The study reviews the information available on the distribution patterns of bottlenose dolphins within the SWAO (04oN-56oS, 25oW-67oW) including the northern portion of Brazil, covering the period from 1894 to 2011.
In this report, we present a compilation of the behavioral patterns of bottlenose dolphins and social structure throughout the Southwest Atlantic Ocean. We have compiled and summarized available data concerning: (i) behavioral activities (states and events), (ii) social structures (group size and composition), (iii) acoustic behavior and (iv) intra and interspecific interactions of bottlenose dolphin populations throughout the SWAO, from northern Brazil to southern Argentina. Lack of systematic and standardized methodologies for data collection precludes robust data analyses in respect of bottlenose dolphin behavior. Available information suggests that the studied populations presented weak intra-population associations and that coastal individuals tend to form smaller groups than their oceanic counterparts. Bottlenose dolphins from SWAO produce stylized whistles in which the acoustic parameters are similar to published ranges around the world and some results indicate significant local inter-population variation in the acoustic parameters of the whistles. Data of intra and interspecific interactions of bottlenose dolphins in the SWAO are scarce and therefore do not fully allow a comprehensive analysis of the situational contexts.
The present study reports the first records of endangered species, dusky grouper Epinephelus marginatus, on the Uruguayan coast. The occurrence of dead or disoriented individuals along the surf zone within the Marine Protected Area (MPA) of Cerro Verde (Uruguay) was recorded. . Continuous monitoring and future studies are needed to reveal the relevance of this MPA in the conservation of this endangered grouper species in the southernmost limit of its distribution in the Southwestern Atlantic.
We combined stomach content analysis and stable isotopes to investigate long-term changes in the feeding ecology of common bottlenose dolphins (Tursiops truncatus) from the Patos Lagoon estuary and adjacent marine coast, southern Brazil, during the past 35 years. Stomach contents of bottlenose dolphins collected between 2002 and 2012 (Period II) were compared to those previously described for this population (1977–1980, Period I), and δ13C and δ15N values in tooth dentine from specimens collected between 1977 and 2012 were used to assess temporal changes in contribution of the main prey to the diet of dolphins over time. Additionally, these data were used to verify the magnitude of trophic overlap between males and females from Period II. Bottlenose dolphins consumed a wide variety of prey. Demersal and demersal–pelagic teleost fish predominated. These results show that bottlenose dolphins from the Patos Lagoon estuary are opportunistic feeders and confirm the plasticity of the species, which preys upon the most available prey. Differences in diet were found between seasons and periods. Stable isotopes and stomach contents detected a significant long-term change in the proportions of their main prey. The contribution of Micropogonias furnieri and Menticirrhus sp. decreased after 1990 while a significant increase in the importance of Trichiurus lepturus was observed. Males consumed a significantly higher proportion of T. lepturus while Mugil liza was the main prey for females. These changes might be due to fishing-related changes in fish abundance.
The genus Tursiops currently includes two recognized species inhabiting inshore, nearshore and offshore waters of the World’s oceans. The common bottlenose dolphin Tursiops truncatus (Montagu, 1821) is cosmopolitan to temperate and tropical waters (see review by Wells and Scott, 2009), while the Indo-Pacific bottlenose dolphin Tursiops aduncus (Ehrenberg, 1833) is restricted to coastal waters and ranges discontinuously in the Indo-Pacific region (Wang and Yang, 2009). A third species, Tursiops australis, has been proposed for coastal waters off southern Australia (Charlton-Robb et al., 2011), however its validity as a separate species is still debatable (Society for Marine Mammalogy Committee on Taxonomy, 2014).
Taxonomy and systematics play a critical role in the conservation of biodiversity (e.g. Ryder, 1986; Mace, 2004; Aleixo, 2009). Taxonomic names are important for recognition and clear definition of the units to be conserved. Usually, species or subspecies levels are the preferred target of conservation policies and biodiversity monitoring programs (e.g. Karl and Bowen, 1999; Haig et al., 2006; Morrison et al., 2009). In addition, for widely distributed species with considerable fine-scale structuring such as bottlenose dolphins (genus Tursiops) (Wells and Scott, 2009), it is important to determine stock units to guide conservation and management procedures at the local level (e.g. Dizon et al., 1992; Moritz, 1994).
