Assoc. Prof. Stefanov: Fish Behaviour in Arctic Ocean Can Serve as Indicator of Global Climate Change

Fish behaviour in the Arctic Ocean can serve as an indicator of global climate change and its impact on the environment, noted in a BTA interview Assoc. Prof. Tihomir Stefanov from the National Museum of Natural History in Sofia, who is part of the 31st Bulgarian Antarctic expedition.

"It is important to know how glacier melting is affecting fish behaviour so we can assess if the process is getting worse. One of the things we expect from climate change is ice melting. The melting of the ice will bring a huge amount of fresh water into the world's oceans, but we do not yet know how it will affect the biodiversity there. Johnsons Dock is a suitable natural laboratory on a small scale, where we can test what changes ice melting provokes in fish behaviour compared to fish not affected by it," Stefanov added.

His project focuses on the hypothesis that the active melting of glaciers in Antarctica has a direct impact on the fish behaviour and specifically on their feeding behaviour. The scientist uses Johnsons Dock, a closed bay located near the Bulgarian polar base "St. Kliment Ohridski" on Livingstone Island, as a natural laboratory. The site is suitable because of its different water composition - there is a melting glacier above the bay, while a sea spit separates it from the open water. Stefanov hopes to make a comparative analysis between specimens inhabiting Johnsons Dock and those from the open sea, which includes the island's South Bay.

"Water from the melting glacier contains a lot of impurities - it is much less clear. This lower transparency leads to less activity of filamentous algae, the photosynthetic agents of the sea. I would also expect the amount of oxygen in Johnsons Docks to be lower because there is not as much photosynthesis activity," he explained. "I'd like to see how these changes associated with glacier melting processes affect the ichthyofauna specifically in these conditions here at Johnsons Dock," Stefanov said, stating that the water in the bay has lower salinity and higher turbidity.

"One of the main goals of the project is to study the spatial distribution of individual fish species - which species dominate at what depths. During my previous stay on Livingston Island, I noticed that the two dominant predatory fish species, Notothenia rossii and Notothenia coriiceps, live in shallower waters. These dominant predators put pressure on smaller species such as the Trematomus, which I only encountered in deeper waters where the predators are declining," added the scientist.

"The second goal has to do with the behaviour and feeding of species in relation to the impact of glacier melting. The third, the main objective of the project, is to establish a monitoring system for the ichthyofauna in the South Bay. If we put the same amount of effort over a period of time, changes in the fish population can be tracked. I laid the groundwork for the monitoring programme during my previous visit to Livingstone Island. My desire now is to repeat the same effort I made then, see what the results are, and refine the fish monitoring methodology. When the same efforts are made over a period of time, we will be able to track trends in the populations of individual species and, consequently, they will serve as an indicator to us if something is happening in the Antarctic ecosystem," he added.

The two-year project is currently in its preparatory phase. Monitoring methodology has to be established and the first real data to be collected and used as a reference against which to compare any other possible deviations that may occur in the coming years, explained Stefanov, setting himself the task of monitoring every five years to track trends in species development.

BTA's Daily News editor Konstantin Karagyozov is the only member of the media who is travelling on board the ship to Livingston Island and back and covering the Bulgarian expedition throughout its stay in Antarctica. All media outlets can use the Bulgaria-Antarctica BTA's Log for free.