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

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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.

     

海洋江豚的研究概述

近年来随着国家政策的重视,人们环保意识的提高,针对珍稀濒危水生野生动物,尤其是鲸类动物的保护工作受到越来越多的关注。截至目前,国内相关研究单位针对鲸类动物开展了大量研究,但研究对象主要局限在中华白海豚(Sousa chinensis)和长江江豚(Neophocaena asiaeorientalis asiaeorientalis)。相比较而言,在我国分布范围更广的海洋江豚得到的研究和保护远远不够,亟需开展系统深入的研究工作。鉴于此,本文对江豚的记载、分类和海洋江豚的研究进行了回顾,重点总结了海洋江豚的生态学、生物学、遗传学、声学以及摄食和繁殖等方面的研究进展,对今后的研究和保护重点提出了建议,包括注重基础研究、强化保护区建设、注重保护技术研发和加强宣传教育,以期对未来的工作提供借鉴。     

海洋江豚的研究概述

近年来随着国家政策的重视,人们环保意识的提高,针对珍稀濒危水生野生动物,尤其是鲸类动物的保护工作受到越来越多的关注。截至目前,国内相关研究单位针对鲸类动物开展了大量研究,但研究对象主要局限在中华白海豚(Sousa chinensis)和长江江豚(Neophocaena asiaeorientalis asiaeorientalis)。相比较而言,在我国分布范围更广的海洋江豚得到的研究和保护远远不够,亟需开展系统深入的研究工作。鉴于此,本文对江豚的记载、分类和海洋江豚的研究进行了回顾,重点总结了海洋江豚的生态学、生物学、遗传学、声学以及摄食和繁殖等方面的研究进展,对今后的研究和保护重点提出了建议,包括注重基础研究、强化保护区建设、注重保护技术研发和加强宣传教育,以期对未来的工作提供借鉴。     

Common bottlenose dolphin (Tursiops truncatus) abundance and distribution patterns in St Andrew Bay,Florida, USA

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Long‐term changes in the distribution and core habitat use of a coastal delphinid in response to anthropogenic coastal alterations

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Averting the baiji syndrome: conserving habitat for critically endangered dolphins in Eastern Taiwan Strait

• 1. Numbering no more than 100 individuals and facing many threats, the geographically isolated Eastern Taiwan Strait population of Indo‐Pacific humpback dolphins (Sousa chinensis) is in peril. The estuarine and coastal waters of central‐western Taiwan have historically provided prime habitat for these dolphins, but environmental conditions today bear little resemblance to what they were in the past.
• 2. The humpback dolphins must share their habitat with thousands of fishing vessels and numerous factories built upon thousands of hectares of reclaimed land.
• 3. They are exposed to chemicals and sewage released from adjacent terrestrial activities. Noise and disturbance associated with construction, vessel traffic and military activities are features of everyday life for these animals.
• 4. Measures to slow the pace of habitat deterioration and reduce the many risks to the dolphins are urgently needed. As one practical step in this direction, this paper describes the habitat needs of these small cetaceans so that decision makers will be better equipped to define ‘priority habitat’ and implement much needed protection measures under the terms of local legislation.
• 5. The preferred habitat of these dolphins in Taiwan consists of shallow (<30 m), near‐shore marine waters with regular freshwater inputs.
• 6. For such a small, isolated and threatened population, ‘priority habitat’ should not be limited to areas of particularly intensive dolphin use or high dolphin density, but rather it should encompass the entire area where the animals have been observed (their current ‘habitat’), as well as additional coastal areas with similar bio‐physical features (‘suitable habitat’). Such a precautionary approach is warranted because the loss of only a few individuals could have serious population‐level consequences.
• 7. While conventional socio‐economic analysis might suggest that implementing protection measures over an area stretching ～350 km north–south along Taiwan's west coast and ～3 km out to sea would be too ‘costly’, the loss of this charismatic species from Taiwan's waters would send a troubling message regarding our collective ability to reconcile human activities with environmental sustainability. Copyright © 2010 John Wiley & Sons, Ltd.

     

Long‐term habitat loss in a lightly‐disturbed population of the Indo‐Pacific humpback dolphin,Sousa chinensis

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

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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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Cetacean occurrence,habitat preferences and potential for cetacean–fishery interactions in Iberian Atlantic waters: results from cooperative research involving local stakeholders

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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.

     

Monitoring Indo-Pacific humpback dolphin occurrences in a highly urbanized estuary for informing conservation and management

1. The estuaries within the Pearl River Delta are sites for large-scale urban development and offshore construction. These projects have conservation stakeholders calling for more protection for the Indo-Pacific humpback dolphins whose habitat overlaps with current and proposed construction sites.
2. Efforts to improve impact assessments are hindered by the lack of baseline data and comprehensive understanding of how often the dolphins are present in areas near or within locations targeted for further development. The Modaomen Estuary within the Pearl River Delta is a good example of this, with little consideration for the dolphins as no data on their diurnal and seasonal occurrences within the estuary exist.
3. A passive acoustic monitoring system was deployed over a calendar year from October 2016 to September 2017 to monitor the presence of humpback dolphins in the Modaomen Estuary.
4. Results indicated that the estuary is an important area for humpback dolphins, with regular diel rhythms and seasonality in detection rates. For example, higher detections were seen during the wet season than during the dry season. However, there was no significant difference in detection rates between the flood and ebb tides, or between high and low tidal phases.
5. Since the Modaomen Estuary is targeted for further development in the near future, these data provide the rationale for resource management and consent processes to consider potential impacts on the dolphins, as well as to aid marine spatial planning and conservation measures.

