Humpback Dolphins Research Articles

High genetic differentiation of Indo-Pacific humpback dolphins (Sousa chinensis) along the Asian Coast of the Pacific Ocean.

The Indo‐Pacific humpback dolphin (Sousa chinensis) is a vulnerable marine mammal species that inhabits shallow, coastal waters from Southeast China, southward throughout Southeast Asia, and westward around the Bay of Bengal to eastern India. Polymorphic microsatellites are useful for elucidating ecological and population genetics‐related questions. Here, 18 new polymorphic microsatellites were developed from S. chinensis genomic DNA by Illumina MiSeq sequencing. Population genetic analyses were conducted on 42 S. chinensis individuals from three geographic locations, including the Xiamen Bay of China, the Western Gulf of Thailand, and Andaman Sea. Our microsatellite data revealed a strong and significant population structure among the three sampling regions (overall F ST = 0.371, p = .001). Pairwise mutual information index also demonstrated high levels of genetic differentiation between different region pairs (values range from 0.272 to 0.339, p < .001). Moreover, Structure analysis inferred three genetic clusters, with the high assignment probabilities of 95.92%, 99.47%, and 99.68%, respectively. Principal coordinate analysis plots of individuals divided entire genotypes into three clusters, indicating high level of genetic differentiation. Our results indicated the strong genetic structure in S. chinensis populations is a result of geographic distances. Other factors such as environmental variables, anthropogenic interference, and social behavior may also have contributed to population differentiation.

Visual Assessment of Contusion-Like Lesions Caused by Live Sharksucker (Echeneis naucrates) Attachment in an Indo-Pacific Humpback Dolphin (Sousa chinensis).

We observed contusion-like lesions caused by live sharksucker (Echeneis naucrates) attachment in an Indo-Pacific humpback dolphin (Sousa chinensis). Our report assists in differentiating epidermal lesions for visual health assessment in this vulnerable species and other cetaceans, and this adds new host and epibiont records for E. naucrates and S. chinensis, respectively.

Temporal Trends of Alternative Halogenated Flame Retardants in Humpback Dolphins from the South China Sea.

Increasing human activities are altering marine ecosystems, which may have ramifications for predator feeding ecology and, thus, the degree of contaminant exposure. We conducted the first investigation of spatiotemporal trends for nine alternative halogenated flame retardants (AHFRs) and their relations with dietary variations in 128 humpback dolphins that were stranded along the northern South China Sea during 2003-2020. We detected the highest levels of seven major AHFRs in humpback dolphins compared with the results reported in cetaceans globally, indicating high AHFR contamination in coastal regions of South China. Dolphins that were stranded near urban regions generally contained higher AHFR concentrations than those that were stranded near rural areas, mirroring the environmental trends of AHFRs occurring in this area. Model-generated diet estimates suggested that humpback dolphins have reduced their consumption of high trophic-level prey in recent years, likely attributable to overfishing-induced prey decline in this region. After adjusting AHFR concentrations due to diet changes, the temporal trends of AHFR contamination in humpback dolphins were only slightly altered. Our results suggest that increasing discharges of AHFRs into the South China Sea during the 2000s and 2010s may have had a greater influence on AHFR trends in humpback dolphins than dietary shifts.

Multilocus DNA metabarcoding diet analyses of small cetaceans: a case study on highly vulnerable humpback dolphins and finless porpoises from the Pearl River Estuary, China.

Accurate diet identification of top predators is crucial to fully understand their ecological roles. Compared to terrestrial animals, gathering dietary information from cetaceans is notoriously difficult. Here, we applied a multilocus metabarcoding approach to investigate the diet of vulnerable Indo-Pacific humpback dolphins and Indo-Pacific finless porpoises from the Pearl River Estuary (PRE), China. Our analyses identified 21 prey fish species from the 42 humpback dolphin stomachs, as well as 10 species of fish and 1 species of cephalopod from the 13 finless porpoise stomachs. All of the taxa were assigned to the species level, highlighting that the multimarker approach could facilitate species identification. Most of the prey species were small- and medium-sized fishes that primarily fed on zooplankton. The calculated similarity index revealed a moderated dietary overlap between the 2 cetaceans, presumably due to the feeding of the 2 predators in association with fishing vessels in the PRE. A more diverse diet was observed in humpback dolphins in the closed fishing season compared to the fishing season, implying the influence on the dolphin diet due to the availability of commercial fishery resources. However, according to the results of species rarefaction curves, our findings on the feeding habits of the 2 cetaceans are still limited by insufficient sample size and therefore should be interpreted with caution. This study represents a first attempt to apply the multilocus DNA metabarcoding technique in the diet analysis of small cetaceans, although more efforts are needed to improve this type of analysis.

