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

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

Accuracy of the Aspartic Acid Racemization Technique in Age Estimation of Mammals and the Influence of Body Temperature

The aspartic acid racemization (AAR) technique has been applied for age estimation of humans and other mammals for more than four decades. In this study, eye lenses from 124 animals representing 25 mammalian species were collected and D/L ratios obtained using the AAR technique. The animals were either of known age or had the age estimated by other methods. The purpose of the study was to: a) estimate the accuracy of the AAR technique, and b) examine the effect of body temperature on racemization rates. Samples from four of the 25 species covered the range of ages that is needed to estimate species-specific racemization rates. The sample size from a single species of known age, the pygmy goat (Capra hircus, n = 35), was also large enough to investigate the accuracy of ages obtained using the AAR technique. The 35 goats were divided into three datasets: all goats (n = 35), goats >0.5 yrs old (n = 26) and goats >2 yrs old (n = 19). Leave-one-out analyses were performed on the three sets of data. Normalized root mean squared errors for the group of goats >0.5 yrs old were found to be the smallest. The higher variation in D/L measurements found for young goats 0.5 yrs old was for three age groups of the goats: 0.934 yrs for young goats 8 yrs (n = 4). Thus, the age of an adult or an old animal can be predicted with approximately 10% accuracy, whereas the age of a young animal is difficult to predict. A goat specific racemization rate, as a 2kAsp value, was estimated to 0.0107 ± 3.8 x 10-4 SE (n = 26). The 2kAsp values from 12 species, four estimated in this study and another eight published, were used to examine the effect of core body temperature on the rate of racemization. A positive relationship between AAR and temperature was found (r2 = 0.321) but results also suggest that other factors besides temperature are involved in the racemization process in living animals. Based on our results we emphasize that non-species-specific racemization rates should be used with care in AAR age estimation studies and that the period of postnatal growth of the eye lens be considered when estimating species-specific D/L0 values and ages of young individuals

Abundance of whales in West and East Greenland in summer 2015

An aerial line transect survey of whales in West and East Greenland was conducted in August-September 2015. The survey covered the area between the coast of West Greenland and offshore (up to 100 km) to the shelf break. In East Greenland, the survey lines covered the area from the coast up to 50 km offshore crossing the shelf break. A total of 423 sightings of 12 cetacean species were obtained and abundance estimates were developed for common minke whale, (Balaenoptera acutorostrata) (32 sightings), fin whale (Balaenoptera physalus) (129 sightings), humpback whale (Megaptera novaeangliae) (84 sightings), harbour porpoise (Phocoena phocoena) (55 sightings), long-finned pilot whale, (Globicephala melas) (42 sightings) and white-beaked dolphin (Lagenorhynchus albirostri) (50 sightings). The developed at-surface abundance estimates were corrected for both perception bias and availability bias if possible. Data on surface corrections for minke whales and harbour porpoises were collected from whales instrumented with satellite-linked time-depth-recorders. Options for estimation methods are presented and the preferred estimates are: minke whales: 5,095 (95% CI: 2,171-11,961) in West Greenland and 2,762 (95% CI: 1,160-6,574) in East Greenland, fin whales: 2,215 (95% CI: 1,017-4,823) in West Greenland and 6,440 (95% CI: 3,901-10,632) in East Greenland, humpback whales: 993 (95% CI: 434-2,272) in West Greenland and 4,223 (95% CI: 1,845-9,666) in East Greenland, harbour porpoises: 83,321 (95% CI: 43,377-160,047) in West Greenland and 1,642 (95% CI: 319-8,464) in East Greenland, pilot whales: 9,190 (95% CI: 3,635-23,234) in West Greenland and 258 (95% CI: 50-1,354) in East Greenland, white-beaked dolphins 15,261 (95% CI: 7,048-33,046) in West Greenland and 11,889 (95% CI: 4,710-30,008) in East Greenland. The abundance of cetaceans in coastal areas of East Greenland has not been estimated before, but the limited historical information from the area indicates that the achieved abundance estimates were remarkably high. When comparing the abundance estimates from 2015 in West Greenland with a similar survey conducted in 2007, there is a clear trend towards lower densities in 2015 for the three baleen whale species and white-beaked dolphins. Harbour porpoises and pilot whales, however, did not show a similar decline. The decline in baleen whale and white-beaked dolphin abundance is likely due to emigration to the East Greenland shelf areas where recent climate driven changes in pelagic productivity may have accelerated favourable conditions for these species

