Bottlenose dolphins

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Ecology and behaviour of bottlenose dolphins (Tursiops truncatus) in a coastal area subject to shellfish farming

Ecology and behaviour of bottlenose dolphins (Tursiops truncatus) in a coastal area subject to shellfish farming

There!are!different!methods!to!estimate!the!abundance!of!cetaceans!including!extrapolating! from!counts!of!individuals!(e.g.!distance!sampling:!Hammond!et!al.!2013),!and!mark–recapture! analyses!using!capture!histories!of!individuals!marked!with!photographs!(e.g.!Speakman!et!al.! 2010).! The! latter! is! the! most! widely! used! technique! for! estimating! the! population! size! and! survival! rates! of! coastal! cetacean! populations! (e.g.! Currey! et! al.! 2008;! Silva! et! al.! 2009;! Speakman!et!al.!2010).!PhotoZidentification!is!a!nonZinvasive!(no!physical!capture,!handling,!or! application! of! a! mark)! markZrecapture! technique! which! consists! of! taking! photographs! (‘capture’)! of! the! natural! markings! of! individual! cetaceans! (Würsig! &! Jefferson! 1990).! This! technique!is!extensively!used!in!coastal!cetacean!studies!and!much!of!what!is!known!about! their!biology!comes!through!photoZidentification!studies!(Hammond!2010).!Several!cetacean! species!can!be!identified!through!natural!marks!present!on!their!dorsal!fin!(e.g.!bottlenose! dolphins:! Wilson! et! al.! 1999,! pilot! whales! Globicephala( melas:! AugerZMéthé! &! Whitehead! 2007),!humpback!whales!Megaptera(novaeangliae!and!sperm!whales!can!be!identified!through! the!marks!present!on!their!flukes,!and!blue!whales!Balaenoptera(musculus!can!be!identified! through!the!coloration!pattern!present!on!their!body!(e.g.!Matthews!et!al.!2001;!Calambokidis! &! Barlow! 2004).! To! estimate! abundance! using! mark–recapture! methods,! the! basic! data! required!are!the!capture!histories!of!individually!identified!animals.!A!capture!history!simply! describes!whether!or!not!an!animal!was!captured!in!a!series!of!sampling!occasions,!discrete! periods! of! data! collection! (Hammond! et! al.! 2013).! The! estimate! of! abundance! obtained! is! therefore!the!number!of!individuals!using!a!study!area!during!a!study!period.!
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A photo-identification catalogue of bottlenose dolphins (Tursiops truncatus) in Northeast Patagonia, Argentina: A tool for the conservation of the species

A photo-identification catalogue of bottlenose dolphins (Tursiops truncatus) in Northeast Patagonia, Argentina: A tool for the conservation of the species

The greater amount of re-identifications in the NPABSA might be a mere reflection of the greater effort in this area compared to the other observation sites. Although no conclusions can be drawn due to the lack of multiple year observations, the number of re-identifications in NPABSA over different seasons might indicate a form of residency in this area of at least 27 dolphins (57%). Even more, the difficulty to photo- identify during land-based observations will inevitably underestimate the overall re-identification frequency. Nevertheless, the variations in time between many of the resightings of identified dolphins might suggest that the NPABSA represents only part of a larger home-range 1 in Northeast Patagonia (Bearzi, 2005). This is further confirmed by the re-identification of 6 individuals in the Río Negro Estuary, 250km East, possibly indicating that the home-range of these dolphins comprises at least the whole northern region of the Gulf of San Matías. This may not seem surprising as bottlenose dolphins are known to swim large distances (Würsig and Würsig, 1977; Würsig, 1978; Wells et al., 1990; Defran et al., 1999; Bastida and Rodriguez, 2003). Moreover, estuarine areas and river mouths have repeatedly been found to be sites of high bottlenose dolphin occurrence (Scott et al., 1990; Berrow et al., 1996; Gubbins, 2002; Zolman, 2002), as they are often characterised by high levels of primary productivity and prey abundance (Acevedo, 1991). In any case, the fact that the study is land-based and the relative low observation effort outside NPABSA, might underestimate the total home-range of these dolphins and their site-fidelity to the distinct areas.
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Seasonal Variation in Abundance and Time-Budget of Bottlenose Dolphins  (Tursiops truncatus) in Bahía San Antonio, Patagonia, Argentina

