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.

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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)

2015台灣聲學學會第28屆學術研討會

2015/11/13

從海洋聲景探討中華白海豚的棲地特徵

 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

淺海聲景受到各地地理環境、生態群聚以及人為活動的影響而具有高度的變異性。許多海洋動物仰賴聲音訊息尋找活動方位,因此聲景可能是海洋動物棲地環境的指標之一。中華白海豚在台灣西岸的族群量少於80隻,主要使用3-15 kHz的哨聲溝通,並使用超音波的生物聲納進行回聲定位,因此聲音的感知對牠們相當重要。然而,目前仍不了解聲景是否在中華白海豚的棲地選擇中扮演重要的角色。本研究於苗栗海域利用SM2+錄音機長期收錄水下聲音,自動偵測回聲定位聲音,以了解中華白海豚的核心活動區域。長期時頻譜分析顯示,苗栗海域的聲景有明顯的日週期變化,且可在中華白海豚核心棲地與非核心棲地之間觀察到不同的頻譜特徵。核心棲地的中、高頻聲壓標準差較大,但平均值較低。顯示核心棲地的聲景特徵,以夜間的石首魚群體鳴唱,和白天較低的環境音為主。非核心棲地則有截然不同的聲景特徵,石首魚群體鳴唱較不明顯,但可偵測到大量槍蝦的寬頻脈衝聲波。未來許多離岸風力發電廠的開發工程將在西岸進行,本研究可協助相關單位了解中華白海豚棲地的海洋聲景變化。

關鍵字:中華白海豚、海洋聲景、生物音、時空變化、聲音偵測器

The soundscape in shallow marine environment displays a high level of spatial variation due to the regional change of geophysical environment, biological community, and human activity. Many marine animals rely on sounds for orientation; therefore the soundscape has been hypothesized as one of the environmental indicators. Indo-Pacific humpback dolphins in western Taiwan waters are critically endangered. The sound perception is essential for humpback dolphins, which communicate through 3-15 kHz whistles and echolocate through ultrasonic clicks. However, the importance of soundscape for their habitat selection remains unclear. In this study, SM2+ recorders were deployed in Miaoli waters to collect long-duration underwater recordings. Echolocation clicks were automatically detected to identify the core habitat of humpback dolphins. The long-term spectral average reveals that the soundscape in Miaoli waters evidently changed among the diurnal cycle. The spectral characteristic varied between the core habitat and non-core habitat. The soundscape at the core habitat was characterized by the higher standard deviations and lower means of SPL in mid- and high-frequency range. It indicates that the nighttime chorus of croakers and the low-level of ambient sound in the daytime represent the classical soundscape at the core habitat. On the contrary, the croaker chorus was less prominent at the non-core habitat. Instead, snapping shrimp sounds dominated the local soundscape. The current results can help understand the soundscape change of humpback dolphin habitat during the future development and operation of offshore wind farms.

Keywords:Sousa chinensis, marine soundscape, biological sound, temporal and spatial variations, sound detector

論文全文 (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。

International Conference on Biodiversity, Ecology and Conservation of Marine Ecosystems 2015 @ Hong Kong

1-4 June 2015

Seasonal changes in habitat use of Indo-Pacific humpback dolphins at an estuary

Tzu-Hao Lin, Chia-Yun Lee, Lien-Siang Chou

Institute of Ecology and Evolutionary Biology, National Taiwan University

Tomonari Akamatsu

National Research Institute of Fisheries Engineering, Fisheries Research Agency

River estuaries are ecotone environments where freshwater and seawater mix together. Seasonal rainfall is likely to influence the salinity, turbidity, and development of estuarine fronts, thus alter the distribution of aquatic animals at an estuary. Indo-Pacific humpback dolphin is a coastal species that use estuaries as their core habitat. According to previous studies, the distribution of humpback dolphins in their estuarine habitat moved seaward during wet seasons. In addition, circling movement associated with the hunt for epipelagic fish increased during flooding tides. However, it remains unclear how seasonal rainfall influences the estuarine habitat use of humpback dolphins. During July 2009 and October 2014, acoustic data loggers were deployed at the Xin Huwei River estuary, Taiwan to record ultrasonic pulsed sounds. Biosonar clicks of humpback dolphins were detected using an automatic detection algorithm. The temporal variations of humpback dolphin behavior were investigated in terms of detection rate, occurrence pattern within the tidal cycle, echolocation behavior. The behavior of humpback dolphins significantly varied among the four monitoring sections and two periods (wet and dry seasons). The tide related occurrence was evident at the entire monitoring area during wet seasons, however, the similar occurrence pattern was only observed at the inner and outer estuary during dry seasons. In addition, long distance biosonars were much frequently detected at the inshore and offshore sections. During drought periods, the inshore and offshore sections are less likely to be influenced by the mixtures between freshwater and seawater. Our results suggest the river runoff may play an important factor in shaping the estuarine habitat use of humpback dolphins. Therefore, it is necessary to consider the interception of river runoff in the conservation management of humpback dolphins in an estuarine habitat.

New article online: Dynamics of soundscape in a shallow water marine environment: A study of the habitat of the Indo-Pacific humpback dolphin

A new article introduce the underwater soundscape in coastal waters of Taiwan has been published in the Journal of Acoustical Society of America.

Dynamics of soundscape in a shallow water marine environment: A study of the habitat of the Indo-Pacific humpback dolphin

J. Acoust. Soc. Am. 137, 2939 (2015)

Shane Guan
Office of Protected Resources, National Marine Fisheries Service, 1315 East-West Highway, SSMC-3 Suite 13826, Silver Spring, Maryland 20910, USA
Department of Mechanical Engineering, The Catholic University of America, 620 Michigan Avenue NE, Washington, DC 20064, USA

Joseph Vignola, John Judge, Diego Turo
Department of Mechanical Engineering, The Catholic University of America, 620 Michigan Avenue NE, Washington, DC 20064, USA

Tzu-Hao Lin, Lien-Siang Chou
Institute of Ecology and Evolutionary Biology, National Taiwan University, Number 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan

The underwater acoustic field is an important ecological element for many aquatic animals. This research examines the soundscape of a critically endangered Indo-Pacific humpback dolphin population in the shallow water environment off the west coast of Taiwan. Underwater acoustic recordings were conducted between late spring and late fall in 2012 at Yunlin (YL), which is close to a shipping lane, and Waisanding (WS), which is relatively pristine. Site-specific analyses were performed on the dynamics of the temporal and spectral acoustic characteristics for both locations. The results highlight the dynamics of the soundscape in two major octave bands: 150–300 Hz and 1.2–2.4 kHz. The acoustic energy in the former frequency band is mainly associated with passing container vessels near YL, while the latter frequency band is from sonic fish chorus at nighttime in both recording sites. In addition, large variation of low frequency acoustic energy throughout the study period was noticed at WS, where the water depths ranged between 1.5 and 4.5 m depending on tidal cycle. This phenomenon suggests that besides certain sound sources in the environment, the coastal soundscape may also be influenced by its local bathymetry and the dynamics of the physical environment.