Abundance of walruses in Eastern Baffin Bay and Davis Strait

Walruses (Odobenus rosmarus) are exploited for subsistence purposes in West Greenland. However, current information about the abundance of walruses subject to harvest in eastern Baffin Bay subject to harvest has been unavailable despite being critical for maintaining sustainable catch levels. Three visual aerial surveys were conducted in 2006 (21 March to 19 April 2006), 2008 (3 to 12 April) and 2012 (24 March to 14 April) to estimate the number of walruses on the wintering grounds in eastern Baffin Bay and Davis Strait. Data on the fraction of walruses that were submerged below a 2m detection threshold during the surveys were obtained from 24 walruses instrumented with satellite-linked-time-depth-recorders in northern Baffin Bay in May-June 2010-2012. An availability correction factor was estimated at 36.5% (cv=0.08) after filtering of data for an observed drift of the pressure transducer of more than 2.5 m. The surveys resulted in walrus abundance estimates that were corrected for walruses submerged below a detection threshold and for walruses that were missed by the observers. The estimates of abundance were 1,105 (cv=0.31, 95% CI 610-2,002) in 2006, 1,137 (0.48, 468-2,758) in 2008 and 1,408 (0.22, 922-2,150) in 2012

Walrus Movements in Smith Sound: A Canada–Greenland Shared Stock + Supplementary Appendix 1 (See Article Tools)

Fifty of 58 walruses (Odobenus rosmarus rosmarus) instrumented with satellite-linked transmitters in four areas in eastern Smith Sound, Northwest Greenland, during May and June of 2010 – 13 and 2015 provided data for this study. These animals departed from the feeding banks along the Greenland coast in June – July (average 14th June), simultaneously with the disappearance of sea ice from these areas. Most of them moved to Canadian waters in western Smith Sound. The most frequently used summering grounds were along the coasts of Ellesmere Island: on the eastern coast, the area around Alexandra Fiord, Buchanan Bay, and Flagler Bay (west of Kane Basin) and Talbot Inlet farther south, and on the southern coast, Craig Harbour. This distribution of tagged walruses is consistent with prior understanding of walrus movements in summer. In addition, however, nine tracks of these tagged animals entered western Jones Sound and four entered the Penny Strait-Lancaster Sound area, crossing two putative stock boundaries. Since these 13 tracks were made by 12 animals, one walrus entered both areas. It is possible that some of the tracked walruses used terrestrial haul-out sites in the largely ice-free areas of Jones Sound and Lancaster Sound for short periods during the summer, though this cannot be confirmed with certainty. The return migration from western Smith Sound to the wintering area in eastern Smith Sound takes place in October. The tracked walrus showed high affinity to coastal areas, while walruses moving between Greenland and Canada also used offshore areas in Smith Sound. This study demonstrates that the walrus population that winters along the northwestern coast of Greenland is shared more widely in Canada than previously thought and should be managed accordingly.En mai et juin 2010 à 2013 et 2015, 50 des 58 morses (Odobenus rosmarus rosmarus) munis d’émetteurs liés à des satellites dans quatre régions à l’est du détroit de Smith, au nord-ouest du Groenland, ont permis de recueillir des données pour cette étude. Ces animaux ont quitté les aires d’alimentation le long de la côte du Groenland aux mois de juin et juillet (en moyenne le 14 juin), au même moment que la disparition de la glace marine de ces régions. La plupart des animaux se sont déplacés vers les eaux canadiennes dans l’ouest du détroit de Smith. Les aires d’été les plus souvent utilisées étaient celles situées le long des côtes de l’île d’Ellesmere : sur la côte est, la région autour du fjord Alexandra, la baie Buchanan et la baie Flagler (à l’ouest du bassin Kane) et le passage Talbot plus au sud, et sur le littoral sud du village Craig Harbour. Cette distribution des morses munis d’émetteurs correspond aux déplacements de morses déjà constatés en été. Toutefois, neuf signaux provenant d’animaux munis d’émetteurs sont entrés dans la partie ouest du détroit de Jones et quatre sont entrés par les détroits de Penny et de Lancaster, traversant les limites de deux aires de stocks présumés. Puisque ces 13 signaux ont été émis par 12 animaux, un morse est entré dans les deux régions. Il se peut que certains des morses suivis aient emprunté la portion terrestre qui entoure les échoueries dans les régions en grande partie dépourvues de glace des détroits de Jones et de Lancaster pendant de courtes périodes durant l’été, mais il est impossible de le confirmer avec certitude. La migration de retour de l’ouest du détroit de Smith vers l’aire d’hivernage dans l’est du détroit de Smith a lieu en octobre. Les morses suivis ont montré une grande affinité pour les zones côtières, tandis que les morses qui se déplaçaient entre le Groenland et le Canada empruntaient également les zones extracôtières du détroit de Smith. Cette étude démontre que la population de morses qui hiverne le long de la côte nord-ouest du Groenland est plus importante au Canada qu’on ne le pensait auparavant et devrait être gérée en conséquence