New article online: Comparison of passive acoustic soniferous fish monitoring with supervised and unsupervised approaches

Comparison of passive acoustic soniferous fish monitoring with supervised and unsupervised approaches

The Journal of the Acoustical Society of America 143, EL278 (2018)
https://doi.org/10.1121/1.5034169

Tzu-Hao Lin
Department of Marine Biodiversity Research, Japan Agency for Marine-Earth Science and Technology, 2-15, Natsushima, Yokosuka City, Kanagawa, 237-0061, Japan

Yu Tsao
Research Center for Information Technology Innovation, Academia Sinica, Number 128, Section 2, Academia Road, Taipei 115, Taiwan, Republic of China

Tomonari Akamatsu
National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, 2-12-4 Fukuura, Yokohama, Kanagawa 236-8648, Japan

Passive acoustics has been used to investigate behavior and relative abundances of soniferous fish. However, because of noise interferences, it remains challenging to accurately analyze acoustic activities of soniferous fish. This study proposes a multi-method approach, which combines rule-based detector, periodicity-coded non-negative matrix factorization, and Gaussian mixture models. Although the three methods performed well when used to detect croaker choruses in quiet conditions, inconsistent results are observed in noisy conditions. A consistency matrix can provide insights regarding the bias of acoustic monitoring results. The results suggest that the proposed approach can reasonably improve passive acoustic monitoring of soniferous fish.

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5th Joint Meeting of the Acoustical Society of America and Acoustical Society of Japan

2016/11/28-12/2 @ Honolulu, USA

Acoustic response of Indo-Pacific humpback dolphins to the variability of marine soundscape

Tzu-Hao Lin, Yu Tsao
Research Center for Information Technology Innovation, Academia Sinica

Shih-Hau Fang
Department of Electrical Engineering, Yuan Ze University

Chih-Kai Yang, Lien-Siang Chou
Institute of Ecology and Evolutionary Biology, National Taiwan University

Marine mammals can adjust their vocal behaviors when they encounter anthropogenic noise. The acoustic divergence among different populations has also been considered as the effect of ambient noise. The recent studies discover that the marine soundscape is highly dynamic; however, it remains unclear how marine mammals alter their vocal behaviors under various acoustic environments. In this study, autonomous sound recorders were deployed in western Taiwan waters between 2012 and 2015. Soundscape scenes were unsupervised classified according to acoustic features measured in each 5 min interval. Non-negative matrix factorization was used to separate different scenes and to inverse the temporal occurrence of each soundscape scene. Echolocation clicks and whistles of Indo-Pacific humpback dolphins, which represent the only marine mammal species occurred in the study area, were automatically detected and analyzed. The preliminary result indicates the soundscape scenes dominated by biological sounds are correlated with the acoustic detection rate of humpback dolphins. Besides, the dolphin whistles are much complex when the prey associated scene is prominent in the local soundscape. In the future, the soundscape information may be used to predict the occurrence and habitat use of marine mammals.

Oceanoise Asia 2016

2016/4/20

Characterization of the marine soundscape at the core habitat of Indo-Pacific humpback dolphins

Tzu-Hao Lin, Lien-Siang Chou
Institute of Ecology and Evolutionary Biology, National Taiwan University

Shane Guan
Office of Protected Resources, National Marine Fisheries Service, Silver Spring, MD, USA

The soundscape in shallow waters displays a high level of spatial variation due to the difference in ocean environments, biological communities, and human activities. Many marine animals rely on sound for orientation; therefore, the soundscape has been hypothesized as one of the environmental indicators for marine animals. The population of Indo-Pacific humpback dolphins in western Taiwan waters is critically endangered. The anthropogenic noise might alter the marine soundscape evidently. However, the importance of soundscape for the habitat selection of cetacean remains unclear until now. In this study, underwater recorders were deployed in inshore waters to compare the difference of soundscape between the core habitat and non-core habitat of humpback dolphins. The result indicates that the composition of soundscape scene is different among our recording stations. At the core habitat, soundscape was characterized by the nighttime chorus of croakers and the quiet ambient sound in the daytime. On the contrary, snapping shrimp sounds represent the most dominated sound at the non-core habitats. The current result indicates that humpback dolphins prefer soundscape dominated by the chorus of their prey resources. The potential impacts of human activities on marine soundscape should be carefully evaluated in the future.

2016 動物行為暨生態研討會

2016/1/25-26

中華白海豚核心棲地的海洋聲景特徵以及保育經營的應用

林子皓、周蓮香

國立台灣大學生態學與演化生物學研究所

Shane Guan

美國國家海洋漁業局保護資源辦公室

海洋聲景由環境音、動物音以及人為噪音所組成,物理環境影響了聲音傳播,各地不同的動物群聚與人類活動也塑造出各種獨特的聲景。聲景中的訊息可讓海洋動物尋找適合的棲地,察知其他個體的活動位置,甚至探測獵物位置,因此可說是海洋動物生存的重要資源之一。台灣西部淺海的中華白海豚族群面臨許多威脅,水下噪音除了可能造成聽力損傷、行為干擾之外,也會改變當地的海洋聲景。但目前仍缺乏對白海豚棲地的聲景研究,也不清楚聲景的變化是否影響白海豚的棲地選擇。本研究於苗栗縣海域收集長時間水下聲音,分析時頻譜圖的時空變化,發現中港溪口的聲景與其他地區之間有明顯差異。中港溪口是中華白海豚的核心棲地,聲景以白天安靜的環境音和夜間吵雜的石首魚鳴唱為主。白海豚鮮少活動在龍鳳漁港外海的定置網區,以及外埔漁港外海的魚礁區,當地聲景則以槍蝦的寬頻脈衝聲與船隻噪音為主,石首魚的夜間鳴唱也較為低頻且不明顯。本研究結果顯示海洋聲景確實在白海豚核心與非核心棲地之間存在差異,高強度的石首魚鳴唱可能代表充足的食餌資源。未來除了可透過海洋聲景了解白海豚的潛在棲地,也可利用水下監聽站自動監測白海豚、石首魚與人為活動在各地海域的動態變化,以協助中華白海豚重要棲息環境的保育經營。

