Report of the Round Table Session
Akamatsu, T.8*, Chen, C.1*, Mooney, T.A.2, Li, S.3, Öztürk, B., 4, Öztürk, A.A.4, Lin, T.5, Kameyama, S.6 and Kimura Soen, S.7
1 Biology Department, Woods Hole Oceanographic Institution, USA
2 Marine Mammal and Marine Bioacoustics Laboratory, Sanya Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, China
3 Faculty of Fisheries, Istanbul University and Turkish Marine Research Foundation, Turkey
4 Department of Engineering Science and Ocean Engineering, National Taiwan University
5 Institute of Ecology and Evolutionary Biology, National Taiwan University, Republic of China (Taiwan)
6 Kyoto University, Japan
7 Graduate School of Environmental Studies, Nagoya University, Japan
8 Fisheries Research Agency, Japan
This report can be referenced as:
Chen, C., Mooney, T.A., Li, S., Öztürk, B., Öztürk, A.A., Lin, T., Kameyama, S., Kimura Soen, S., and Akamatsu, T. (2015). Report of the Riverine and Coastal Session, oceanoise2017, Vilanova i la Geltrú, Barcelona, Spain, 10-15 May. (Editors Michel André & Peter Sigray). Retrieved from https://2023.oceanoise.com
The soundscapes of riverine and coastal waters are vastly different from those of deep the open ocean. Ship traffic, offshore wind farms, snapping shrimps and many other anthropogenic and natural acoustic sources often combine to create a complex sound field in a confined space. Yet we know little regarding characteristics of these sounds and natural background noise in riverine and coastal environments. Sound propagation and effect on marine organisms are variable in shallow waters such as estuary and freshwater ecosystems. This session addressed issues of riverine and coastal noise measurements and the impacts of riverine and coastal sounds on marine organisms in those respective environments, with a particular emphasis on small odontocetes and fishes. Small odontocetes residing in shallow waters are potentially affected by the human coastal activities. Environmental impact assessments should be implemented in riverine and coastal waters especially in quickly developing countries in the Asian region. Management and regulations are also required across borders and among neighbour countries which share coastal and riverine waters.
Soundscapes in riverine and coastal waters
Our society is now highly depends on ship traffic, renewable energy, and construction of ports, bridges and airports in the ocean. The impacts of noise on aquatic animals can be especially high in riverine and coastal waters. Yet mitigation and management of such noise conditions is quite different compared to offshore countermeasures.
For example, the Turkish Strait Systems is a highly urbanized international ship lane. Huge numbers of cargo ships, recreational boats and even submarines frequently transit both from bank to bank or up and down the river. This strait system is also the habitat of three odontocetes species. Bayram Öztürk and Ayaka Amaha Öztürk observed that the bottlenose dolphins appear year-round in this area; common dolphins and harbour porpoises are occasionally sited in the spring. A resident population of 40-50 bottlenose utilizes the southern part of the strait as its primary habitat. However, the region is dynamic and even with observations from the Istanbul Strait spanning the past 20 years, it is still difficult to predict the current population trends. An extensive future research effort would help provided abundance information across 10 years. According to the noise assessment in the strait, the dolphins respond more to high-speed boats rather than to larger ships spanning 200 m in length. The large cargo ships follow standard routes, however small boat movements tend to be more erratic. The dolphins potentially predict the movement of the large ships unlike high-speed boats. Thus impacts to dolphins and porpoises might not only depend on noise characteristics but also ship type and operation.
Natural background sound-field characteristics are vital for noise impact assessment, however it is quite difficult quantify such ambient sounds in heavily trafficked waters. It is impossible to shut down vessel traffic or offshore wind turbines completely. The definition of “natural noise” is not clear in well-developed waters. In the west coast of Taiwan, 600 offshore wind turbines will be constructed by 2030. Chi-Fang Chen recently started monitoring the background noise before the construction of these focal waters. In the Turkish Strait System, heavy fog occasionally stops all ship traffic, which may offer a way to collect “baseline” background noise levels. But we still do not know the historic ambient soundscape conditions before the industrial revolution.
Issues in noise assessment and impacts on marine organisms
Previously, potential noise of cargo ships or big containers have been focused. Tzu-Hao Lin quantified the noise produced from high speed fishing boats and ferries, which create ultrasonic sounds within the hearing range of small odontocetes. Small fishing boats do not deploy Automatic Identification System (AIS) but appear in highly biologically productive areas, which tend to overlap the habitat of top predators such as small odontocetes. High speed commuting ferries were even recommended in various coastal waters as a means of reducing onshore car traffic.
Ships are major noise sources in the ocean. A major difference between small and large ships is the visualization. AIS provides a way to quantify the movement of commercial ships above 300 gross tonnage. This is not the case for small boats, leaving recreational or small fishing boats difficult to quantify and highlight the question: How will we potentially deal with these issue and compromise influence in these area?
