site.btaIchthyologist Tihomir Stefanov on Foraging, Reproduction of Fish and Crustaceans near Livingston Island

Assoc Prof Tihomir Stefanov, an ichthyologist from the National Museum of Natural History in Sofia and a member of the ongoing 32nd Bulgarian Antarctic Expedition, told BTA about the foraging, reproduction and movement of the separate species of fish and crustaceans (isopods) near Livingston Island. He presented the individuals caught by the expedition and explained their characteristics to Nikola Vatsarov Naval Academy head Boyan Mednikarov and BTA Director General Kiril Valchev, who arrived at the Bulgarian Antarctic base on Livingston Island on Monday. 

The caught fish and isopods will be exhibited in the aquatory of the National Museum of Natural History in Sofia. “We won [funding for] a very big project for the museum. We will build an additional floor on the building where new exhibition space will be available. That is where the Arctica-Antarctica polar room will be. That is why one of my goals is to collect more materials that we can put there in the new exhibition,” Stefanov said.

He presented isopods from the Glyptonotus antarcticus and the Spinoseriolis trilobitoides species. The former species can be found only in Antarctica, the ichthyologist noted. The live individuals will be frozen and stored at minus 70C to be studied by Assoc Prof Lyobomir Kenderov, a hydrobilogist, within his project on the genome of Glyptonotus antarcticus.

Stefanov said his project looks into the special distribution of the separate species in Livingston Island’s South Bay. “We mapped which species live where and at what depth,” he specified. He showed individuals from three fish species.

The dusky rockcod (Trematomus newnesi), of which only one individual was caught, has proven the hypothesis on the habitat of small and big fish in the Livingston Island area. “Small species live at a very big depth, because the big species eat everything in the shallows, they are absolute predators. Smaller species hide in the deep where the main predators have a much smaller biomass,” the ichthyologist explained. This year’s studies have confirmed that.

An interesting discovery made this year is related to the biology of the marbled rockcod (Notothenia rossii) and the black rockcod (Notothenia coriiceps). The marbled rockcod does not reproduce in South Bay: once it reaches reproduction age (7 to 8 years), it migrates. Not a single adult individual of this species, which lives for some 30 years, has been found in the area. Stefanov believes the species reproduces in the South Georgia island area. The black rockcod is the main species reproducing near Livingson Island; it is the dominant predator, he added. 

The blackfin icefish (Chaenocephalus aceratus) turned out to be less rare than expected. It lives in colonies, but the scientists could not catch an individual.

This year, we have collected many interesting data on the fecundity of the three fish species. In the blackfin icefish, the fecundity is low. The male cares for the nest, which he forms by digging with fins into the sea floor and placing stones around the nest. The male attracts the female, and she lays eggs in the nest, which is then guarded by the male. In the black rockcod, the female lays eggs in seaweed and abandons them, Stefanov explained.

***

During the 32nd Bulgarian expedition to Antarctica, which started on November 8, 2023, the Bulgarian News Agency (BTA) is publishing interviews with Antarctic researchers. The Bulgaria-Antarctica BTA's Log again provides coverage of the voyage of the Sv. Sv. Kiril i Metodii to Antarctica and back and its stay there, as it did during the 31st expedition between December 27, 2022 and May 2, 2023. Back then, only BTA had a correspondent, Daily News Editor Konstantin Karagyozov, who covered the 127-day expedition with text, video and photos during the entire voyage (including across the Atlantic in both directions) and throughout the stay in Antarctica. In June 2023, BTA published in Bulgarian and in English an issue of its LIK magazine "To Antarctica and Back under the Bulgarian Flag" dedicated to the historic expedition.

Again, all of BTA's information on the Bulgarian scientific research in Antarctica and the support provided by the Bulgarian naval research vessel, as well as on the other activities at the Bulgarian Antarctic Base, will be available to all media outlets in Bulgarian and in English on BTA's website in the Bulgaria - Antarctica: BTA's Log section.

BTA has a National Press Club on board the ship and is planning to open a National Press Club at the Bulgarian Antarctic Base on Livingston Island.