A vast breeding colony of a fish species called the Jonah’s icefish (Neopagetopsis ionah) has been discovered in the southern Weddell Sea, Antarctica.
The Jonah’s icefish is a species of notothenioid fish in the family Channichthyidae (crocodile icefishes).
First described in 1947 by the Swedish ichthyologist Orvar Nybelin, it belongs to the monotypic genus Neopagetopsis.
The species is found in the Southern Ocean at depths of from 20 to 900 m.
In February 2021, a team of researchers aboard the German research vessel Polarstern spotted numerous nests of the Jonah’s icefish on the seafloor of the Antarctic Weddell Sea.
“The unique observations were made with the Ocean Floor Observation and Bathymetry System (OFOBS),” said Autun Purser, a marine biologist with the Alfred Wegener Institute at the Helmholtz Centre for Polar and Marine Research.
“It is a camera sledge built to survey the seafloor of extreme environments, like ice-covered seas.”
“It is towed on a special fiber-optic and power cable normally at a speed of about one half to one knot, about 1.5 m above the seafloor.”
The colony was estimated to cover at least 240 km2 of the eastern flank of the Filchner Trough, comprised of fish nests at a density of 0.26 nests per m2.
It represents an estimated total of 60 million active nests and associated fish biomass of over 60,000 tons.
The majority of nests were each occupied by one adult icefish guarding 1,735 eggs.
“The idea that such a huge breeding area of icefish in the Weddell Sea was previously undiscovered is totally fascinating,” Purser said.
“After all, the Alfred Wegener Institute has been exploring the area with its icebreaker Polarstern since the early 1980s.”
“So far, only individual Neopagetopsis ionah or small clusters of nests have been detected here.”
According to the team, it is the most spatially expansive continuous fish breeding colony discovered to date globally at any depth, as well as an exceptionally high Antarctic seafloor biomass.
“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,” Purser said.
“The nests are three quarters of a meter in diameter — so they are much larger than the structures and creatures, some of which are only centimeters in size, that we normally detect with the OFOBS system.”
“So, we were able to increase the height above ground to about 3 m and the towing speed to a maximum of three knots, thus multiplying the area investigated.”
“We covered an area of 45,600 m2 and counted an incredible 16,160 fish nests on the photo and video footage.”
A paper describing the discovery was published in the journal Current Biology.
Autun Purser et al. A vast icefish breeding colony discovered in the Antarctic. Current Biology, published online January 13, 2022; doi: 10.1016/j.cub.2021.12.022
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