Real-time identification of marine mammal calls based on convolutional neural networks

Animal vocalization is one of the most important ways to identify the existence and occurrence of marine mammals. Accurately detecting and identifying marine mammal species in real time is significant in the field of marine mammal research. In this study, we developed a novel method based on convolutional neural networks (CNNs) to precisely identify the calls of bottlenose dolphins (Tursiops), dugongs (Dugong dugong), and the Indo-Pacific humpback dolphin (Sousa chinensis). Compared with traditional detection and classification techniques, the proposed method is a one-step algorithm that combines detection and classification. It can automatically learn the features of different marine mammal calls and position the target calls with bounding boxes in a spectrogram. Furthermore, the whole process can be conducted in real time. With this method, the raw data are cut into fixed lengths and spectrograms are created. Next, the annotated sound data are sent to the CNNs to train an identification model. Experimental results showed that the proposed method achieved >91% precision and >84% recall of test data with real-time speed. In the future, this method can be applied to passive acoustic observation equipment for quick, accurate pre-detection of marine mammal calls.

Bycatch mitigation requires livelihood solutions, not just fishing bans: A case study of the trammel-net fishery in the northern Beibu Gulf, China

Fishery bycatch is an acute threat endangering survival of coastal delphinids. While mitigation measures aim at restricting fishing activities by spatial, temporal and gear management, these measures undoubtedly decrease fishery production and trigger conservation-livelihood conflicts, particularly in artisanal fisheries associating with ‘poverty traps’. This study surveyed spatio-temporal activities of trammel-net fisheries and fishers’ education-household livelihood background in a rural fishing village in the northern Beibu Gulf, China to investigate dolphin-fishing interactions and the willingness of fishers to exit fishing and their ability to engage in alternative livelihoods with regard to fishers’ household livelihood baselines. Within the survey region, overlap between humpback dolphins and trammel-net fishing was high (at least 43.35%). Spatial closures through MPAs would help reduce 46.9% of trammel-net fishing. While labor force aging and low education levels were observed in fishing, farming and casual labor livelihoods, fishers showed an unwillingness to exit fishing and inability to engage in alternative livelihoods. The suspended MPA plan should be enacted immediately to reduce fishing-gear entanglements. Implementation of a permanent trammel-net ban or ‘exit-fishing’ policy, however, should address the household livelihood consequences to fishers. Though ecotourism is often recommended to fishers as an alternative livelihood, low education level hinders fishers’ ability to engage in dolphin-watching tourism in a sustainable manner. Fishing-gear modification, an ad hoc training program focusing on sustainable ecotourism, motivating and mobilizing local people in MPA monitoring and management, and integration of traditional ecological knowledge into livelihood diversification programs are critical components to deal with the complexity of this issue.

Abundance estimation, group dynamics, and residence patterns of Indian Ocean humpback dolphin (Sousa plumbea) in the Dayer-Nakhiloo Marine National Park, Northern Persian Gulf, Iran

Abundance estimation, group dynamics, and residence patterns of Indian Ocean humpback dolphin (Sousa plumbea) in the Dayer-Nakhiloo Marine National Park, Northern Persian Gulf, Iran

Dolphin Distribution and Habitat Suitability in North Western Australia: Applications and Implications of a Broad-Scale, Non-targeted Dataset

