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<p>Recently, cyanobacterial blooms have become a major problem in many lakes and reservoirs. Certain cyanobacterial species produce cyanotoxins that are harmful to animals. However, few studies have quantified the spatial distributions of cyanobacteria and fish simultaneously, and the influence of cyanobacterial blooms on fish distribution remains poorly understood. In the present study, the effects of cyanobacterial distribution on fish distribution in Lake Onuma, a eutrophic lake in southern Hokkaido, Japan, where cyanobacterial blooms occur annually during the summer and autumn, were evaluated. Acoustic surveys using a split-beam echosounder (120&#xa0;kHz) and water quality measurements were conducted between August and October 2024. The volume backscattering strength (SV) derived from acoustic data was used as an indicator of the spatial distributions of cyanobacteria and fish. To distinguish acoustic signals from cyanobacteria and fish, a threshold value of − 65.3 dB was determined based on concurrent phycocyanin sensor data. The results showed that cyanobacteria were concentrated in the upper 2–3&#xa0;m during August and September, whereas fish tended to avoid the cyanobacteria-rich layers and were distributed mainly at greater depths. A Generalized Additive Model revealed that fish distribution was influenced significantly by cyanobacterial SV, water temperature, and dissolved oxygen, in addition to their interactions. Fish abundance decreased as cyanobacterial SV increased, indicating avoidance behavior toward cyanobacteria-dense areas. The findings suggest that cyanobacterial blooms alter the vertical distribution of fish through changes in habitat quality, highlighting the importance of considering cyanobacterial dynamics when assessing fish ecology in eutrophic lakes.</p>

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Influence of cyanobacteria on fish distribution based on spatial distribution patterns

  • 期刊论文

  • 发表日期：

    2026年6月2日

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  • Yota Kondo,
  • Kenji Minami,
  • Yanhui Zhu,
  • Sangyeob Kim,
  • Kyosuke Seki,
  • Kohei Yoshida,
  • Kazushi Miyashita

摘要

Recently, cyanobacterial blooms have become a major problem in many lakes and reservoirs. Certain cyanobacterial species produce cyanotoxins that are harmful to animals. However, few studies have quantified the spatial distributions of cyanobacteria and fish simultaneously, and the influence of cyanobacterial blooms on fish distribution remains poorly understood. In the present study, the effects of cyanobacterial distribution on fish distribution in Lake Onuma, a eutrophic lake in southern Hokkaido, Japan, where cyanobacterial blooms occur annually during the summer and autumn, were evaluated. Acoustic surveys using a split-beam echosounder (120 kHz) and water quality measurements were conducted between August and October 2024. The volume backscattering strength (SV) derived from acoustic data was used as an indicator of the spatial distributions of cyanobacteria and fish. To distinguish acoustic signals from cyanobacteria and fish, a threshold value of − 65.3 dB was determined based on concurrent phycocyanin sensor data. The results showed that cyanobacteria were concentrated in the upper 2–3 m during August and September, whereas fish tended to avoid the cyanobacteria-rich layers and were distributed mainly at greater depths. A Generalized Additive Model revealed that fish distribution was influenced significantly by cyanobacterial SV, water temperature, and dissolved oxygen, in addition to their interactions. Fish abundance decreased as cyanobacterial SV increased, indicating avoidance behavior toward cyanobacteria-dense areas. The findings suggest that cyanobacterial blooms alter the vertical distribution of fish through changes in habitat quality, highlighting the importance of considering cyanobacterial dynamics when assessing fish ecology in eutrophic lakes.