Abundance of the Indo-Pacific bottlenose dolphin<i>Tursiops aduncus</i>off south-west Mauritius

Webster, Imogen; Cockcroft, Victor G.; Cadinouche, Adèle

doi:10.2989/1814232x.2014.946448

Cited by 8 publications

(18 citation statements)

References 43 publications

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“…Consistent with this general trend and the findings from our study, relatively high survival rates have also been shown in other T. aduncus populations (e.g., Reisinger and Karczmarski, 2010;Mansur et al, 2012;Webster et al, 2014). Our research provides an example for estimating sex-specific survival rates, which is especially important to determine for threatened populations (e.g., Baker et al, 2013) and for populations with sex-biased threats (e.g., Baird et al, 2015).…”

Section: Survival Rates Were High and Constantsupporting

confidence: 90%

Sex-Specific Patterns in Abundance, Temporary Emigration and Survival of Indo-Pacific Bottlenose Dolphins (Tursiops aduncus) in Coastal and Estuarine Waters

et al. 2016

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Inherent difficulties in determining the sex of free-ranging, sexually monomorphic species often prevents a sex-specific focus on estimating abundance, movement patterns and survival rates. This study provides insights into sex-specific population parameters of Indo-Pacific bottlenose dolphins (Tursiops aduncus). Systematic, boat-based photo-identification surveys (n = 417) were conducted year-round from 2007 to 2013 in coastal and estuarine waters off Bunbury, Western Australia. Pollock's Robust Design was used to quantify population parameters for three datasets: (i) adults and juveniles combined, (ii) adult females and, (iii) adult males. For all datasets, abundance estimates varied seasonally, with general highs during summer and/or autumn, and lows during winter. Dolphins had seasonally structured temporary emigration rates with similar trends between sexes. The derived return rate (1-γ ') of temporary emigrants into the study area was highest from winter to spring, indicating that dolphins had a high probability of return into the study area during spring. We suggest that the return of dolphins into the study area and increase in abundance is influenced by the breeding season (summer/autumn). Prey availability is likely a main driver responsible for the movement of dolphins out of the study area during winter. Seasonal apparent survival rates were constant and high (0.98-0.99) for all datasets. High apparent survival rates suggest there is no permanent emigration from the study area. Our sex-specific modeling approach offers a comprehensive interpretation of the population dynamics of a top predator in a coastal and estuarine environment and acts as a model for future sex-based population studies on sexually monomorphic species.

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Section: Survival Rates Were High and Constantsupporting

confidence: 90%

Sex-Specific Patterns in Abundance, Temporary Emigration and Survival of Indo-Pacific Bottlenose Dolphins (Tursiops aduncus) in Coastal and Estuarine Waters

et al. 2016

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“…To date population abundances have only been estimated for two cetacean species in restricted areas of the SWIO: Indian Ocean humpback (Sousa plumbea) and IndoPacific bottlenose dolphins (Tursiops aduncus) in the Pauly and Zeller (2015) Menai Bay Conservation Area off the south coast south of Unguja Island, Zanzibar and in the KisiteMpunguti Marine Protected Area (MPA), Kenya (Meyler et al 2012;Pérez-Jorge et al 2015Stensland et al 2006); and T. aduncus off the southwest of Mauritius (Webster et al 2014), around Mayotte (Pusineri et al 2014) and La Réunion (Dulau et al 2017). Capture rate estimates are only available for Zanzibar, with these showing unsustainable levels of fisheries mortality for both species (Amir 2010;Amir et al 2002).…”

Section: Marine Mammal Interaction With Small-scale Fisheriesmentioning

confidence: 99%

Marine megafauna interactions with small-scale fisheries in the southwestern Indian Ocean: a review of status and challenges for research and management