Here, we review information on the biology and ecology of common bottlenose dolphin (Tursiops truncatus) - hereafter referred to as bottlenose dolphin - in the Southwest Atlantic Ocean (SWAO) with emphasis on growth, feeding ecology, epizootics and parasites, predation and pathologies. A total of 34 scientific studies were revised, including 17 reviewed articles, one undergraduate monograph, three master’s dissertations, one doctoral thesis, two books, three technical reports and six working papers. The working papers were presented in the First Workshop on the Research and Conservation of Tursiops truncatus: Integrating knowledge about the species in the Southwest Atlantic Ocean, held in Rio Grande, Rio Grande do Sul (RS) State, Brazil 21-23 May 2010. When necessary, we included personal communications to complement the information provided in this report.
In this work we compiled the available information about humans and bottlenose dolphin interactions in the Southwest Atlantic Ocean (SWAO), including issues as historical direct takes, incidental captures in fisheries, positive interactions with fisheries, interactions of dolphins with tourism and boat traffic, habitat modification or degradation, and environmental pollution. The data compiled in this review demonstrated that coastal bottlenose dolphins are under anthropogenic pressure in the SWAO. Direct take of bottlenose dolphins in the wild does not appear to be an issue of conservation concern in the SWAO. Although the species is exposed to bioaccumulation of micropollutants, it is suggested that contamination level is lower when compared to bottlenose dolphins from other continents. Coastal works can impact bottlenose dolphin behavior and habitat use in a short-term, but those seem to be reversible when works stop. Bycatch occurs throughout the species distribution and seems to be occasional in Uruguayan and Argentinean waters, where there is evidence of a historic decline in dolphin sightings. In Brazil, bycatch is apparently low in the northeast and southeast coasts, but is frequent in certain areas of southern Brazil. Studies on the subject are scarce or preliminary and a great effort is still required to understand the real impact of human activities on bottlenose dolphins in the SWAO.
The information herein presented were compiled from six scientific articles, one undergraduate monographs, four master and three doctoral thesis and six working papers presented during the “I South American Meeting of Research and Conservation of Tursiops truncatus”, which was held in Rio Grande, Rio Grande do Sul, Brazil between May 21-23, 2010. Some personal communications complement the information. Each topic discussed in the present report followed the geographical sub-divisions established in the Report of the Working Group on Distribution (this volume): a) Northern Brazil; b) North-eastern Brazil; c) South-eastern Brazil; d) Southern Brazil and Uruguay and e) Argentina.
Ethnobiological studies and educational projects related to bottlenose dolphins (Tursiops truncatus, Montagu, 1821) are still incipient in the Southwest Atlantic Ocean (SWAO). We review studies conducted in the region, especially Brazil, where more information is available. Proposals to implement studies related to ethnobiology and environmental education in relation to the species are also presented.
Despite bottlenose dolphins being well studied in several regions around the world, there is very limited information about the reproduction of these animals in the Southwestern Atlantic Ocean (SWA). In this study, data from a long-term mark-recapture and stranding monitoring program were used to estimate life history traits of female bottlenose dolphins inhabiting the Patos Lagoon estuary, a sub-tropical coastal region in the SWA. From the analysis of 32,296 high-quality dorsal fin photographs, the fate of 37 individual females and 66 of their calves was tracked. Results supported a birth pulse dolphin community, with most births occurring during late spring and summer, in association with increasing water temperature and food supply. Female bottlenose dolphins first reproduced at a minimum age of 8 years. Mean inter-birth interval was 3 years (mode = 2), and fecundity was 0.11. A clear change in the δ13C and δ15N profiles in teeth from stranded carcasses near age 2 indicated the most probable weaning age. First and second year annual calf survival estimates were 0.84 (95 % CI 0.72–0.90) and 0.86 (95 % CI 0.74–0.94), respectively. No evidence was found to support that timing of birth plays a role in calf survival, suggesting that variability in water temperature and food resources within the year is unlikely to impact upon survival of calves. Older females reproduced at lower rates, suggesting an age-related decrease in reproductive fitness. At an individual level, marked variation in reproductive success was observed. Our findings highlight the importance of long-term studies for long-lived mammals to yield individual- and population-level parameters for demographic and viability analyses that are useful for conservation and management.
