Age Estimation Techniques Research Articles

A DESIGN OF APPARENT-AGE ESTIMATION SYSTEM BY THE EMPIRICAL MODE DECOMPOSITION

Recently, the automation of the age estimation technique is hoped for in various fields. Therefore, we propose an apparent-age estimation system using empirical mode decomposition (EMD). Conventional study reported that the time-frequency features are important for age estimation. However, these cannot necessarily extract the time-frequency feature in detail, because the classical technique that have a relationship of trade-off between the time resolution and the frequency resolution are used. On the other hand, the EMD is the novel time-frequency analysis technique that do not have the relationship of trade-off between the time resolution and the frequency resolution. The EMD gives a time-frequency analysis decomposing a signal into several intrinsic mode functions (IMFs). The IMF together with their Hilbert transforms are called the Hilbert–Huang spectrum, which leads to instantaneous frequency and amplitude. We use these features effectively for extracting human's age perception. We estimate the age by a neural network that learns pairs of face image and the Hilbert–Huang spectrum. Furthermore, we compress the data for neural network by using the simple principal component analysis (SPCA). In order to show the effectiveness of the proposed method, computer simulations are done by the actual human data.

A Synthesis of Cisco Recovery in Lake Superior: Implications for Native Fish Rehabilitation in the Laurentian Great Lakes

AbstractPopulations of cisco Coregonus artedi in the Laurentian Great Lakes supported large‐scale commercial fisheries and were the primary forage of piscivores during the first half of the 20th century. However, by 1970 populations had collapsed in all of the lakes. Since then, ciscoes have staged a recovery in Lake Superior. In this synthesis, we describe the status of ciscoes in Lake Superior during 1970–2006 and provide a comprehensive review of their ecology. Better understanding of age estimation techniques, application of hydroacoustic and midwater trawl sampling, and compilation of long‐term data sets have advanced our understanding of the species. Management agencies contemplating rehabilitation of cisco populations should recognize that (1) knowledge of cisco ecology and population dynamics is increasing; (2) ciscoes are long‐lived; (3) Great Lakes populations are probably composed of both shallow‐water and deepwater spawning forms; (4) large year‐classes can be produced from small adult stocks; (5) large variation in year‐class strength is probably intrinsic to Great Lakes populations; (6) despite the longevity and early maturity of ciscoes, stocks can be overfished because large year‐classes are produced infrequently; (7) regional environmental factors appear to play a large role in reproductive success; and (8) rainbow smelt Osmerus mordax are likely to have a negative effect on cisco recruitment under certain conditions. A top‐down approach for rehabilitating lake trout Salvelinus namaycush in Lake Superior probably benefited cisco recovery through lake trout predation on invasive rainbow smelt populations. We argue that managing for populations of exotic alewives Alosa pseudoharengus to support popular recreational fisheries of exotic Pacific salmonids in the other Great Lakes conflicts with stocking efforts to rehabilitate native lake trout in those lakes. If native fish rehabilitation is a serious and primary goal for management agencies in the Great Lakes basin, we propose that an ecosystem‐based approach to modifying the environment for the benefit of native fish species (i.e., decimation or eradication of invasive species) is required.

Hierarchical Bayesian analysis to incorporate age uncertainty in growth curve analysis and estimates of age from length: Florida manatee (Trichechus manatus) carcasses

Age estimation of individuals is often an integral part of species management research, and a number of age-estimation techniques are commonly employed. Often, the error in these techniques is not quantified or accounted for in other analyses, particularly in growth curve models used to describe physiological responses to environment and human impacts. Also, noninvasive, quick, and inexpensive methods to estimate age are needed. This research aims to provide two Bayesian methods to (i) incorporate age uncertainty into an age–length Schnute growth model and (ii) produce a method from the growth model to estimate age from length. The methods are then employed for Florida manatee ( Trichechus manatus ) carcasses. After quantifying the uncertainty in the aging technique (counts of ear bone growth layers), we fit age–length data to the Schnute growth model separately by sex and season. Independent prior information about population age structure and the results of the Schnute model are then combined to estimate age from length. Results describing the age–length relationship agree with our understanding of manatee biology. The new methods allow us to estimate age, with quantified uncertainty, for 98% of collected carcasses: 36% from ear bones, 62% from length.

