Survival of Bowhead Whales, Balaena mysticetus, Estimated from 1981-1998 Photoidentification Data

Zeh, Judith; Poole, David; Miller, Gary W.; Koski, William R.; Baraff, Lisa; Hugh, David

doi:10.1111/j.0006-341x.2002.00832.x

Cited by 45 publications

(50 citation statements)

References 31 publications

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“…The magnitude of both trends is not known. This value lies in the range of other baleen whale species such as bowhead whales Balaena mysticetus, for which a survival rate of 0.984 was estimated (Zeh et al 2002). Best & Kishino (1998) presented similar values for reproductively active southern right whale females Eubalaena australis.…”

Section: Survival Ratesupporting

confidence: 62%

Survival of adult blue whales Balaenoptera musculus in the Gulf of St. Lawrence, Canada

Ramp¹,

Bérubé²,

Hagen³

et al. 2006

Mar. Ecol. Prog. Ser.

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Blue whales in eastern Canadian waters are regarded as endangered, mainly due to the lack of knowledge on their abundance and life parameters. Here, we analysed sighting histories of 362 photo-identified blue whales in the Gulf of St. Lawrence over 24 yr to estimate, for the first time, the adult survival rate of this species. The results revealed that some whales have high site fidelity while others are only visitors to the St. Lawrence. Low sighting reliability of transient whales resulted in an age structure for which there is no obvious biological justification and led us to discard the data set with all blue whales. Based on sighting records of individuals of known sex, we consider the best estimate for adult blue whale survival to be 0.975 (95% CI 0.960 to 0.985). This estimate is likely to be biased upwards by long-term records of individuals first sighted in the 1980s and sexed from biopsy samples in the 1990s, but biased downwards by emigration from the study area. The relative magnitude of these biases is, at present, unquantifiable. Trap dependency affects the probability of capture and varies between the sexes, but no significant difference in survival was found between the sexes. KEY WORDS: Survival rate · Blue whale · Modelling transients · Trap dependenceResale or republication not permitted without written consent of the publisher

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Section: Survival Ratesupporting

confidence: 62%

Survival of adult blue whales Balaenoptera musculus in the Gulf of St. Lawrence, Canada

Ramp¹,

Bérubé²,

Hagen³

et al. 2006

Mar. Ecol. Prog. Ser.

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“…Caswell et al (1999) estimated survival of the highly endangered western North Atlantic right whale Eubalaena glacialis population, but these time-varying markrecapture estimates (from about 0.99 to about 0.94) are of crude survival and are not directly comparable to the non-calf survival estimate presented here. Likewise, a mark-recapture survival estimate for adult bowhead whales Balaena mysticetus of the Bering-Chukchi-Beaufort Seas stock (0.984, SD = 0.014; Zeh et al 2002) and indirect survival estimates for adult female southern right whales Eubalaena australis off South Africa (0.986, 95% CI = 0.976 to 0.999; Best et al 2001) and Argentina (0.981, SE = 0.005; Cooke et al 2001) are not directly comparable. Finally, the western gray whale non-calf survival point estimate is lower than an indirect estimate of 0.987 (90% credibility interval = 0.972 to 0.998) by Wade & Perryman (2002) for the eastern gray whale population.…”

Section: Survivalmentioning

confidence: 99%

Survival estimates of western gray whales Eschrichtius robustus incorporating individual heterogeneity and temporary emigration

Bradford¹,

Wade²,

Weller³

et al. 2006

Mar. Ecol. Prog. Ser.

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Gray whales Eschrichtius robustus exist as 2 geographically and genetically distinct populations in the eastern and western North Pacific. Subjected to intensive commercial whaling during the 19th and 20th centuries, the western population presently numbers approximately 100 individuals and is regarded as one of the most endangered baleen whale populations in the world. Since 1997, ongoing studies of western gray whales have resulted in a photographic dataset that can be used for mark-recapture survival estimation. Pollock's robust design was applied to 129 individual whale encounter histories spanning 25 monthly capture occasions from 1997 to 2003. Using Akaike's Information Criterion (AICc) model selection, models incorporating individual heterogeneity in residency patterns and higher temporary emigration probabilities for younger whales provided better fits to the data. Non-calf and calf (1st year post-weaning) survival were estimated as 0.951 (SE = 0.0135, 95% CI = 0.917 to 0.972) and 0.701 (SE = 0.0944, 95% CI = 0.492 to 0.850), respectively, averaging across the best models (n = 13) in order to account for model uncertainty. The non-calf survival point estimate is similar to mark-recapture estimates for Gulf of Maine humpback whales, but lower than an indirect estimate for the eastern gray whale population. Although no statistically robust direct estimates of baleen whale calf survival exist for comparison to the current study, the calf survival estimate is markedly lower than a value suggested for Gulf of Maine humpback whales. Estimation of survival is necessary for assessing the status of western gray whales, which can contribute to increased protection, conservation, and management planning for this critically endangered population.