In 2009, a geophysical survey using an air gun array was conducted in the waters around Taiwan. In the shallow coastal water of the west coast, namely 100 m in depth, the exposure level exceeded 180 dB re 1uPa due to the cylindrical propagation rather than spherical one. Unlike east coast of Taiwan which steeply drops to 2000 m in depth, sound propagation on the shallow western coastline could be intensified, reflecting that noise in coastal ecosystem is quite different from open oceans. This is likely also true for biological sound sources such as snapping shrimps and various soniferous fish. Noise characteristics in riverine and coastal waters seem to be location specific.
Sounds may not always deter animals, and can conversely be used as an attractant. An audience member of this session spent 3 months on the boat of fisheries ship, using a 300 Hz tone to attract squid, producing some of the highest catches in that area. Aran Mooney pointed “we need calibrated works”, in addition to behavioural or hearing studies using underwater sounds. For example, vibratory particle motion of a struggling prey could be sensed by squid. Squid forage in the night and the struggling motion can be attractive. Squid are not sensitive for sound pressure but sensitive for particle motion (Mooney et al 2010). Special care is needed for the playback experiment of sound. A transducer could elicit vibration of the experimental tank wall that could cause unintended projection of particle motion in addition to the sound pressure. Special care is needed for vibration isolation in the experimental condition.
Focal species in riverine and coastal systems
Humpback dolphins (Sousa sp.) are widely distributed in coastal waters of Africa, Asia and Australia, regions which are undergoing rapid development. Although humpback dolphins throughout the entire Indo-Pacific region were listed as being “Near Threatened” on the IUCN Red List as a single species, in recognition of their probable taxonomic distinctness (Jefferson and Rosenbaum, 2014), the humpback dolphins distributed in the coastal waters of central (near the mouth of the Yangtze River) to southern China would qualify as vulnerable, if assessed separately (Reeves et al., 2008). Recently, evidence from skeletal and external morphology, coloring, genetics and distribution support the recognition of three species of the humpback dolphins in the Indo-Pacific region [S. plumbea, S. sahulensis, and S. chinensis (Jefferson and Rosenbaum, 2014. Yet, local migration and population separations are not clear except for S. plumbea and S. chinensis, which separate near India. Among the three species, S. chinensis has a relatively larger dorsal fin with no prominent hump and largely white adult coloring. It ranges from coastal waters of eastern India to central China and throughout Southeast Asia (Jefferson, 2014). Conservation of S. chinensis in Chinese waters has been on the agenda of local scientific and conservation communities since the 1980s, despite the little research conducted. Since 1988, this species has been listed as one of the Grade 1 National Key Protected Animals by the Chinese State Council, similar to the Yangtze River dolphin (baiji, Lipotes vexillifer), which is now functionally extinct (Turvey et al., 2007). In recent years, the effects of underwater noise have been a major concern for this species because of a number of maritime developments such as underwater explosions, pile driving, and bridge constructions. The big challenge is the measurement of anthropogenic sound characteristics of specific sources in broadband frequency range. So far, only a few studies have investigated the effects of noise on humpback dolphins, and these have only covered a limited number of anthropogenic noise sources within low frequency range (Würsig et al., 2000; Würsig and Greene, 2002; Sims et al., 2012; Wang et al., 2014). Songhai Li presented in this conference that small high-speed boats produced substantial mid- to high-frequency noise components with frequencies up to > 100 kHz. These high-frequency sounds could potentially affect the humpback dolphins which utilize sounds in the mid- and high-frequencies (Li et al., 2012, 2013). Effects could include auditory masking, temporary threshold shifts (TTS), and behavioral and physiological responses.
Finless porpoises are distributed from the Persian Gulf to Japanese coastal waters including Yangtze River, China. These animals occur in shallow waters generally less than 50 m in depth. The recognition of two externally distinct morphological forms of finless porpoises as separate biological species (Neophocaena phocaenoides and N. asiaeorientalis) was accepted recently (IUCN Red List). Saho Kameyama noted that the similarity of threats for finless porpoises and Sousa because both habitats are close to the coastline or river. Numerous offshore windmills will start operation in Japan in the near future. Many of the bottom-mounted wind turbines will be located in finless porpoise habitat. Passive acoustic monitoring was recently initiated by the Japanese Environmental Agency to address potential influence of offshore windfarm development on local finless porpoise populations.
EIA and regulations
Environmental Impact Assessments (EIA) are primarily needed for the mitigation and management of ocean noise. However, effective management is not well implemented in Asian waters, even in areas which provide protection zones for dolphins and porpoises, in an effort to limit anthropogenic activities exists. For example, a mismatch between documented protection zones and high density areas of Yangtze finless porpoises were reported (Zhao et al 2013). Such data suggests the adjustment of the protection areas, based on currently available data, would improve the effectiveness of such protection zones. However, updated data providing the abundances and distribution of target species as well as the local background and anthropogenic noise characteristics are often needed to identify the primary concerns and tailor regulations to mitigate noise impacts on marine organisms.