We report on the epidemiology of lobomycosis-like disease (LLD), a cutaneous disorder evoking lobomycosis, in 658 common bottlenose dolphins Tursiops truncatus from South America and 94 Indo-Pacific bottlenose dolphins T. aduncus from southern Africa. Photographs and stranding records of 387 inshore residents, 60 inshore non-residents and 305 specimens of undetermined origin (inshore and offshore) were examined for the presence of LLD lesions from 2004 to 2015. Seventeen residents, 3 non-residents and 1 inshore dolphin of unknown residence status were positive. LLD lesions appeared as single or multiple, light grey to whitish nodules and plaques that may ulcerate and increase in size over time. Among resident dolphins, prevalence varied significantly among 4 communities, being low in Posorja (2.35%, n = 85), Ecuador, and high in Salinas, Ecuador (16.7%, n = 18), and Laguna, Brazil (14.3%, n = 42). LLD prevalence increased in 36 T. truncatus from Laguna from 5.6% in 2007−2009 to 13.9% in 2013−2014, albeit not significantly. The disease has persisted for years in dolphins from Mayotte, Laguna, Salinas, the Sanquianga National Park and Bahía Málaga (Colombia) but vanished from the Tramandaí Estuary and the Mampituba River (Brazil). The geographical range of LLD has expanded in Brazil, South Africa and Ecuador, in areas that have been regularly surveyed for 10 to 35 yr. Two of the 21 LLD-affected dolphins were found dead with extensive lesions in southern Brazil, and 2 others disappeared, and presumably died, in Ecuador. These observations stress the need for targeted epidemiological, histological and molecular studies of LLD in dolphins, especially in the Southern Hemisphere.
Groupers are large-bodied fishes with broad global distribution and commercial and ecological importance. Many grouper species are endangered, but information on trophic ecology of groupers outside the Mediterranean Sea is limited. We integrated stomach contents analyses (SCA) and stable isotope analyses (SIA) to test the hypotheses that diets of dusky grouper Epinephelus marginatus differ between littoral and neritic zones in the southwestern Atlantic, but exhibit similar ontogenetic shifts in prey size and consumption of fishes. SCA were dominated by fishes, crabs, and shrimp and differed significantly between habitats, but prey size and consumption of fishes increased with grouper body size at both sites. Grouper stable isotope ratios were similar between sites and among size classes, but integrating SCA and SIA distinguished ingested versus assimilated dietary components, improved dietary resolution, and provided a more comprehensive assessment of grouper in the food webs. Dusky grouper integrate benthic and pelagic trophic pathways, as well as estuarine and marine food webs via consumption of migratory prey. Our findings have applications to other threatened grouper populations, for example, in managing fragmented populations or for reserve designs considering inclusion of artificial substrates as grouper habitat, and more broadly for approaches examining trophic ecology of generalist predators.
Many anthropogenic actions have an impact on coastal dolphins, with bycatch being one of the main threats. We describe the distribution patterns of common bottlenose dolphins Tursiops truncatus and periods of higher entanglement risk by the artisanal gillnet fishery in the Patos Lagoon estuary and along the adjacent coast of southern Brazil. A total of 136 dolphin groups and 187 gillnets were encountered in 69 surveys conducted between September 2006 and July 2009. Data were analyzed in relation to environmental, spatial and temporal variables using generalized additive models and a spatially adaptive local smoothing algorithm for model selection. In both areas, dolphin densities increased as distance to the estuary mouth decreased. For the estuary area, water salinity and temperature influenced dolphin distribution. Along the adjacent coast, dolphin densities were higher with distance to shore as well as in the north area during the warm period. Patterns of dolphin distribution were probably a response to the presence of preferred prey or avoidance of human-related disturbance. Kernel density showed that fishing effort was distributed along the entire surveyed area inside the estuary, while along the adjacent coast it was higher in the south compared to the north area in the warm period. The overlap between gillnets and dolphins increased considerably from the cold (33.8%) to the warm (48.6%) period. Seasonal variation in fishing effort and distribution affect the overlap and the risk of dolphin entanglement. Based on the findings of this study, a fishing exclusion area aimed at reducing bycatch was established by the Brazilian Environmental Agency.
The genetic structure of bottlenose dolphin communities found along the southern Brazilian coast is reported in this study. Genetic structure analysis using biopsy samples from free ranging dolphins and tissue samples from stranded dolphins revealed a fine-scale population structure among three distinct groups. The first genetically distinct group was composed of resident dolphins of Laguna with a high degree of site fidelity. The second group was composed of one photo-identified dolphin, previously recognised by its interaction with fishermen, and dolphins that stranded near the mouth of Tramandaí Lagoon. Moderate nuclear and low mitochondrial gene diversity was found in dolphins of those coastal communities, whereas most of the dolphins stranded along the coast showed markedly higher levels of gene diversity at both markers. These stranded dolphins of unknown origin formed the third distinct group, which may be part of a larger offshore community. These results demonstrate the presence of at least three bottlenose dolphin clusters along this portion of the Brazilian coast, with the coastal specimens appearing to be only neighbours of a larger offshore community that eventually strands along the coast, highlighting the importance of the establishment of management and conservation measures for the species at a local scale.