Understanding species’ distribution patterns and the environmental and ecological interactions that drive them is fundamental for biodiversity conservation. Data deficiency exists in areas that are difficult to access, or where resources are limited. We use a broad-scale, non-targeted dataset to describe dolphin distribution and habitat suitability in remote north Western Australia, where there is a paucity of data to adequately inform species management. From 1,169 opportunistic dolphin sightings obtained from 10 dugong aerial surveys conducted over a four-year period, there were 661 Indo-Pacific bottlenose dolphin (Tursiops aduncus), 191 Australian humpback dolphin (Sousa sahulensis), nine Australian snubfin dolphin (Orcaella heinsohni), 16 Stenella sp., one killer whale (Orcinus orca), one false killer whale (Pseudorca crassidens), and 290 unidentified dolphin species sightings. Maximum Entropy (MaxEnt) habitat suitability models identified shallow intertidal areas around mainland coast, islands and shoals as important areas for humpback dolphins. In contrast, bottlenose dolphins are more likely to occur further offshore and at greater depths, suggesting niche partitioning between these two sympatric species. Bottlenose dolphin response to sea surface temperature is markedly different between seasons (positive in May; negative in October) and probably influenced by the Leeuwin Current, a prominent oceanographic feature. Our findings support broad marine spatial planning, impact assessment and the design of future surveys, which would benefit from the collection of high-resolution digital images for species identification verification. A substantial proportion of data were removed due to uncertainties resulting from non-targeted observations and this is likely to have reduced model performance. We highlight the importance of considering climatic and seasonal fluctuations in interpreting distribution patterns and species interactions in assuming habitat suitability.

Using Environmental DNA to Detect Whales and Dolphins in the New York Bight

Determining how cetaceans and other threatened marine animals use coastal habitats is critical to the effective conservation of these species. Environmental DNA (eDNA) is an emerging tool that can potentially be used to detect cetaceans over broad spatial and temporal scales. In particular, eDNA may present a useful complementary method for monitoring their presence during visual surveys in nearshore areas, and for co-detecting prey. In conjunction with ongoing visual surveys, we tested the ability of eDNA metabarcoding to detect the presence and identity of cetaceans in the New York Bight (NYB), and to identify fish species (potential prey) present in the area. In almost all cases in which humpback whales and dolphins were visually observed, DNA from these species was also detected in water samples. To assess eDNA degradation over time, we took samples in the same location 15 and 30 min after a sighting in seven instances, and found that eDNA often, but not always, dropped to low levels after 30 min. Atlantic menhaden were detected in all samples and comprised the majority of fish sequences in most samples, in agreement with observations of large aggregations of this important prey species in the NYB. While additional data are needed to better understand how factors such as behavior and oceanographic conditions contribute to the longevity of eDNA signals, these results add to a growing body of work indicating that eDNA is a promising tool to complement visual and acoustic surveys of marine megafauna.

Species diversity and spatiotemporal patterns based on cetacean stranding records in China, 1950–2018

Stranding data can provide conservation-valuable information on cetaceans over long time and large space, representing a low-cost but useful approach to monitor these indicator species and their inhabiting environments. Here, we established a national dataset by collating all available records of cetacean strandings (CSs) along >30,000-km coastline of China over seven decades. Between 1950 and 2018, a total of 1763 CSs were recorded across 36 cetacean species from eight families. Importantly, 30.5% of the recorded species are currently recognized as threatened levels on the IUCN Red List. In quantity, Odontocete species accounted for 89.9% of total CSs. In 1763 CSs, 91.8% were events of single individual. Furthermore, 31.9% and 42.4% were events of alive and dead animals, respectively. The number of CSs increased gradually from 1950 to 2018, and more rapidly between 1990 and 2018. CSs occurred in all months, while a seasonal pattern could be observed with 38.5% reports between March and June. The most commonly recorded species were finless porpoises (Neophocaena spp., n = 492) and Indo-Pacific humpback dolphin (Sousa chinensis, n = 291). The highest number of CSs (n = 478) was documented in Hong Kong, while the greatest species richness (n = 28) and the highest stranding density (24.6 CSs per 100-km coastline) were observed in Taiwan. Several CS hotspots were identified in the southern and eastern China, while hotspots differed among taxonomic categories. To conclude, these findings provided a comprehensive understanding of cetacean communities in the coastal waters of China, which are beneficial for improving further research, conservation, and management on cetaceans.

