A comparison of age determination techniques for the harbour porpoise, Phocoena phocoena L.

1989 ◽  
Vol 67 (7) ◽  
pp. 1832-1836 ◽  
Author(s):  
Peter Watts ◽  
David E. Gaskin
Keyword(s):  
North Atlantic ◽  
Age Determination ◽  
Harbour Porpoise ◽  
Phocoena Phocoena ◽  
Growth Layer ◽  
Single Cross Section ◽  
Living Bone ◽  
Layer Groups ◽  
Annual Deposition ◽  
Age Estimates

The maximum life-span of the harbour porpoise has been estimated at 13 years (based upon dentinal growth layer groups in the teeth) and at 21 years (based upon growth layers in the periosteal bone of the mandible). We used both techniques to estimate the ages of 120 harbour porpoises from the western North Atlantic, in an attempt to determine the relative reliability of each technique. Dentinal layering was the better predictor of body length. Mandibular layering was highly variable even within a single cross section in most specimens, as a result of both common bifurcation of the layers and destruction of the inner layers by growth and remodelling of the living bone. Furthermore, mandibular layers appear to be deposited at a rate of 2 layers/year, double the deposition rate of dentinal growth layer groups. Age estimates which assume annual deposition of mandibular layers therefore overestimate true age.

scholarly journals Two techniques of age estimation in cetaceans: GLGs in teeth and earplugs, and measuring the AAR rate in eye lens nucleus

2017 ◽  
Vol 10 ◽  
Author(s):  
Nynne H Nielsen ◽  
Gísli A. Víkingsson ◽  
Steen H. Hansen ◽  
Susanne Ditlevsen ◽  
Mads Peter Heide-Jørgensen
Keyword(s):  
Aspartic Acid ◽  
North Atlantic ◽  
Von Bertalanffy ◽  
Phocoena Phocoena ◽  
Growth Layer ◽  
Balaenoptera Acutorostrata ◽  
Aspartic Acid Racemization ◽  
Minke Whales ◽  
Fin Whales ◽  
Layer Groups

The ages of three species of cetaceans were estimated by counting the growth layer groups (GLG) and measuring the aspartic acid racemization rate (kAsp) by what is referred to as the Aspartic Acid Racemization (AAR) technique. Data on kAsp and the D/L ratio of aspartic acid at birth [(D/L)0] in North Atlantic common minke whales (Balaenoptera acutorostrata) are presented along with data on fin whales (B. physalus) and harbour porpoises (Phocoena phocoena) already published by Nielsen et al. (2012). The kAsp specific for minke whales was 1.40 x 10-3 yr-1 (SE ± 0.00005) and the (D/L)0 was 0.0194 (SE ± 0.0012). The correlation of GLG age and D/L ratio for all three species was highly significant; however, the correlation coefficient varied greatly (fin whales: R2 = 0.59, p <0.0001; minke whales: ­R2=0.96, P <0.0001; harbour porpoises: ­R2=0.36, P <0.0001). Asymptotic body length for all three species was estimated by a von Bertalanffy growth model on both the GLG and AAR techniques, and showed no difference.

Données préliminaires sur la présence de lignes d'arrêt de croissance périostiques dans la mandibule du marsouin commun, Phocoena phocoena (L.), et leur utilisation comme indicateur de l'âge

1982 ◽  
Vol 60 (11) ◽  
pp. 2557-2567 ◽  
Author(s):  
V. de Buffrenil
Keyword(s):  
Bone Growth ◽  
Harbour Porpoise ◽  
Phocoena Phocoena ◽  
Growth Layer ◽  
Thin Sections ◽  
Hematoxylin Staining ◽  
Layer Groups ◽  
Age Determinations

Sharply defined growth lines are revealed by hematoxylin staining of thin sections of mandibular periosteal bone of the harbour porpoise, Phocoena phocoena (L.). The comparison of these lines to dentinal growth layer groups (GLG) suggests that they are deposited at the rate of one per annum. In this species, bone growth lines allow more reliable and much more complete age determinations than do dentinal GLG's. The actual longevity of the harbour porpoise, as determined by growth lines in bone, is at least 21 years.

scholarly journals The biology behind the counts: tooth development related to age estimation in beluga (Delphinapterus leucas)

2014 ◽  
Vol 8 ◽  
Author(s):  
Barbara E Stewart ◽  
Robert EA Stewart
Keyword(s):  
Tooth Development ◽  
Delphinapterus Leucas ◽  
Key Factors ◽  
Growth Layer ◽  
Diagnostic Features ◽  
Developmental Factors ◽  
Occlusal Wear ◽  
Layer Groups ◽  
Pulp Stones ◽  
Age Estimates

The widely accepted method of determining ages of beluga is to count dentine growth layer groups (GLGs) in median, longitudinal sections of a tooth. It is essential to understand how these growth layers form and to consider developmental factors that can confound their enumeration to be able to provide meaningful age estimates. Here we provide information on, and illustrate, the developmental biology of beluga teeth as it relates to interpreting GLGs. Key factors are: evaluating the presence and occlusal wear of fetal dentine; interpreting early-formed diagnostic features such as the neonatal line; assessing the last-formed growth layer adjacent to the pulp cavity; identifying the presence of nodes at the dentine-cementum interface to assist in counting GLGs; and recognizing  pulp stones and accessory lines in the dentine which may hinder the age estimate process.