Seasonal Variation in Abundance and Time-Budget of Bottlenose Dolphins (Tursiops truncatus) in Bahía San Antonio, Patagonia, Argentina

Free University of Brussels, Department of Biology, Pleinlaan 2, Brussels, Belgium Contact e-mail: elsvermeulen5@gmail.com The abundance and time-budget of bottlenose dolphins (Tursiops truncatus) was assessed in Bahía San Antonio, Patagonia (Argentina) in the years 2009 and 2010. A total of 366.4 boat-based survey hours resulted in 64 contact hours with a total of 88 dolphin groups. Mark-recapture abundance estimations, based on 63 identified dolphins, resulted in a corrected maximum estimate of 97 and 83 individuals during winter, and a minimum of 34 and 38 individuals during autumn of 2009 and 2010 respectively. Between 25% and 68% of the population consisted of unidentifiable individuals depending on the season, indicating the high presence of juveniles and calves.
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Records of bottlenose dolphins, Tursiops spp., in New Caledonian waters

Records of bottlenose dolphins, Tursiops spp., in New Caledonian waters

Exocoetidae sp., in the open sea (22°35’S 166°28’E; Feb. 2002). DISCUSSION The similarities in pigmentation patterns and habitat characteristics of morphotype-A and morphotype-B bottlenose dolphins from New Caledonia (present report), and, respectively, T. aduncus and T. truncatus from southern Queensland (Hale et al. 2000) and from elsewhere in the Indo-Pacific (Wang and Yang 2009) are strong enough to suggest that morphotype A corresponds to T. aduncus under its current definition (Rice 1998) and morphotype B, to T. truncatus. However, pending more genetic evidence, in the following we will refer to “T. aduncus-like” and ‘T. truncatus-like” bottlenose dolphins in New Caledonian waters. Also, adult T. aduncus generally exhibit dark spots on the posterior ventral half of the body (Hale et al. 2000), but T. aduncus populations from New South Wales and southeastern Australia are “apparently more or less unspotted” (Ross and Cockroft 1990; Wang and Yang 2009). When present, only light spotting on the posterior part of the body was noticed by us on some New Caledonian morphotype-A individuals (Fig. 1D). The presence or absence of a pale-grey blaze below the dorsal fin remained the easiest way to distinguish between the two forms in the field.
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Spatial variation in the accumulation of POPs and mercury in bottlenose dolphins of the Lower Florida Keys and the coastal Everglades (South Florida)

Spatial variation in the accumulation of POPs and mercury in bottlenose dolphins of the Lower Florida Keys and the coastal Everglades (South Florida)

pollutants across various tissues of the female leading to POP transfer from the mother to the offspring ( Habran et al., 2012, 2013; Honda et al., 1987; Leonel et al., 2012; Sager and Girard, 1994; Wagemann et al., 1988 ). The reason why a LFK female presented S 6 NDL-PCBs concentrations more than 10 times higher than the second most contaminated female, remains unclear. We can hy- pothesize that there was no transfer to the offspring or that this female came from another highly contaminated population. One interesting result was the higher concentrations in CB 28 and CB 52 in LFK females than in FCE females. These congeners are the less chlorinated molecules among the measured PCBs and consequently the less hydrophobic ones. Several studies showed a reduced ef fi- ciency in maternal transfer for the higher halogenated compounds ( Dorneles et al., 2010; Ikonomou and Addison, 2008 ). FCE females could have had a signi ficantly higher number of pregnancies during their lives than LFK females. Moreover, this geographical difference in CB 28 (the less hydrophobic among the PCBs measured) con- centrations was veri fied for females, but not for males. Low levels of pollutants in female dolphins does not preclude the possibility of harmful effects on their health, or that of their calves. Levels of S 6 NDL-PCBs in LFK male dolphins were below the concentrations previously described in dolphins from other locations in Florida and in the Gulf of Mexico (Balmer et al., 2011, 2015; Fair et al., 2007; Johnson-Restrepo et al., 2005; Kucklick et al., 2011; Salata et al., 1995 ) ( Fig. 6 ). The highest PCB concentrations have been described in bottlenose dolphins from Brunswick, GA where Aroclor 1268-a highly chlorinated PCB mixture-was released into the aquatic environment during decades of local industrial activities ( Balmer et al., 2011; Kucklick et al., 2011; Wirth et al., 2014 ). In our study region, the S 6 NDL-PCBs concentrations were low compared to other locations in the southeastern US. Highly dynamic marine currents in South Florida may serve to dilute pollutants and help explain the low concentrations observed. In addition, the remedi- ation efforts implemented in 2000 to protect the LFK and FCE en- vironments may also contribute ( Finkl and Charlier, 2003 ). 4.2. PBDEs
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Captive bottlenose dolphins and killer whales harbor a species-specific skin microbiota that varies among individuals