To conduct EIAs, legal frameworks of research are important. Chi-Fang Chen’s project has been supported by the government as a result of the EIA of offshore windmill. Several years ago, plans for a petro-industrial port were terminated because of concerns for impacts to the local population of Sousa. The EIAs of EU and USA are well advanced and can be modified for each country, which does not have sufficient guidelines and regulations. Growing scientific and conservation communities could induce the government to establish EIA protocols where needed. One more issue is the generally low public awareness of surround the impacts of underwater noise. People might know dolphins or porpoise species exist locally, but usually are unaware how noisy the coastal and riverine waters may be, and the effects that such noise may have on the dolphin or porpoise populations.
Regulating noise in coastal environment can appear easier because it is in the territorial sea of each country. In contrast, completely offshore environments in the deep ocean can be complicated to regulate human activity because it remains the prevue of many countries (and at the same time none). However, even in coastal waters, each country has each country has own territory and approach. The core strategy for organizations such as the EU is regional cooperation. Cross boundary conversations among different countries are necessary. The requirement for EIAs already exists. Member states should work together and regional EIA can be referred to each other.
This could also happen more broadly. Companies and developers in Taiwan are going to do the monitoring of dolphins during operation of windmill farm. The domestic guidelines followed those of EU. International criteria or concept as well as the local guidelines should be established based on the data. This session clarified the issues but did not yet provide solutions, especially for complex coastal and riverine waters in Asia. Thus, international discussions are anticipated following the model that oceanoise2017 provided.
- Jefferson, T. A., and Rosenbaum, H. C. (2014). Taxonomic revision of the humpback dolphins (Sousa spp.), and description of a new species from Australia, Marine Mammal Science. 30, 1494-1541.
- Li, S., Wang, D., Wang, K., Taylor, E. A., Cros, E., Shi, W., Wang, Z., Fang, L., Chen, Y., and Kong, F. (2012). Evoked-potential audiogram of an Indo-Pacific humpback dolphin (Sousa chinensis). Journal of Experimental Biology. 215, 3055-3063.
- Li, S., Wang, D., Wang, K., Hoffmann-Kuhnt, M., Fernando, N., Taylor, E. A., Lin, W., Chen, J., and Ng, T. (2013). Possible age-related hearing loss (presbycusis) and corresponding change in echolocation parameters in a stranded Indo-Pacific humpback dolphin. Journal of Experimental Biology. 216, 4144-4153.
- Mooney, TA, Hanlon, RT, Christensen-Dalsgaard, J, Madsen, PT, Nachtigall, PE Ketten, DR. (2010). Sound detection by the longfin squid (Loligo pealeii) studied with auditory evoked potentials: sensitivity to low-frequency particle motion and not pressure, Journal of Experimental Biology. 213, 3748-3759.
- Reeves, R. R., Dalebout, M. L., Jefferson, T. A., Karczmarski, L., Laidre, K., O’Corry-Crowe, G., Rojas-Bracho, L., Secchi, E. R., Slooten, E., Smith, B. D., Wang, J. Y., and Zhou, K. (2008). Sousa chinensis. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 22 March 2015.
- Sims, P. Q., Hung, S. K., and Würsig, B. (2012). High-speed vessel noises in west Hong Kong waters and their contributions relative to Indo-Pacific humpback dolphins (Sousa chinensis). Journal of Marine Biology. 2012, 2012, Article ID 169103, 11 pages, doi:10.1155/2012/169103.
- Turvey, S. T., Pitman, R. L., Taylor, B. L., Barlow, J., Akamatsu, T., Barrett, L. A., Zhao, X., Reeves, R. R., Stevart, B. S., Wang, K., Wei, Z., Zhang, X., Pusser, L. T., Richlen, M., Brandon, J. R., and Wang, D. (2007). First human-caust extinction of a cetacean species? Biology Letters. 3, 537-540.
- Wang, Z., Wu, Y., Duan, G., Cao, H., Liu, J., Wang K., and Wang, D. (2014). Assessing the underwater acoustics of the world’s largest vibration hammer (OCTA-KONG) and its potential effects on the Indo-Pacific humpbacked dolphin (Sousa chinensis). PLoS ONE 9, doi:10.1371/journal.pone.0110590.
- Würsig, B., Greene, C. R. J., and Jefferson, T. A. (2000). Development of an air bubble curtain to reduce underwater noise of percussive piling. Marine Environmental Research. 49, 79-93.
- Würsig, B., and Greene, C. R. J. (2002). Underwater sounds near a fuel receiving facility in western Hong Kong: relevance to dolphins. Marine Environmental Research. 54, 129-145.
- Zhao, X., Wang, D., Turvey, S.T., Taylor, B., Akamatsu, T. (2013). Distribution patterns of Yangtze finless porpoises in the Yangtze River: Implications