scholarly journals Accuracy, precision, and error in age estimation of Florida manatees using growth layer groups in earbones

2019 ◽  
Vol 100 (4) ◽  
pp. 1350-1363 ◽  
Author(s):  
Gina L Lonati ◽  
Amber R Howell ◽  
Jeffrey A Hostetler ◽  
Paul Schueller ◽  
Martine de Wit ◽  
...  
Keyword(s):  
Age Estimation ◽  
Wildlife Conservation ◽  
Absolute Error ◽  
Large Sample Size ◽  
Growth Layer ◽  
Florida Manatee ◽  
Data Set ◽  
Photo Identification ◽  
Layer Groups ◽  
Age Estimates

AbstractAges of Florida manatees (Trichechus manatus latirostris) can be estimated by counting annual growth layer groups (GLGs) in the periotic dome portion of the tympanoperiotic complex of their earbones. The Florida Fish and Wildlife Conservation Commission manages an archive of more than 8,700 Florida manatee earbones collected from salvaged carcasses from 1989 to 2017. Our goal was to comprehensively evaluate techniques used to estimate age, given this large sample size and changes to processing protocols and earbone readers over time. We developed new standards for estimating ages from earbones, involving two independent readers to obtain measurements of within- and between-reader precision. To quantify accuracy, precision, and error, 111 earbones from manatees with approximately known ages (first known as calves: “KAC”) and 69 earbones from manatees with minimum known ages (“MKA,” based on photo-identification sighting histories) were processed, and their ages were estimated. There was greater precision within readers (coefficient of variation, CV: 2.4–8.5%) than between readers (CV: 13.1–13.3%). The median of age estimates fell within the true age range for 63.1% of KAC cases and was at least the sighting duration for 75.0% of MKA cases. Age estimates were generally unbiased, as indicated by an average raw error ± SD of −0.05 ± 3.05 years for the KAC group. The absolute error (i.e., absolute value of raw error) of the KAC data set averaged 1.75 ± 2.50 years. Accuracy decreased and error increased with increasing known age, especially for animals over 15 years old, whose ages were mostly underestimated due to increasing levels of resorption (the process of bone turnover that obscures GLGs). Understanding the degree of uncertainty in age estimates will help us assess the utility of age data in manatee population models. We emphasize the importance of standardizing and routinely reviewing age estimation and processing protocols to ensure that age data remain consistent and reliable.

Rencular morphology and renal vascular system of the harbour porpoise Phocoena phocoena (L.)

1979 ◽  
Vol 57 (4) ◽  
pp. 868-875 ◽  
Author(s):  
N. A. Hedges ◽  
D. E. Gaskin ◽  
G. J. D. Smith
Keyword(s):  
Body Weight ◽  
North Atlantic ◽  
Vascular System ◽  
Vascular Supply ◽  
Harbour Porpoise ◽  
Phocoena Phocoena ◽  
Parasympathetic Nerves ◽  
Injection Techniques ◽  
Renal Vascular

The kidneys of 35 harbour porpoises, Phocoena phocoena (L.), from the western North Atlantic were studied. Kidneys are large (0.84% of body weight) and multirenculate (approximately 300 renculi per kidney). Renculi have well developed medullary papillae (71–80% of rencular thickness) which correlates well with an ability to produce concentrated urine. Zonation of the vascular system within the medulla is also present, another characteristic of mammals producing concentrated urine.The intrarencular vascular supply is typically mammalian and similar to other cetaceans. As a result of excellent injection techniques, we found greater complexity and variability in the vascular system in our specimens than has been previously reported.Vascular control is discussed in relation to diving bradycardia. Parasympathetic nerves may stimulate vasodilation to quickly restore rencular circulation at the end of a dive.

scholarly journals Accuracy and precision of age determination using growth layer groups for California sea lions ( Zalophus californianus ) with known ages

2019 ◽  
Vol 35 (4) ◽  
pp. 1355-1368 ◽  
Author(s):  
Lauren B. Rust ◽  
Kerri Danil ◽  
Sharon R. Melin ◽  
Brent Wilkerson
Keyword(s):  
Age Determination ◽  
Zalophus Californianus ◽  
Growth Layer ◽  
California Sea Lions ◽  
Sea Lions ◽  
Accuracy And Precision ◽  
Layer Groups

Age determination of harbour porpoise, Phocoena phocoena (L.), in the western North Atlantic

1977 ◽  
Vol 55 (1) ◽  
pp. 18-30 ◽  
Author(s):  
D. E. Gaskin ◽  
B. A. Blair
Keyword(s):  
North Atlantic ◽  
Age Determination ◽  
Simple Relationship ◽  
Phocoena Phocoena ◽  
Progressive Reduction ◽  
Opaque Zone ◽  
Translucent Zone ◽  
Males And Females ◽  
Calving Season