Captive bottlenose dolphins and killer whales harbor a species-specific skin microbiota that varies among individuals

M. Chiarello , S. Villéger, C. Bouvier, J. C. Auguet & T. Bouvier Marine animals surfaces host diverse microbial communities, which play major roles for host’s health. Most inventories of marine animal surface microbiota have focused on corals and fishes, while cetaceans remain overlooked. The few studies focused on wild cetaceans, making difficult to distinguish intrinsic inter- and/or intraspecific variability in skin microbiota from environmental effects. We used high-throughput sequencing to assess the skin microbiota from 4 body zones of 8 bottlenose dolphins (Tursiops truncatus) and killer whales (Orcinus orca), housed in captivity (Marineland park, France). Overall, cetacean skin microbiota is more diverse than planktonic communities and is dominated by different phylogenetic lineages and functions. In addition, the two cetacean species host different skin microbiotas. Within each species, variability was higher between individuals than between body parts, suggesting a high individuality of cetacean skin microbiota. Overall, the skin microbiota of the assessed cetaceans related more to the humpback whale and fishes’ than to microbiotas of terrestrial mammals. Marine animals’ surfaces are associated with highly diverse microbial communities, which play major roles for their health, including protection against macrofouling, and pathogens 1 , 2 . These surface microbiota were shown
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Variation in external morphology of resident bottlenose dolphins in Bahía San Antonio, Patagonia, Argentina

Variation in external morphology of resident bottlenose dolphins in Bahía San Antonio, Patagonia, Argentina

In Argentina, two geographic variations of bottlenose dolphins were described by Bastida & Rodriguez in 2003 (3). The bottlenose dolphins living along the coasts of the province of Buenos Aires are characterized by their triangular dorsal fin shape whereas bottlenose dolphins living more south along the coasts of the province of Chubut are characterized by their falcate dorsal fin shape. Bastida & Rodriguez further stated that ‘their clear difference would indicate that both geographic forms are isolated’ (3). Although it still remains unknown to which extent this morphologic variation is genetically correlated, this communication is meant to document the residency and interaction of both regional forms in Bahía San Antonio (province of Río Negro; Figure 1).
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High gene flow in oceanic bottlenose dolphins (Tursiops truncatus) of the North Atlantic

High gene flow in oceanic bottlenose dolphins (Tursiops truncatus) of the North Atlantic

may be transient (Wells et al. 1999). Bottlenose dolphins are present year-round in the two Portuguese archipelagos. Separate photo-identification surveys carried out in each archipelago have shown that some individuals are sighted repeatedly in the same area at different seasons (Silva 2006; L.F., unpublished results). These animals are probably resident. On the opposite, some individuals are rarely observed in the main study area and can travel large distances. They may be visitors. Thus, it can be hypothesised that the individuals ranging in each archipelago are from at least two populations, at least one population of coastal / residents and at least one population of pelagic / transients. Alternatively, or in combination with that hypothesis, population structure could follow the geographical and physical structure of the archipelagos. Different populations could occupy the two archipelagos and there may be some population differentiation between groups of islands. In that case, a correlation between geographical and genetic distances can be expected.
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Selection on ancestral genetic variation fuels parallel ecotype formation in bottlenose dolphins

