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Damage Of Oil Spill To Bluefin Spawning Ground Minor

A recently published scientific paper has found that less than 10% of the spawning habitat of west Atlantic bluefin tuna was impacted by the Deepwater Horizon oil spill.
Preliminary estimates made in the months just after the spill were much higher, ranging from 20 to 30 percent, reflects the American Bluefin Tuna Association (ABTA), who hail the new findings as very good news for west Atlantic bluefin, and those who make their livelihoods from fishing for them.
The paper was published in Marine Pollution Bulletin and entitled, “Overlap between Atlantic bluefin tuna spawning grounds and observed Deepwater Horizon surface oil in the northern Gulf of Mexico.”

The findings state that: “Overall, less than 10% of the bluefin tuna spawning habitat was predicted to have been covered by surface oil, and less than 12% of larval bluefin were predicted to have been located within contaminated waters in the northern Gulf of Mexico, on a weekly basis.”

An early Draft Research Plan released seven months ago by the Highly Migratory Species Division of the National Marine Fisheries Service (NMFS) performed a preliminary analysis based upon the assumption of 20% larval mortality, but this Draft Plan lacked sufficient data. In the Draft Plan, NMFS concluded that, even under the assumption of 20% larval mortality, impacts on future bluefin stock biomass appeared “negligible”.  Findings in the present study validate a much lower percentage of probable larval mortality. The Draft Plan also noted that all mature bluefin that were electronically tagged in the region of the spill during the 2010 spawning season survived long after leaving the Gulf.
The locations in the Gulf of Mexico preferred by bluefin tuna for spawning is a question that has been the subject of several scientific studies during the last few decades.  This paper establishes that: “High abundance of larvae were located elsewhere, especially in the western Gulf of Mexico”, finally establishing that bluefin overwhelmingly prefer to spawn in the western Gulf of Mexico, far from the oil spill.
“This is excellent news indeed for the bluefin, because early estimates of damage to bluefin spawning grounds were much higher, in the region of 20-30%,” stated Rich Ruais, Executive Director of the American Bluefin Tuna Association.  “And we are pleased that with these findings, scientists have finally established that most bluefin spawning takes place in the western Gulf, far from the oil spill. This very thorough study could only have been done with the close collaboration of NOAA and NASA and the group of highly regarded scientists who collaborated on the research.”
The scientific paper was authored by scientists from the National Marine FIsheries Service, the University of Miami, the University of South Florida and Roffer’s Ocean Fishing Forecasting Service of West Melbourne, Florida.
West Atlantic bluefin tuna spawn in the Gulf of Mexico in certain areas in which bathymetric, eddy, sea surface temperature, current and other factors are desirable for bluefin spawning activity. Their habitat and spawning grounds were the subject of an intense study undertaken by NOAA over a period of nearly a year, pursuant to a petition tendered in May of 2010 to place Atlantic bluefin tuna under protection of the Endangered Species Act. The findings of NOAA were published in May 2011 and established that the species did not warrant protection under ESA because it was not threatened with endangerment.