Body Count Continues

spawn right where the well is…

The 700-pound giant Atlantic bluefin tuna carrying satellite radio tag number 5108024 entered the Gulf of Mexico on March 23, 2009, hugging the coast of Cuba, and speeding along a straight line to the warm water body’s center.

The huge fish meandered north toward what would become its spawning and feeding territory over the next two months, the deep Gulf slope between Louisiana and western Florida. Finally, it left the Gulf for colder water in the Atlantic on May 24. Its tag was jettisoned for pickup by scientists a few days later.

More than once, the fish’s squiggly path took it right across the mouth of the Mississippi River, alongside the drilling ship developing BP’s Deepwater Horizon well.

If the fish had been tagged this year, the tag would likely have shown the tuna following the same path, where it and its eggs would have been swimming or floating in the oil being released from the sunken Deepwater Horizon rig, said Barbara Block, a Stanford University marine biologist who has participated in the tagging of more than 1,000 bluefins during the past 10 years.

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During their two months in the Gulf, the huge tuna reach their warmest body temperatures of the year, as they expend energy to court, mate and spawn, each female laying as many as a million eggs. The resulting stress means the tuna will breathe much more rapidly than usual, and their gills are much more likely to capture tiny droplets of oil suspended in the water column, the result of dispersants used to break up the oil spill, Block said.

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“They’re skimming the surface in that mixed layer right where these animals are putting their eggs and larvae,” she said. “It’s an insult this fish can’t afford at this time, when they’re really considered an endangered species in the same vein as pandas, tigers and rhinoceroses.”

The bluefin is at the top of the Gulf’s food chain, and that means its lifespan is much longer than shrimp, which live for eight or nine months, or the other smaller creatures on which it feeds. Just growing to sexual maturity takes as long as 10 years, which means the loss of a significant number of fish from a single year-class can threaten the species, she said.

“When you lose a year class, the effects come to bear on the fishery 10 years from now, when you don’t have enough fish to spawn a new generation,” she said.

Bluefin tuna particularly vulnerable to Gulf of Mexico oil leak, NOLA.com