The first confirmed decline of a delphinid population from Brazilian waters: 2000–2015 abundance of Sotalia guianensis in Guanabara Bay, South-eastern Brazil

Azevedo, Alexandre F.; Carvalho, Rafael R.; Kajin, Maja; Sluys, Monique Van; Bisi, Tatiana L.; Cunha, Haydée A.; Lailson‐Brito, José

doi:10.1016/j.ecolind.2017.03.045

Cited by 53 publications

(50 citation statements)

References 42 publications

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“…In the marine environment, social species such as odontocetes (toothed whales) may experience additive mortality events caused by anthropogenic activities, primarily through harvesting or lethal interactions with fisheries. These interactions involve incidental bycatch or lethal responses from fishers when odontocetes directly remove and consume fish caught on fishing gear (31)(32)(33)(34)(35)(36). Such behavior, known as depredation, may cause fishers to use firearms or explosives to repel odontocetes from fishing gear.…”

mentioning

confidence: 99%

Role of sociality in the response of killer whales to an additive mortality event

Busson

Authier

Barbraud

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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In highly social top predators, group living is an ecological strategy that enhances individual fitness, primarily through increased foraging success. Additive mortality events across multiple social groups in populations may affect the social structure, and therefore the fitness, of surviving individuals. This hypothesis was examined in a killer whale (Orcinus orca) population that experienced a 7-y period of severe additive mortality due to lethal interactions with illegal fishing vessels. Using both social and demographic analyses conducted on a unique long-term dataset encompassing periods before, during, and after this event, results indicated a decrease in both the number and the mean strength of associations of surviving individuals during the additive mortality period. A positive significant correlation between association strength and apparent survival suggested that the fitness of surviving individuals was impacted by the additive mortality event. After this event, individuals responded to the loss of relatives in their social groups by associating with a greater number of other social groups, likely to maintain a functional group size that maximized their foraging success. However, these associations were loose; individuals did not reassociate in highly stable social groups, and their survival remained low years after the mortality event. These findings demonstrate how the disruption of social structure in killer whales may lead to prolonged negative effects of demographic stress beyond an additive mortality event. More importantly, this study shows that sociality has a key role in the resilience of populations to humaninduced mortality; this has major implications for the conservation of highly social and long-lived species. sociality | survival | social structure | anthropogenic disturbances | killer whales

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mentioning

confidence: 99%

Role of sociality in the response of killer whales to an additive mortality event

Busson

Authier

Barbraud

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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“…Concerns about the health of Sotalia guianensis populations in Brazil are on the rise since there is quantitative evidence of a decline in the size of the Guanabara Bay population (Azevedo et al . ). Therefore, further research on cetacean behavioral ecology is fundamental to achieve a better understanding of how certain species may respond to different environmental impacts and help to inform necessary conservation actions.…”

Section: Discussionmentioning

confidence: 97%

Whistle variability of Guiana dolphins in South America: Latitudinal variation or acoustic adaptation?

Moron

Lopes

Reis

et al. 2018

Marine Mammal Science

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A previous comparison of whistles using data sampled at 48 kHz suggested that certain frequency parameters vary along a latitudinal gradient. This geographical pattern may be biased because whistles sampled at higher frequencies could potentially have very different frequency contents. The current study compared the acoustic parameters of Guiana dolphin (Sotalia guianensis) whistles recorded at a higher sampling rate (96 kHz) and from groups occupying two never before sampled sites, Benevente Bay, Espírito Santo, Brazil, and Formosa Bay, Rio Grande do Norte, Brazil, with recordings of other populations in South America. By only considering data sampled at a rate of at least 96 kHz, we aimed to detect differences in whistles across locations. Contrary to previous findings, our analyses do not indicate any clear separation between northern and southern populations based on whistles, and do not corroborate the hypothesis of latitudinal acoustic variation in this species. The variation in Guiana dolphin whistle parameters found here appears to be influenced by latitude to some extent, but several other factors, including sampling method, environmental fluctuations, and social influence on vocal learning, may be confounding the detection of a geographic pattern in these whistle samples.