An Evaluation of the Precision of Fin Ray, Otolith, and Scale Age Determinations for Brook Trout

AbstractThe ages of brook trout Salvelinus fontinalis are typically estimated using scales despite a lack of research documenting the effectiveness of this technique. The use of scales is often preferred because it is nonlethal and is believed to require less effort than alternative methods. To evaluate the relative effectiveness of different age estimation methodologies for brook trout, we measured the precision and processing times of scale, sagittal otolith, and pectoral fin ray age estimation techniques. Three independent readers, age bias plots, coefficients of variation (CV = 100 × SD/mean), and percent agreement (PA) were used to measure within‐reader, among‐structure bias and within‐structure, among‐reader precision. Bias was generally minimal; however, the age estimates derived from scales tended to be lower than those derived from otoliths within older (age > 2) cohorts. Otolith, fin ray, and scale age estimates were within 1 year of each other for 95% of the comparisons. The measures of precision for scales (CV = 6.59; PA = 82.30) and otoliths (CV = 7.45; PA = 81.48) suggest higher agreement between these structures than with fin rays (CV = 11.30; PA = 65.84). The mean per‐sample processing times were lower for scale (13.88 min) and otolith techniques (12.23 min) than for fin ray techniques (22.68 min). The comparable processing times of scales and otoliths contradict popular belief and are probably a result of the high proportion of regenerated scales within samples and the ability to infer age from whole (as opposed to sectioned) otoliths. This research suggests that while scales produce age estimates rivaling those of otoliths for younger (age < 3) cohorts, they may be biased within older cohorts and therefore should be used with caution.

Current Status and Review of Freshwater Fish Aging Procedures Used by State and Provincial Fisheries Agencies with Recommendations for Future Directions

In 2006, the Fisheries Management Section of the American Fisheries Society formed the ad hoc Assessment of Fish Aging Techniques Committee to assess the current status of aging freshwater fish in North America. For seven species groups that included black bass (Micropterus spp.), crappie/sunfish (Pomoxis spp./Lepomis spp.), catfish (Ictaluridae), morinids, percids, salmonids, and esocids, a survey of U.S. and Canadian fisheries agencies (N = 51 agencies responding) revealed that scales, otoliths, and spines were the most common structures used to age fish. Latitudinal clines existed for some of the structures that were examined, with scales typically used more in northern latitudes than otoliths. Many agencies conducted some validation of age estimation techniques and most assessed precision at least for some of the age samples collected. Providing personnel with training to age fish was common. Reasons for the structures used and the types of inferences and information generated from age data were reported. Scales were the most common structure used to age esocids, black bass, crappie/sunfish, and moronids, but only 27% of all respondents felt that scales accurately aged fish to the maximum age. Alternatively, most agencies felt that otoliths provided accurate estimates. From a review of published papers, otoliths were more accurate when compared to other aging structures and showed higher precision. Most agencies conducted back-calculation of lengths from annuli that provided additional information on growth, even though back-calculation procedures contain complex and inconsistent interpretation and computation issues. Currently, many studies are being conducted where known-age fish were chemically or physically marked, stocked, then recaptured after a number of years which can furnish data for age validation. Recommendations include the development of a known-age reference database to allow sharing of information, publication of validation studies, and careful considerations for conducting back-calculation of lengths from presumed annuli.