We conducted a mark-recapture (MR) analysis from 8 years (2005–2012) of photo-identification data collected systematically to investigate demographic parameters of a community of bottlenose dolphins (Tursiops truncatus) inhabiting the Patos Lagoon Estuary and adjacent marine coast in southern Brazil. Under the most parsimonious model of Pollock’s robust design, which disregarded the effects of temporary emigration, the estimate of annual apparent survival was higher for adult females (0.97, 95% CI: 0.91–0.99) than for adult males (0.88, 95% CI: 0.75–0.94) and juveniles (0.83, 95% CI: 0.64–0.93), which may explain an observed bias in sex ratio (1 male:2 females) of known adult dolphins in this community. An increase in abundance of marked individuals was observed during the first 6 years of sampling when the number of new recruits surpassed mortality, followed by a remarkable decrease in the last 2 years when an inverse ratio of recruits/deaths occurred. Yearly changes in abundance ( ) varied from −0.1 to 0.07. Total abundance estimates were highly precise (the highest coefficient of variation was 0.053) and did not exceed 88 individuals. Abundance estimates were similar to a previous MR study conducted in the same area almost a decade earlier, suggesting a relative stable dolphin community over the last 14 years. The apparent stability in abundance, however, should be viewed with caution since this community would need a substantial mortality of at least 10% before a decline in abundance is detected with a desirable statistical power of 90%.
Knowledge about the ecology of bottlenose dolphins in the Southwestern Atlantic Ocean is scarce. Increased by-catch rates over the last decade in coastal waters of southern Brazil have raised concerns about the decline in abundance of local dolphin communities. Lack of relevant data, including information on population structure and connectivity, have hampered an assessment of the conservation status of bottlenose dolphin communities in this region. Here we combined analyses of 16 microsatellite loci and mitochondrial DNA (mtDNA) control region sequences to investigate genetic diversity, structure and connectivity in 124 biopsy samples collected over six communities of photographically identified coastal bottlenose dolphins in southern Brazil, Uruguay and central Argentina. Levels of nuclear genetic diversity were remarkably low (mean values of allelic diversity and heterozygosity across all loci were 3.6 and 0.21, respectively), a result that possibly reflects the small size of local dolphin communities. On a broad geographical scale, strong and significant genetic differentiation was found between bottlenose dolphins from southern Brazil-Uruguay (SB-U) and Bahia San Antonio (BSA), Argentina (AMOVA mtDNA I broken vertical bar(ST) = 0.43; nuclear F-ST = 0.46), with negligible contemporary gene flow detected based on Bayesian estimates. On a finer scale, moderate but significant differentiation (AMOVA mtDNA I broken vertical bar(ST) = 0.29; nuclear F-ST = 0.13) and asymmetric gene flow was detected between five neighbouring communities in SB-U. Based on the results we propose that BSA and SB-U represent two distinct evolutionarily significant units, and that communities from SB-U comprise five distinct Management Units (MUs). Under this scenario, conservation efforts should prioritize the areas in southern Brazil where dolphins from three MUs overlap in their home ranges and where by-catch rates are reportedly higher.
We investigated the reproductive parameters of a dusky grouper Epinephelus marginatus population at the southern limit of its distribution in the south-western Atlantic. The analysed specimens were captured between January 2008 and April 2011 at Carpinteiro Bank (CB) (32°16'S; 051°47'W), a seamount located at the 20 m isobath ~16 nautical miles from the coast. The gonads of a total of 201 individuals (184 females, 16 males and 1 individual in sexual transition) with a total length (TL, mm) between 278 and 1160 mm were analysed microscopically. Histological analyses of the gonads suggested that the species is a partial spawner with a long spawning period (between November and March) and with a reproductive peak between November and January. The average female length at first maturity (L50) was 496 (TL, mm). We also observed partially spawned ovaries and partially spawned testes, which indicated reproductive activity, and we noted the presence of hyalinised follicles. These findings reveal that CB is the southernmost portion of the south-western Atlantic in which the dusky grouper reproduces. Additionally, an inshore-offshore comparison suggested that deeper (>20 m) rocky bottoms, such as the studied seamount, constitute higher quality habitats for this species when compared with littoral (<5 m) rocky reefs.
