Indo‐Pacific humpback dolphins (Sousa chinensis) in the Moyang River Estuary: The western part of the world's largest population of humpback dolphins

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上川岛至海陵岛海域中华白海豚种群特征初探

珠江口中华白海豚(Sousa chinensis)种群从伶仃洋一直连续分布至上川岛海域。为探究上川岛以西海域是否也有中华白海豚分布,于2013-2015年采用船基截线法在上川岛至海陵岛海域进行了8个航次的考察。结果显示各个航次均有中华白海豚的目击记录,考察期共目击到78群次(约623头次),部分个体有重复目击记录,证实了该海域常年栖息着一定数量的中华白海豚。海豚的目击分布以下川岛、漭洲岛周围水域,以及东平港至庙湾角近岸水域较为集中。海豚的平均目击率与珠江东部河口(伶仃洋)和珠江西部河口区处于同一水平,海豚聚群规模较大并发现有大于30头的超大规模聚群,整体的年龄组成较为年轻化,表明上川岛至海陵岛海域是中华白海豚的重要栖息地,具有较好的保护潜力。     

Abundance estimates of three cetacean species in the coastal waters of Matang,Perak, Peninsular Malaysia

1. The paucity of baseline data on coastal cetaceans due to a lack of research in developing countries frequently precludes assessment of their status and informed management actions for conservation.
2. This study provides the first abundance estimates of Indo-Pacific humpback dolphins, Irrawaddy dolphins, and Indo-Pacific finless porpoises in the coastal waters of Matang, Peninsular Malaysia.
3. Boat-based surveys covering 1,152 km² of coastal waters with 4,108 km of survey effort were conducted between 2013 and 2016 to collect data for line transect analysis of Irrawaddy dolphins and finless porpoises. Photo-identification data of humpback dolphins were concurrently collected for mark–recapture analysis.
4. Estimates of abundance from four sampling strata totalled 763 Irrawaddy dolphins (CV = 13%, 95% confidence interval (CI) [588, 990]) and 600 Indo-Pacific finless porpoises (CV = 27%, 95% CI [354, 1,016]).
5. The annual abundance estimates of humpback dolphins ranged between 171 (95% CI [148, 208]) in 2014–2015 and 81 (95% CI [67, 98]) in 2015–2016, likely due to the presence of offshore individuals that moved in and out of the study area. The estuarine strata were inhabited by 68 (95% CI [63, 73]) inshore humpback dolphins in 2013–2014 to 87 (95% CI [78, 97]) dolphins in 2014–2015.
6. As an International Union for Conservation of Nature important marine mammal area, the productive coastal waters of Matang are shown to support a high density of small coastal cetaceans, and the results serve as an important baseline for future studies to identify population trends for conservation management plans.

     

Seasonal use of a macrotidal estuary by the endangered dwarf sawfish,Pristis clavata

1. Sawfishes (Family: Pristidae) are one of the most imperilled fish families worldwide. There is an increasingly urgent need to better understand the biology, ecology, and population status of the five sawfish species to develop more effective conservation measures. The dwarf sawfish, Pristis clavata, is one of the least researched members of the pristids, with literature limited to analysing disparate datasets or collations of rare encounters in northern Australia.
2. This study examined the spatial ecology of dwarf sawfish using targeted surveys and acoustic telemetry to determine its habitat use in a macrotidal estuary in northern Australia. Seventeen dwarf sawfish were tagged with acoustic transmitters and monitored in the Fitzroy River estuary and adjacent King Sound (Kimberley, Western Australia) between August 2015 and November 2017.
3. Dwarf sawfish observed within the Fitzroy River estuary and King Sound were juveniles, ranging between 740 and 2,540 mm in total length. Catch per unit effort of dwarf sawfish in the late dry season was relatively high in the estuary, with the catch rate in 2015 being one of the highest reported for any sawfish species.
4. Acoustic detections revealed a distinct seasonal pattern in the use of different parts of the estuary and King Sound, which was found to be driven by salinity. Dwarf sawfish predominately occupied a single large pool near the terminus of the tidal limit in the late dry season (August–November), before transitioning to regions in closer proximity to the river mouth or in King Sound in the wet and early dry seasons (December–July).
5. Given the high abundance and residency of dwarf sawfish in the Fitzroy River estuary, this area is an important nursery for the species during the late dry season and should be formally recognized as a habitat protection area for the species.

