2025_programme: A hydroacoustic look at the changes in Kongsfjorden fish community under the influence of climate warming

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  • Day: June 20, Friday
      Location / Time: D. CHLOE at 09:50 - 10:10
  • Last minutes changes: -
  • Session: 02. Acoustics in polar environments
    Organiser(s): Espen Storheim, Lora van Uffelen, Oskar Glowacki
    Chairperson(s): Lora Van Uffelen
  • Lecture: A hydroacoustic look at the changes in Kongsfjorden fish community under the influence of climate warming
    Paper ID: 2179
    Author(s): Natalia Gorska, Beata Schmidt, Jan Marcin Węsławski, Miłosz Grabowski, Agata Dragan-Górska, Joanna Szczucka, Agnieszka Beszczynska-Möller
    Presenter: Natalia Gorska
    Abstract: Climate warming stimulates a general shift of boreal fish species north towards the Arctic and their colonization in this region. The fjords of Svalbard, such as Kongsfjorden, are feeling the effects of these changes: for example, the numbers of Atlantic cod (Gadus morhua), which is not endemic to the fjords, are increasing. It creates a threat to the economically and ecologically valuable native species of polar cod (Boreogadus Saida), in view of which adult Atlantic cod is a predator. Therefore it is important to study the variability of fish community in the fjords. It stimulated our hydroacoustic research with the main goal: to understand how the fish community in the Kongsfjorden changed over the decade 2013 - 2022.\n\nIn the Kongsfjorden in the years 2013, 2014 and 2022 we collected the backscatter data at the frequency 70 kHz using splitbeam SIimrad EK60 echosounder. The data were analyzed with Echoview software (Echoview 4.90.81.19054). The histograms of fish target strength (TS) were obtained. Fish behavior observed at the echograms was analyzed taking into account the Kongsfjorden’s thermohaline structure, Atlantic and Polar cod’s habits and the history of “predator-prey” relationships in the fjord’s fish community. \n\nThe analysis of the TS histograms indicated that the fish size composition in warmed Kongsfjorden becomes more complicated: fish size distribution changed from near-unimodal - in 2013 to trimodal distribution in 2022. Acoustic information obtained on the behavior of fish of these classes confirmed that these classes concern polar cod, juvenile and adult Atlantic cod. It was demonstrated that the process of establishment of Atlantic cod (adults and juveniles) continues in the Kongsfjorden. \n
  • Corresponding author: Prof Natalia Gorska
    Affiliation: Institute of Oceanology, Polish Academy of Sciences
    Country: Poland

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