Bomb radiocarbon dating calibrates beluga (Delphinapterus leucas) age estimates

The ages of many mammals are estimated by counting growth layers in tooth sections, yet validation of age estimation techniques using free-ranging mammals has been problematic. Contrary to age estimates for most other animals in which it is assumed that one bipartite growth increment forms annually, beluga whale ( Delphinapterus leucas (Pallas, 1776)) age estimates have been calculated assuming that two growth layer groups (GLGs) form each year. Here we report the age validation for belugas based on date-specific incorporation of atomic bomb radiocarbon into tooth GLGs. Radiocarbon assays of dentinal layers formed in belugas harvested between 1895 and 2001 indicated that radiocarbon from atmospheric testing of nuclear weapons was incorporated into growing teeth and retained for the remaining life of the animal. Comparison of age determined by bomb radiocarbon with age determined by GLG counts indicated that GLGs form annually, not semiannually, and provide an accurate indicator of age for belugas up to at least 60 years old. Radiocarbon signatures of belugas were temporally and metabolically stable and were apparently derived more from the radiocarbon content of their prey than from water. Our understanding of many facets of beluga population dynamics is altered by the finding that this species lives twice as long as previously thought.

Growth and age determination of African savanna elephants

AbstractUnderstanding the population dynamics of savanna elephants depends on estimating population parameters such as the age at first reproduction, calving interval and age‐specific survival rates. The generation of these parameters, however, relies on the ability to accurately determine the age of individuals, but a reliable age estimation technique for free‐ranging elephants is presently not available. Shoulder heights of elephants were measured in 10 populations in five countries across southern and eastern Africa. Data included shoulder height measurements from two populations where the age of each individual was known (i.e. Addo Elephant National Park, South Africa and Amboseli National Park, Kenya). From the known‐age data, Von Bertalanffy growth functions were constructed for both male and female elephants. Savanna elephants were found to attain similar asymptotic shoulder heights in the 10 populations, while individuals in the two known‐age populations grew at the same rate. The Von Bertalanffy growth curves allowed for the accurate age estimation of females up to 15 years of age and males up to 36 years of age. The results indicate that shoulder height can serve as an indicator of chronological age for elephants below 15 years of age for females and 36 years of age for males. Ages derived from these growth curves can then be used to generate age‐specific population variables, which will help assess the demographic status of savanna elephant populations across Africa.

How old is your fold?

At present there exists no age estimate for the different protein structures found in nature. It has become clear from occurrence studies that different folds arose at different points in evolutionary time. An estimation of the age of different folds would be a starting point for many investigations into protein structure evolution: how we arrived at the set of folds we see today. It would also be a powerful tool in protein structure classification allowing us to reassess the available hierarchical methods and perhaps suggest improvements. We have created the first relative age estimation technique for protein folds. Our method is based on constructing parsimonious scenarios, which can describe occurrence patterns in a phylogeny of species. The ages presented are shown to be robust to the different trees or data types used for their generation. They show correlations with other previously used protein age estimators, but appear to be far more discriminating than any previously suggested technique. The age estimates given are not absolutes but they already offer intriguing insights, like the very different age patterns of alpha/beta folds compared with small folds. The alpha/beta folds appear on average to be far older than their small fold counterparts. Example trees and additional material are available at http://www.stats.ox.ac.uk/~abeln/foldage http://www.stats.ox.ac.uk/~abeln/foldage.

Comparing methods for analysing mortality profiles in zooarchaeological and palaeontological samples

In this study, I examine three methods that are currently used for comparing mortality profiles from zooarchaeological and palaeontological samples: (1) histograms with 10% of life-span age classes; (2) boxplots showing tooth crown height medians; and (3) triangular plots of the proportions of young, prime and old animals. I assess the advantages and disadvantages of each method using data collected on two samples of Northern Yellowstone elk (Cervus elaphus nelsoni) with known, or cementum annuli-determined, ages at death. One sample was hunted by wolves (n = 96), and the other was hunted by recent humans using rifles (n = 226). I tested each method with the known or cementum annuli age distributions and with age estimation techniques appropriate for archaeological assemblages. Histograms are best used when the relationship between dental eruption/attrition and age is well established so that individuals can be confidently assigned into 10% of life-span groups, and when more than 30 or 40 individuals are present in the assemblage. Boxplots employ raw crown heights, thus removing the error introduced by assigning specimens to age classes, and therefore they allow the analysis of species where the relationship between dental eruption/attrition and age is unknown. Confidence intervals around the medians allow samples to be statistically compared. Triangular plots are easy to use and allow multiple samples and species to be considered simultaneously, but samples cannot be statistically compared. Modified triangular plots bootstrap samples to provide 95% confidence ellipses, allowing for statistical comparisons between samples. When possible, samples should be examined using multiple methods to increase confidence in the results. Copyright © 2005 John Wiley & Sons, Ltd.