     

Determining spatial use of the world's second largest humpback dolphin population: Implications for place‐based conservation and management

1. Place‐based management can be an effective conservation tool to protect cetaceans from anthropogenic pressures. The spatial use of the world's second largest population of the threatened Indo‐Pacific humpback dolphins (Sousa chinensis) is not well‐documented, which makes it challenging to designate protected areas for this population.
2. To address this knowledge gap and to test the efficacy of an existing dolphin protected area (Zhanjiang Leizhou Bay Municipal Humpback Dolphin Nature Reserve, ZLBMHDNR), boat‐based surveys were conducted to document dolphin occurrence from 2015 to 2018, covering an area of 1221 km² in the eastern waters off Zhanjiang, China. In total, 253 dolphin group sightings were obtained during 174 survey days.
3. Spatial analysis showed that humpback dolphins aggregated in three core‐use areas with higher sighting density within the survey area. Furthermore, intermediate‐use and broad‐use areas were identified that could be essential for the movements of humpback dolphins among these core‐use areas.
4. The spatial usage of humpback dolphins was compared inside and outside the ZLBMHDNR. Results suggest that the ZLBMHDNR is insufficient to encompass a significant portion of dolphin habitat. The ZLBMHDNR (21 km²) is not large enough, and thus it should be expanded for effective place‐based conservation management in this region.
5. For developing a protected area network, important dolphin habitats identified in this study should be protected as a single management unit. Additionally, mitigation of anthropogenic pressures is needed to be taken into consideration as conservation initiatives in the study area.
6. This study provides support for a more science‐informed protected area network, and highlights the necessity of implementing place‐based conservation and management for the world's second largest humpback dolphin population.

     

珠江西部河口中华白海豚的分布和季节变化

2007-2008年采用船基截线法每月在珠江西部河口进行海豚调查,以评估该水域中华白海豚(Sousa chinensis)的分布、季节变化和群体组成。研究发现,珠江西部河口中华白海豚主要分布于从三灶岛南至大襟岛西侧水深10m的水域,20m等深线可能为该水域海豚离岸分布的界限,分布区在丰水期趋向河口北部浅水区,枯水期趋向离岸水域,季节性南北移动趋势与珠江东部河口相反;海豚目击率以丰水期较高,枯水期较低,本调查区与珠江东部河口伶仃洋周年各月目击率(头/100km)的相关分析结果呈显著的负相关(n=12,r=-0.65,P0.05),显示目击率的季节变化趋势也与珠江东部河口相反。据此推测,珠江东、西部河口种群之间可能存在海豚个体的交流。比较本调查区和以往珠江东部河口各调查区(包括伶仃洋及其邻近水域)的海豚目击率表明,西部河口也是珠江河口中华白海豚的重要栖息地之一。有必要进一步深入研究珠江西部河口中华白海豚种群的生物学及其与东部河口种群之间的关系,以便全面有效地保护珠江河口的中华白海豚。     

Environmental models for predicting habitat of the Indo‐Pacific humpback dolphins in Fujian,China

1. The coast of Fujian Province is a key area for the Indo‐Pacific humpback dolphin (Sousa chinensis), but the characteristics of their preferred habitats are poorly defined.
2. The species distribution model, MaxEnt, was used to predict suitable habitat distributions of humpback dolphins in Fujian, China. The model indicated that the distance to the coastline (63.5% contribution), chlorophyll‐a levels (20.2%) and the bathymetry (15.6%) were important predictors of humpback dolphin habitats.
3. The model predicted 2,043.96 km² of highly suitable habitat that was concentrated in five areas. Four are known to be within the area of the current distribution of humpback dolphins; Putian was identified as a new area with suitable habitat, however, it is unclear if dolphins are present.
4. The predicted locations of suitable humpback dolphin habitats provided in this study should be the focus of future research and nature reserve designs.

     

Food risk trade‐off in the Indo‐Pacific humpback dolphin: An exploratory case study

1. Based on optimal foraging theory, animals are expected to maximize foraging benefits whilst minimizing risks. Despite risking being subjected to anthropogenic impacts such as water contamination, marine traffic, and underwater noise, estuaries have been identified as the preferred habitat of the Indo‐Pacific humpback dolphin (Sousa chinensis, IPHD). However, it remains unclear why this vulnerable species favours such risky habitats.
2. Here, an exploratory case study in Zhanjiang estuary, China, was conducted to test the hypothesis that IPHDs select estuarine habitats as a trade‐off that maximizes foraging opportunities whilst minimizing the risk of mortality.
3. The results showed that IPHDs accept greater mortality risks for higher food rewards but select habitats with lower risks when food rewards are similar between two locations.
4. Although this type of information is important for underpinning models for individual dolphins, its principal role is to show environmental protection agencies why IPHDs favour estuaries despite the increased mortality risks.
5. Habitat conservation plans should carefully consider prey stocks, possibly through the presence of marine protected areas near estuaries, as local overfishing may lead vulnerable cetacean populations to take greater risks.