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“…In comparison with the Guiana dolphin populations found in neighbouring areas, such as Sepetiba and Guanabara bays, which are both located in Rio de Janeiro state, the dolphins of Ilha Grande Bay inhabit a more pristine environment, which may provide more ideal conditions and resources for the maintenance of the large local dolphin population. In contrast with Ilha Grande Bay, Sepetiba and Guanabara bays have extensive industrial installations and intense shipping, which have been shown to have a negative influence on the local biodiversity, including Guiana dolphin (Araújo, Pinto, Neves, & de Azevedo, ; Azevedo et al, ; Molisani et al, ; Perin et al, ; R. Tardin, unpublished data). However, Ilha Grande Bay is subject to certain impacts, such as intense boat traffic during the summer months (included in the rainy season model), noise pollution, and other fishing activities, such as trawling, which were not included in the model, and may have potential impacts, either directly or indirectly, on the local Guiana dolphin population.…”

Section: Discussionmentioning

confidence: 99%

“…Recently, the species was included in the National List of Endangered Species (ICMBio, ) as ‘Vulnerable’. Meanwhile, in Rio de Janeiro State, it is currently considered as ‘Critically Endangered’ due to the confirmation of a population decline of almost 80% in Guanabara Bay, an area nearby to Ilha Grande (Azevedo et al, ; SEA, ).…”

Section: Introductionmentioning

confidence: 99%

Modelling habitat use by the Guiana dolphin, Sotalia guianensis, in south‐eastern Brazil: Effects of environmental and anthropogenic variables, and the adequacy of current management measures

Tardin

Maciel

Espécie

et al. 2020

Aquatic Conservation

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1. Species distribution modelling has been used to identify critical habitats for the delimitation of Marine Protected Areas. Although Marine Protected Areas may often overlap with the distribution of key marine species, illegal human activities often continue within these areas, causing negative impacts on the local biodiversity. 2. A generalized linear model with spatial eigenvector mapping was used to investigate, for the first time, the influence of environmental variables and anthropic activities on the number of Guiana dolphin, Sotalia guianensis sightings/grid, and to determine whether a Marine Reserve, in south-eastern Brazil, is adequate for the protection of the local population. Data were collected between May 2007 and October 2013 onboard a 7.5-m vessel with an inboard engine.3. The models for the different periods (annual, dry, and rainy seasons) all indicated that depth, the distance to seafood farms and fishing grounds, and mean sea surface temperatures influenced the distribution of the dolphins within the study area. The annual and seasonal models predicted that the dolphins prefer a continuous area between Cedro and Pico Islands, a large area that lies outside the limits of the Marine Reserve. 4. Although the habitat of Ilha Grande bay is still much less degraded than that inhabited by other nearby Guiana dolphin populations, the results of the present study indicate that anthropic activities in this area influence habitat use by the dolphins. Less than 30% of the area used by the dolphins is protected by the Tamoios Ecological Station (ESEC Tamoios). 5. Sotalia guianensis is classified as 'Vulnerable' in Brazil, although the marine reserve (ESEC Tamoios) does not protect the core area used by the local dolphin population. The results of the present study provide specific locations for the creation of a new multiple-use MPA, as suggested by the Brazilian National Action Plan for the Conservation of Small Cetaceans, or the inclusion of a special management programme for the area between Cedro and Pico islands to better protect the dolphins in the ESEC Tamoios buffer zone. The continuation of surveys to better

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The first confirmed decline of a delphinid population from Brazilian waters: 2000–2015 abundance of Sotalia guianensis in Guanabara Bay, South-eastern Brazil

Cited by 53 publications

References 42 publications

Role of sociality in the response of killer whales to an additive mortality event

Role of sociality in the response of killer whales to an additive mortality event

Whistle variability of Guiana dolphins in South America: Latitudinal variation or acoustic adaptation?

Modelling habitat use by the Guiana dolphin, Sotalia guianensis, in south‐eastern Brazil: Effects of environmental and anthropogenic variables, and the adequacy of current management measures

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