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(CNN) -- Dr David Rawson knows a thing or two about fish.
A professor at the University of Bedfordshire, Dr Rawson has been working at the cutting edge of cryo-preservation for many years.
His mission is to establish a cryo-bank of endangered and non-endangered fish species from the waters around the British Isles.
"The big concern is that certain groups are particularly vulnerable to extinction, and fish probably most of all," he explains to CNN.
"Something like 30 percent of them are considered highly vulnerable, which is a big concern in the [U.N.'s] Year of Biodiversity."
To create his "frozen ark", Dr Rawson must collect DNA samples from all over the British Isles.
On a windy day in July, CNN gets a chance to see first-hand how his work is carried out.
We load the gear -- including liquid nitrogen storage containers and scientific instruments, as well as our camera equipment -- on to a fishing vessel and head to the fishing grounds of the North Sea.
It's a particularly choppy day and we cannot help but notice that we are one of the few fishing boats braving the conditions. But Dr Rawson is not deterred.
"Fish occupy something like 50 percent of all vertebrates on the planet. They're the very earliest in vertebrates so they're very useful in telling us how different vertebrate groups evolved including ourselves," explains Rawson as he dons his waterproof coveralls.
"Dramatic changes to the environment can suddenly result in a species which, today, is relatively common suddenly becoming on the verge of extinction."
Soon enough, we have our first catch. Skate is particularly common in these waters, but we also catch sea bass and several types of small shark.
Dr Rawson needs to collect samples from the fin and the tail for his work. The conditions are uncharacteristically rough and it is increasingly difficult for us to film, but even as we are tossed around like bath toys on the rough waves Dr Rawson gamely gets out his sterilized instruments and begins to take his samples.
However, as the waters become increasingly choppy even Dr Rawson cannot continue with his work. We have no choice but to return to the harbor.
Back in the safety of Lowestoft marina, Dr Rawson and his assistant finally get a chance to collect their samples. It's ideal to do as much of the work as possible on the ship so that the material can be collected while it's still fresh.
Dr Rawson makes an incision in the tail of the fish and carefully disinfects it before placing it in a test tube. The samples must be stored in liquid nitrogen at temperatures of around -196°C, where, in effect, life is held in suspended animation for as long as it is needed.
With more than 30,000 species of fish, establishing a record of their entire DNA is an enormous task, but Dr Rawson is undaunted.
"I think it's making us recognize the value of our biodiversity," he tells me back at his lab.
"In 100 years it will be very useful to be able to look back on. That's why we're taking snapshots of our biodiversity, so that it's there to be looked at for future generations."