     

Habitat configuration for an obligate shallow‐water delphinid: The Indo‐Pacific humpback dolphin,Sousa chinensis,in the Beibu Gulf (Gulf of Tonkin)

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Beware of changes: Conservation of Indo‐Pacific humpback dolphins in disturbed habitats

1. Protecting critical habitats of the Indo‐Pacific humpback dolphin, Sousa chinensis, is a hot topic of discussion for marine biodiversity conservation in China and many Southeast Asian countries. In practice, sound habitat protection action (HPA) planning often suffers from information gaps in macroscopic habitat configurations and changes in the habitat conditions of humpback dolphins.
2. Recent publications in the journal Aquatic Conservation: Marine and Freshwater Ecosystems (AQC) have served to advance humpback dolphin conservation in Chinese waters by resolving such habitat configurations and indicating significant changes in distribution patterns and habitat characteristics under intense coastal anthropogenic activity.
3. We highlight an integrative research framework to investigate habitat configuration and long‐term habitat changes when planning a holistic HPA programme for humpback dolphins. When constructing habitat configuration baselines, field surveys should be designed and conducted in a systematic manner to ensure survey efforts cover diverse environments equally, in either a spatially stratified or gridded pattern, to minimize potential spatial sampling biases. Long‐term habitat changes can be revealed by comparing satellite images from different decades. Changes in habitat preferences and habitat characteristics can be explored through questionnaire surveys on local ecological knowledge, associating historical occurrences with coastline features and projecting historical habitat configuration by species distribution modelling exercises.
4. A lack of good communication and sharing of information between research and management sectors can still be an obstacle to the implementation of sound conservation practices, however, even though there is robust scientific evidence to fill knowledge gaps in distribution and habitat baselines. We have addressed the need to establish a mechanism to improve and streamline information sharing between research teams, management sectors, and stakeholder groups.

     

Seasonal distribution of the Indo-Pacific humpback dolphins: Implications for coastal habitat management

1. Organisms utilize suitable habitat patches wherein they optimize fitness. For marine megafauna such as cetaceans, foraging is generally the explanation for their utilization distribution. However, an explicit link between cetaceans' distribution and spatio-temporal pattern of food resource is usually lacking.
2. The Indo-Pacific humpback dolphin (Sousa chinensis; VU listed in the IUCN Red List) inhabits the coastal waters from south-east China to eastern India. Seasonal distribution of the humpback dolphin was explored in the northern Beibu Gulf, China. Sightings of the humpback dolphin were systematically collected at monthly intervals from 2012 winter till 2018 spring and used to derive distribution patterns from kernel density estimates. Satellite remotely sensed net primary productivity (NPP) and bathymetry were used to present oceanographic characteristics in the study region.
3. Seasonal variations were observed in oceanographic characteristics and spatial distribution of the humpback dolphin. Although the core distribution area of the humpback dolphin showed seasonal expansion and contraction, it had consistently higher NPP and shallower depth than the survey range throughout the seasons.
4. Our findings indicate a clear profile of these two oceanographic characteristics (i.e. NPP and bathymetry) in the humpback dolphin's core distribution area. Food resource utilization could play an important role in the humpback dolphin's distribution within the study site. The seasonal dynamics imply that not only food abundance, but also efficiency in accessing/capturing the prey may affect distribution of the humpback dolphin.
5. In the study site, human activities that can change regional topography and productivity of the coastal water through land reclamation, dredging, sand mining and bottom trawling, should be mitigated, regulated or avoided. Proactive conservation should incorporate catchment management of the main rivers to address potential sediment and nutrient load into the estuary to protect local habitat configuration in terms of NPP and bathymetry.

     

Indian Ocean humpback dolphin in the Menai Bay off the south coast of Zanzibar,East Africa is Critically Endangered

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Indian Ocean humpback dolphin (Sousa plumbea) movement patterns along the South African coast

