Spinner dolphins Stenella longirostris off south-west Mauritius: abundance and residency

Spinner dolphins Stenella longirostris longirostris off the south-west coast of Mauritius are subject to ongoing anthropogenic disturbance in the form of daily dolphin tourism, which has intensified since 1998. Abundance of this species was estimated using photo-identification data and mark-recapture analysis. Between April 2008 and June 2010, identification photographs were collected from dolphins occurring along a 30 km length of the coast of south-west Mauritius. A total of 250 groups were encountered over 229 survey days. Mark-recapture analyses were performed on a photographic dataset of more than 8 000 good- and excellent-quality images and 83 animals were identified as distinctively marked individuals. The majority (85.5%) were seen more than once and resightings indicated a resident population. The compiled version of SOCPROG 2.4 was used to investigate the lagged identification rate. The fitted model supported a mostly resident population with additional animals moving in and out of the study area. The estimated abundance of the total population in the study area ranged between 138 and 399 individuals. Our results can be used for monitoring the population for fluctuations and for encouraging both the enforcement of laws regarding dolphin watching and the development of further means of management needed to ensure the long-term presence of this population.     

Bottlenose dolphin Tursiops truncatus group dynamics,site fidelity,residency and movement patterns in the Madeira Archipelago (North-East Atlantic)

The bottlenose dolphin Tursiops truncatus is one of the most frequently sighted cetacean species in the Madeira Archipelago (North-East Atlantic); however, little is known about its population ecology in these waters. Photo-identification undertaken during systematic, non-systematic and opportunistic surveys conducted between 2001 and 2012 was used to assess group dynamics, site fidelity, residency and movement patterns of bottlenose dolphins in the archipelago. Three different patterns of residency were assigned, based on individual sighting histories. Group size ranged between 2 and 90 individuals (median 12), with no significant monthly difference in group size. All resident dolphins formed a core, complex network with migrant and transient dolphins. In contrast, satellite clusters were formed exclusively by transient individuals. The lagged identification rate (LIR) model indicated that a dolphin remained in the area for an average of 90 days, whereas the average time an individual spent outside the study area was approximately 313 days. The Madeira Archipelago appears to be only a section of a much larger home range for this population, with the dolphins exhibiting three different patterns of occurrence that associate with each other. The information gained about this poorly studied population contributes to the overall knowledge of bottlenose dolphins in insular oceanic habitats.     

抗风浪海水网箱中南瓶鼻海豚行为谱的初步构建

采用目标取样法,对饲养于抗风浪网箱中的4只南瓶鼻海豚（Tursiops aduncus）的行为进行了观察和记录,最终定义了南瓶鼻海豚的7种姿势和70种行为.在此基础上,根据行为发生时的姿势、动作、环境以及可能具有的功能,将这些行为划分为水面运动行为、空中行为、社群行为、索食、性行为、玩耍、休息及杂类等8个行为模式,从而初步构建了南瓶鼻海豚的行为谱.还进一步对某些行为,如社会行为的生物学和生态学意义进行了探讨.     

From catching to watching: Moving towards quality assurance of whale/dolphin watching tourism in Taiwan

Taiwan has shifted from harvesting whales and dolphins to protecting all cetacean species since 1990. Whales and dolphins have become major tourist attractions. With an eye on foreseeable future growth and increasing concerns about environmental impact, service delivery, and educational efficacy, the government seeks to achieve the overall quality assurance of whale/dolphin watching tourism by introducing an ecolabelling program. The aim of this study is to examine this program by analyzing its impact on tour operators and visitors. A survey method was used to assess the impact. The results showed that the program is having a positive impact on operators by seeking environmental sustainability and has brought about educational benefits for visitors, including: site-based knowledge, awareness of marine conservation and reinforcing intentions to perform environmentally responsible behaviors. However, money cost is a major factor discouraging tour operator’s participation, even though ecolabels help to construct an image of responsibility. With potential educational benefits for visitors in mind, the study highlights the need for increasing public awareness of the program, expanding marketing of ecolabelled products, and providing economic incentives for tour operators to engage in ecolabelling.     

