The aim of this study is to evaluate the presence of biodiversity hotspots in Agrigento waters (Mediterranean Sea) to define the conservation area for bottlenose dolphins (Tursiops truncatus) and ...seabirds (Calonectris diomedea, Puffinus yelkouan, and Hydrobates pelagicus), according to European directives. With this purpose, the maximum entropy algorithm (MaxEnt) was applied to the sighting points of the focal species. They co-occur in the study area and have been documented to forage behind trawlers. In this study, a fishing rate was designed and used as an explanatory variable of the species distribution, together with physiographic variables. Data were collected during 68 surveys in the waters off Agrigento province. MaxEnt models showed a strong predictive power, with distance from the coast being the greatest predicting variable, followed by slope, depth, and fishing rate. For all the species considered, the probability of presence increased as the fishing rate grew. Cartographic analysis revealed one area shared by the species, which occupies 529 km2, from the shoreline to 100 m depth. This study increases knowledge on the distribution and habitat preferences of the target species in the Sicilian waters. Evaluating the influence of fisheries is a promising method that needs further testing to apply effective management measures.
A population of bottlenose dolphins inhabits 7 of the 14 fjords that compose Fiordland, New Zealand. One of these fjords, Milford Sound, supports a large tourism industry that results in intense boat ...traffic. Bottlenose dolphins regularly visited Milford Sound and tour boats interacted with them during these visits. I studied the factors affecting the frequency of visits of Milford Sound by relating the residency pattern of dolphins in this fjord to oceanographic parameters and variations in boat traffic between December 1999 and February 2002. Boat traffic was the only variable that could explain the frequency of dolphin visits to Milford Sound. Dolphins spent less time in Milford Sound during seasons of intense boat traffic. Moreover, when dolphins visited this fjord, they spent more time at the entrance of the fjord when boat traffic was intense, out of the reach of tour boats. It seems that dolphins avoid Milford Sound when traffic is heavy. This avoidance could have long-term implications for the demography of the population.
Exposure of common bottlenose dolphins (
Tursiops truncatus
) to brevetoxins (PbTx) produced by blooms of the toxic phytoplankton
Karenia brevis
frequently results in severe health impacts, including ...illness and large-scale mortality events. Although PbTx accumulation in dead-stranded dolphins is well documented, there are limited data for corresponding brevetoxin exposure in live dolphins. In addition, the severity of impacts on living survivors of such toxic blooms is difficult to assess due to a lack of data on the relationship between
K. brevis
bloom severity and corresponding PbTx concentrations in exposed animals. Here we present results of PbTx analysis of urine, serum, milk, gastric fluid, and feces samples collected from live, free-ranging dolphins (
n
= 253) from Sarasota Bay, Florida during 2000–2018, and investigate the relationship between PbTx concentrations detected and corresponding
K. brevis
cell abundances that are temporally (within 30 days) and spatially (within 16 km) associated with each individual. We found that 28% of dolphins were associated with elevated
K. brevis
abundances (10,000–60,000,000 cells/L), with 41% (
n
= 104) of dolphins testing positive for PbTx in at least one sample type. The proportion of PbTx-positive animals was significantly greater in animals exposed to elevated cell abundances vs. those exposed to background cell abundances (<10,000 cells/L), with 60 and 34% testing positive, respectively (
p
< 0.001). PbTx was detected most frequently in feces (57%,
n
= 38), followed by gastric (35%,
n
= 37), urine (32%,
n
= 55), and blood (7%,
n
= 17). PbTx concentrations by sample type were highest in feces (2–231 ng/g; mean 46), followed by urine (0.8–90 ng/g; mean 7.2), gastric (0.8–61 ng/g; mean 12), and blood (0.3–5 ng/g; mean 1.3). Regression analyses of
K. brevis
cell abundance as an index of exposure vs. corresponding PbTx concentration found no statistically significant relationship for feces (
p
= 0.120), gastric (
p
= 0.349), urine (
p
= 0.053), or blood (
p
= 0.729) samples. PbTx concentrations typically ranged over two orders of magnitude between minimum and maximum values and did not scale with corresponding indices of exposure, which ranged over three orders of magnitude or more. Our results indicate that
K. brevis
cell abundance alone is a poor predictor of brevetoxin accumulation in bottlenose dolphins, and suggest that alternative methods (e.g., endocrine or immunological biomarkers) should be investigated as more appropriate methods for determining the severity of health impacts due to red tides.