Age, based on analysis of dentinal growth layers, was determined in a sample of 121 harbour porpoises, Phocoena phocoena (L.), from western North Atlantic waters. One growth layer, consisting of a thick opaque zone and a relatively thin translucent zone, is deposited each year.Mean thicknesses of opaque and translucent zones in males and females were 347 μm, 114 μm, 432 μm, and 125 μm, respectively. Significant reduction in thicknesses of growth layers with age was found in both sexes, the major contribution in both cases being progressive reduction in thickness of the opaque zones. Translucent-zone thickness decreased with age in males, but significantly increased in thickness in females. Formation of the opaque zone occurs from June through February, and formation of the translucent zone from January to early September. This overlap is attributed to the protracted calving season of this population, and precludes any simple relationship between food supply and zonation, as proposed by others. Age–length relationships based on numbers of dentinal layers were calculated for males and females using regression analysis. Best fits of body length (b) against age (expressed by completed dentinal layers) (d) were obtained from the curvilinear equations: d = [b/(−1.30b + 209.35)] −1 for males, and d = [b/(−0.84b + 156.15)] −1 for females.

Variability of Dentin Deposits in Tursiops truncatus

1980 ◽  
Vol 37 (4) ◽  
pp. 712-716 ◽  
Author(s):  
Clifford A. Hui
Keyword(s):  
Tursiops Truncatus ◽  
Age Determination ◽  
Growth Layer ◽  
Posterior Teeth ◽  
Annual Cycles ◽  
Left And Right ◽  
Layer Groups

Dentin is deposited in approximately annual cycles in Tursiops truncatus for at least the first 11 yr. There were no consistent differences in the dentinal layer count between the left and right sides nor between the mandible and maxilla in the teeth of nine animals studied. The posterior teeth, however, have a greater number of growth layer groups (GLGs). The differences in the number of GLGs among teeth of the same individual increase unpredictably when there are more than about 15 GLGs in the posterior teeth. Only minimal age may be determined using dentinal counts.Key words: age determination, dentin, dolphins, odontocetes, teeth, Tursiops

scholarly journals A note on the age at sexual maturity of humpback whales

2020 ◽  
pp. 71-73
Author(s):  
Peter B. Best
Keyword(s):  
Sexual Maturity ◽  
Gulf Of Maine ◽  
Accumulation Rate ◽  
Age Determination ◽  
Biological Data ◽  
Humpback Whales ◽  
Natural Mortality ◽  
Growth Layer ◽  
Younger Age ◽  
Layer Groups

The conclusion of researchers in the 1950s that humpback whales reached sexual maturity at about age five was largely influenced by their interpretation of baleen tracings, and to achieve consistency with these tracings the accumulation rate of ear plug laminations (growth layer groups: GLGs) was assumed to be two per year. However, ovulation and natural mortality rates calculated by these researchers under the same assumption produced estimates that are difficult to reconcile with other biological data or with more recent estimates using individual re-sighting data. Such disparities are reduced or disappear when an annual accumulation rate is used, in which case their ear plug data would have indicated a mean age at sexual maturity of 9–11 years. Recent estimates of the age of female humpback whales at first calving using longitudinal studies of photoidentified individuals have produced conflicting results, some (from southeastern Alaska) being compatible with the earlier age-determination studies, others (from the Gulf of Maine) suggesting a much younger age.

scholarly journals Harbour porpoise (Phocoena phocoena) in the North Atlantic: Abundance, removals, and sustainability of removals

2003 ◽  
Vol 5 ◽  
pp. 271 ◽  
Author(s):  
G B Stenson
Keyword(s):  
North Atlantic ◽  
Harbour Porpoise ◽  
Phocoena Phocoena ◽  
The North ◽  
Number Of Factors ◽  
The Status ◽  
Substantial Progress ◽  
Potential Population ◽  
The North Atlantic ◽  
The Impact

The status of harbour porpoise (Phocoena phocoena) populations in the North Atlantic has raised numerous concerns. Although a number of factors that may be adversely affecting harbour porpoise populations have been identified, focus has been on the impact of removals, primarily due to incidental catches in fishing gear. As a result, considerable efforts have been made to determine the levels and/or impact of bycatch in a number of areas. Unfortunately, many areas remain little studied. Currently, harbour porpoise are listed as threatened or vulnerable in many parts of their range. In order to determine if the current levels of removals are sustainable, information on stock identity and seasonal movements, population parameters, abundance, and the magnitude of removals is required. Although substantial progress has been made to improve our knowledge of these parameters in the last decade, significant gaps still exist. After reviewing the available data for each sub-population in the North Atlantic, it is clear that the information required to assess the status of harbour porpoise populations is still not available for most areas. Attempts have been made to assess the status of harbour porpoise based on trends in sightings or, in areas where information on abundance and bycatch are available, on models using arbitrary criteria and/or theoretical estimates of potential population growth. Detailed case-specific population models have been proposed but are not yet available.

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