Short-term survival of severe propeller strike injuries and observations on wound progression in a bottlenose dolphin

Until recently, vessel collisions with small cetaceans were presumed rare, mainly as a consequence of limited reporting. Observations on dolphin wound healing from propeller strike injuries also remain scarce. We present an extreme case of a bottlenose dolphin (Tursiops truncatus) with multiple propeller wounds, including a penetration to the bone, where survival was possible for at least 23 days post injury. We used photographic records in conjunction with field observations to describe wound progression in the absence of treatment. Considering the severity of the wounds, it was surprising that the injuries were not immediately fatal. A practical solution remains to be found for the problem of odontocete vessel collisions, in particular for small highly mobile species using neritic waters. In view of the ongoing problem in the Hauraki Gulf and, indeed, worldwide, we recommend continued evaluation of cases and reporting of incidents, in addition to investigations into mechanisms that may reduce the risk of occurrence of vessel collisions with cetaceans.     

Behavioral response of Indo-Pacific humpback dolphin (Sousa chinensis) to vessel traffic

A series of land-based surveys were conducted at two vantage points of known dolphin abundance in Hong Kong. The purpose of this study was to determine the behavioral response of Indo-Pacific humpback dolphin (Sousa chinensis) to vessel traffic. Results indicated that dolphins dove for a longer duration in areas of heavy vessel traffic or when there was the presence of an oncoming vessel. Dependent upon the type of vessel and the relative distance, dolphins might flee, continue their ongoing activity, perform a new activity, or approach the vessel. Whilst slow-moving vessels appeared not to cause immediate stress on the dolphin community, fast-moving vessels often cause disruption of behavior and social life. In order to ensure a better environment for the animals, we suggest that proactive conservation measures such as the creation of a marine park, rules and regulations for dolphin watching activities, and regional control of vessel speed should be implemented.     

Abundance and degree of residency of humpback dolphins Sousa plumbea in Mossel Bay,South Africa

Indian Ocean humpback dolphins Sousa plumbea inhabit nearshore waters from South Africa to eastern India. Humpback dolphins are vulnerable to conservation threats due to their naturally small population sizes and use of nearshore habitats, where human activities are highest. We investigated the abundance and residency of this species inhabiting Mossel Bay, South Africa, using photographic mark-recapture. Data were collected during 81 surveys in Mossel Bay between 2011 and 2013. Open population modelling using the POPAN parameterisation produced a ‘super-population’ estimate of 125 individuals (95% CI: 61–260) and within-year estimates of between 33 and 86 individuals (2011: 71 [95% CI: 30–168]; 2012: 33 [15–73], 32 [15–70]; 2013: 46 [20–108]). Although less appropriate, closed capture models were also run for comparison with previous studies in the region and generated similar, but slightly smaller, population estimates within each year. We compared our catalogue with opportunistic data collected from East London, Plettenberg Bay, De Hoop and Gansbaai. The only catalogue matches attained were between Plettenberg Bay (n = 44 identified) and Mossel Bay (n = 67 identified), separated by 140?km. Population exchange was moderate, with nine individuals resighted in multiple years between these two areas. This study supports previous findings of long-range movements for this species and provides a baseline from which to assess future impacts on the population.     

Distribution,behaviour and photo-identification of Atlantic humpback dolphins Sousa teuszii off Flamingos,Angola

