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Commercial Fisheries News
Volume 32 Number 12
July 2005
Block paper stirs praise, controversy
DURHAM, NH - The scientific paper on bluefin tuna migration patterns published by Stanford University researcher Barbara Block this spring has stirred up both praise and controversy.
The paper is the most convincing scientific report so far to make the case that bluefin tuna from both sides of the Atlantic Ocean intermix. As such, it boosts the argument by western nations at the International Commission for the Conservation of Atlantic Tunas (ICCAT) that eastern countries must stop rampant, unregulated fishing in order for the resource on both sides of the ocean to rebuild.
Yet the paper’s statement that the eight-year tagging program shows “the existence of two North Atlantic bluefin tuna stocks with discrete spawning areas primarily in the Gulf of Mexico and the Mediterranean Sea” raises some serious questions, according to other bluefin experts and industry people.
Molly Lutcavage, scientific director of the Center for Large Pelagics Research at the University of New Hampshire, has headed up electronic tagging efforts in New England since 1997. Over that time, she has seen little evidence that western fish spawn only in the Gulf of Mexico.
“Only one of the dozens of giants whose tags remained attached until April through July (spawning season) of the following year has reported from or near the Gulf of Mexico,” she said. “All the others were located near the Gulf Stream margin or in the central North Atlantic.”
Lutcavage added that she and her collaborators believe the spawning habits of some of the bluefin found in this region are “much broader” than what Block’s study indicates.
She cited research conducted by graduate student Jenn Goldstein on adult bluefin sampled off New England in June and July, which showed signs of “recent spawning capability.”
This, Lutcavage said, lends further support to historic studies by earlier bluefin scientists Frank Mather and Ray Baglin, who concluded that some bluefin spawn in warm water along the edge of the Gulf Stream before they enter the New England region.
Another possibility is that the fish don’t spawn every year, she said.
No unilateral action
Rich Ruais, executive director of the East Coast Tuna Association, who works closely with both Block and Lutcavage, also had reservations about some of conclusions in Block’s paper.
“I don’t agree with the spawning site fidelity finding,” he said. “I think it’s too small a sample to make such a determination.”
He added that “exhaustive research” by genetic scientists has been unable to show any difference between eastern and western bluefin tuna.
Ruais also strongly disagreed with Block’s call on the US government to shut down the Gulf of Mexico to pelagic longliners during spawning season. Following publication of the paper, the environmental group Oceana and others filed a petition with the federal government requesting such a shutdown.
Ruais argued that the US has already sacrificed much and should only take further steps if it gets a conservation action from other fishing nations in return.
“First off, I don’t believe in management by petition. Second, we need to get something out of Japan in the central Atlantic for closing the Gulf of Mexico,” he said. “Unilateral action only weakens the US position and our ability to get something done at ICCAT.”
Ultimately, though, Ruais said Block’s paper will help put pressure on eastern Atlantic and Mediterranean countries to “accept the new biological reality of pervasive mixing of bluefin in the central and northeast Atlantic Ocean.”
Science vs. management
Glenn Delaney, a former US ICCAT commissioner and a lobbyist for Blue Water Fishermen’s Association, which represents US longliners, called Block’s research “outstanding.”
However, he expressed serious reservations with her advocacy for closing spawning areas in the Gulf of Mexico.
Delaney pointed out that the US has already implemented “substantial, comprehensive, and highly effective measures” to protect spawning bluefin in the Gulf of Mexico and Straits of Florida – measures he called “unprecedented and unmatched by any other nation.”
“While I appreciate Dr. Block’s constructive intent to apply her research to assist fishery managers, in this case (further restrictions) would come at substantial and unjustified cost to other important US fisheries and would not yield a measurable benefit to the bluefin population,” he said.
Lorelei Stevens
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