Coastal dolphins and marine megafauna in Exmouth Gulf, Western Australia: informing conservation management actions in an area under increasing human pressure

Context Exmouth Gulf is adjacent to the Ningaloo Marine Park, a UNESCO-listed area in Western Australia. The gulf remains largely unprotected, and is under increasing anthropogenic pressure from proposed industrial activities that pose threats to marine megafauna inhabiting the gulf. Threatened and near threatened species, such as the Australian humpback dolphin (Sousa sahulensis) and Indo-Pacific bottlenose dolphin (Tursiops aduncus), reside in the gulf; however, detailed information on their ecology and behaviour is lacking. Aims The aim was to (1) provide baseline data on the distribution, encounter rate, group size and behaviour of coastal dolphins over an area where current industrial developments are proposed, and (2) report on the occurrence of other marine megafauna within this area. Methods Boat-based photo-identification surveys were conducted on the western coastline of Exmouth Gulf along pre-determined line transects (150 km2) over austral autumn/winter 2021. Key results Across 809.35 km of surveyed waters (181 h), a total of 93 bottlenose dolphin, 15 humpback dolphin, and six interspecific dolphin groups were sighted. Bottlenose dolphin groups were encountered at a rate of 0.077/km, humpback dolphin groups at 0.015/km and interspecific dolphin groups at 0.005/km. Dolphins were predominantly recorded in shallow (mean 10 m) and warm (mean 21°C) waters, and were commonly travelling and foraging. In total, 199 individual bottlenose dolphins and 48 humpback dolphins were photo-identified (excluding calves). There were 30 bottlenose dolphin calves (including three newborns) and four humpback dolphin calves (including two newborns) identified. Other marine megafauna group sightings included humpback whales (Megaptera novaeangliae; n = 32), southern right whales (Eubalaena australis, n = 1), dugongs (Dugong dugon, n = 25), turtles (n = 54), sea snakes (n = 27), manta rays (Mobula alfredi, n = 13) and sharks (n = 2). Conclusions The presence of threatened marine species feeding, socialising, and resting highlights the importance of these waters for the identified species. Implications The information provided is applicable for the spatial management and conservation efforts of these species, and aids in informing environmental impact assessments of individual and cumulative pressures.

Misuse of molecular tools results in misleading dates for the ancestor of the Indo‐Pacific humpback dolphin

Misuse of molecular tools results in misleading dates for the ancestor of the <scp>Indo‐Pacific</scp> humpback dolphin

Reply to “Misuse of molecular tools results in misleading dates for the ancestor of the Indo‐Pacific humpback dolphin” by Chen

Reply to “Misuse of molecular tools results in misleading dates for the ancestor of the <scp>Indo‐Pacific</scp> humpback dolphin” by Chen

Habitat preference of two sympatric coastal cetaceans in Langkawi, Malaysia, as determined by passive acoustic monitoring

Little is known about the ecology of the Indo-Pacific finless porpoiseNeophocaena phocaenoidesor the Indo-Pacific humpback dolphinSousa chinensisin Southeast Asia. The present study describes the distribution and habitat preferences of these species around the Langkawi Archipelago of Malaysia. Vessel-based passive acoustic monitoring surveys were conducted 5 times between 2012 and 2013. Both species mainly preferred relatively shallow waters, especially on the east sides of the islands at &lt;15 m depth. However, the species differed in number of detections and spatial distribution, preferred distance from shore, chlorophyllaconcentration in the water where they resided, and season in which they were detected, indicating that they have different habitat preferences. The best spatial habitat model for the prediction of finless porpoise distribution included bathymetric depth and longitude. The distribution of finless porpoises was relatively stable around the islands and especially in the eastern waters, whereas humpback dolphins may only seasonally visit specific regions of the waters around the islands. Their detection sites were too patchy to enable distribution modeling. The results of this study provide baseline information that can facilitate conservation planning for these species according to their habitat preferences and core areas.