Selection on ancestral genetic variation fuels parallel ecotype formation in bottlenose dolphins

Our results together with previous studies on human populations represent rare examples of species with long generation time for which parallel evolution has been uncovered (7, 21). In humans, parallel adaptation was facilitated by similar stable lifestyles (e.g. life in high altitudes (7)), or same cultural revolutions (e.g. cattle domestication for lactase persistence (21)). Non- human examples of socially driven local adaptation are scarce, but killer whale ecotypes have likely evolved as a result of demographic history, ecological opportunity and cultural transmission (24). Bottlenose dolphins (Tursiops sp.) also exhibit complex behaviors, such as habitat specialisation or social learning of foraging techniques, that strongly influence their patterns of genetic variability (28, 31, 38), and we hypothesize that these also facilitate their ability to adapt to novel conditions.
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Spatial variations in concentrations of mercury and persistent organic pollutants in coastal bottlenose dolphins, Tursiops truncatus, from the Lower Florida Keys and the coastal Everglades (South Florida)

Spatial variations in concentrations of mercury and persistent organic pollutants in coastal bottlenose dolphins, Tursiops truncatus, from the Lower Florida Keys and the coastal Everglades (South Florida)

5 Tropical Dolphin Research Foundation, USA * Corresponding author. E-mail: fdamseaux@ulg.ac.be The bottlenose dolphin (Tursiops truncatus) is a major apex predator and the most common cetacean species found in nearshore waters of South Florida, including the Lower Florida Keys (LFK) and the Everglades National Park (ENP). The objective of this study was 1) to assess contamination levels of total mercury (T-Hg) in skin and persistent organic pollutants (PCBs, PBDEs, DDT, HCH, HCB, DLCs and PCDD/Fs) in blubber samples of bottlenose dolphins from the LFK (T-Hg : n males = 10; POPs : n males
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Stable isotopes of captive Cetaceans (Killer Whales and Bottlenose  dolphins)

Stable isotopes of captive Cetaceans (Killer Whales and Bottlenose dolphins)

SUMMARY There is currently a great deal of interest in using stable isotope methods to investigate diet, trophic level and migration in wild cetaceans. In order to correctly interpret the results stemming from these methods, it is crucial to understand how diet isotopic values are reflected in consumer tissues. In this study, we investigated patterns of isotopic discrimination between diet and blood constituents of two species of cetaceans (killer whale, Orcinus orca, and bottlenose dolphin, Tursiops truncatus) fed controlled diets over 308 and 312  days, respectively. Diet discrimination factors (!; mean ± s.d.) for plasma were estimated to ! 13 C 2.3±0.6‰ and ! 15 N 1.8±0.3‰, respectively, for both species and to ! 13 C 2.7±0.3‰ and ! 15 N 0.5±0.1‰ for red blood cells. Delipidation did not have a significant effect on carbon and nitrogen isotopic values of blood constituents, confirming that cetacean blood does not serve as a reservoir of lipids. In contrast, carbon isotopic values were higher in delipidated samples of blubber, liver and muscle from killer whales. The potential for conflict between fisheries and cetaceans has heightened the need for trophic information about these taxa. These results provide the first published stable isotope incorporation data for cetaceans, which are essential if conclusions are to be drawn on issues concerning trophic structures, carbon sources and diet reconstruction.
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Why do dolphins form mixed-species associations in the Azores ?

Why do dolphins form mixed-species associations in the Azores ?

