Ice Fishing

Deep beneath the near-frozen Weddell Sea in Antarctica there are icefish. Millions and millions of them on the ocean floor, sitting on nests the size of hula hoops. Each clutch holds an average of 1735 eggs, each with a male icefish standing guard against the starfish, polychaete worms, and sea spiders that would eat them.

Last year the research vessel Polarstern recorded somewhat shocking images of the icefish colony. In four hours the ship’s remote camera documented a total of 16,160 nests at about 1000 feet deep. After a couple more dives, the researchers were able to estimate the extent of the active nests: across 92 square miles of the Antarctic sea there were an astounding 60 million active nests – only the largest fish-breeding colony ever discovered. The find was written up this week in the journal Current Biology.

The researchers can only speculate why this area is so fecund. Little is known about the icefish – how they build the nests, whether they reuse them, whether the adult sentries die after the eggs hatch, and most puzzling: why here? About 30 miles to the west, the scientists found a patch of seafloor similarly littered with nests, but these are abandoned, overtaken by sponges and corals. This area is also home to the Weddell seal, which grows quite fat, primarily on icefish.

The researchers have now begun photographing the site twice a day for the next two years. We should know more about the life cycle of this enigmatic creature soon.

Photo credit: PS118, AWI OFOBS team