Tursiops truncatus ssp. gephyreus: Vermeulen, E., Fruet, P., Costa, A., Coscarella, M. &amp; Laporta, P.

Vermeulen, Els; Fruet, Pedro F.; Costa, Ana P. B.; Coscarella, Mariano Alberto; Laporta, Paula

doi:10.2305/iucn.uk.2019-3.rlts.t134822416a135190824.en

Cited by 8 publications

(4 citation statements)

References 35 publications

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“…These costal dolphins were recently recognized as a different species (Lahille's bottlenose dolphin, Tursiops gephyreus- Wickert et al, 2016;Hohl et al, 2020) of the abundant, worldwide-distributed common bottlenose dolphin (T. truncatus), although Marine Mammalogy's Committee on Taxonomy argues that the lineages should be recognized at subspecies level 2018 (Costa et al, 2016(Costa et al, , 2019Marine Mammalogy's Committee on Taxonomy, 2018). Due to the low number of individuals representing the entire lineage, and evidence of decline at least in part of its range due to bycatch and other unknown factors, the Lahille's bottlenose dolphin was recently listed as Vulnerable under criterion D1of the IUCN (Vermeulen et al, 2019).…”

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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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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“…Furthermore, 1 min sample size is sufficient to record echolocation clicks with frequencies of 24 and 48 kHz, considering the limitations of these frequencies. Ultimately, our results can expand the use of PAM as an accessible tool to ecological studies that can help conserve bottlenose dolphins, especially T. t. gephyreus, an endemic subspecies that occurs from southern Brazil to central Argentina and has recently been categorized as vulnerable [69].…”

Section: Discussionmentioning

confidence: 89%

Low-frequency sampling rates are effective to record bottlenose dolphins

et al. 2021

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Acoustic monitoring in cetacean studies is an effective but expensive approach. This is partly because of the high sampling rate required by acoustic devices when recording high-frequency echolocation clicks. However, the proportion of echolocation clicks recorded at different frequencies is unknown for many species, including bottlenose dolphins. Here, we investigated the echolocation clicks of two subspecies of bottlenose dolphins in the western South Atlantic Ocean. The possibility of recording echolocation clicks at 24 and 48 kHz was assessed by two approaches. First, we considered the clicks in the frequency range up to 96 kHz. We found a loss of 0.95–13.90% of echolocation clicks in the frequency range below 24 kHz, and 0.01–0.42% below 48 kHz, to each subspecies. Then, we evaluated these recordings downsampled at 48 and 96 kHz and confirmed that echolocation clicks are recorded at these lower frequencies, with some loss. Therefore, despite reaching high frequencies, the clicks can also be recorded at lower frequencies because echolocation clicks from bottlenose dolphins are broadband. We concluded that ecological studies based on the presence–absence data are still effective for bottlenose dolphins when acoustic devices with a limited sampling rate are used.

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“…O turismo desordenado, o trânsito de embarcações comerciais e de lazer, capturas incidentais em redes de pesca e a poluição ameaçam diretamente os botos do gênero Tursiops no litoral brasileiro (Fruet et al, 2016). A espécie ocorrente no estuário do rio Tramandaí, T. gephyreus, está ameaçada de extinção, tanto em âmbito global (Vermeulen et al, 2019) quanto no Rio Grande do Sul (Rio Grande do Sul, 2014).…”

Section: Botosunclassified

Diagnóstico ambiental do estuário do rio Tramandaí, litoral norte do Rio Grande do Sul, Brasil

et al. 2021

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A finalidade deste trabalho foi desenvolver um diagnóstico ambiental dos atores sociais e da fauna de vertebrados do estuário do rio Tramandaí, Rio Grande do Sul, Brasil. Esse diagnóstico foi elaborado a partir de (1) entrevistas com atores sociais e monitoramen-to das atividades antrópicas, (2) inventariamento da ictiofauna, avifauna e mastofauna e (3) monitoramento da população de botos-de-Lahille (Tursiops gephyreus). Os atores sociais identificados incluem, em sua maioria, residentes dos municípios que compõem o estuário (Imbé e Tramandaí) e da região metropolitana de Porto Alegre, capital do Estado. Diferentes formas de uso foram registradas, sendo as atividades de lazer e a pesca amadora e profissio-nal as mais frequentes. Foram registradas sete espécies da fauna brasileira ameaçadas de extinção: duas de peixes (Genidens barbus e Pogonias courbina), três de aves (Sterna hirundinacea, Thalasseus acuflavidus e Thalasseus maximus) e duas de mamíferos (Tursiops gephyreus e Ctenomys flamarioni). No estuário do rio Tramandaí, a ocupação humana desordenada resulta em uma série de impactos ambientais, tais como poluição, in-trodução de espécies invasoras, perda de habitat, ameaça à existência de espécies e de práti-cas culturais. Nesse sentido, propõe-se como prioridades de conservação: a pesca cooperati-va entre botos e pescadores artesanais, a tainha (Mugil liza) e as aves migratórias. O diálogo entre tomadores de decisão, cientistas e atores sociais do estuário do rio Tramandaí é funda-mental para a definição de políticas públicas para a conservação da biodiversidade da região.

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Tursiops truncatus ssp. gephyreus: Vermeulen, E., Fruet, P., Costa, A., Coscarella, M. & Laporta, P.

Cited by 8 publications

References 35 publications

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

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

Low-frequency sampling rates are effective to record bottlenose dolphins

Diagnóstico ambiental do estuário do rio Tramandaí, litoral norte do Rio Grande do Sul, Brasil

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