In dolphins, it is usually not possible to determine the gender of individuals at sea. Population sex ratio has to be inferred indirectly from dead specimens or samples obtained from free- ranging individuals. Stranding and by-catch records revealed a biased sex ratio in several dolphin species and populations (e.g. Perrin and Reilly 1984, Silva and Sequeira 2003; Viricel et al. 2008). However, these records may not accurately represent population sex ratio due to gender segregation in relation to habitat features or differential probability of being caught in fishery nets. Alternatively, gender can be inferred from tissue samples collected from free- ranging dolphins using molecular sexing techniques (e.g. Abe et al. 2001). Population genetic studies of dolphins based on biopsy samples do not provide information on sex ratio (most studies) or do not show any significant bias (Krützen et al. 2002, 2004; Möller and Beheregaray 2004; Bilgmann et al. 2007). However, skewed sex ratio was reported in samples of New Zealand’s dusky dolphins, Lagenorhynchus obscurus, obtained by skin swabbing (Harlin et al. 2003). In that study, sex ratio varied between locations and collecting periods, and was assumed to reflect seasonal variations in space occupation. Another recent study revealed a strongly male-biased sex ratio in samples of bottlenose dolphins, Tursiops
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Sensory perception in cetaceans: Part II – Promising experimental approaches to study chemoreception in dolphins

Sensory perception in cetaceans: Part II – Promising experimental approaches to study chemoreception in dolphins

nerve V is, just as cranial nerve VII, able to excite the gustatory neurons in the nucleus of the solitary tract in the medulla ( Purves et al., 2001; Boucher et al., 2003 ). Thirdly, although OR genes are reported to be functionally reduced by pseudogenization in Odontoceti ( Kishida et al., 2007 ), bottlenose dolphins in particular possess 23 G protein-coupled OR genes that are not pseudogenized, thus potentially functional (SEVENS database of G-protein coupled receptor genes; available at: http://sevens. cbrc.jp/search.php?db=ttru&level=4). Similarly, taste receptor genes were found to be mostly pseudogenized in Odontoceti: in bottlenose dolphins sweet, umami, bitter and sour taste receptor genes were found to be inactivated, whereas salty taste receptor genes are intact and potentially functional ( Jiang et al., 2013; Feng et al., 2014; Kishida et al., 2015 ). Finally, go/no- go behavioral tests with trained bottlenose dolphins showed that they can perceive sour, bitter and salty tastes nearly as well as humans ( Nachtigall and Hall, 1984; Friedl et al., 1990; Kuznetzov, 1990 ). The authors of these behavioral studies noticed that dolphins were able to perceive orally what other mammals perceive by smell wherefore they called this perception “quasi- olfaction” ( Kuznetzov, 1990 ) or “water-borne sense of smell” ( Nachtigall, 1986 ). Taken together, this second set of studies suggests that cetaceans might have, to some extent, access to chemosensory information through the olfactory ( Thewissen et al., 2011 ) and/or taste systems ( Watkins and Wartzok, 1985; Pihlström, 2008 ). As anatomical, neuroanatomical, and molecular evidence draw unclear conclusions, behavioral studies are needed.
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Molecular insight into the population structure of common and spotted dolphins inhabiting the pelagic waters of the Northeast Atlantic

Molecular insight into the population structure of common and spotted dolphins inhabiting the pelagic waters of the Northeast Atlantic

structure in D. delphis was caused by low levels of divergence associated with recent population differentiation following the last glacial maximum. Actually, the significant inbreeding coefficients obtained for the whole sample and within the Azores suggest that populations are not at the mutation-drift equilibrium, not panmictic, or undergoing selection. Deviation from panmixia could be caused by a Wahlund effect, i.e. the existence of undetected sub-populations. In the Azores, it is possible that there are resident and non- resident individuals who do not fully interbreed. It is noteworthy that genotyping revealed three cases of re-sampling of common dolphins that occurred within a small geographic range and with a time interval of up to one year. These events indicate some degree of site fidelity, and suggest that there might be resident individuals in the Azores. Residency has been shown to be associated with population differentiation in other species (e.g., bottlenose dolphins of the species T. aduncus in Australia, Möller and Beheregaray 2004; spinner dolphins in the South Pacific, Oremus et al. 2007). However, in the Azores, no population differentiation was found in T. truncatus despite the existence of known resident individuals (Quérouil et al. 2007; Silva et al. 2008). The extent of differentiation might depend on the proportion of individuals that are resident. A more detailed genetic study would possibly reveal population differentiation and seasonal variations in D. delphis population structure within the Azores. In the Atlantic spotted dolphins, lack of population structure could be expected, given that they are temporary visitors in the Azores and Madeira and tend to prefer offshore waters. Although spotted dolphins occur in both archipelagos during the same period of the year (Freitas et al. 2004; Quérouil et al. 2008), it is likely that the individuals frequenting the Azores and Madeira belong to the same population. Interestingly, the observed pattern contrasts with the population structure existing in the western Atlantic, where oceanic and coastal populations can be distinguished (Adams and Rosel 2006). This discrepancy is likely due to differences in habitat structure, related to the presence of a continental shelf in the western Atlantic.
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Adult survival and reproduction in an Argentine bottlenose dolphin population: The science needed for its conservation

