Report of the Working Group on Population Parameters and Demography of Tursiops truncatus in the Southwest Atlantic Ocean

Fruet, Pedro F.; Laporta, Paula; Flores, Paulo A. C.

doi:10.5597/00217

Cited by 6 publications

(7 citation statements)

References 25 publications

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“…Despite no abundance estimates are yet available, the species was frequently sighted across the offshore sampling area and in large groups (mean = 37 individuals; SE = 8; Di Tullio et al., ). On the other hand, remarkably low levels of genetic diversity for the coastal ecotype likely reflects small population sizes of possibly a few hundred individuals (Fruet, Flores, et al., ; Fruet, Zappes, et al., ). Mark‐recapture data from long‐term studies of coastal populations along the SWA indicate critical small population sizes (populations not exceeding 90 individuals) and high site fidelity of individuals (e.g., Daura‐Jorge, Ingram, & Simões‐Lopes, ; Fruet, Daura‐Jorge, Möller, Genoves, & Secchi, ; Giacomo & Ott, ; Laporta, Fruet, et al., ; Vermeulen & Cammareri, ).…”

Section: Discussionmentioning

confidence: 99%

“…Nevertheless, it is important to point out that the genetic isolation observed in the coastal ESUs (Fruet et al., ) increases the risk of inbreeding depression and extinction of the coastal ecotype. This ecotype is restricted to a relatively small area and is currently genetically depauperated, with small population sizes and evidence of increasing threats from several anthropogenic activities (Fruet et al., ; see Fruet, Flores, et al., ; Fruet, Zappes, et al., for review) and local population declines (Coscarella, Dans, Degrati, Garaffo, & Crespo, ; Vermeulen & Bräger, ). Thus, conservation measures to enhance the long‐term viability of this possible endemic ecotype need to be prioritized as previously recommended (see Fruet et al., for specific recommendations for the conservation of coastal ESUs).…”

Section: Discussionmentioning

confidence: 99%

“…The occurrence of coastal populations is restricted to southeastern and southern Brazil (27°S) down to central Argentina (43°S), despite some records of sporadic movements beyond these limits (e.g., Simões‐Lopes & Fábian, ). These coastal populations are small (<100 individuals) and associated with estuaries, river mouths, and lagoons (see Simões‐Lopes, ; Lodi et al., ; Laporta, et al., ; Fruet, Flores, & Laporta, ; Fruet et al., ; for reviews). Sighting data suggest no movement of coastal bottlenose dolphins to deep waters (i.e., >20 m depth), although movements of individuals between coastal areas frequently occur (Würsig, ; Simões‐Lopes & Fábian, ; Laporta, Di Tullio, et al., ; Laporta, Fruet, & Secchi, ).…”

Section: Introductionmentioning

confidence: 99%

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Genetic divergence between two phenotypically distinct bottlenose dolphin ecotypes suggests separate evolutionary trajectories

Fruet¹,

Secchi

Tullio³

et al. 2017

Ecology and Evolution

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Due to their worldwide distribution and occupancy of different types of environments, bottlenose dolphins display considerable morphological variation. Despite limited understanding about the taxonomic identity of such forms and connectivity among them at global scale, coastal (or inshore) and offshore (or oceanic) ecotypes have been widely recognized in several ocean regions. In the Southwest Atlantic Ocean (SWA), however, there are scarce records of bottlenose dolphins differing in external morphology according to habitat preferences that resemble the coastal‐offshore pattern observed elsewhere. The main aim of this study was to analyze the genetic variability, and test for population structure between coastal (n = 127) and offshore (n = 45) bottlenose dolphins sampled in the SWA to assess whether their external morphological distinction is consistent with genetic differentiation. We used a combination of mtDNA control region sequences and microsatellite genotypes to infer population structure and levels of genetic diversity. Our results from both molecular marker types were congruent and revealed strong levels of structuring (microsatellites F ST = 0.385, p < .001; mtDNA F ST = 0.183, p < .001; ΦST = 0.385, p < .001) and much lower genetic diversity in the coastal than the offshore ecotype, supporting patterns found in previous studies elsewhere. Despite the opportunity for gene flow in potential “contact zones”, we found minimal current and historical connectivity between ecotypes, suggesting they are following discrete evolutionary trajectories. Based on our molecular findings, which seem to be consistent with morphological differentiations recently described for bottlenose dolphins in our study area, we recommend recognizing the offshore bottlenose dolphin ecotype as an additional Evolutionarily Significant Unit (ESU) in the SWA. Implications of these results for the conservation of bottlenose dolphins in SWA are also discussed.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Genetic divergence between two phenotypically distinct bottlenose dolphin ecotypes suggests separate evolutionary trajectories

