Fish vocalization and diel variation patterns of Pacific cod (Gadus macrocephalus) and bluefin gurnard (Chelidonichthys kumu) were investigated using passive acoustic monitoring at a sea-cage facility off Tongyeong, Korea. Autonomous recordings were collected from February 3 to 15, 2023 (Pacific cod) and from September 19 to October 2, 2025 (bluefin gurnard). Power spectral density (PSD) was used to quantify spectral structure and diel variability, and pulse-based grunt detection was applied to time vocal events. For both species, dominant spectral energy occurred below 1 kHz, concentrated at 0.1 – 0.5 kHz for Pacific cod and 0.1 – 0.8 kHz for bluefin gurnard. Pacific cod exhibited a pattern of consistently increasing acoustic activity throughout the night. Bluefin gurnard activity was primarily restricted to approximately 2 hours after sunset and sunrise, exhibiting relatively low chorus signals. The SPL were approximately 107-125 dB re 1 μPa for Pacific cod and approximately 103 – 110 dB re 1 μPa for bluefin gurnard. Based on the diel variation pattern, high-activity (22:00 – 06:00 KST) and low-activity (10:00 – 18:00 KST) phases were defined, and empirical probability density profiles summarized frequency-dependent distribution shifts between phases. The acoustic characteristics and diel variation patterns of the two fish species' sounds will help manage fishery resources and identify spawning and fishing grounds.

서 론
재료 및 방법
    연구 대상 및 실험 환경
    생물음 측정 장비 및 자료 수집 방법
    생물음 자료 신호 처리 및 분석 방법
결과 및 고찰
결 론
사 사
References

• 임승욱(한국해양과학기술원 해양력강화,방위연구부 연구원) | Seung-Uk IM (Research Scientist, Sea Power Reinforcement, Security Research Department, Korea Institute of Ocean Science and Technology (KIOST), Busan 49111, Korea)
• 윤영글(한국해양과학기술원 해양력강화,방위연구부 연구원) | Young Geul YOON (Research Scientist, Sea Power Reinforcement, Security Research Department, Korea Institute of Ocean Science and Technology (KIOST), Busan 49111, Korea)
• 조성호(한국해양과학기술원 해양력강화,방위연구부 연구원) | Sungho CHO (Research Scientist, Sea Power Reinforcement, Security Research Department, Korea Institute of Ocean Science and Technology (KIOST), Busan 49111, Korea)
• 김선효(한국해양과학기술원 해양력강화,방위연구부 연구원) | Sunhyo KIM (Research Scientist, Sea Power Reinforcement, Security Research Department, Korea Institute of Ocean Science and Technology (KIOST), Busan 49111, Korea)
• 강돈혁(한국해양과학기술원 해양력강화,방위연구부 연구원) | Donhyug KANG (Research Scientist, Sea Power Reinforcement, Security Research Department, Korea Institute of Ocean Science and Technology (KIOST), Busan 49111, Korea)
• 김한수(한국해양과학기술원 해양력강화,방위연구부 연구원) | Hansoo KIM (Research Scientist, Sea Power Reinforcement, Security Research Department, Korea Institute of Ocean Science and Technology (KIOST), Busan 49111, Korea) Corresponding author
• 정윤환(한국해양과학기술원 통영해상실증기지 연구원) | Yun-Hwan JUNG (Research Scientist, Tongyeong Maritime Test and Evaluation Station, Korea Institute of Ocean Science and Technology (KIOST), Tongyeong 53087, Korea)