Long-term trends in the use of a protected area by small cetaceans in relation to changes in population status

Cheney, Barbara; Corkrey, Ross; Durban, John W.; Grellier, Kate; Hammond, Philip S.; Islas-Villanueva, Valentina; Janik, Vincent M.; Lusseau, David; Parsons, Kim M.; Quick, Nicola J.; Wilson, Ben; Thompson, Paul M.

doi:10.1016/j.gecco.2014.08.010

Cited by 41 publications

(67 citation statements)

References 44 publications

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“…Even with our most precise abundance estimates, it would take a minimum of seven years to detect modest rates of change with high statistical power, by which time populations could be depleted to very low levels (Table 5). Furthermore, trends in the abundance of cetaceans can be complicated by natural variability, such as movements in or out of a study site (Forney, 2000;Parra et al, 2006a;Cheney et al, 2014). This reinforces the recommendation that implementing conservation measures should not be contingent upon statistically robust proof of a decline for small populations of cetaceans (Taylor and Gerrodette, 1993;Thompson et al, 2000;Taylor et al, 2007).…”

Section: Implications For Conservation and Managementsupporting

confidence: 54%

“…The value of long-term data to support conservation and adaptive management of wildlife populations is well-recognized (e.g., Clutton-Brock and Sheldon, 2010;Cheney et al, 2014), and recent expert-led prioritization exercises have emphasized the need for long-term studies of population dynamics of inshore dolphins in northern Australia (Department of the Environment, 2013aEnvironment, , 2015. They encourage multi-year, multidisciplinary studies at appropriate reference sites (representing a range of levels of human impact), including data on abundance and habitat use, to facilitate: detecting trends in the abundance of local populations; the investigation of natural variability in characteristics of populations (e.g., abundance and habitat use) and their relationship to environmental stochastic events (e.g., cyclones); collecting life history data to inform assessments of population viability; and, developing a greater understanding of threatening processes and mitigation options (Department of the Environment, 2015).…”

Section: Implications For Conservation and Managementmentioning

confidence: 99%

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Site-Specific Assessments of the Abundance of Three Inshore Dolphin Species to Inform Conservation and Management

et al. 2016

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Assessing the abundance of wildlife populations is essential to their effective conservation and management. Concerns have been raised over the vulnerability of tropical inshore dolphins in waters off northern Australia to anthropogenic impacts on local populations, yet a lack of abundance data precludes assessment of their conservation status and the management of threats. Using small vessels as cost-effective research platforms, photo-identification surveys and capture-recapture models were applied to provide the first quantitative abundance data for Australian snubfin (Orcaella heinsohni), Australian humpback (Sousa sahulensis), and Indo-Pacific bottlenose dolphins (Tursiops aduncus) at five sites in the Kimberley region of north-western Australia. The abundance of each species was highly variable between different sites, likely reflecting species-specific habitat preferences. Within the c. 130 km 2 study sites, the estimated abundance of most species was ≤60 individuals (excluding calves), and fewer than 20 humpback dolphins were identified at each site in any one 3-5 week sampling period. However, larger estimates of c. 130 snubfin and c. 160 bottlenose dolphins were obtained at two different sites. Several local populations showed evidence of site fidelity, particularly snubfin dolphins. By implementing a standardized, multi-site approach, data on local populations were provided within a broader, regional context, and indicated that each species is patchily distributed in the region. This highlights the need for site-specific baseline data collection using appropriate survey techniques to quantitatively assess the potential impacts of threatening activities to local populations. These findings further illustrate the need to gain a greater understanding of known and potential threats to inshore dolphin populations, their relative impacts, and to mitigate where necessary. An ideal candidate site for a long-term study of snubfin dolphin population dynamics is identified, where trends in abundance and their influencing factors could be investigated. The methods employed herein provide an example of rigorous, site-specific population assessments of inshore dolphins that are broadly applicable to such studies elsewhere.