We examined the age and growth of dusky grouper (Epinephelus marginatus) at offshore Carpinteiro Bank (32 degrees 16'S; 52 degrees 47'W) in the southwestern Atlantic through the analysis of growth increments in otoliths. We also examined the hypothesis that this offshore habitat represents a superior site for fish growth compared with inshore habitats. Samples consisted of 211 groupers captured by small-scale fisheries between 2008 and 2011 and with total lengths ranging from 150 to 1160 mm. Otolith growth increments were deposited once per year, and opaque bands formed mostly during the summer, as determined through marginal increment analysis. Ages ranged from 1 to 40 years, and most fish were aged to be between 2 and 8 years (global mean: 7.4 years, standard deviation 6.9). Von Bertalanffy growth parameters for pooled sexes were L-infinity=900.9 mm, K=0.129 and t(0)=-1.45. Fish from the offshore habitat were generally older and their mean sizes were significantly larger at ages 3, 4, 5, and 6 than those of fish from the inshore habitat. Our findings highlight the importance of Carpinteiro Bank as an important growth habitat for dusky groupers in the southwestern Atlantic and indicate that fishery management measures should be implemented to ensure the maintenance of this endangered species in this offshore bank in the future.
The dusky grouper Epinephelus marginatus by fisheries is a marine species historically exploited showing slow growth, late maturation and protogynous hermaphroditism. Currently, it is considered as endangered by the IUCN. Therefore, it is essential to increase the knowledge about its biology and ecology to help conservation of this species. The present study reports the first record of a dusky grouper individual undergoing sexual transition, from female to male, in the Atlantic Ocean based on histological analyses of gonads. The specimen with total length: 770 mm; total weight: 8.1 kg and age: 21 years was captured in a rocky bottom along the coastline of the southernmost in state Brazil.
The mortality of the bottlenose dolphin, Tursiops truncatus, on the southern portion of Rio Grande do Sul State coast was investigated based on 914 beach surveys conducted between 1969 and 2006. A total of 188 stranded bottlenose dolphins were recorded during this period, indicating a 1.8M:1F sex-ratio of those animals sexed (N ¼ 79). Mortality was low in calves, high in juveniles and sub-adults and slightly lower than in adults. The overall mortality was clearly seasonal overlapping with higher fishing efforts in the Patos Lagoon Estuary and adjacent coastal areas, where most individuals washed ashore.
Analysis of a continuous 14-year long subset (1993–2006) of the data indicated relatively low levels of mortality between 1995 and 2000 and a marked increase between 2002 and 2005 followed by an apparent drop in 2006. By-catch was responsible for at least 43% of the recorded mortality between 2002 and 2006. Juvenile males were more susceptible to incidental catches.
Among females, by-catch of adults represented 75%. Results of a potential biological removal analysis suggest that current levels of fishing-related mortality are unsustainable for the small resident population of bottlenose dolphins that inhabits the Patos Lagoon Estuary, and that this population may be declining.
A new mark-recapture abundance estimate and a photographic census were carried out to investigate the possible decline in the abundance of the bottlenose dolphins, Tursiops truncatus (Montagu, 1821), in the Patos Lagoon estuary due to the high levels of bycatch mortality which occurred between 2002 and 2006 in oceanic coastal areas close to the estuary. Fourteen systematic boat surveys were conducted between August and early December 2005 to photo-identify the bottlenose dolphins. The estimated number of animals, with long-lasting marks, in the population obtained from Chapman’s and Mth models were 51 (95% CI = 49-53) and 52 (95% CI = 51-60), respectively. Taking into account the proportion of dolphins with long-lasting marks in the population,the total estimated population size ranged between 84 (95% CI = 76-93) and 86 (95% CI = 78-95) individuals, respectively, which was very similar to the 84 individuals revealed by the population census. Our results did not differ from the abundance estimate carried out in 1998, prior to the high fishing-related mortality event, suggesting that the population is stable. Plausible argument to explain the stability of the population is that some carcasses found on the oceanic coastal beaches near Patos Lagoon estuary come from animals that do not belong to the estuary community. Future studies should investigate fine-scale habitat partition between estuarine and adjacent coastal dolphins. If the existence of different communities living in close proximity (estuarine and coastal areas near to the estuary) is confirmed, a new abundance estimate is needed to access the conservation status of bottlenose dolphins in this region.