珠江口伶仃洋中华白海豚栖息地利用对海岸线等变迁的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 珠江口伶仃洋中华白海豚栖息地利用对海岸线等变迁的响应 DOI: 10.5846/stxb202101070066 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 中国水产科学研究院南海水产研究所中央级公益性科研院所基本科研业务费专项资金资助（2017YB20）；广东省科技计划项目（2019B121201001）；农业农村部财政项目"中华白海豚保护行动计划" Long-term changes in habitat use of Indo-Pacific humpback dolphins (Sousa chinensis) in response to anthropogenic coastline shift in Lingding Bay of Pearl River Estuary, China Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:沿岸鲸豚类栖息地易受人类活动的干扰，导致其分布和核心栖息地发生变化。珠江口-漠阳江口中华白海豚种群是目前所知全球范围内最大的种群，其中伶仃洋水域是其重要的栖息地。近年来，珠江口伶仃洋周边城市发展带来的人类活动增加，白海豚的生存压力日益增大，分析伶仃洋中华白海豚对栖息地环境变化的响应，研究对应的保护策略显得非常迫切。以多源陆地资源卫星Landsat为数据源，通过影像分析近43年珠江口伶仃洋围填海造成的海域流失，结合近20年来采用截线抽样法收集的海豚观测数据，运用含障碍核插值（Kernel interpolation with barriers）方法，分析白海豚的分布及核心栖息地的变化。结果显示：1986-2015年期间，研究区域内流失的海域面积为344.08km2；目击分布离人工海岸线的平均距离大于自然海岸线的平均距离，目击分布到自然海岸线和人工海岸线的平均距离均在减小，表明过去20年白海豚的栖息地使用选择发生了一些变化，被迫适应人类活动的干扰；1997-2016年白海豚的分布范围呈现先增加后减小，白海豚栖息地使用的重心偏向伶仃洋东部水域，核心栖息地趋向主航道和无人海岛附近水域萎缩，可能是海豚因海域食物资源减少而迫不得已的选择。不同时期，珠江口中华白海豚国家级自然保护区所覆盖的核心栖息地比例呈递减趋势，占比由79.9%下降到49.4%，当前有必要对保护区范围和功能区作出一些优化调整，以适应栖息地使用的变化格局。 Abstract:Cetacean living coastal habitat often suffer from anthropogenic disturbance, which would change their original distribution and core habitat use. Pearl River Estuary-Moyang River Estuary (PRE-MRE) population is the largest known (putative) population of Indo-Pacific humpback dolphin in the world. Lingding Bay is a critical habitat of PRE-MRE population, where human activities have become frequently in recent years and dolphin survival pressure is increasing. Analysis the response of Indo-Pacific humpback dolphin to environment change and making corresponding conservation strategy are urgent. This research mainly discussed coastal waters loss process in the past 43 years from sea reclamation in the Lingding Bay using the multi-source Landsat imageries. To examine the change of distribution and core habitat of dolphins, a new kernel density estimation approach that accounted for physical barriers to movements was applied with sighting records from line-transect surveys during past 20 years. Our results showed that about 344.08 km2 waters became unavailable from 1986 to 2015; average proximity of sighting sites to artificial shoreline was farther than to natural shoreline and average proximity of sighting sites to artificial shoreline and natural shoreline decreased, which indicated that dolphin habitat use changed and dolphin had to adapt anthropogenic disturbance; habitat use of dolphin focused on eastern Lingding Bay waters and distribution range reached peak in 2005-2006, but fell sharply in 2015-2016; dolphin's core habitat approaching main channels and around undeveloped islands might be the only option result from resource depletion. The proportion of core habitat showed a decreasing trend in the Chinese White Dolphin National Nature Reserve of Guangdong Pearl River Estuary, which decreased from 79.9% to 49.4% in different period. We recommend that the government should adjust current protected range to fulfill the change pattern from habitat use. 参考文献 相似文献 引证文献

Blubber Cortisol-Based Approach to Explore the Endocrine Responses of Indo-Pacific Humpback Dolphins (Sousa chinensis) to Diet Shifts and Contaminant Exposure.

The detrimental effects of contaminant exposure and changes in the availability of food resources are still of concern for Indo-Pacific humpback dolphins (Sousa chinensis) of the Pearl River Estuary (PRE). Here, we validated and applied a blubber cortisol biomarker approach to assess the physiological responses of PRE dolphins to various pollutants and diet changes during 2008-2018 (n = 70). For calves, generalized additive models (GAMs) revealed that cortisol levels varied significantly by month and were positively correlated with the body length, owing to significant maternal transfer of hormones. The significantly positive correlation between length-adjusted cortisol levels in calf and the annual calf mortality ratios suggested that during years of high calf mortality, these animals were highly stressed before they die. For noncalves, blubber cortisol levels in diseased animals were significantly higher than those in "healthy" ones. Chromium (Cr) and dichlorodiphenyltrichloroethanes displayed a significant and positive relationship with blubber cortisol levels, suggesting that contaminant-mediated endocrine disruption effects may have occurred in noncalves. The GAMs indicated a decreasing trend of noncalf's blubber cortisol levels over an 11-year span, which can be explained by their declining contaminant accumulation levels due to a significant dietary shift from eating highly contaminated fishes to less polluted ones.