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Section: Implications For Conservation and Managementsupporting

confidence: 54%

Section: Implications For Conservation and Managementmentioning

confidence: 99%

Site-Specific Assessments of the Abundance of Three Inshore Dolphin Species to Inform Conservation and Management

et al. 2016

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“…The trajectory of this bottlenose dolphin population is currently stable [26,27] and, despite the biases deriving from the small sample size, the simulation study suggested that the proposed developments are unlikely to cause a substantial disruption of calf survival (or, at least, the effect cannot be distinguished from natural individual heterogeneity). In the light of these results, the condition of individuals should now be monitored, so that any deterioration following increased exposure to disturbance can be rapidly detected, before it translates into longer-term changes in the population's trend.…”

Section: Discussionmentioning

confidence: 93%

“…We focused on the sighting history of calves that were consistently associated with the same female [39], because we anticipated that disturbance was more likely to affect calf survival rather than female pregnancy rate [40,41]. Details of the photo-identification data collection are provided in [26,27,37]. We developed a multi-stage model of calf history, where each calf could transition between four different stages: -stage 1: newborn (age 0, born in that same year); -stage 2: age 1 or 2 years; -stage 3: age 3 or more; or -stage 4: dead.…”

Section: (B) a Multi-stage Model For Calf Survivalmentioning

confidence: 99%

Predicting the effects of human developments on individual dolphins to understand potential long-term population consequences

et al. 2015

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Human activities that impact wildlife do not necessarily remove individuals from populations. They may also change individual behaviour in ways that have sublethal effects. This has driven interest in developing analytical tools that predict the population consequences of short-term behavioural responses. In this study, we incorporate empirical information on the ecology of a population of bottlenose dolphins into an individual-based model that predicts how individuals' behavioural dynamics arise from their underlying motivational states, as well as their interaction with boat traffic and dredging activities. We simulate the potential effects of proposed coastal developments on this population and predict that the operational phase may affect animals' motivational states. For such results to be relevant for management, the effects on individuals' vital rates also need to be quantified. We investigate whether the relationship between an individual's exposure and the survival of its calves can be directly estimated using a Bayesian multi-stage model for calf survival. The results suggest that any effect on calf survival is probably small and that a significant relationship could only be detected in large, closely studied populations. Our work can be used to guide management decisions, accelerate the consenting process for coastal and offshore developments and design targeted monitoring.

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“…Known-age cetacean and sirenian studies require other methods; photoidentification is now a commonly used method to identify and follow several species (e.g., bottlenose dolphins (e.g., Cheney et al 2014), manatees (e.g., Langtimm et al 2004), killer whales (e.g., Young et al 2011) and humpback whales (e.g., Mizroch et al 2004)), so the number of known-aged animals for a wider variety of species, should become increasingly available. Photo-id is being conducted using nicks and notches on the dorsal ridge of narwhals (Auger-Méthé et al 2010) so in the future, known-age animals should be available.…”

Section: Known Age or Known Historymentioning

confidence: 99%

A review of age estimation methods in marine mammals with special reference to monodontids

2018

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This paper presents a critical review of methods for estimating absolute or relative age in marine mammals. Absolute age is achieved by counting growth layer groups (GLGs) in hard structures such as teeth, ear plugs, baleen, bones and claws. Relative age can be obtained by methods such as aspartic acid racemisation, genetic telomeres, bone mineral density, fatty acid signatures and other methods. Each method is discussed in detail. Accuracy and precision, including inter-reader calibration and anomalies, as well as methods of validating GLG deposition rates are also addressed. Each section concludes with methods of age estimation applicable to monodontids, and suggestions on the focus of future age-estimation research.

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Long-term trends in the use of a protected area by small cetaceans in relation to changes in population status

Cited by 41 publications

References 44 publications

Site-Specific Assessments of the Abundance of Three Inshore Dolphin Species to Inform Conservation and Management

Site-Specific Assessments of the Abundance of Three Inshore Dolphin Species to Inform Conservation and Management

Predicting the effects of human developments on individual dolphins to understand potential long-term population consequences

A review of age estimation methods in marine mammals with special reference to monodontids

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