Adult survival and reproduction in an Argentine bottlenose dolphin population: The science needed for its conservation

Several small populations of bottlenose dolphins (Tursiops truncatus) are known to inhabit the Atlantic coast of Argentina, however, apparently with little exchange between them. The study population in Bahia San Antonio (San Matías Gulf, province of Río Negro) appears to be one of the southernmost populations (42°S/65°W). Adult survival and calving rates are critical for the survival of this population.

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Assessing the Effect of Persistent Organic Pollutants on Reproductive Activity in Common Dolphins and Harbour Porpoises

Assessing the Effect of Persistent Organic Pollutants on Reproductive Activity in Common Dolphins and Harbour Porpoises

reflect its dietary preferences, it is influenced by its body size, body condition, nutritive condition, disease, metabolism, excretion, age and sex (Aguilar et al., 1999). Furthermore, it is an indication of the conditions it experienced in early life: contaminant levels in its mother, the duration of nursing, birth order and the length of the calving interval preceding its birth (Hickie et al., 1999; Hickie et al., 2000; Ross et al., 2000; Ylitalo et al., 2001; Hickie et al., 2007). Females, through mobilization of lipid-associated toxins from the blubber during periods of high energy requirements, transfer toxic compounds to their offspring during gestation (via the placenta) and lactation (via their lipid rich-milk), resulting in a high exposure of newborns to those chemicals (O'Hara and O'Shea, 2005). In contrast, male cetaceans become increasingly contaminated as they grown older. In free ranging bottlenose dolphins (Tursiops truncatus), concentrations of OCs declined with female reproductive activity: blubber OC concentrations of nulliparous females were signifi cantly greater than those of primiparous and multiparous females (Wells et al., 2005). In this species, approx. 80% of OCs are transferred to fi rst born calves during the fi rst seven weeks of lactation (Cockcroft et al., 1989). In captive T. truncatus, ∑PCB was more than 2.5 times higher and ∑DDT was three times higher in females whose calves died compared with females whose calves survived beyond six months (Reddy et al., 2001).
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Bioaccumulation of persistent organic pollutants in female common dolphins (Delphinus delphis) and harbour porpoises (Phocoena phocoena) from western European seas: geographical trends, causal factors and effects on reproduction and mortality

Bioaccumulation of persistent organic pollutants in female common dolphins (Delphinus delphis) and harbour porpoises (Phocoena phocoena) from western European seas: geographical trends, causal factors and effects on reproduction and mortality

The links between feeding, reproduction, condition and con- taminant burdens in marine mammals are undoubtedly com- plex. Important insights have been provided from studies on populations in which individual reproductive history is known (e.g. bottlenose dolphins in Sarasota Bay, Wells et al., 2005 ) but there have been no experimental studies on captive ceta- ceans comparable to the work on seals undertaken by Reijnders (1986) . For a large-scale survey, the use of stranded animals has several advantages over taking biopsies from living animals in the wild. Sampling from dead animals is less expensive, raises no ethical issues, and provides access to all tissues, not simply blubber, as well as a wealth of ancillary information on size, age, reproductive status, condition and pathology. Restricting sampling to relatively fresh carcasses can assure high sample quality, while analysis of the ancillary data can assist in inter- pretation of contaminant data, including helping to control for possible biases associated with such opportunistic sampling.
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Dolphins of the Bay