Automated fish age estimation from otolith images using statistical learning

Abstract The acquisition of age and growth data is of key importance for fisheries research (assessment, marine ecology issues, etc.). Consequently, automating this task is of great interest. In this paper, we investigate the use of statistical learning techniques for fish age estimation. The core of this study lies in the definition of relevant image-related features. We rely on the computation of a 1D representation summing up the content of otolith images within a predefined area of interest. Features are then extracted from this non-stationary representation depicting the alternation of seasonal growth rings. Thus, fish age estimation can be viewed as a multi-class classification issue using statistical learning strategies. In particular, a procedure based on demodulation and remodulation of fish growth patterns is used to improve the generalization properties of the trained classifiers. The experimental evaluation is carried out over a dataset of 320 plaice otolith images from age groups 1–6. We analyze both, the performances of several statistical classifiers, namely SVMs (support vector machines) and neural networks, and the relevance of the proposed image-based feature sets. In addition, the combination of additional biological and shape features to the image-related ones is considered. We reach a rate of correct age estimation of 88% w.r.t. the expert ground truth. This demonstrates the relevance of the proposed approach for the automation of routine aging and for computer-assisted aging.

Non-adult dental age assessment: correspondence analysis and linear regression versus Bayesian predictions

This study focuses on the evaluation of factors influencing the quality (accuracy and reliability) of non-adult dental age assessment from radiographic stages of permanent teeth (excluding the third molar). We used four distinct cross-sectional samples of 1,528 healthy children: 3 of known geographic origin (Ivory Coast, Iran and France) and 1 additional sample of children whose grandparents originated from a different continent. Two different methods of calculations are compared: the correspondence analysis combined with linear regression (CAR) and Bayesian predictions (with no independence assumption). Our results indicate that the quality of age assessment does not seem to depend predominantly on the use of geographic-specific standards. In the case of Bayesian predictions, we observed a clear trend in favour of significantly higher accuracy and reliability levels when using non-geographic-specific standards. One of the main advantage of Bayesian predictions over maximum likelihood methods of estimation is an overall increase in accuracy with high levels of reliability on a fraction of the test sample and, importantly, across all age categories (contrary to methods based on regression analysis). Importantly, in the case of Bayesian non-adult predictions, and contrary to age estimation techniques based on regression, a better quality does not depend on age.

Age Estimation for Shovelnose Sturgeon: A Cautionary Note Based on Annulus Formation in Pectoral Fin Rays

AbstractNumerous studies have examined the age and growth of shovelnose sturgeon Scaphirhynchus platorynchus, but only one study attempted to validate age estimation techniques. Therefore, our objective was to use marginal increment analysis to validate annulus formation in pectoral fin rays of shovelnose sturgeon collected from the Missouri River. We also compared the precision of age estimates between two different readers. Marginal increment distance indicated that for most of the populations an opaque band was laid down in pectoral fin rays during the summer. However, opaque bands were formed throughout the year in some individuals, which could be problematic when using fin rays for age estimation. The agreement of age estimates by two readers for shovelnose sturgeon was only 18%, and differences in ages between the two readers increased for older fish. The presence of split annuli, false annuli, spawning bands, imbedded rays, and deteriorating sections made individual growth rings difficult to separate. Our findings verified that opaque bands are formed annually during the summer in the pectoral fin rays of most shovelnose sturgeon, but some individuals form opaque bands during other times. Pectoral fin rays will probably continue to be the most practical method of age estimation in shovelnose sturgeon, but ages estimated by this method should be used with caution.

