Toothfish stones help polar geologists


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Russian geologists have found a new use for Antarctic toothfishes - as low-capacity bottom dredges for sampling the geological composition of the Antarctic sea floor.

Researchers at the All-Russian Research Institute of Fish Industry and Oceanography and the Institute of Mineralogy, Geochemistry and Crystal Chemistry of Rare Elements have gained insights into the geology of the Antarctic sea floor by examining stones swallowed by the toothfishes (Dissostichus mawsoni).

The Antarctic toothfish, a nototheniid fish capable of reaching up to 1.75 m in length and up to weights of 80kg, is found in circumpolar waters around the Antarctic.

Picture by Paul Cziko (Creative Commons).

The reasons for the fish swallowing the stones are unclear, but researchers hypothesize that the stones may be used to grind up food items in the stomach (the toothfish is a predator that feeds on smaller fishes and squid), or that they serve as ballast to help the fish move up and down the water column.

Analysis of the swallowed stones have allowed geologists to study areas of sea floor previously considered inaccessible because of the ice cover.

So far, geologists have captured toothfishes in two fishing seasons from the Ross Sea and the Amundsen Sea and the stones in the gut have helped understand the geological composition of these regions.

Although it is not known how far the toothfish swim after picking up the stones, the relative uniformity of the composition of stones found in the toothfishes caught from one area suggests that this method has some merit.