Understanding species distributions, and how they change in space and time, is vital when prioritising conservation or management initiatives. We assessed the distribution and density patterns of ...common dolphins (Delphinus sp.), bottlenose dolphins (Tursiops truncatus) and Bryde's whales (Balaenoptera edeni) in the Hauraki Gulf, New Zealand. Dedicated boat-based surveys were conducted in the inner Hauraki Gulf (IHG) and off Great Barrier Island (GBI) during 2010-2012. Generalised linear models were used to investigate temporal changes in relative densities and kernel density estimation was implemented to examine spatial trends. Common dolphins were widely distributed during all seasons, with higher densities observed during winter and spring in the IHG but during autumn off GBI. There was inter-annual variation in Bryde's whale distribution, with high densities recorded off GBI in 2011. Bottlenose dolphins were infrequently sighted in the IHG but regularly encountered off GBI, with the highest densities during spring and summer.
The Mediterranean Sea common bottlenose dolphin population has been assessed as Vulnerable according to the IUCN Red List Criteria. The species is also included in several International Agreements, ...European Union Regulations and Directives. Amongst them, a strict protection and identification of special conservation areas are requested by the EU Habitats Directive. Despite direct takes, by-catch, chemical and acoustic pollution, and prey depletion, general habitat degradation and fragmentation have been indicated as detrimental for the species, the degree to which these threats pose population risk is still largely unknown. At present it is thus not possible to depict the actual status of the population and to assess prospective trends. To address this gap in the current knowledge, line transect distance sampling aerial surveys were conducted in a wide portion of the Western Mediterranean Sea between the summer of 2010 and winter 2011. A total of 165 parallel transects equally spaced at 15 km were designed providing homogeneous coverage probability. Overall, 21,090 km were flown on effort and 16 bottlenose dolphin sightings were recorded and used for the analysis. The surface abundance and density estimates resulted in 1676 animals (CV = 38.25; 95% CI = 804–3492) with a density of 0.005 (CV = 38.25%). These results represent the first ever estimates for the common bottlenose dolphin over a wide portion of the Western Mediterranean Sea Subregion, with the potential to be useful baseline data to inform conservation. Specifically, they could be used as indicators under the Marine Strategy Framework Directive requirements, in conjunction with other study methods.
•We used line transect aerial surveys, implementing distance sampling methodology.•We obtained abundance estimates for the Mediterranean bottlenose dolphins.•Species distribution and occurrence are uneven within the study area.•Results are the first of this kind for a wide portion of the Western Mediterranean.•Results are essential towards the Marine Strategy Framework Directive requirements.
Interactions between marine mammals and fisheries are a growing problem, and effective management requires assessment of the factors driving the interaction and of the impacts on fisheries. We used ...data from interactions between artisanal fisheries and bottlenose dolphins around the Balearic Islands to assess these factors and impacts. Observers collected data during 1,040 fishing operations over 3 yr. Location and year were important factors affecting interaction probability, with some areas showing large increases over the study period. We estimated the combined cost of catch loss and net damage as 6.5% of the total catch value (95% CI -12.3%, -1.6%), and the annual loss to be 3.4% (95% CI -6.5%, -0.1%) of the total catch by weight. This weight equates to the dietary needs of ~12 dolphins (95% CI 0.2, 22), suggesting the fishery is not a vital food source for the dolphin population. Two dolphins died through entanglement during the observed fishing operations. We observed 3% of the total fishing activity, by weight, in 2003; scaling up this mortality directly suggests that as many as sixty dolphins may be dying in nets each year. This interaction likely has serious conservation implications for the dolphin population.
This is the first study estimating cetacean by-catch in the Turkish western Black Sea turbot fishery. One turbot fishing boat was observed during two fishing seasons, from April through July 2007 and ...April through mid-September 2008. During this time, 24 harbour porpoises and one bottlenose dolphin were caught in turbot trammel nets. The by-catch rate was found to be 0.18 for harbour porpoise and 0.01 for bottlenose dolphin individuals per kilometre in 2007, and 0.19 for harbour porpoise individuals in 2008. It is estimated that the total numbers of harbour porpoises killed in the Turkish western Black Sea during the legal fishing period (April and July) were 167 ± 153 (CV: 0.92) in 2007 and 329 ± 220 (CV: 0.67) in 2008, and the number killed during both legal and illegal periods of turbot fishing were 2011 ± 742 (CV: 0.37) in 2007 and 2294 ± 806 (CV: 0.35) in 2008. The estimated range of harbour porpoise by-catch in the turbot fishery on the Turkish western Black Sea coast is between these two estimates. The by-caught harbour porpoises were between 1–8 years of age. About half of them were within the age range of 4 (26%) and 5 (21%) years old, and 78% were physically immature individuals. Turbot fishing carried out with bottom nets, especially in May and June, when turbot fishing is banned, is a threat to the sustainability of harbour porpoise stocks.
Defining the activity patterns and social relationships of animals can provide valuable information related to animal welfare. Bottlenose dolphins under professional care engage in a variety of ...social and solitary activities, which may be influenced by conspecifics, time of day, and maternal behaviors. This study examined the social, solitary, and maternal behaviors of eight dolphins at one zoological facility. Data about social and solitary behaviors, nursing occurrences, and mother–calf pair swimming were collected five days per week over a ten-month period. The simple ratio index was used to calculate association rates for all dyads. Affiliative behaviors were the dominant behavior class and all behavior categories and swim states showed temporal oscillations throughout the day. The high association values within the mother–calf dyads suggested these ties remain strong through the second and third years of life. Preferred associates remained the same for some individuals in both social group compositions, while they differed for others. However, no large reductions in associations were recorded, suggesting strong relationships in the subgroups continued when other individuals were present. Examining sociality and activity levels may be a useful tool in continuing to improve welfare as they may be related to social groupings and environmental factors.