     

Dolphins in a bottle: abundance,residency patterns and conservation of bottlenose dolphins Tursiops truncatus in the semi‐closed eutrophic Amvrakikos Gulf,Greece

• 1. Boat surveys were conducted between 2002 and 2005 to study bottlenose dolphins living in the 400 km² Amvrakikos Gulf, western Greece. During 116 survey days, 4705 km of total effort resulted in the individual photo‐identification of 106 animals, through long‐term natural markings on their dorsal fins.
• 2. Mark–recapture analyses based on the M_th model provided estimates of 82 marked individuals in 2003 (95% CI=80–91), 92 in 2004 (95% CI=86–108) and 98 in 2005 (95% CI=94–110). To include the unmarked portion of the population, the proportion of unmarked individuals was computed based on the number of photographs of marked and unmarked dorsal fins. The mean proportion of unmarked animals in the population was 0.338 (95% CI=0.288–0.389). By adding this to the estimate for marked animals in 2005, considered as the most robust, a total population estimate of 148 individuals (95% CI=132–180) was obtained.
• 3. Dolphin encounter rates in 2003–2005 did not show significant variations, and averaged 7.2 groups per 100 km or 72.5 individuals per 100 km. Encounter rates within the Gulf were about one order of magnitude greater than those found for bottlenose dolphins in nearby eastern Ionian Sea coastal waters.
• 4. Mean dolphin density in the Gulf was 0.37 animals km^?2. This relatively high density, together with high levels of site fidelity shown by most individuals, was thought to be related primarily to prey availability, particularly of epipelagic schooling fish.
• 5. The importance of the semi‐closed Amvrakikos Gulf for bottlenose dolphins and other threatened species encourages the adoption of measures aimed to conserve its valuable ecosystems and raise the naturalistic profile of the area, while promoting environment‐conscious development. Meaningful action includes restoring natural hydrology (e.g. freshwater input from rivers), curtailing pollution from various sources, responsible fisheries and aquaculture management, and control of illegal fishing. Interactions between dolphins and fisheries also deserve careful quantitative investigation.

Copyright © 2007 John Wiley & Sons, Ltd.     

Present distribution of common dolphin Delphinus delphis in French Mediterranean and adjacent waters as obtained from small boat surveys

1. Common dolphin distribution in the western Mediterranean is still poorly known, with the exception of the Alboran Sea. In French waters, the species occurrence is suspected to have strongly decreased during the 20th century.
2. Small boat dedicated surveys from 1988 to 2012 were undertaken to describe common dolphin distribution in five regions of French waters and three southern regions of the western basin. A total survey effort of 38,561 km resulted in sightings of 25 common dolphin groups in the western basin.
3. Common dolphins were rarely observed off the French continental coast, more frequently around Corsica, and were quite frequent in waters off western Sardinia. Their most favoured habitat was found to be in neritic or upper slope waters.
4. The analysis of stranding records suggested that common dolphins were more abundant in French inshore waters prior to 1980.
5. A major increase of pelagic fish landings occurred from the beginning of the 1960s in the western part of French waters. Local populations of common dolphins may have declined as a consequence of prey depletion.

     

Population abundance and habitat preference of the Yangtze finless porpoise in the highest density section of the Yangtze River

1. Habitat loss and degradation together represent one of the five major factors contributing to the rapid decline of the Yangtze finless porpoise in the Yangtze River. Protecting key habitat patches and maintaining migration corridors between habitat patches are major conservation objectives to ensure the in situ viability of the Yangtze finless porpoise. Baseline information essential for addressing these two objectives includes that pertaining to distribution and habitat preference.
2. To investigate the distribution and habitat preferences of the Yangtze finless porpoise, five transect surveys were conducted in the Anqing section of the Yangtze River, which has the highest porpoise density among all sections of the river. Porpoise abundance estimates were calculated, and preferences for different habitat types were evaluated.
3. The calculated porpoise abundance in the Anqing section was 181 (95% CI 125–239) animals on average. The inter‐annual and inter‐seasonal differences in porpoise abundance estimates were not significant. The natural river banks and sandbar shores were the most preferred habitats, representing 46.3 and 29.8% of the porpoise observations, respectively. In contrast, 8.1% of the porpoises were observed in habitats along reinforced river banks, which account for 38.7% of the total coastline. In subsections with natural habitat patches, porpoises were observed in almost every survey, while porpoise occurrence became highly stochastic in subsections with long reinforced river banks. These results indicate a significant tendency of the Yangtze finless porpoise to prefer natural habitats with natural river bank or sandbars but to keep away from reinforced river‐bank habitats.
4. According to porpoise density in different subsections, free migration may be impeded or only one migration corridor remains in some subsections.
5. Although protecting finless porpoise habitats has become a primary conservation objective, this study highlights the need to protect frequently used habitat patches and migration corridors, particularly those near natural river banks and sandbars, and to restore ecological environments along reinforced river banks.

     

Decreasing population trend in coastal bottlenose dolphin (Tursiops truncatus) from the Gulf of Guayaquil,Ecuador

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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。     

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.

     

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.