Recommendations for photo‐identification methods used in capture‐recapture models with cetaceans

Urian, Kim W.; Gorgone, Antoinette M.; Read, Andrew J.; Balmer, Brian C.; Wells, Randall S.; Berggren, Per; Durban, John W.; Eguchi, Tomoharu; Rayment, William; Hammond, Philip S.

doi:10.1111/mms.12141

Cited by 169 publications

(203 citation statements)

References 58 publications

(75 reference statements)

Supporting

Mentioning

203

Contrasting

Order By: Relevance

“…Briefly, image file names were encoded with survey and sighting numbers and then sorted in Adobe Photoshop 7.0, from which the best left and/or right-side dorsal fin image of each individual from each sighting was obtained. The resulting sorted images were graded for photographic quality based on focus, contrast, angle, dorsal fin visibility/obscurity, and proportion of the frame filled with diagnostic attributes (Urian et al 1999(Urian et al , 2015. Images of individual dolphins were matched using a combination of 3 methods: freeze brand numbers on their dorsal fins, tag placement, and/or fin notches (Fig.…”

Section: Photo Analysismentioning

confidence: 99%

Low reproductive success rates of common bottlenose dolphins Tursiops truncatus in the northern Gulf of Mexico following the Deepwater Horizon disaster (2010-2015)

Kellar¹,

Speakman²,

Smith³

et al. 2017

Endang. Species. Res.

View full text Add to dashboard Cite

Following the Deepwater Horizon (DWH) oil spill, reproductive success rates in 2 northern Gulf of Mexico (GoM) bottlenose dolphin stocks exposed to oil were evaluated for 4 yr during and after the spill (2010 to 2015) in efforts to assess population-level reproductive health. Pregnancy was determined from either (1) ultrasound examinations of the reproductive tract during capture-release health assessments, or (2) endocrine evaluations of blubber tissue collected from dart biopsies of free-ranging dolphins. Follow-up photo-identification was then used to track the status of pregnant females and any associated neonatal calves for a minimum of 1 yr after the initial pregnancy detection (IPD). For all pregnant females observed following IPD, individuals seen with a calf (reproductive success) and without one (reproductive failure) were recorded. The resulting estimated reproductive success rates for both GoM stocks (19.4%; 7/36) were less than a third of those previously reported in other areas not impacted by the spill (i.e. Sarasota Bay, FL; Indian River Lagoon, FL; and Charleston Harbor, SC) using similar techniques (64.7%; 22/34). We also evaluated the relationships between reproductive success and 13 potential covariates, including stock, ordinal date, progesterone, cortisol, thyroid hormone concentrations, leukocyte count, lung health score, and total body length. Among these, the results only provide strong evidence (Bayes factor > 20) of a relationship between reproductive failure and the total leukocyte count covariate. The high reproductive failure rates measured in both GoM stocks following the DWH oil spill are consistent with mammalian literature that shows a link between petroleum exposure and reproductive abnormalities and failures.

show abstract

Section: Photo Analysismentioning

confidence: 99%

Low reproductive success rates of common bottlenose dolphins Tursiops truncatus in the northern Gulf of Mexico following the Deepwater Horizon disaster (2010-2015)

Kellar¹,

Speakman²,

Smith³

et al. 2017

Endang. Species. Res.

View full text Add to dashboard Cite

show abstract

“…Three different observers independently scored each individual (excluding calves) as D1 (highly distinctive), D2 (distinctive), or D3 (indistinctive) based on the number, and distinctiveness of their dorsal fin features (Urian et al, 1999(Urian et al, , 2015. The final score was that given by ≥ two of the three observers.…”

Section: Image Processingmentioning

confidence: 99%

“…The underlying assumption was that the least distinctive individual should be readily identifiable from the lowest quality image used in the analyses (Nicholson et al, 2012;Urian et al, 2015); images not meeting this criterion were excluded from the analyses. For consistency, the lead author performed all image quality assessments.…”

Section: Image Processingmentioning

confidence: 99%

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

et al. 2016

View full text Add to dashboard Cite

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.

show abstract

“…All photographs were graded according to photographic quality and distinctiveness to minimise the introduction of bias and to reduce misidentification (Urian et al 2015). Only highly distinctive (D1) fins in photographs of excellent and good quality were included in the capture-recapture analyses (Gowans and Whitehead 2001;Urian et al 2015).…”

Section: Capture-recapture Analysismentioning

confidence: 99%

“…Only highly distinctive (D1) fins in photographs of excellent and good quality were included in the capture-recapture analyses (Gowans and Whitehead 2001;Urian et al 2015). A capture was defined as a photograph of sufficient quality of an individual dolphin's distinctly marked dorsal fin.…”

Section: Capture-recapture Analysismentioning

confidence: 99%

Evaluating monitoring methods for cetaceans

Tyne

Loneragan

Johnston

et al. 2016

Biological Conservation

View full text Add to dashboard Cite

With increasing human pressures on wildlife comes a responsibility to monitor them effectively, particularly in an environment of declining research funds. Scarce funding resources compromise the level and efficacy of monitoring possible to detect trends in abundance, highlighting the priority for developing cost-effective programs. A systematic and rigorous sampling regime was developed to estimate abundance of a small, genetically isolated spinner dolphin (Stenella longirostris) population exposed to high levels of human activities. Five monitoring scenarios to detect trends in abundance were evaluated by varying sampling effort, precision, power and sampling interval. Scenario 1 consisted of monthly surveys, each of 12 days, used to obtain the initial two consecutive annual abundance estimates. Scenarios 2, 3 and 4 consisted of a reduced effort, while Scenario 5 doubled the effort of Scenario 1. Scenarios with the greatest effort (1 and 5) produced the most precise abundance estimates (CV=0.09). Using a CV=0.09 and power of 80%, it would take nine years to detect a 5% annual change in abundance compared with 12 years at a power of 95%. Under this best-case monitoring scenario, if the trend was a decline, the population would have decreased by 37% and 46%, respectively, prior to detection of a significant decline. With the potential of a large decline in a small population prior to detection, the lower power level should be used to trigger a management intervention. The approach presented here is applicable across taxa for which individuals can be identified, including terrestrial and aquatic mammals, birds and reptiles.3

show abstract

Recommendations for photo‐identification methods used in capture‐recapture models with cetaceans

Cited by 169 publications

References 58 publications

Low reproductive success rates of common bottlenose dolphins Tursiops truncatus in the northern Gulf of Mexico following the Deepwater Horizon disaster (2010-2015)

Low reproductive success rates of common bottlenose dolphins Tursiops truncatus in the northern Gulf of Mexico following the Deepwater Horizon disaster (2010-2015)

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

Evaluating monitoring methods for cetaceans

Contact Info

Product

Resources

About