A comparison of age estimation methods for the saiga antelope Saiga tatarica

Age estimation is particularly crucial for the conservation of the saiga antelope Saiga tatarica, but modern laboratory methods for aging have not previously been applied to this species. There is an urgent need for evaluation of the techniques that could be used for age estimation in order that long‐term ecological data sets can be correctly interpreted and conservation advice given. We evaluated the repeatability, practical feasibility and comparability of three techniques for age estimation of saiga antelopes; the tooth sectioning technique (TS), the tooth eruption and wear technique (TEW), and a visual aging technique routinely used in field studies. We found that TS and TEW gave repeatable results, and agreed well. The visual method underestimated the age of males compared to laboratory methods. It assigned animals consistently to the age class of at least one year old, but less consistently to the age class less than one year old. Although studies of known‐age animals are needed to evaluate precision and accuracy of these methods, we suggest that either TS or TEW would be suitable for aging saiga antelopes, with the choice being determined by practicalities such as the availability of the necessary expertise and equipment.

Non-destructive dental-age calculation methods in adults: intra- and inter-observer effects

The aim of the present study was to obtain data on the reliability and reproducibility of two non-destructive dental-age estimation methods in adults by calculating inter- and intra-observer effects. Both a morphological and a radiological technique available in the scientific literature were evaluated on a number of recently extracted teeth: the morphological technique was evaluated on a total of 160 teeth by two examiners, while three examiners applied the radiological technique on apical radiographs of 72 extracted teeth. Paired t-tests were used to calculate intra- and inter-observer differences. For the morphological method, both examiners were able to produce dental-age estimations that did not differ significantly from the real age of the teeth, obtaining a mean error between 0.5 and 1.8 years and a standard deviation of this error between 9.0 and 11.3 years. When using the radiological technique according to the original protocol, all three examiners produced age estimations that were statistically comparable to the real age of the teeth with a mean error of 0.5–2.5 years and a standard deviation of 4.6–9.8 years. For both techniques, intra-observer differences were observed. Based on the results of this study, it can be concluded that both non-destructive dental-age estimation techniques were able to produce reasonably accurate dental-age estimations, at least when these techniques were applied appropriately. However, the forensic odontologist is recommended to use different age estimation techniques and perform repetitive measurements in order to verify the reproducibility of the calculations performed.

Do enamel microstructures have regular time dependency? Conclusions from the literature and a large-scale study.

This paper is structured in two parts. The first briefly reviews a number of lines of published evidence, including direct experimental evidence, supporting the contention that enamel microstructures are time dependent and have a regular periodicity. The second presents the results of a large-scale study designed to test a central assumption underlying most histological ageing approaches in enamel: that the number of cross striations between adjacent striae of Retzius, called the circaseptan interval, are uniform within a tooth and between all teeth in the dentition of an individual. The study uses a sample of 158 anterior teeth from three modern human populations. Teeth were sectioned and circaseptan intervals were determined by dividing measurements of the distance between adjacent striae of Retzius, by cross-striation length. In order to exercise as much procedural rigour as possible, all measurements were made from photomicrographs. Two sections were taken from each tooth, the sampling location within each tooth was recorded, and all populations included multiple teeth from single individuals. Results statistically validate the uniformity hypothesis within the anterior dentition. These, together with the weight of published evidence, suggest that data derived from the use of enamel microstructures in age estimation techniques and growth and development studies, are valid.

