In Antarctica, silverfish account for 90% of fish populations and as well as being at the heart of the food chain, they also lay eggs, which benefits the entire water column and the bottom of the continental shelf. An important aspect within the carbon cycle and climate stability.
Antarctic silverfish wriggle by the thousands in the Southern Ocean. Penguins chase them. Whales set bubble nets for them. They devour plankton themselves, among masses of copepods and diatoms, under icebergs, sea ice, or in the open waters of Antarctica. Long considered by scientists to be a part of the food chain, these fish are also a link between the surface and the continental shelf. The continental shelf, at a depth of about 500 meters, can receive half of the annual organic carbon in the form of sunken fish eggs lost to reproduction. This carbon sink, essential for climate stability, was recently revealed in the journal Communication Biology on April 11 by Dr. Clara Manno, an oceanographer with the British Antarctic Survey, and her research colleagues in Italy.
This latest theory is based on the idea that all Antarctic silverfish have the same reproductive behavior. Like many fish, they lay an excessive number of eggs to cope with the predators that come to feast on these delicacies. While this is highly likely, the scientists still need to prove their hypothesis. “This is a pilot study. After this initial experiment, the next step is to extend the study to the Antarctic Peninsula and other fish species,” explains Dr. Clara Manno. Silverfish make up 90% of the fish population on the Antarctic continental shelf.
The researchers used data from the mooring line installed in 1999 near the Italian Mario Zucchelli station for the sampling in this study. It lies close to the coast in the Ross Sea, in an internationally recognized spawning ground and marine protected area. Adult silverfish do not exceed 25 centimeters in length. They lay their eggs in the asperities of ice floes to protect them. This unique environment is formed when water that is fresher and colder than the sea—from melting ice—rises to the surface and crystallizes, taking on the appearance of a submerged ice palace.
“The eggs are deposited close to the ice, but don’t touch it. We haven’t yet discovered how, but a buoyancy system keeps them close without touching the ice, otherwise they would freeze,” explains the researcher. For those that don’t hatch, aren’t fertilized or fall off, a long descent to the bottom awaits. Very rich in carbon, they feed the ecosystems that inhabit the ocean floor.
“As we know, global warming is having an impact on melting ice, and this could have major consequences for the survival of Antarctic silverfish,” she adds. In fact, their eggs could become as rare as caviar.
Camille Lin, Polar Journal AG
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