Clinical and epidemiological features of tattoo skin disease (TSD) are reported for 257 common bottlenose dolphins held in 31 facilities in the Northern Hemisphere. Photographs and biological data of ...146 females and 111 males were analyzed. Dolphins were classified into three age classes: 0-3 years, 4-8 years, and older than 9 years. From 2012 to 2014, 20.6% of the 257 dolphins showed clinical TSD. The youngest dolphins with tattoo lesions were 14 and 15 months old. TSD persisted from 4 to 65 months in 30 dolphins. Prevalence varied between facilities from 5.6% to 60%, possibly reflecting variation in environmental factors. Unlike in free-ranging Delphinidae, TSD prevalence was significantly higher in males (31.5%) than in females (12.3%). Infection was age-dependent only in females. Prevalence of very large tattoos was also higher in males (28.6%) than in females (11.1%). These data suggest that male T. truncatus are more vulnerable to TSD than females, possibly because of differences in immune response and susceptibility to captivity-related stress.
Reports of diseases in marine mammals are increasing worldwide, however our understanding of the microorganisms associated with marine mammals is still limited. In this study, we cultured bacteria ...and fungi isolated from the upper respiratory tract (blowhole), gastric fluid and anus of 180 wild bottlenose dolphins (
Tursiops truncatus) from two estuarine locations along the southeastern Atlantic Coast of the United States. A total of 339 and 491 isolates from Charleston, SC (CHS) and Indian River Lagoon, FL (IRL) dolphins, respectively, were cultured from gastric (70 CHS/82 IRL), fecal (141 CHS/184 IRL), and blowhole (128 CHS/225 IRL) swabs on selective media used for routine clinical microorganisms of human concern. The most frequently cultured Gram-negative bacteria from all sample and study types were
Plesiomonas shigelloides,
Aeromonas hydrophila,
Escherichia coli, and
Pseudomonas fluorescens. Among the Gram-positive bacteria,
Clostridium perfringens,
Bacillus sp., and
Staphylococcus Coag. Neg were the predominant organisms. For fungi, the most abundant species were
Candida glabrata,
budding yeasts, and
Candida tropicalis. Of concern, the MRSA strain of
Staphylococcus aureus was detected in the blowhole and gastric swabs from CHS dolphins. In general, a greater prevalence of bacteria and fungi (four-fold increase) were cultured from IRL than CHS animals. Together, these culture-dependent studies, coupled to on-going culture-independent approaches, should help establish a baseline of microorganisms associated with bottlenose dolphins and aid in the identification of organisms responsible for infectious diseases(s) in these animals.
We provide first data on the life span, growth and seasonal aspects of the life history of Black Sea bottlenose dolphins Tursiops truncatus in the wild and compare these with historical data and ...conspecific populations in other geographical regions. Average life span is 20 to 32 yr; the oldest record is 41 yr. The reproductive season lasts at least from February to September or October and includes the coldest months of the year (February and March). Average adult body lengths are 240 ± 14 cm for females and 255 ± 10 cm for males. Rapid early body growth ceases by 3 to 4 yr. Two morphs, one large (offshore) and one small (coastal), possibly co-exist in the Black Sea. The larger morph may include winter-breeding migrants or immigrants from the Mediterranean Sea. The small coastal form is similar in body size and growth patterns to coastal populations in the eastern Mediterranean region and the Gulf of Mexico, but is characterized by early growth to maturity and small asymptotic body size. Small-sized dolphin populations in enclosed water bodies can be treated as an example of the ‘island rule’, and their dwarfism may hypothetically be explained as an effect of smaller prey size.
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.
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