Report of the Riverine and Coastal Session

Chi-Fang Chen¹*, Tomonari Akamatsu²*, Songhai Li³, Shashidhar Siddagangaiah¹, Matthew Pine⁴, Chiao-Ming Peng⁵

¹      National Taiwan University, Taiwan
²      The Sasakawa Peace Foundation, Japan
³      Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, China
⁴      University of Victoria, Canada
⁵      OceanSound CO. LTD., Taiwan

* Session Chairs and Corresponding Authors; E-mail: chifang@ntu.edu.tw – Akamatsu.tom@gmail.com

This report can be referenced as: Chen, C.F., Akamatsu, T., Li, S., Siddagangaiah, S., Pine, M., and Peng, C.-M. (2023). Report of the Riverine and Coastal Session, OCEANOISE2023, Vilanova i la Geltrú, Barcelona, Spain, 22-26 May. Retrieved from https://2023.oceanoise.com

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Introduction

Riverine and coastal areas are the typical conflict zones between aquatic animal conservation and human activities. In these decades, marine engineering technologies have been highly developing. Many offshore wind farms are in operation or in the construction phase worldwide. Long bridges, seashore airports, fisheries and recreational use in the coastal waters are extensive. In this session, we focus on the monitoring methodologies and noise impacts on coastal endangered species.

Roundtable discussion

Songhai Li from Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences presented “Large-scale monitoring of Indo-Pacific humpback dolphins and finless porpoises using multiple static acoustic sensors”. Shashidhar Siddagangaiah from National Taiwan University presented “Impact of Pile-driving and Assessment of Offshore Windfarm Operational Noise on Fish Vocalization Behaviour”. Matthew Pine from University of Victoria presented “Foiling yachts and dolphins: how international regattas temporarily change regional soundscapes, and the potential impacts for dolphins”. Chiao-Ming Peng from OceanSound CO., LTD presented “The impact of underwater noise generated by offshore wind farm construction on the ecology of cetaceans in the western waters of Taiwan”. Tomonari Akamatsu from the Sasakawa Peace Foundation, presented “A guidance on measurement and evaluation methods for underwater sounds focusing on offshore windfarms”. Chi-Fang Chen from National Taiwan University presented “Acoustic and Visual Investigation of Estuary Habitat on Indo-Pacific Humpback Dolphin (Sousa chinensis) in Yunlin, Taiwan”.

Based on these presentations, we discussed how we sustainably co-exist our economic activities and nature conservation. Ocean engineering works have been expanding. Previously maritime traffic was the major noise source in the ocean. In these years, construction and operation noise from offshore windmills gained attention and many of the presentations of this session focused on this issue. In addition, recreational activities are not negligible. Pleasure activities including yachts, scuba diving, whale dolphin watching and small submersibles are in operation.  After the previous Oceanoise in 2017, monitoring and analysis have been highly advanced. Autonomous underwater recorders are deployed worldwide. Because of the advances in battery capacity and memory size, fixed long-term recording is commonly conducted. Flood of sound data accelerates evolution of analysis as well. However, noise impact assessment on each oceanic species is still on the way. Although presentations of this session and many other sessions showed potential effects on fish and dolphins, we do not have consensus on the criteria of acceptable noise exposure level. Decision by stakeholders is important to reach agreement of the “acceptable” level. The fishermen targeting tuna may claim the change of the migration route of tuna offshore. For the wind farm developer, especially in the area with no fisheries, may employ a much higher acceptable level. Our knowledge of the long-term effect of noise on aquatic animals is quite limited. For the conservation purpose, effects on reproduction rate and population size should be clarified, which is supported by very limited and in-direct evidence. Another issue to understand the noise effect is the complex sound propagation in shallow waters. Most marine engineering works exist in shallow water areas such as several tens meters in depth. Due to the reflections by sea surface and bottom, noise may not easily be calculated just by the source spectrum level. To assess the effect of noise, comparison of noise maps and distribution of concerned species is the basic information. A guidance of noise measurement and evaluation was also presented in this session, but it does not have any species-specific criteria.

In riverine and coastal waters, two major items are needed. The first one is to identify focal species and effort to establish acceptable noise exposure levels based on discussion among stakeholders. The second one is to draw a sensitivity map considering shallow water sound propagation and distribution of focal species, which may be monitored by passive acoustic means simultaneously.