Atlantic humpback dolphins Sousa teuszii are a priority for research due to their restricted geographic range, narrow ecological niche and the paucity of existing information. The distribution and behaviour of S. teuszii off Flamingos, southern Angola, was investigated during summer and winter 2008 using boat- and shore-based surveys. In all, 71 S. teuszii sightings were recorded, ranging from one to eight animals. Sousa teuszii inhabited shallow, nearshore waters throughout the region, with the exception of southern areas adjacent to fishing villages. Small bays, sheltered waters behind reef-breaks and areas off dry river mouths were used for foraging/feeding behaviour, whereas most travelling occurred along exposed coast. Ten individual S. teuszii were photo-identified. Multiple resightings (and absence of unmarked animals) indicate that all individuals present at the time of the surveys were photocaptured, exhibited high site fidelity and had year-round occurrence. Association indices of 0.77-1.0 indicated strong social affiliation between eight individuals, particularly in winter. Off Flamingos, S. teuszii occurs in small numbers and exhibits high site fidelity to a relatively small stretch of nearshore habitat, making the species vulnerable to local extirpation. Wider-scale surveys and development of a management plan are crucial to ensuring the long-term conservation of S. teuszii off Flamingos.     

长吻飞旋海豚的一些生物学测量数据

2003年11月山东省石岛的渔民在黄海水域偶然误捕了一头海豚，经作者鉴定，系长吻飞旋海豚（Stenella longirostris），国家Ⅱ级重点保护动物，是黄海水域的首次记录。其主要鉴别特征：喙细长；背鳍略呈三角形；尾柄很高，具有结缔组织构成扩大的嵴；齿数：右上颌47枚，右下颌50枚，左上颌47枚，左下颌51枚。同时，还对其进行了较详细的观察和测量：此海豚系雄性，体长1．828m。为长吻飞旋海豚的保护以及管理措施的制定提供了基本的参考资料。     

Abundance of fin whales (Balaenoptera physalus) in the north-western Mediterranean Sea,using photo-identification and microsatellite genotyping

The Mediterranean fin whale population, Balaenoptera physalus, is resident, with almost no exchanges with the Atlantic population. The entire population was estimated at 1300 or 13,300 individuals by a recent project depending on the platform used. This disparity shows the importance of long-term monitoring with a unique protocol of survey. Capture-recapture approaches using dorsal photographs and genetic identity collections over a 10 years period were used to estimate the abundance of the north-western Mediterranean fin whale. We identified 332 individuals using photographs and 470 using genotypes, with a total of 546 individuals identified between 2008 and 2019, when some whales were double-marked. The inter-annual percentage of recapture varied between 15% and 17% respectively for genotypes and photographs methods. Using Cormack-Jolly-Seber models, the abundance of fin whales in the north-western Mediterranean is estimated at 1295 individuals (95% CI: 1116–1474) with a survival probability of 0.945 (95% CI: 0.690–0.993) from genotypes. Abundance estimates from combined collections (photographs and genotypes) and corrected photograph estimates were similar to the genetic ones. Future studies might prioritize the genetic approach which is the least biased and with a narrower confidence interval. The genetic abundance estimates show relative stability over time, when compared to 1990 estimates, and should be included in future conservation actions.     

Occurrence of bottlenose dolphins Tursiops truncatus in natural gas fields of the northwestern Adriatic Sea

Common bottlenose dolphins, Tursiops truncatus, were surveyed in offshore gas fields off Ravenna, Italy, between Spring and Autumn, 2001–2005. These visual surveys provide the first density estimates of bottlenose dolphins in the Northwestern Adriatic Sea south of the Po River. Since no study has examined the distribution of bottlenose dolphins relative to gas platforms, when dolphins were encountered, their distance from the nearest gas platform was estimated and behaviour was assessed. Dolphins were sighted on ca. 36% of survey trips, which varied in duration from 1 to 6 h. Group size ranged from 1 to ~50 individuals, with no seasonal trend evident in the likelihood of encounter. Dolphin density was estimated to be approximately 80% higher within 750 m of gas platforms, relative to densities >750 m from platforms, although variability around the estimates was high. From a limited number of behavioural observations, slightly higher frequencies of feeding and milling behaviour were observed closer to gas platforms, whereas dolphins observed further away exhibited higher frequencies of socialising and travelling. Gas platforms are known to provide habitat for demersal fishes and act as aggregation points for pelagic fishes, and these data provide some support for the idea that bottlenose dolphins may utilise gas platforms opportunistically as feeding sites.     