Conference presentation: 21st Biennial Conference on the Biology of Marine Mammals

13-18 Dec 2015

A noisy dinner? Passive acoustic monitoring on the predator-prey interactions between Indo-Pacific humpback dolphins and croakers

Tzu-Hao Lin, Wen-Ching Lien, Chih-Kai Yang, and Lien-Siang Chou
Institute of Ecology and Evolutionary Biology, National Taiwan University

Shane Guan
Office of Protected Resources, National Marine Fisheries Service, Silver Spring, MD, USA

The spatio-temporal dynamics of prey resources have been considered as important factors for shaping the distribution and behavior of odontocetes. Indo-Pacific humpback dolphin (Sousa chinensis) is a costal species, which primary feeds on benthic croakers. It has been hypothesized that the distribution pattern and periodic occurrence of humpback dolphins are results of their prey movement. However, the interactions between humpback dolphins and croakers remain unclear. During May 2013 and November 2014, underwater sound recordings were collected in western Taiwan waters. Croaker choruses and humpback dolphin echolocation clicks were automatically detected using custom developed algorithms. Both croaker choruses and dolphin clicks were frequently detected in shallow estuarine waters during spring and summer. In addition, shorter inter-click intervals were detected with higher frequencies in these areas, indicating more likely foraging behavior. Current results suggest that the core habitats of humpback dolphins show an agreement with the areas of prominent croaker chorus. Diurnal cycle analysis showed that croaker choruses were most evident after sunset to until approximately 4 A.M. In estuarine waters, humpback dolphin clicks were most frequently detected during the nighttime, with reduced detection rates after 8 A.M. This suggests that the diurnal behavior of humpback dolphins could be associated with the calling behavior of croakers. Although whether the position of a calling croaker could be passively localized by a dolphin remains unknown, our results indicate that the foraging probability of humpback dolphins may be elevated during the nighttime chorus of croakers. Information regarding the spatio-temporal dynamics of croaker chorus can be important for the conservation management of humpback dolphins. Further details on the predator-prey interactions between humpback dolphins and croakers can be investigated by using hydrophone arrays.

Poster (pdf)

[聲物誌] 白海豚之家

Sousa_bye

白海豚所生活的海洋是甚麼樣子的? 在混濁的海中只能仰賴聽覺了解一切,海表面下的浪花、雨聲、水流聲,透漏了所在之處的環境與位置,更聽見了各種海洋生物活動的蹤跡。聽著哨聲在旅途中尋找同伴,社交之外也合作覓食,但記得小心高速開過的船隻,不注意的話可是會命喪黃泉的。越來越頻繁的噪音,降低了聽到同伴聲音的機會,也減少了利用聲音來尋找食物的效率。這是白海豚的家園,一個正受到噪音侵蝕的海洋。

[聲物誌] 錄音機漂流記

近期颱風肆虐,連帶著海洋觀測也跟著遭殃。前一陣子就因為蓮花颱風和昌鴻颱風接連靠近台灣,造成研究團隊在苗栗外海所放置的海下錄音機因為不明原因而脫離錨錠裝置、漂流上岸。還好遇到當地的好心人通報之後,得以將錄音機尋回,今天也才有機會讓大家聽聽錄音機迷途的這段過程。 

這段漂流的時間其實不長,大約5至6個小時後錄音機就被浪打上岸。錄音機漂流的路徑根據推測應是從後龍外海約15公尺水深的礁石區一路北漂至附近的中港溪口南岸,再進入潮間帶與碎波帶。然而,在這段濃縮的3分半鐘錄音裡,卻可以聽到海洋聲景有著非常大幅度的改變。

0:00 – 1:00
礁石區內眾多的槍蝦聲音。注意1分鐘後的水花聲,顯示錄音機已經浮上水面 (痛心)。

1:00 – 1:30
脫離礁石區,槍蝦聲音明顯減少。當時已進入傍晚,可以聽見河口附近的石首魚開始發出低頻的鳴聲。

1:30 – 2:57
台灣西部河口附近著名的石首魚群體鳴唱。注意這段時間之中,石首魚聲音的音頻特徵隨錄音機漂流進入潮間帶後的改變趨勢。

2:57 – 3:39
碎波帶的浪花與水流聲。這段聲音是透過水下麥克風所錄製,和空氣中聽到的略有不同。
 

從這段錄音之中,其實我們不難發現在不同型態的海床、地區之間,可能受到當地生態系組成的不同,而造就了多樣化的海洋聲景。許多海洋動物,也可能是透過各地聲景的不同,以此來尋找其偏好的棲地位置。因此,自然的海洋聲景是否受到人為噪音的干擾,將會是海洋保育非常重要的課題,亟需我們更多的關注。