Fruet¹,

Secchi

Tullio³

et al. 2017

Ecology and Evolution

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“…By-catch in gillnets is recognized as the main threat for these dolphins, and it is known to occur throughout their range (Fruet et al, 2012(Fruet et al, , 2016a, but others agents such as coastal habitat degradation, chronic skin-diseases, boat strikes, chemical pollution and underwater noise also impact upon them in southern Brazil (e.g., Van Bressem et al, 2015;Fruet et al, 2016a;Righetti et al, 2019). The Patos Lagoon estuary (PLE) population is possibly the largest of all five within the Southern Brazil-Uruguay Evolutionarily Significant Unit, numbering approximately 90 individuals (Fruet et al, 2016b). Bycatch of animals from this population used to occur sporadically and was not considered a reason for concern in the past (e.g., Pinedo, 1986).…”

Section: Introductionmentioning

confidence: 99%

Dynamics and Viability of a Small, Estuarine-Resident Population of Lahille’s Bottlenose Dolphins From Southern Brazil

2021

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Identifying threatened populations and quantifying their vulnerability is crucial for establishing priorities for conservation and providing robust information for decision-making. Lahille’s bottlenose dolphins have been long subjected to by-catch mortality in gillnet fisheries in coastal waters of southern Brazil, particularly in the Patos Lagoon estuary (PLE) and adjacent coastal waters, where dolphins from three populations (or Management Units) show overlapping home ranges. In this study we used a stage-classified matrix population model to conduct a demographic analysis of the PLE’s population with life-history data estimated through an 8 years mark-recapture study. A population viability analysis (PVA) was used to run a series of simulations where the risk was assessed under different by-catch scenarios, taking into account the effects of parameter uncertainty and stochasticity in the projections. In the absence of by-catch, we estimated that this dolphin population would growth at a rate of about 3% annually (95% CI: 1.2–5.8%). Under current by-catch rates, prognoses indicated high probabilities of viability over the next 60 years. These optimistic prognoses appear to be associated with the high survival of adult females. However, the eventual removal of very few mature females (one every year or two) would result in a prominent likelihood of decline from its current abundance at all pre-specified levels. The viability of the population would be substantially improved if the survival of juveniles/sub-adults could be increased. This may be achieved through the recently implemented dolphin protection area, which prohibits gillnet fisheries in the core area of this population. If the protection area reduces the entanglement rates of the most impacted life-stages (i.e., juvenile/sub-adult dolphins), there would be a substantial chance of the PLE’s dolphin population increasing above 20% of its current size, which is here proposed as conservation goal. If met, this goal has the potential to promote habitat quality, increase genetic diversity and connectivity with adjacent populations, enhancing the ability of bottlenose dolphins in southern Brazil to cope with environmental change and potential disease outbreaks.

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“…The content of some reports presented during scientific meetings and personal communications complemented the information. When possible, data were examined according to geographical sub-divisions established in the workshop: a) northern Brazil; b) northeast Brazil; c) southeast Brazil; d) south Brazil-Uruguay; and e) Argentina (see more details of division criteria in Fruet et al, 2016 Introduction, this volume).…”

Section: Introductionmentioning

confidence: 99%

Report of the Working Group on Interactions between Humans and Tursiops truncatus in the Southwest Atlantic Ocean

Fruet

Zappes

Bisi

et al. 2017

Lat. Am. J. Aquat. Mamm.

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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.

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Report of the Working Group on Population Parameters and Demography of Tursiops truncatus in the Southwest Atlantic Ocean

Cited by 6 publications

References 25 publications

Genetic divergence between two phenotypically distinct bottlenose dolphin ecotypes suggests separate evolutionary trajectories

Genetic divergence between two phenotypically distinct bottlenose dolphin ecotypes suggests separate evolutionary trajectories

Dynamics and Viability of a Small, Estuarine-Resident Population of Lahille’s Bottlenose Dolphins From Southern Brazil

Report of the Working Group on Interactions between Humans and Tursiops truncatus in the Southwest Atlantic Ocean

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