Dolphins of the Bay

But you must wonder how is it possible to study all these aspects from an animal that spends most of its life underwater? One solution is to identify each individual and recognise them when they surface to breathe. But, how do we know which dolphin we are observing? We can identify each dolphin through the physical characteristics of their dorsal fin and other parts of their body, looking closely at the shape and markings such as cuts and important scars, all which are considered unique and permanent, making it possible to tell one animal from another. This is the reason why scientists try to get the best pictures while observing dolphins, as they try to capture these distinctive markings from all individuals. Each dolphin can then be assigned an identification code to help scientists recognise them when observed in a different area or at different times. Typically, it is an alphanumeric code. For example, RN- BSA-6/06 means that the dolphin has been observed in Río Negro, in the Bay of San Antonio, that it is individual number 6, identified in 2006. Every identified dolphin is then gathered into an identification catalogue. This method is known among scientists as “photo-identification” and is the fundamental basis for studying animal populations over time. As we will see in the following pages, these kinds of studies also help us understand the life stories and lifecycles of bottlenose dolphins.
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The role of metallothioneins, selenium and transfer to offspring in mercury detoxification in Franciscana dolphins (Pontoporia blainvillei)

The role of metallothioneins, selenium and transfer to offspring in mercury detoxification in Franciscana dolphins (Pontoporia blainvillei)

immediately frozen in liquid nitrogen and stored at − 80 °C until analysis. Integral analysis during necropsy and Relative Body condition Index de Le Cren close to 1 (one) revealed no signi ficant indication of an unhealthy condition of any dolphin. Age of the same dolphins was determined in a parallel study by Denuncio et al. (2013) using dentine and cementum dental layers to determine Growth Layer Groups (GLGs). According to Polizzi et al. (2013) , the estimated fine scale age was determined and dolphins were classi fied into four categories of maturity ( Table 1 ).

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PCDD, PCDF AND PCB DETERMINATION IN DOLPHINS REVEALS A WORLD HOTSPOT FOR PCBS IN GUANABARA BAY, BRAZIL

PCDD, PCDF AND PCB DETERMINATION IN DOLPHINS REVEALS A WORLD HOTSPOT FOR PCBS IN GUANABARA BAY, BRAZIL

The possible public health problem The possibility of occurrence of a human health problem due to consumption of fish from Guanabara Bay is raised when data on stable nitrogen isotope ratios are considered. With the only exception of the comparison between Atlantic anchoveta and mullet, all the remaining pairwise inter-species comparisons yielded significant differences in δ 15 N values (Fig. 1). Interestingly, significant higher δ 15 N values were verified in whitemouth croakers than in marine tucuxi dolphins (p=0.007), implying further that this fish species feeds higher than marine tucuxi dolphins in Guanabara Bay food web. A recent study on digestive content analyses of marine tucuxi dolphins from Guanabara Bay revealed that the whitemouth croaker constituted the prey species of highest frequency of occurrence in the stomachs 9 . An explanation for these seemingly contradictory data may be found if the size of the whitemouth croaker specimens is considered. The body length on which marine tucuxi dolphins exert predation fits between 6.3 and 32.2 (14.4 ± 4.4) 9 ; however, all the whitemouth croakers obtained for stable isotope measurements were lengthier than 50 cm. The higher δ 15 N values observed in whitemouth croaker tissues strengthen the possibility of occurrence of high PCB concentrations in this fish species, which is marketed for human consumption, including the body length size obtained for stable isotope measurements. The longevity of the species may play a key role in the observation of higher concentrations in predator marine mammals 15 . It is expected that contaminants accumulate with increasing age 15 , and cetaceans are frequently older than their prey 16 . However, the maximum estimated age for marine tucuxi dolphins was 30 years 17 , and the longevity of the whitemouth croaker was estimated to be 35 years 18 . Consequently, the possibility of the human health problem due to consumption of highly contaminated fish is reinforced if the longevity of this fish species is taken into account. Therefore, risk assessment studies on human exposure to PCBs through consumption of fish from Guanabara Bay are of fundamental importance.
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