Temple

Kiszka

Stead

et al. 2017

Rev Fish Biol Fisheries

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In developing regions, coastal communities are particularly dependent on small-scale fisheries for food security and income. However, information on the scale and impacts of small-scale fisheries on coastal marine ecosystems are frequently lacking. Large marine vertebrates (marine mammals, sea turtles and chondrichthyans) are often among the first species to experience declines due to fisheries. This paper reviews the interactions between small-scale fisheries and vulnerable marine megafauna in the southwestern Indian Ocean. We highlight an urgent need for proper documentation, monitoring and assessment at the regional level of small-scale fisheries and the megafauna affected by them to inform evidence-based fisheries management. Catch and landings data are generally of poor quality and resolution with compositional data, where available, mostly anecdotal or heavily biased towards easily identifiable species. There is also limited understanding of fisheries effort, most of which relies on metrics unsuitable for proper assessment. Management strategies (where they exist) are often created without strong evidence bases or understanding of the reliance of fishers on resources. Consequently, it is not possible to effectively assess the current status and ensure the sustainability of these species groups; with indications 123Rev Fish Biol Fisheries (2018Fisheries ( ) 28:89-115 https://doi.org/10.1007 of overexploitation in several areas. To address these issues, a regionally collaborative approach between government and non-governmental organisations, independent researchers and institutions, and smallscale fisheries stakeholders is required. In combination with good governance practices, appropriate and effective, evidence-based management can be formulated to sustain these resources, the marine ecosystems they are intrinsically linked to and the livelihoods of coastal communities that are tied to them.

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“…However, the same area was covered for both survey types and photoidentification was always performed, with effort focused on obtaining photographs of every individual in the group. Detailed descriptions of surveys and data collection are available in Webster et al (2014).…”

Section: Study Areamentioning

confidence: 99%

“…Log-normal 95% confidence intervals were calculated using the method described in Burnham et al (1987). See Webster et al (2014) for detail.…”

Section: Population Estimatementioning

confidence: 99%

“…With their predictable, almost daily, occurrence in the bays, and large group sizes, the local population of spinner dolphins, as well as that of the Indo-Pacific bottlenose dolphin Tursiops aduncus (Webster et al 2014), has become the target of tourism operations. In 2009, the MMCS recorded more than 60 operators (>120 boats) offering dolphin-watching and swim-with-dolphins activities every day of the year (IW unpublished data).…”

Section: Management and Conservationmentioning

confidence: 99%

See 1 more Smart Citation

Spinner dolphinsStenella longirostrisoff south-west Mauritius: abundance and residency

Webster¹,

Cockcroft

Cadinouche³

2015

African Journal of Marine Science

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Spinner dolphins Stenella longirostris longirostris off the south-west coast of Mauritius are subject to ongoing anthropogenic disturbance in the form of daily dolphin tourism, which has intensified since 1998. Abundance of this species was estimated using photo-identification data and mark-recapture analysis. Between April 2008 and June 2010, identification photographs were collected from dolphins occurring along a 30 km length of the coast of south-west Mauritius. A total of 250 groups were encountered over 229 survey days. Mark-recapture analyses were performed on a photographic dataset of more than 8 000 good-and excellent-quality images and 83 animals were identified as distinctively marked individuals. The majority (85.5%) were seen more than once and resightings indicated a resident population. The compiled version of SOCPROG 2.4 was used to investigate the lagged identification rate. The fitted model supported a mostly resident population with additional animals moving in and out of the study area. The estimated abundance of the total population in the study area ranged between 138 and 399 individuals. Our results can be used for monitoring the population for fluctuations and for encouraging both the enforcement of laws regarding dolphin watching and the development of further means of management needed to ensure the long-term presence of this population.

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Abundance of the Indo-Pacific bottlenose dolphinTursiops aduncusoff south-west Mauritius

Cited by 8 publications

References 43 publications

Sex-Specific Patterns in Abundance, Temporary Emigration and Survival of Indo-Pacific Bottlenose Dolphins (Tursiops aduncus) in Coastal and Estuarine Waters

Sex-Specific Patterns in Abundance, Temporary Emigration and Survival of Indo-Pacific Bottlenose Dolphins (Tursiops aduncus) in Coastal and Estuarine Waters

Marine megafauna interactions with small-scale fisheries in the southwestern Indian Ocean: a review of status and challenges for research and management

Spinner dolphinsStenella longirostrisoff south-west Mauritius: abundance and residency

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