Aging steller sea lions by growth layer groups in teeth

2019 ◽  
Vol 43 (2) ◽  
pp. 238-243
Author(s):  
Takeomi Isono ◽  
Yumi Kobayashi ◽  
Vladimir N. Burkanov ◽  
Orio Yamamura
Keyword(s):  
Growth Layer ◽  
Steller Sea Lions ◽  
Sea Lions ◽  
Layer Groups

Ageing live New Zealand sea lions (Phocarctos hookeri) using the first post-canine tooth

2004 ◽  
Vol 31 (2) ◽  
pp. 177 ◽  
Author(s):  
S. Childerhouse ◽  
G. Dickie ◽  
G. Hessel
Keyword(s):  
New Zealand ◽  
Age Estimation ◽  
Growth Layer ◽  
Canine Tooth ◽  
Sea Lions ◽  
Glass Slides ◽  
Significant Difference ◽  
Layer Groups ◽  
Phocarctos Hookeri ◽  
Age Estimates

Live New Zealand sea lions (Phocarctos hookeri) were aged from growth layer groups (GLGs) in the cementum of a lower first post-canine tooth. A single post-canine (PC1) was removed from individuals of known-age (n = 74) between 1997 and 2001 while under a full anaesthetic. Teeth were decalcified, sectioned on a cryostat, stained and then mounted on glass slides. Age was estimated by counting GLGs in the cementum multiple times. Age estimates were calibrated with known-aged individuals and confirmed the annual formation of cementum annuli in PC1 tooth. While there is some variation in assigning exact age to individuals, it was possible to age 94% of teeth to the exact year or to within 1 year of actual age. There was no significant difference in the slope of regression lines associated with actual and estimated age using this technique (t-test, t = 0.309, d.f. = 144, P < 0.05). Accuracy in ageing was improved by discarding sets of readings with low precision and re-reading the tooth until a precise set of estimates was made. GLGs in the cementum were more accurate and robust for age estimation than using GLGs in the dentine. This paper describes a reliable method for the preparation and ageing of the first post-canine tooth (PC1) from live New Zealand sea lions.

Diet composition of Steller sea lions (Eumetopias jubatus) in Frederick Sound, southeast Alaska: a comparison of quantification methods using scats to describe temporal and spatial variabilities

2015 ◽  
Vol 93 (5) ◽  
pp. 361-376 ◽  
Author(s):  
D.J. Tollit ◽  
M.A. Wong ◽  
A.W. Trites
Keyword(s):  
Pacific Salmon ◽  
Biomass Energy ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Southeast Alaska ◽  
Merluccius Productus ◽  
Sea Lions ◽  
Sampling Protocols ◽  
Dietary Indices

We compared eight dietary indices used to describe the diet of Steller sea lions (Eumetopias jubatus (Schreber, 1776)) from 2001 to 2004 in Frederick Sound, southeast Alaska. Remains (n = 9666 items) from 59+ species categories were identified from 1684 fecal samples (scats) from 14 collection periods. The most frequently occurring prey were walleye pollock (Theragra chalcogramma (Pallas, 1814) = Gadus chalcogrammus Pallas, 1814; 95%), Pacific herring (Clupea pallasii Valenciennes in Cuvier and Valenciennes, 1847; 30%), Pacific hake (Merluccius productus (Ayres, 1855); 29%), and arrowtooth flounder (Atheresthes stomias (Jordan and Gilbert, 1880) = Reinhardtius stomias (Jordan and Gilbert, 1880); 21%). These species, along with Pacific salmon (genus Oncorhynchus Suckley, 1861) and skate (genus Raja L., 1758), accounted for 80%–90% of the reconstructed biomass and energy contribution, with pollock contributing 37%–60%. Overall, 80% of fish were 14–42 cm long and mainly pelagic, though 40% of scats contained benthic-associated prey. Steller sea lions switched from adult pollock to strong cohorts of juvenile pollock, and took advantage of spawning concentrations of salmon in autumn and herring in late spring and summer, as well as a climate-driven increase in hake availability. Observed temporal and site differences in diet confirm the need for robust long-term scat sampling protocols. All major indices similarly tracked key temporal changes, despite differences in occurrence and biomass-energy-based diet estimates linked to prey size and energy-density effects and the application of correction factors.

Maternal attendance patterns of Steller sea lions (Eumetopias jubatus) from stable and declining populations in Alaska

2003 ◽  
Vol 81 (2) ◽  
pp. 340-348 ◽  
Author(s):  
Linda L Milette ◽  
Andrew W Trites
Keyword(s):  
Prey Availability ◽  
A Priori ◽  
Population Decline ◽  
Perinatal Period ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Sea Lions ◽  
First Feeding ◽  
Attendance Patterns ◽  
The Mean

Maternal attendance patterns of Alaskan Steller sea lions (Eumetopias jubatus) were compared during the summer breeding seasons in 1994 and 1995 at Sugarloaf Island (a declining population) and Lowrie Island (a stable population). Our goal was to determine whether there were differences in maternal attendance between the two populations that were consistent with the hypothesis that lactating Steller sea lions in the area of decline were food-limited during summer. Our a priori expectations were based on well-documented behavioural responses of otariids to reduced prey availability. We found that foraging trips were significantly shorter in the area of population decline, counter to initial predictions. The mean length of foraging trips in the declining area was 19.5 h compared with 24.9 h in the stable area. In contrast, the mean perinatal period (time between parturition and first feeding trip) was significantly longer in the area of decline (9.9 versus 7.9 days), again countering initial predictions. The mean length of shore visits for the declining population was also significantly longer (27.0 h compared with 22.6 h where the population was stable). For both populations, the mean time that mothers foraged increased as pups grew older, whereas the time that they spent on shore with their pups became shorter. Behavioural observations of maternal attendance patterns are inconsistent with the hypothesis that lactating Steller sea lions from the declining population had difficulty obtaining prey during summer.

High diving metabolism results in a short aerobic dive limit for Steller sea lions (Eumetopias jubatus)

2013 ◽  
Vol 183 (5) ◽  
pp. 699-708 ◽  
Author(s):  
Carling D. Gerlinsky ◽  
David A. S. Rosen ◽  
Andrew W. Trites
Keyword(s):  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Sea Lions ◽  
Aerobic Dive Limit

Abundance Estimates of Steller Sea Lions (Eumetopias jubatus) Off the Western Coast of Hokkaido, Japan

Mammal Study ◽  
2021 ◽  
Vol 46 (1) ◽  
Author(s):  
Kaoru Hattori ◽  
Toshihide Kitakado ◽  
Takeomi Isono ◽  
Orio Yamamura
Keyword(s):  
Western Coast ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Sea Lions ◽  
Abundance Estimates
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