How deep can fish go?

Five fish hauled up from near-record depths off the coast of New Zealand are providing scientists with new insights into how deep fish can survive.

This photo taken in late 2011 and released by University of Aberdeen, shows hadal snailfish 7,500 meters down, at the bottom of the Kermadec Trench near New Zealand. Scientists say the snailfish are providing new insights into how deep fish can survive.. (Picture from: http://www.mysanantonio.com/)

In a paper published this week in the Proceedings of the National Academy of Sciences journal, scientists from the United States, Britain, and New Zealand describe catching translucent hadal snailfish at a depth of 7 kilometers (4.3 miles).

By measuring the levels of compounds in the fish which helped offset the effect of pressure, the scientists say they have concluded that the fish might not survive under approximately 8,200 m (5.1 miles). That would mean no fish live in the deepest one-quarter of the world's oceans.

The snailfish have almost no pigment due to the lack of light in their environment.

New Zealand marine ecologist Ashley Rowden, a co-author of the paper, said nobody had caught a snailfish in nearly 60 years and so he wasn't overly hopeful when they sent down a box-like trap into the Kermadec Trench near New Zealand in late 2011.

He said they used mackerel as bait to attract the small sandhopper-like creatures the snailfish feed upon. "When it came up, it was just amazing to see. It was 'Oh my God, we've got the fish, and we've got more than one,'" Rowden said. *** [EKA | FROM VARIOUS SOURCES | THE NEW ZEALAND HERALD]
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