Distribution and abundance of the dugong in New Caledonia, southwest Pacific

Garrigue, Claire; Patenaude, Nathalie J.; Marsh, Helene

doi:10.1111/j.1748-7692.2007.00173.x

Cited by 21 publications

(25 citation statements)

References 15 publications

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“…In the southern Nicobars, local extirpations (despite presence of extensive meadows) are probably linked to the long present ritual hunting of dugongs by these tribes [26]. Such hunting by indigenous tribes [66], [67], (though legal) can negatively affect dugong populations, if it does not follow practices of sustainable harvest [68]. It is important to motivate these indigenous groups to implement self-imposed voluntary bans on hunting; or to set harvest thresholds over time periods that may allow local population recovery to take place [66], [70].…”

Section: Discussionmentioning

confidence: 99%

Long-Term Occupancy Trends in a Data-Poor Dugong Population in the Andaman and Nicobar Archipelago

et al. 2013

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Prioritizing efforts for conserving rare and threatened species with limited past data and lacking population estimates is predicated on robust assessments of their occupancy rates. This is particularly challenging for elusive, long-lived and wide-ranging marine mammals. In this paper we estimate trends in long-term (over 50years) occupancy, persistence and extinction of a vulnerable and data-poor dugong (Dugong dugon) population across multiple seagrass meadows in the Andaman and Nicobar archipelago (India). For this we use hierarchical Bayesian dynamic occupancy models accounting for false negatives (detection probability<1), persistence and extinction, to two datasets: a) fragmentary long-term occurrence records from multiple sources (1959–2004, n = 40 locations), and b) systematic detection/non-detection data from current surveys (2010–2012, n = 57). Dugong occupancy across the archipelago declined by 60% (from 0.45 to 0.18) over the last 20 years and present distribution was largely restricted to sheltered bays and channels with seagrass meadows dominated by Halophila and Halodule sp. Dugongs were not found in patchy meadows with low seagrass cover. In general, seagrass habitat availability was not limiting for dugong occupancy, suggesting that anthropogenic factors such as entanglement in gillnets and direct hunting may have led to local extinction of dugongs from locations where extensive seagrass meadows still thrive. Effective management of these remnant dugong populations will require a multi-pronged approach, involving 1) protection of areas where dugongs still persist, 2) monitoring of seagrass habitats that dugongs could recolonize, 3) reducing gillnet use in areas used by dugongs, and 4) engaging with indigenous/settler communities to reduce impacts of hunting.

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Section: Discussionmentioning

confidence: 99%

Long-Term Occupancy Trends in a Data-Poor Dugong Population in the Andaman and Nicobar Archipelago

et al. 2013

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“…Ils ont également été pris en compte dans les études sur le métabolisme des fonds meubles (Clavier & Garrigue, 1999) ou encore à l'occasion des travaux réalisés sur l'ichtyofaune lagonaire (travaux de Kulbicki), sur les populations de dugongs (Dugong dugon) associées à ces formations végétales (Garrigue et al, 2008) et sur la macrofaune mobile liée aux herbiers (Cesa, 1998). …”

Section: Les Herbiers De Nouvelle-caledonie Etat Des Connaissancesunclassified

“…Enfin, le dugong Dugong dugon, espèce remarquable, fréquente les herbiers de Nouvelle-Calédonie et forme la troisième population mondiale et la plus grande d'Océanie (Garrigue et al, 2004(Garrigue et al, et 2008.…”

Section: Biodiversite (Faune Et Flore) Des Herbiersunclassified

Drivers of change in the relative abundance of dugongs in New Caledonia

et al. 2017

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Context Sound understanding of temporal changes in the abundance of wildlife species is required for assessing their status and for effective conservation and management. In New Caledonia, a single baseline aerial survey of dugongs in 2003 estimated a population of 2026 (± 553 s.e.) individuals. A second, similar survey in 2008 produced a lower estimate of 606 (± 200 s.e.) individuals, leading to concerns that the dugong population was experiencing a decline. Aims This study used data collected from additional aerial surveys with the aim of updating information on the current size of the dugong population in New Caledonia and investigating the drivers of change in the estimates. Methods Four additional surveys were conducted: one in each of the cool (June) and warm (November) seasons of 2011 and 2012 around the main Island of New Caledonia. Dugong relative abundance and density were calculated and compared among survey years and survey regions. Drivers of change in the dugong population size were then investigated. Key results The abundance estimates obtained from our four surveys ranged from 649 (± 195 s.e.) to 1227 (± 296 s.e.) dugongs. These new results were not significantly different to the 2008 estimate but were significantly lower than the 2003 estimate. There was no significant variation in the proportion of calves throughout the entire time series of surveys. Conclusions The dugong population of New Caledonia was relatively stable between 2008 and 2012. We could not find sufficient evidence to show whether the discrepancy between 2003 and the remainder of the time series is due to a real decline in the population or the result of the confounding effects of variation in environmental conditions, animal behaviour and sampling biases. Implications The stability of the dugong population between 2008 and 2012 is a positive outcome for local conservation and management of dugongs. This study also highlights the advisability of replicating baseline surveys to enable robust interpretation of temporal variation in population size estimates, and in turn, to improve the management of wildlife species.

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“…Laake et al (1997) combined the proportion of time submerged with comparisons between aerial and land survey platforms to take into account availability and perception bias for harbor porpoise Phocoena phocoena surveys. Artificial models for dugongs Dugong dugon (Pollock et al 2006;Garrigue et al 2008) and whale sharks Rhincodon typus (Rowat et al 2009) have also been deployed to assess vertical visibility in the water at differing depths, turbidities and sea-states to adjust for g (0).…”

Section: Introductionmentioning

confidence: 99%

Modelling heterogeneity in detection probabilities in land and aerial abundance surveys in humpback whales (Megaptera novaeangliae)

2018

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The effective management and conservation of animal populations relies on statistically‐sound and replicable surveys to obtain estimates of abundance and assess trends. Surveys of cetaceans, such as humpback whales Megaptera novaeangliae, are difficult to conduct and are particularly affected by bias in detection probability. For example, the probability of detection of whales from land decreases substantially with increased distance from the platform. This distance effect is also true for aerial surveys, combined with the problem that animals are unavailable for detection (underwater) whilst in the field of view. We present a novel approach that combines corrected double‐platform land surveys with corrected aerial surveys to obtain a robust estimate of g(0), the probability of detection on the survey line, for aerial surveys of migrating humpback whales. Several sources of heterogeneity in detection probabilities were identified within the land and aerial surveys (including group composition, bearing of first sighting, number of groups being tracked simultaneously and cloud cover). After including these into our estimate of ĝ(0), we found that only 29% of available whales are being detected on the survey line (ĝ(0) = 0.288), which is a considerably smaller estimate than many available for humpback whales using other methods. Incorporating heterogeneity into the population surveys shows that we are likely to be underestimating the population size of whales on the east coast of Australia. The implications of this result for their conservation and management in light of increased whale‐human conflict is discussed.

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Distribution and abundance of the dugong in New Caledonia, southwest Pacific

Cited by 21 publications

References 15 publications

Long-Term Occupancy Trends in a Data-Poor Dugong Population in the Andaman and Nicobar Archipelago

Long-Term Occupancy Trends in a Data-Poor Dugong Population in the Andaman and Nicobar Archipelago

Drivers of change in the relative abundance of dugongs in New Caledonia

Modelling heterogeneity in detection probabilities in land and aerial abundance surveys in humpback whales (Megaptera novaeangliae)

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