The breeding colony of fish spanned at least 150 square miles and included about 60 million active icefish nests. Finding a colony this large has been unprecedented, representing a biomass of more than 60,000 tons - or over 135 million lbs. Each of the nests was occupied by a single adult icefish, that would guard more than 1,700 eggs.

       The researchers noted there were many fish carcasses found within and near the site, suggesting that the notothenioids, or icefish, play an important role in the wider food web.

       These creatures were particularly under threat from seals and other predators.

       Dr Autun Purser, lead author of the findings, reported in journal Current Biology, said: "A great many seals spend much of their time in close proximity to the fish nests.

       "We know this from historical tracking data and fresh tracking data from our cruise. The nests are exactly where the warmer water is upwelling.

       "These facts may be coincidence, and more work is needed, but the recorded seal data show seals do indeed dive to the depths of the fish nests, so may well be dining on these fish."

       The mysterious icefish colony is located in the southern Weddell Sea on the eastern side of the Peninsula.

       Their bodily fluids contain antifreeze proteins that enable them to survive the very cold temperatures of the Southern Ocean.

       As a result, blood is less thick and sticky - increasing supply of oxygen to organs.

       READ MORE: Antarctica discovery offered stunning evidence for life

       Dr Purser, of the Alfred Wegener Institute, Bremerhaven, said: "Our most important finding is the pure existence of such an extensive icefish brooding colony.

       "A few dozen nests have been observed elsewhere in the Antarctic - but this find is orders of magnitude larger."

       Dr Purser said: "We did not know to expect any sort of fish nest ecosystem."

       That part, he adds, came as a "total surprise."

       Dr Purser said: "After the spectacular discovery of the many fish nests, we thought about a strategy on board to find out how large the breeding area was - there was literally no end in sight."

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