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“…For these data, factors that influence the decision of which data set to use include the sample size, the distribution of photographic quality categories, and the variability in the evaluation of photographic quality. The decision of which data to include will be even more complex for populations where the ability to correctly reidentify individuals is reduced because not all individuals are distinctively marked, for example, bowhead whales (Balaena mysticetus) (Rugh et al 1998, da Silva et al 2000, Zeh et al 2002, bottlenose dolphins (Wilson et al 1999, Read et al 2003, and Mediterranean monk seals (Forcada and Aguilar 2000).…”

Section: Modelmentioning

confidence: 99%

“…Photo-identification has been used in a number of capture-recapture studies to estimate animal abundance and survival rates of several species (e.g., Buckland 1990, Hammond et al 1990, Flatt et al 1997, Langtimm et al 1998, Baker 1999, Zeh et al 2002, Calambokidis and Barlow 2004, Mizroch et al 2004. When photo-identification is used in capture-recapture studies, the ability to accurately identify individuals from photographs needs to be examined.…”

Section: Introductionmentioning

confidence: 99%

Balancing bias and precision in capture‐recapture estimates of abundance

Friday¹,

Smith

Stevick

et al. 2008

Marine Mammal Science

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Capture-recapture estimates of abundance using photographic identification data are sensitive to the quality of photographs used and distinctiveness of individuals in the population. Here analyses are presented for examining the effects of photographic quality and individual animal distinctiveness scores and for objectively selecting a subset of data to use for capture-recapture analyses using humpback whale (Megaptera novaeangliae) data from a 2-year study in the North Atlantic. Photographs were evaluated for their level of quality and whales for their level of individual distinctiveness. Photographic quality scores had a 0.21 probability of changing by a single-quality level, and there were no changes by two or more levels. Individual distinctiveness scores were not independent of photographic quality scores. Estimates of abundance decreased as poor-quality photographs were removed. An appropriate balance between precision and bias in abundance estimates was achieved by removing the lowest-quality photographs and those of incompletely photographed flukes given our assumptions about the true population abundance. A simulation of the selection process implied that, if the estimates are negatively biased by heterogeneity, the increase in bias produced by decreasing the sample size is not more than 2%. Capture frequencies were independent of individual distinctiveness scores.Key words: abundance estimation, capture-recapture, humpback whale, individual animal distinctiveness, individual identification, mark-recapture, Megaptera novaeangliae, North Atlantic, photographic identification, photographic quality.Photographs of natural markings are used to identify individual animals in a process known as photo-identification. Photo-identification has been used in a number of capture-recapture studies to estimate animal abundance and survival rates of several species (e.g., Buckland 1990, Hammond et al. 1990, Flatt et al. 1997, Langtimm et al. 1998, Baker 1999, Zeh et al. 2002, Calambokidis and Barlow 2004, Mizroch et al. 2004. When photo-identification is used in capture-recapture studies, the ability to accurately identify individuals from photographs needs to be examined. Accurate identification of individuals will depend on the quality of the photographs used and the distinctiveness of the natural markings of the individuals (Hammond 1986). Errors in identification can occur as false negatives and false positives and affect the accuracy of the resulting estimates.Photographic quality (hereafter referred to as quality) includes the clarity and contrast of the photograph, the angle of the markings to the plane of the photograph (angle), and the proportion of the animal or identifying feature that is photographed. Natural markings include color patterns, the shape of features, and scars. The distinctiveness of markings can depend on the complexity of a color pattern or a feature's shape and the number and size of scars.False-positive errors occur when different individuals are incorrectly identified as the same ...

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Survival of Bowhead Whales, Balaena mysticetus, Estimated from 1981-1998 Photoidentification Data

Cited by 45 publications

References 31 publications

Survival of adult blue whales Balaenoptera musculus in the Gulf of St. Lawrence, Canada

Survival of adult blue whales Balaenoptera musculus in the Gulf of St. Lawrence, Canada

Survival estimates of western gray whales Eschrichtius robustus incorporating individual heterogeneity and temporary emigration

Balancing bias and precision in capture‐recapture estimates of abundance

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