Aquaculture for all

Bluefin Tuna Experts Dispute Assessment of Fish Populations

Tuna Husbandry Sustainability +4 more

US - Leading Bluefin tuna researchers at the universities of Massachusetts and Maine issued a rebuttal to a "factsheet" they say is an "irresponsible distortion of the information available" issued by the Pew Charitable Trusts this week, as the International Commission for the Conservation of Atlantic Tuna's (ICCAT) expert working groups meet in Montral beginning today to discuss tuna stocks.

As ICCAT prepares to revise its Atlantic Bluefin tuna stock assessment in 2015, experts are fighting over whose methods and evaluations of tuna populations provide the most accurate and valid basis for fishing regulations.

Molly Lutcavage, fish ecologist and research professor at the University of Massachusetts Amherst and director of the Large Pelagics Research Center (LPRC) in Gloucester, with Walt Golet at Maine, Ben Galuardi at LPRC and Steve Cadrin of the UMass Dartmouth School for Marine Science and Technology, say the Pew statement "lacks scientific credibility." Lutcavage has directed a program since 1993 to study Atlantic Bluefin tuna migration routes, reproduction and spawning areas by tracking them for a year from summer feeding grounds in New England and Canada.

Pew this week sent ICCAT a factsheet calling positions they support "the best available science" and dismissing as "unsupported" several theories that ICCAT considers valid but that remain the subject of continuing scientific debate.

Lutcavage and colleagues note that scientific understanding of Bluefin tuna remains "highly uncertain," that "many aspects of Atlantic Bluefin tuna biology are not known definitively, and that alternative hypotheses should be considered by scientists and fisheries managers."

She and co-authors explain that the difference in outlook for Bluefin tuna in western Atlantic waters, which includes New England, is rooted in two competing population models: A "high recruitment" and "low recruitment" scenario. The high model predicts that the Bluefin population should be much larger than it currently is, suggesting that severe catch reductions are in order. The low model estimates the natural population at levels close to those currently seen, suggesting that the current catch levels can be maintained or increased.

Lutcavage, Golet and colleagues say: "The Pew factsheet is a subjective selection of information, lacks scientific credibility and appears to be agenda-driven. Fishery managers should be aware of the uncertainties involved in Atlantic Bluefin tuna biology and stock assessment and should consider the alternative hypotheses identified by the [ICCAT's] Standing Committee on Research and Statistics process, the 2012 Bluefin tuna stock assessment session and the 2013 Bluefin Meeting on Biological Parameters Review."

American fishermen have felt betrayed by United States negotiators in the past, observers state. Ernie Panacek, president of the Blue Water Fishermen's Association, says: "Positions advanced by U.S. negotiators at ICCAT have ignored the interests of our American fishermen. As a result, valuable U.S. fisheries, including Bluefin tuna and swordfish, are being strangled by our own government."

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