The fission–fusion society of bottlenose dolphins seems particularly well suited to balancing the costs and benefits of grouping. Here, we examined four nonmutually exclusive hypotheses regarding the ...causes and/or functions of calf grouping patterns when with and away from the mother: maternal influence, same-sex bond formation, protection and social skill development. We evaluated the role of calf (calf sex, age and separation from their mothers) and maternal characteristics (foraging time and sociality) in shaping the size and composition of mother–calf groups using focal observations of 49 mothers and 89 calves. Mother–calf groups were biased towards association with females of all ages and with male calves, but contained relatively few juvenile and adult males. Although there was some support for all of the hypotheses, the social skills hypothesis best explained male calf social patterns, and maternal influence better explained female calf social patterns. While maternal sociality influenced calves of both sexes, daughters mirrored the mother during separations, whereas sons did the opposite, seeking more social contact if their mothers were solitary and seeking less social contact if their mothers were sociable. During mother–calf separations, calves of both sexes preferentially associated with immatures over adults, but male calves preferred juvenile and adult male associates, which female calves, like their mothers, avoided. Calf social patterns illustrate the specific social and ecological challenges that they face in relation to and independent of their mothers.
Adult survival is arguably the most important demographic parameter for long-lived species as it has a large impact on population growth, and it can be estimated for cetacean populations using ...natural markings and mark-recapture (MR) modelling. Here we describe a 26-year study of a genetically discrete, resident population of bottlenose dolphins in the Shannon Estuary, Ireland, conducted by an NGO using multiple platforms. We estimated survival rates (SRs) using Cormack-Jolly-Seber models and explored the effects of variable survey effort, multiple researchers, and changes in camera equipment as well as capture heterogeneity induced by changes in marks and site fidelity variation, all common issues affecting longitudinal dolphin studies. The mean adult SR was 0.94 (±0.001 SD) and thus comparable to the estimates reported for other bottlenose dolphin populations. Capture heterogeneity through variation in mark severity was confirmed, with higher capture probabilities for well-marked individuals than for poorly marked individuals and a “transience” effect being detected for less well-marked individuals with 43% only recorded once. Likewise, both SR and capture probabilities were comparatively low for individuals with low site fidelity to the Shannon Estuary, and SR of these individuals additionally decreased even further toward the end of the study, reflecting a terminal bias. This bias was attributed to non-random temporal migration, and, together with high encounter rates in Brandon Bay, supported the hypothesis of range expansion. Our results highlight the importance of consistent and geographically homogenous survey effort and support the differentiation of individuals according to their distinctiveness to avoid biased survival estimates.
Little is known about common bottlenose dolphin
(Tursiops truncatus) seasonal migration along the United
States southeastern Atlantic coast, or what factors influence
migratory patterns. Therefore, ...our objectives were to: 1)
document evidence for seasonal movement of dolphins in
this region (that would indicate migratory behavior) and 2)
determine if seasonal changes in abundance and temporary
emigration (i.e., migration indicators) for dolphins along
South Carolina and Georgia coasts are related to changes
in water quality variables. Previously collected capturerecapture
data (from visual sightings of individual
dolphins) and water quality data from Charleston, South
Carolina and St. Catherine’s Island, Georgia were used to
achieve our objective. Robust design models were used to
estimate seasonal abundance and temporary emigration
for the Charleston population, whereas closed population
capture-recapture models were used to estimate seasonal
abundances for the St. Catherine’s Island population.
The Charleston population showed seasonal abundance
and temporary emigration patterns with low estimates in
winter, which increased in spring, peaked in summer, and
decreased in fall. Seasonal temporary emigration was best
explained by water temperature, which followed the same
general pattern. Seasonal abundance in the St. Catherine’s
population was best explained by salinity, but no consistent
pattern in abundance was observed. Our results not only
provide the first evidence of a clear seasonal migration of
dolphins in this region, but can aid in conservation and management efforts by increasing accuracy of abundance
estimates.
Dolphin-Assisted Therapies (DAT) are alternative therapies aimed to reduce anxiety levels, stress relief and physical benefits. This paper is focused on measuring and analyzing dolphins brain ...activity when DAT is taking place in order to identify if there is any differences in female dolphin's neuronal signal when it is interacting with control or intervention subjects, performing our research in Delfiniti, Ixtapa, Mexico facilities. We designed a wireless and portable electroencephalographic single-channel signal capture sensor to acquire and monitor the brain activity of a female bottle-nose dolphin. This EEG sensor was able to show that dolphin activity at rest is characterized by high spectral power at slow-frequencies bands. When the dolphin participated in DAT, a 23.53% increment in the 12-30 Hz frequency band was observed, but this only occurred for patients with some disease or disorder, given that 0.5-4 Hz band keeps it at 17.91% when there is a control patient. Regarding the fractal or Self-Affine Analysis, we found for all samples studied that at the beginning the dolphin's brain activity behaved as a self-affine fractal described by a power-law until the fluctuations of voltage reached the crossovers, and after the crossovers these fluctuations left this scaling behavior. Hence, our findings validate the hypothesis that the participation in a DAT of a Patient with a certain disease or disorder modifies the usual behavior of a female bottle-nose dolphin.
PDF