Estimation of Age for Trachemys scripta and Deirochelys reticularia by Counting Annual Growth Layers in Claws

The need for accurate methods of age determination in life-history studies is well recognized. Techniques used to estimate the age of turtles include analysis of body size (Balazs, 1982; Frazer and Ehrhart, 1985; Frazer and Ladner, 1986), weighing eye lenses (. Frazier,J. Ballon, and S. Salas, unpubl.), counting growth zones on plastral scutes (Cagle, 1946; Sexton, 1959; Gibbons, 1983), and skeletochronology (Mattox, 1935; Zug, 1990; Klinger and Musick, 1992). Each technique has its disadvantages, and finding a technique that is accurate and can be applied objectively has been difficult (Zug, 1991). An ideal age estimation technique would not cause stress or mortality to the individual being aged, would be valid for all age/size classes, would be based on a clearly recognizable structure that is permanent throughout the life of the individual, and would not require subjective judgment. The use of claws could potentially satisfy three of these requirements for turtle age estimation. Zug (1991) suggested that because claws grow continuously throughout the life of a turtle and because growth is affected by environmental factors, the formation of seasonal growth layers might be expected. The objective of our study was to determine whether annual layers could be observed in sections of claws from Trachemys scripta and Deirochelys reticularia and whether counts based on such layering could provide reliable data for age estimation.

The Role of Forensic Anthropology in the Recovery and Analysis of Branch Davidian Compound Victims: Assessing the Accuracy of Age Estimations

Age-at-death estimations of 44 individuals (27 adults, 17 children) from the Branch Davidian sample were compared with their actual ages. Estimations were evaluated for bias and accuracy for the actual age at death. Although the overall average estimates correlated well with the actual ages (r = 0.946), several individuals displayed high residual requiring further analysis and review. These individuals displayed age-related features that did not correspond with the expected morphology for individuals of their ages. Several age estimation techniques scored these individuals with all bias in the same direction. These examples should serve as cautionary reminders that biology does not always correlate with expected outcomes, particularly in such multifaceted traits such as age.

The Morphological Basis of Fish Age Estimation Methods Based on the Otolith of Nemadactylus macropterus

Relationships between the anatomy of the endolymphatic sac, sac otoconia, sagitta and astericus of Nemadactylus macropterus (Cheilodactylidae: Teleostei) are described and the variation in opaque and hyaline zones, sulcal checks, and daily microincrement widths along different growth axes of the otolith measured. The quantitative morphology of the otolith is used to compare the different age estimation techniques for N. macropterus that are based on opaque and hyaline zones, sulcal checks, and daily microincrements. Comparison of the different methods shows that at the present state of knowledge daily microincrements present the most credible age estimation method for N. macropterus.

Cranial suture closure and its implications for age estimation

AbstractThree age estimation techniques using ectocranial and/or endocranial suture closure are tested on a sample of known age from Spitalfields, London in order to determine the value of cranial suture closure as an indicator of age at death. The three techniques are those proposed by Acsádi and Nemeskéri, Meindl and Lovejoy and Perizonius. Results indicate that the Acsádi and Nemeskéri technique, which is based on endocranial sutures, can be used to distinguish young and middle‐aged individuals in the Spitalfields sample but gives no information for crania over the age of 50 years. Age estimation using the Meindl and Lovejoy and Perizonius (Old system) techniques, which use ectocranial sutures, was found to be subject to a number of complicating factors, of which sexual dimorphism in the rate and pattern of closure is the most significant. A method of estimating age at death based on both endocranial and ectocranial suture closure is developed on the basis of the Spitalfields sample. The technique attempts to overcome some of the problems associated with both intra‐ and interpopulation variation in cranial suture closure. For a truly accurate age‐estimation technique based on cranial suture closure we would need to know more about the causes and functions of suture closure in human populations.

Reply to comment by J.-Ch. Fontes and J.N. Andrews on “The 36Cl ages of the brines in the Magadi-Natron basin, East Africa”

This article is a response to a criticism of the authors previous work on estimating the age of brines using chlorine-36. They defend critical points related to fallout rates, water sources of chlorine-36, age estimation techniques, and chemical mass balances for runoff, brine formation, etc. 13 refs., 2 figs., 1 tab.