address the disturbing truth that some of the ocean’s greatest predators are carrying the burden of our modern society, transferring harmful waste across great ocean basins.  The most recent studies of the depleted Bluefin tuna population in the Pacific shows they have elevated levels of radioactive materials in their tissues due to the earthquake in Japan and the Fukushima Nuclear disaster over a year ago. It reminds us how everything is connected.

At three quarters of a ton and up to 15 feet (4.5m) long, the Bluefin swims at amazing speeds, migrating across entire ocean basins.  They dive 3,000 feet (915m) deep in complete darkness but may be guided across the planet by a patch of colourless skin enabling sunlight to enter their brains through the pineal gland. Simply put, the Bluefin tuna can out eat, out grow, out swim, out dive and out migrate any fish in the sea, which makes finding and studying it one of the great modern adventure stories. But today, the Bluefin tuna populations are endangered. The population of the Western Atlantic Bluefin tuna has declined by 72 per cent just in the last 40 years. Overfishing, incidental by-catch and habitat destruction are just some of the stresses impacting these great ocean wanderers.

Radioactive Isotopes

Recently three scientists joined together to examine the levels of radiation material in Pacific Bluefin tuna caught off San Diego, California.  Daniel J. Madigan, a marine ecologist at Stanford University’s Hopkins Marine Station, Nicholas Fisher, a marine scientist known as a radiation hazard specialist from Stony Brook University, and Zofia Baumann, a staff scientist at Fisher’s lab, discovered Bluefin to be contaminated. In their scientific paper Pacific Bluefin Tuna Transport Fukushima-derived Radionuclides from Japan to California, the scientists published that in the 15 tuna they tested they found two radioactive isotopes, cesium-134 and cesium-137. The most likely explanation for their findings is that the tuna migrated from the coast of Japan where radiation contaminated the ocean after the Fukushima nuclear reactors meltdown, all the way to California waters.

The radioactive isotopes are stored in the fatty tissues of the tuna, which happen to be the most valuable part of Bluefin we like to consume. The fact that these fish show some levels of radioactive materials is of obvious concern, but fortunately the radioactivity is still much lower than health regulators caution is unacceptable. Also, we must be concerned with mercury and PCB levels in these populations, which are dangerously high and, potentially, pose a health risk to anyone who consumes Bluefin tuna on a regular basis.

Death by Sushi

But another fundamental challenge is that we are using our advanced fishing technologies to fish these predators faster than they are reproducing, causing drastic depletion of Bluefin stocks in all oceans – the Pacific, Atlantic, Southern oceans and Mediterranean. Seventy per cent of Pacific Bluefin tuna caught by the Japanese is for sushi, and more than 90 per cent of those fish are younger than two years old, never having a chance to reproduce and help restock a depleting population.

Like the buffalo that once roamed the prairies of the western United States and numbered in the millions, so the Bluefin tuna, crossing entire oceans silently and in vast numbers, may also disappear. Hunters and entrepreneurs chase the fish for profit alongside scientists who are racing to learn enough to protect and save the Bluefin.  We could influence the outcome of that race; our choices can doom or help restore this evolutionary marvel of a fish.

My motto has long been that “everything is connected,” and now we as consumers may be obliged to better understand the connection between epic struggles for survival of entire species, and the items on our dinner plates.  While not simple, that may be the critical connection that determines the future of the Bluefin tuna not only in terms of our health, but also in protecting one of the ocean’s greatest predators.

As consumers it is time we unselfishly restrict the consumption of Bluefin tuna today to allow their populations to be restored to healthy numbers so we can sustainably harvest them again in the future. It starts with you!

Sustainability is the key. Many countries are fighting to protect Bluefin tuna around the world. It takes bold stewardship measures at all levels of conservation from governments to individual consumers. We owe it to ourselves; we owe it to our water planet to make sure these conservation measures are in place to ensure our seas are still abundant with the Bluefin tuna.

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