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珠江口大型底栖动物数量与生物多样性的分布特征

为了更好地了解河口生物多样性的演变规律及退化机制,根据2015年1—12月珠江口大型底栖动物调查资料对珠江口大型底栖动物现存量和生物多样性的分布特征进行了研究。结果表明,11次采样(受台风影响7月珠江口未采集到大型底栖动物)共获取大型底栖动物67种,其中环节动物多毛纲27种,节肢动物24种,软体动物12种,其它类群4种,主要是底栖鱼类、刺胞动物和纽形动物。2015年珠江口各站位大型底栖动物丰度的变化范围在8~1192个·m^-2之间,珠江口大型底栖动物丰度的高值出现在6月和9月的崖门(分别为1192个·m^-2和1048个·m^-2)以及9月的虎跳门(1048个·m^-2),日本大螯蜚(Grandidierella japonica)、中华拟亮钩虾(Paraphotis sinensis)、凸壳肌蛤(Musculus senhousei)和彩虹明樱蛤(Moerella iribescens)丰度较高。大型底栖动物生物量变化范围在0.02~42.50g·m^-2之间,生物量的高值出现在9月的崖门、5月的鸡啼门、2—3月的磨刀门及4月的蕉门,上述站位的生物量均大于30.00g·m^-2,缢蛏(Sinonovacula constricta)、光滑河篮蛤(Potamocorbula laevis)、黑龙江河篮蛤(P.amurensis)、凸壳肌蛤和日本大螯蜚生物量较高。珠江口大型底栖动物香浓威纳指数高值出现在3月鸡啼门,为2.46;低值出现在10月磨刀门,为0.21。香浓威纳指数均值在1.11~1.81之间。鸡啼门和虎跳门大型底栖动物香浓威纳指数值月际变化较稳定。运用ABC曲线对珠江口大型底栖动物扰动状况进行评价,结果表明,1月珠江口大型底栖动物受到中等程度扰动,2—4月大型底栖动物群落有受到中等程度干扰的趋势。     

Another dolphin in peril? Photo‐identification,occurrence, and distribution of the endangered Indian Ocean humpback dolphin (Sousa plumbea) in Algoa Bay

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Investigating seasonal habitat-use of saltwater crocodiles in the Ayeyarwady Delta to identify potential conservation areas in Myanmar

1. Understanding the impact of land-cover mosaics on crocodile distribution and habitat patterns is essential to prioritize areas for their conservation in human-dominated landscapes. This is especially important for species with specialist requirements; or where there is human–wildlife conflict, as is the case in many areas with crocodiles, such as Myanmar's Ayeyarwady Delta.
2. The saltwater crocodile is used as a surrogate species in this study to identify important conservation areas, and to propose potential protected areas for the Ayeyarwady coastal mangrove ecoregion. In total, 684 locations of saltwater crocodile encounters were collected, 444 for the wet season (May to June), and 240 for the dry season (December to January) between 1999 and 2018. Suitable habitats of saltwater crocodiles in the Ayeyarwady Delta were modelled for wet and dry seasons, using 12 predictor variables at 300-m resolution.
3. The area of suitable habitat in the wet season is about 1,272.3 km² but reduces to 563.7 km² in the dry season. Distance to the cropland, distance to the sea, mangrove cover, and wetland cover are identified as the key landscape variables that contributed to the seasonal habitat distribution of saltwater crocodiles in the Ayeyarwady Delta.
4. Protecting core and buffer areas in Kadonkani Reserved Forest and Pyindayae Reserved Forest would safeguard the seasonal habitats of saltwater crocodiles. Khaing Thaung Island, an unprotected area with suitable habitat areas for saltwater crocodiles, is proposed as a potential marine protected area in the Ayeyarwady Delta of Myanmar.

     

Distribution and habitat characteristics of three sympatric cetacean species in the coastal waters of Matang,Perak, Peninsular Malaysia

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Conservation of fish communities: Extending the ‘research life cycle’ by achieving practical effects

1. This article highlights the practical impact of our 2018 Aquatic Conservation: Marine and Freshwater Ecosystems publication, ‘Importance of peripheral basins: Implications for the conservation of fish assemblages’, which described fish communities in a Polish river.
2. Data on the fish assemblages of the Dniester River (Black Sea basin) are scarce; however, evidence indicates that the assemblages have declined. In our 2018 study, we hypothesized that the peripheral basin (the small basin on the edge) of the larger Upper Dniester River basin (the Strwi?? River) could maintain good ecological status and contained unique fish assemblages.
3. To examine the influence of historical factors and assess the role of peripheral basins on fish conservation, data from the Strwi?? basin were compared with the adjacent but unconnected Wiar basin (the Vistula basin; Baltic Sea basin). The Strwi?? River fish assemblages featured higher species richness and a greater number of native Ponto–Caspian species that function near the edge of their ranges.
4. This article focuses on four impacts of the 2018 publication: increasing awareness by various groups and organizations of the unique character of the surveyed river basin; highlighting important issues in assessing the ecological status of European rivers; driving the red‐listing of species and the development of stream fish conservation strategies; and identifying possible future impacts.
5. Our 2018 publication demonstrated the value of studying peripheral basins, which may affect conservation strategy development and encourage study of the importance of other peripheral basins and their role in aquatic resources conservation. Our article influenced the interpretation of fish‐based biotic indices and the conduct of monitoring work and its evaluation. It also strongly emphasized the native origin of the racer goby (Babka gymnotrachelus) in the Strwi?? River, which was important for subsequent works seeking to change the legal status of the species in Poland.

     

New urban habitat for endangered humpback whales: San Francisco Bay

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