Application of a novel method for age estimation of a baleen whale and a porpoise. Issue 2 (21st August 2012)

• Record Type: Journal Article
• Authors: Nielsen, Nynne H.; Garde, Eva; Heide‐Jørgensen, Mads Peter; Lockyer, Christina H.; Ditlevsen, Susanne; Òlafsdóttir, Droplaug; Hansen, Steen H.
• Is Part Of: Marine mammal science. Volume 29:Issue 2(2013)
• Page Start: E1
• Page End: E23
• Publication Date: 2012-08-21
• Subjects: Marine mammals -- Congresses; Marine mammals -- Periodicals; Marine mammals, Fossil -- Periodicals; Mammifères marins -- Périodiques; 599.5
• DOI: 10.1111/j.1748-7692.2012.00588.x
• Languages: English
• ISSNs: 0824-0469

Abstract

<abstract abstract-type="main" id="mms588-abs-0001"> <title>Abstract</title> <p>Eyeballs from 121 fin whales (<italic>Balaenoptera physalus</italic>) and 83 harbor porpoises (<italic>Phocoena phocoena</italic>) were used for age estimation using the aspartic acid racemization (AAR) technique. The racemization rate (<italic>k</italic><sub>A</sub><sub>sp</sub>) for fin whales was established from 15 fetuses (age 0) and 15 adult whales where age was estimated by reading growth layer groups (GLGs) in the earplugs. The (<italic>k</italic><sub>A</sub><sub>sp</sub>) for harbor porpoises was derived from 15 porpoises (two calves and 13 > 1 yr old) age‐estimated by counting GLGs in the teeth and two calves classified to age based on length. The (<italic>k</italic><sub>A</sub><sub>sp</sub>) values were estimated by regression of GLGs against D/L ratios. For the fin whales an (<italic>k</italic><sub>A</sub><sub>sp</sub>) of 1.15 × 10<sup>−3</sup>/yr (SE ± 0.00005) and a D/L ratio at birth [(D/L)<sub>0</sub>] of 0.028 (SE ± 0.0012) were estimated, which is in agreement with rates for other mysticeti. For the harbor porpoises a (<italic>k</italic><sub>A</sub><sub>sp</sub>) of 3.10 × 10<sup>−3</sup>/yr (SE ± 0.0004) and a (D/L)<sub>0</sub> value of 0.023 (SE ± 0.0018) were estimated, which is considerably higher than found for other cetaceans. Correlation between chosen age estimates from AAR and GLG counts indicated that AAR might be an alternative method for estimating age in marine mammals.</p> </abstract>