中华白海豚SRAP分子标记多态性的初步研究

首次将SRAP(sequence-related amplified polymorphism)方法引入中华白海豚(Sousa chinensis)多态性研究中,利用高分辨率的毛细管凝胶电泳分析了模板DNA、Mg2+、dNTP、引物、Taq DNA聚合酶等因素对SRAP-PCR扩增结果的影响.确定了me1-em5为扩增中华白海豚基因组DNA的最佳引物对.并进一步确立了适合中华白海豚的SRAP最佳反应体系:25 mm3体系中,模板DNA浓度为0.8 ng/mm3,Mg2+浓度为1.0 mmol/dm3,dNTP浓度为0.1 mmol/dm3,引物浓度为0.2μmol/dm3,Taq DNA聚合酶浓度为0.04 U/mm3.利用该反应体系对10个白海豚样品进行SRAP分析的结果表明,不同样品间DNA谱带清晰、多态性丰富.证实该体系稳定可靠,可以用于中华白海豚的分子标记研究.     

中国沿海中华白海豚种群的分布区

中华白海豚Sousa chinensis(Osbeck,1765)首先在我国发现,是我国沿海仅有的定居性海洋鲸豚类.本文根据中华白海豚目击事件和研究报道,分析了中华白海豚在中国的分布、种群隔离及其差异.认为我国南方福建、广东以南沿海为中华白海豚种群的主要分布区,明确指出我国沿海存在5个主要的中华白海豚种群栖息地.通过分析,划分出中华白海豚活动的边缘区和栖息地两个部分.由于中华白海豚种群不断缩小,在保护中华白海豚栖息地的基础上,加强对中华白海豚栖息地外的边缘区的保护显得尤为重要.本文分析将为科学划定中华白海豚保护区提供依据.     

Genetic diversity and population structure of the franciscana dolphin,Pontoporia blainvillei,in Southern Buenos Aires,Argentina

The franciscana dolphin, Pontoporia blainvillei, is endemic to the coastal waters of the southwestern Atlantic Ocean and the most endangered dolphin in the area. Four Franciscana Management Areas (FMAs) are currently recognised; however, results of genetic studies suggest the requirement for additional FMAs and highlight the need for more detailed studies in the southern extreme of the species distribution. With this aim, we studied the genetic diversity and population structure of the species analysing an mtDNA control region fragment (434?bp) in 44 individuals collected in four sampling sites located in Southern Buenos Aires. Haplotype diversity (H?=?0.75?±?0.05) was mostly higher than the observed in endangered or near threatened odontocetes. Population structure analyses suggest that three different genetic populations should be recognised within FMA IV: Northern, Eastern and Southern Buenos Aires. Altogether, these results should be taken into account in future conservation plans for the species.     

Influence of seasonal forcing on habitat use by bottlenose dolphinsTursiops truncatus in the Northern Adriatic Sea

Bottlenose dolphins are the only cetaceans regularly observed in the northern Adriatic Sea, but they survive at low densities and are exposed to significant threats. This study investigates some of the factors that influence habitat use by the animals in a largely homogeneous environment by combining dolphin data with hydrological and physiographical variables sampled from oceanographic ships. Surveys were conducted year-round between 2003 and 2006, totalling 3,397 km of effort. Habitat modelling based on a binary stepwise logistic regression analysis predicted between 81% and 93% of the cells where animals were present. Seven environmental covariates were important predictors: oxygen saturation, water temperature, density anomaly, gradient of density anomaly, turbidity, distance from the nearest coast and bottom depth. The model selected consistent predictors in spring and summer. However, the relationship (inverse or direct) between each predictor and dolphin presence varied among seasons, and different predictors were selected in fall. This suggests that dolphin distribution changed depending on seasonal forcing. As the study area is relatively uniform in terms of bottom topography, habitat use by the animals seems to depend on complex interactions among hydrological variables, caused primarily by seasonal change and likely to determine shifts in prey distribution.     