Evidence of interactions between sharks and Indo‐Pacific humpback dolphins (Sousa chinensis) in the northern South China Sea

Marine Mammal ScienceEarly View NOTE Evidence of interactions between sharks and Indo-Pacific humpback dolphins (Sousa chinensis) in the northern South China Sea Agathe Serres, Agathe Serres orcid.org/0000-0003-2279-9143 Marine Mammal and Marine Bioacoustics Laboratory, Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya, China Contribution: Conceptualization, Formal analysis, Writing - original draftSearch for more papers by this authorWenzhi Lin, Wenzhi Lin orcid.org/0000-0002-0477-0753 Marine Mammal and Marine Bioacoustics Laboratory, Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya, China Contribution: Conceptualization, ​Investigation, Writing - review & editingSearch for more papers by this authorEric E. G. Clua, Eric E. G. Clua EPHE, PSL Research University, CRIOBE USR3278 EPHE-CNRS-UPVD, Perpignan, France Labex Corail, CRIOBE, Moorea, French PolynesiaSearch for more papers by this authorMingli Lin, Mingli Lin Marine Mammal and Marine Bioacoustics Laboratory, Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya, China Contribution: ​Investigation, Writing - review & editingSearch for more papers by this authorMingming Liu, Mingming Liu orcid.org/0000-0003-3802-1002 Marine Mammal and Marine Bioacoustics Laboratory, Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya, China Contribution: ​Investigation, Writing - review & editingSearch for more papers by this authorSonghai Li, Corresponding Author Songhai Li lish@idsse.ac.cn orcid.org/0000-0003-4977-1722 Marine Mammal and Marine Bioacoustics Laboratory, Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya, China Correspondence Songhai Li, Marine Mammal and Marine Bioacoustics Laboratory, Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya, 572000, China. Email: lish@idsse.ac.cn Contribution: Conceptualization, Funding acquisition, Project administration, Supervision, Writing - review & editingSearch for more papers by this author Agathe Serres, Agathe Serres orcid.org/0000-0003-2279-9143 Marine Mammal and Marine Bioacoustics Laboratory, Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya, China Contribution: Conceptualization, Formal analysis, Writing - original draftSearch for more papers by this authorWenzhi Lin, Wenzhi Lin orcid.org/0000-0002-0477-0753 Marine Mammal and Marine Bioacoustics Laboratory, Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya, China Contribution: Conceptualization, ​Investigation, Writing - review & editingSearch for more papers by this authorEric E. G. Clua, Eric E. G. Clua EPHE, PSL Research University, CRIOBE USR3278 EPHE-CNRS-UPVD, Perpignan, France Labex Corail, CRIOBE, Moorea, French PolynesiaSearch for more papers by this authorMingli Lin, Mingli Lin Marine Mammal and Marine Bioacoustics Laboratory, Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya, China Contribution: ​Investigation, Writing - review & editingSearch for more papers by this authorMingming Liu, Mingming Liu orcid.org/0000-0003-3802-1002 Marine Mammal and Marine Bioacoustics Laboratory, Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya, China Contribution: ​Investigation, Writing - review & editingSearch for more papers by this authorSonghai Li, Corresponding Author Songhai Li lish@idsse.ac.cn orcid.org/0000-0003-4977-1722 Marine Mammal and Marine Bioacoustics Laboratory, Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya, China Correspondence Songhai Li, Marine Mammal and Marine Bioacoustics Laboratory, Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya, 572000, China. Email: lish@idsse.ac.cn Contribution: Conceptualization, Funding acquisition, Project administration, Supervision, Writing - review & editingSearch for more papers by this author First published: 25 December 2021 https://doi.org/10.1111/mms.12902 Funding information National Natural Science Foundation of China, Grant/Award Numbers: 41306169, 41406182, 41422604; Ocean Park Conservation Foundation, Hong Kong, Grant/Award Numbers: AW02-1920, MM02-1516 Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Early ViewOnline Version of Record before inclusion in an issue RelatedInformation

