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|Bluefin tuna hit hard by 'Deepwater Horizon' disaster
|The Gulf of Mexico oil spill couldn't have occurred at a worse time for bluefin tuna: they had come to the area â€“ a major spawning ground â€“ to produce offspring.
Satellites are helping assess the damage from the disaster on the fish's spawning habitat.
The majestic Atlantic bluefin tuna, among the largest fish able to grow the size of a Volkswagen Beetle, come to the Gulf yearly from January to June. Their peak spawning time in the Gulf is April and May â€“ just when some 10 million litres of oil a day was pouring into the water following the explosion of the Deepwater Horizon rig on 20 April.
The commercially valuable fish spawn in surface waters, with females
releasing eggs and males following behind to fertilise them. The presence of
surface oil could harm eggs, larvae and even adults. With the western Atlantic
tuna population's spawning stock declining by 82% over the last 30 years, it is
imperative they spawn without disturbance.
In an effort to safeguard their spawning grounds, the Ocean Foundation â€“ a non-profit organisation involved in protecting ocean environments and species â€“ needed to know which habitats throughout the northeastern part of the Gulf had been the most affected. This required knowing the extent of the oil spill and the locations that provided favourable conditions for tuna spawning.
Radar data from ESA's Envisat and other European and international satellites
were used transformed into weekly maps showing the location, shape and size of
Quickly after hatching, larvae begin searching for food close to the surface.
That means the presence of oil there is likely fatal for such tiny organisms.
"This analysis will help us and our colleagues elevate our understanding of
these impacts to another level and guide the development of strong policy
recommendations," said Dr David Guggenheim of the Ocean Foundation.
By the time the Deepwater Horizon well was finally plugged on 15 July, some
750 million litres of crude oil had spewed into the Gulf.
Natural habitat protection is coming under the spotlight this week at the UN Convention on Biological Diversity's 10th Conference of the Parties (COP 10), being held in Nagoya, Japan. ESA is attending the COP10 with an exhibition booth and a side event.