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More fish lurk in the deep than we thought

Thu, 12th Aug 2010

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A team of researchers from the University of Aberdeen have found that there may be more fish living at extreme depths in the ocean than previously thought.

The group, led by Toyonobo Fujii, used a free-fall lander baited with mackerel and equipped with a camera to observe life in the hadal zone of the Japan Trench, in the Pacific Ocean. Alvin submersible

The hadal zone describes depths of between 6000m and the full ocean depth of 11000m.

The evidence for fish living at these depths has in the past been uncertain and mainly based on trawl records Ė which are unreliable as itís often not clear at what depth the fish actually entered the nets.

By using direct observation with a camera, the team were able to record the deepest ever observation of a group of fish, known as snailfish, at 7703m depth. What was also exciting about using a camera rather than a trawl net was that they were also able to observe the behaviour of the fish, which isnít something that has been done before.

From their observations, the team argued that although numbers of these particular fish were much higher than expected, the diversity of fish species at great depths was probably much lower than previously estimated, although they did also stress that our knowledge of the hadal zones of the deep ocean is still very inadequate and incomplete.



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