Feasibility of Using Small UAVs to Derive Morphometric Measurements of Australian Snubfin (Orcaella heinsohni) and Humpback (Sousa sahulensis) Dolphins

Analysis of animal morphometrics can provide vital information regarding population dynamics, structure, and body condition of cetaceans. Unmanned aerial vehicles (UAVs) have become the primary tool to collect morphometric measurements on whales, whereas on free ranging small dolphins, have not yet been applied. This study assesses the feasibility of obtaining reliable body morphometrics from Australian snubfin (Orcaella heinsohni) and humpback dolphins (Sousa sahulensis) using images collected from UAVs. Specifically, using a dolphin replica of known size, we tested the effect of the altitude of the UAV and the position of the animal within the image frame on the accuracy of length estimates. Using linear mixed models, we further assessed the precision of the total length estimates of humpback and snubfin dolphins. The precision of length estimates on the replica increased by ~2% when images were sampled at 45–60 m compared with 15–30 m. However, the precision of total length estimates on dolphins was significantly influenced only by the degree of arch and edge certainty. Overall, we obtained total length estimates with a precision of ~3% and consistent with published data. This study demonstrates the reliability of using UAV based images to obtain morphometrics of small dolphin species, such as snubfin and humpback dolphins.

First evaluation of quantitative fatty acid signature analysis (QFASA) in dolphins

Accurate diet estimation of marine mammals is fundamental to investigate their ecological roles in marine habitats, but it remains a pervasive challenge to researchers due to the constraints associated with conventional methods based on stomach contents or feces analysis, which are imprecise, limited to last meal and often biased. Quantitative fatty acid signature analysis (QFASA), an emerging method for diet estimations, has been demonstrated to be reliable in reconstructing long-term diets of many marine mammal predators; however, its application has not been seriously evaluated in dolphins. To this end, we compared the QFASA estimates obtained using 8 pre-existing calibration coefficient sets, 3 fatty acid subsets, and 3 prey library subsets to the true diet of a captive Indo-Pacific humpback dolphin (Sousa chinensis) that was fed a long-term diet of mostly gizzard shad (Clupanodon thrissa) with smaller proportions of Japanese seabass (Lateolabrax japonicus), pumpkinseed (Lepomis gibbosus), roughscale tonguesole (Cynoglossus lida), and Chinese herring (Ilisha elongate). The diet of the dolphin was best reconstructed using the calibration coefficients derived from captive feeding trials of American mink (Mustela vison) that were fed herring with the “main” fatty acid subset; this process correctly identified gizzard shad as the main prey source of the dolphin with the highest actual diet proportions and lowest predator signature proportions outside the range of the mean prey proportions. In addition, high accuracy and consistency were acquired in the diet estimations obtained using the calibration coefficients derived from minks fed herring and herring plus seal oil even though pseudo-prey were included in our model, revealing the high robustness and reliability of QFASA in reconstructing the dolphin diet. We recommend caution in selecting fatty acid subsets when using fatty acid signatures derived from different studies. Overall, QFASA offers a promising tool to quantify the long-term diets of humpback dolphins and other odontocetes.

Acoustic identification of the sympatric species Indo-Pacific finless porpoise and Indo-Pacific humpback dolphin: an example from Langkawi, Malaysia

ABSTRACT The passive acoustic monitoring (PAM) technique has been widely used to detect odontocetes that emit echolocation clicks. However, identifying sympatric dolphins and porpoises using clicks, which is important especially for conservation purposes, remains challenging. In this study, a species identification technique at the family group level using PAM was applied to classify the click trains of two sympatric odontocetes, the Indo-Pacific finless porpoise (Neophocaena phocaenoides, N.p.) and Indo-Pacific humpback dolphin (Sousa chinensis, S.c.). A threshold was identified to discriminate between the two species using the two-band intensity ratios at 130 and 70 kHz. In addition to the significant difference in the two-band intensity ratio, analyses of the click train characteristics revealed that the click train duration and inter-click interval were significantly longer for S.c. than for N.p., indicating that these parameters enable more accurate species identification. Although this study provides a clear means of discriminating between the two species to reveal their distributions and habitat usage, additional studies are recommended to determine whether the same method can be employed to discriminate between other species known to have overlapping distributions in the region, such as Tursiops aduncus or Orcaella brevirostris.