Exploring the applicability of biological and socioeconomic tools in developing EAFM plans for data absent areas: Spinner dolphin EAFM for Kalpitiya,Sri Lanka

The ecosystem approach to fisheries management (EAFM) methodology is currently considered the preferred option for long-term sustainability of fisheries and ecosystem services and is widely popularised. Manuals, guidelines and training have been given to many nations, but the actual existence and execution of an EAFM plan is rare. The applicability and relevance of biological and socioeconomic tools to follow EAFM planning guidelines in a data absent area were explored in Kalpitiya, northwest Sri Lanka, where there is a population of spinner dolphins that the local community are especially dependent on through tuna-dolphin association fishing and dolphin-watching tourism. This paper provides background to the design and collection of information leading to the formulation of an EAFM management plan. Scoping and the determination of a fishery management area were completed through stakeholder consultations using a combination of interviewer-administered questionnaires, interviews, meetings, dolphin distribution data and existing management plans. Threats and stakeholder prioritisation were compiled and the final agreed fisheries management area covers a total area of 2445 km² adjacent to the Kalpitiya peninsula. The completed EAFM plan contains 4 goals, 16 actions and 72 sub-actions agreed by stakeholders. It was concluded that both willingness of higher level stakeholders responsible for implementing regulations and working with grass-root level stakeholders are critical in developing a realistic and implementable EAFM plan. This work also highlights how data absence should not remain the bottleneck that hinders moving forward with EAFM approaches.     

Abundance and distribution of avian and marine mammal predators of sardine observed during the 2005 KwaZulu-Natal sardine run survey

Opportunistic observations to determine the relative abundance and distribution of marine mammal and seabird predators of sardine Sardinops sagax were carried out during a dedicated multidisciplinary research survey off the South African east coast in June and July of 2005 that was timed to coincide with the annual sardine run. Associations between different predator species, between predators and clupeoids, and between predators and oceanographic variables, were examined. Species’ distributions were primarily separated by latitude and distance from shore. Bryde's whale Balaenoptera edeni, African penguin Spheniscus demersus, Cape cormorant Phalacrocorax capensis and West Coast round herring Etrumeus whiteheadi were predominantly found in the cool southern part of the survey region. Peak sardine run activity occurred within 4 km of shore at the northward limit of a strip of cool water (<21 °C) stretching along the East Coast. The principal predators associated with this activity were common dolphins Delphinus capensis and Cape gannets Morus capensis, and their nearshore distribution was associated with sardine and East Coast round herring E. teres. Few clupeoids were encountered along the KwaZulu-Natal continental shelf, although patches of high sardine abundance were recorded near the shore immediately south of Durban. It is clear that during the 2005 survey the sardine run terminated in this region, probably as a result of the nearshore intrusion of warm water from the Agulhas Current.     

Abundance and distribution of ichthyoplankton in the upwelling zone off Oregon during anomalous El Niño conditions

The abundance and distribution patterns of nearshore ichthyoplankton were investigated during a year of anomalously high sea temperatures off Oregon. Samples collected from 2 to 18 km offshore from April through September of 1983 showed increased occurrences and higher abundances of taxa usually found at distances offshore of 37 km in other years. The dominant species collected, comprising more than half of the total larval fish abundance, was the northern anchovy (Engraulis mordax). Larval anchovy have rarely been collected inshore in previous studies. Many of the dominant taxa normally found inshore, especially osmerids, were present in reduced numbers in 1983. Changes in the hydrographic conditions associated with onshore surface drift and reduced summer upwelling during the 1983 El Niño could explain the distributional patterns observed. The warm inshore waters apparently provided a substantial spatial and temporal expansion of the spawning habitat for E. mordax.     

Effects of hypoxia on macrobenthos of the inner shelf off Cameron,Louisiana

The effects of hypoxic bottom water, an annual event, were documented on the inner shelf off Cameron, Louisiana during the summer of 1981. Populations of most species of macrobenthos were dramatically reduced. In an area of fine sediment that was numerically dominated by polychaetous annelids, the most severely affected populations were those of tube-dwelling and surface-feeding species. Burrowing species were less influenced by the hypoxia.