COUNTS OF GROWTH LAYER GROUPS IN CEMENTUM AND DENTINE IN RINGED SEALS (PHOCA HISPIDA)

Stewart, Robert E.; Stewart, Barbara E.; Stirling, Ian; Street, Elaine

doi:10.1111/j.1748-7692.1996.tb00591.x

Cited by 111 publications

(85 citation statements)

References 21 publications

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“…For seals over 10 years of age, a statistically signficant correlation has been reported for ages obtained using the two methods (Stewart et al, 1996). In our study, we used the same aging method (dentinal) that was used in our 1970s data set, to ensure the data sets were comparable.…”

Section: Methodsmentioning

confidence: 99%

Variation in Reproduction and Body Condition of the Ringed Seal (Phoca hispida) in Western Prince Albert Sound, NT, Canada, as Assessed Through a Harvest-based Sampling Program

Harwood¹,

Smith²,

Melling³

2000

ARCTIC

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ABSTRACT. Between 1992 and 1998, 869 ringed seals taken in the subsistence harvest in western Prince Albert Sound were sampled by two Inuvialuit seal monitors from Holman, Northwest Territories. Considering the 1992-98 data along with data from 1971 -78, we found that the mean body-mass index (BMI) values for females (≥ 7 yr) were significantly lower in 1974 than in all other years examined. At the same time, ovulation rates fell from 100% in 1971 and 1972 to lows of 42. 9% (1974) and 64.3% (1975), with a return to 93.8% in 1976. Mature females that had ovulated had significantly higher BMI values than those that had not ovulated. In eastern Amundsen Gulf, 1974 was the most severe ice year on recent record, with the latest date of clearing of the landfast ice (6 September), the earliest date of new ice formation (4 October), and the fewest number of open water days (28 days). There were no years between 1992 and 1998 that compared to 1974 in reduced ovulation rates, reduced body condition, or severity of ice conditions. Between 1992 and 1998, mean BMI values for adult females and males were lowest in 1994 and highest in 1998, and all annual mean BMI values were between the extremes of the 1970s. This variation in condition in the 1990s did not coincide with a reduction in ovulation rates of mature females, which remained high (93.5-100%) from 1992 to 1998. In 1998, the landfast ice cleared 43 days earlier than the average clearing date for the 1990-98 period, apparently interrupting the lactation period for seal pups located at the periphery of the core breeding habitat. The apparent effects on growth and condition of unweaned pups came at a time when marine food appeared to be abundant and available to all age classes of ringed seals.

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Section: Methodsmentioning

confidence: 99%

Variation in Reproduction and Body Condition of the Ringed Seal (Phoca hispida) in Western Prince Albert Sound, NT, Canada, as Assessed Through a Harvest-based Sampling Program

Harwood¹,

Smith²,

Melling³

2000

ARCTIC

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“…Ringed seal ages determined from counts of dentinal layers tend to be lower than ages derived by reading of cementum layers, particularly for seals older than 10 years. For younger seals, however, ages obtained using the two methods were well correlated (Stewart et al, 1996). In this study, we used the same ageing method and readers that were used in the 1970s series in order to maintain consistency in the full data set.…”

Section: Methodsmentioning

confidence: 99%

Ringed Seals and Sea Ice in Canada’s Western Arctic: Harvest-Based Monitoring 1992–2011

Harwood¹,

Smith²,

Melling³

et al. 2012

ARCTIC

115

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ABSTRACT. We examined the relationship between ringed seal body condition and reproduction and spring sea ice conditions in prime ringed seal habitat in Canada's western Arctic during 1992 -2011. Since 1970, ice conditions in east Amundsen Gulf and west Prince Albert Sound have shown only a slight trend toward earlier ice clearance (breakup) in spring (3 -7 days per decade) (p < 0.10) and no trend toward later freeze-up or increased variability in timing of spring ice clearance. A subsistence harvest -based sample of 2281 ringed seals was obtained during 1992 -2011 from Masoyak, a traditional hunting camp located on the northwest shore of west Prince Albert Sound and less than 5 km from east Amundsen Gulf. The results revealed a statistically significant trend of decreasing mean annual body condition of ringed seals (using an index of length-mass-blubber depth [LMD]: adults, 0.14 m /y) over the past two decades. A parallel result was that mean annual body condition of adults and subadults was correlated with the timing of fast ice clearance in spring (later ice clearance = worse condition). This correlation was most obvious in the extreme ice years in all sex/age groupings and was statistically significant for subadults. In mature females sampled since 1992, annual ovulation rates averaged 92.4 ± 16.3% (SD) and were greater than 80%, and mostly at 100%, in all years but two. Failure to ovulate was obvious in 2005, the most extreme late ice clearance year in our series, when only 30.0% of the mature adult females sampled ovulated. At the same time, values for seal body condition indices (adult females, LMD = 11.3; adult males, LMD = 12.4) and percent pups in the harvest (3.3%) were among the lowest recorded, and spring ice clearance was 38 d later than the 1992 -2011 average. While this and previous studies indicate that the seal population in this core habitat has recovered from natural and extreme-year sea ice fluctuations over the past four decades, the potentially magnified effect of several consecutive extreme ice years, compounded by the concurrent decline in seal body condition that we have now detected over the past 20 years, is of particular concern.Key words: ringed seal, Phoca hispida, ovulation, reproductive failure, body condition, Amundsen Gulf, Prince Albert Sound, sea ice, subsistence harvest, ice clearance RÉSUMÉ. Nous avons examiné le lien qui existe entre l'état corporel du phoque annelé, l'état de reproduction de ce phoque et l'état de la glace de mer printanière dans son habitat d'élection de l'ouest de l'Arctique canadien et ce, entre 1992 et 2011. Depuis 1970, l'état de la glace dans l'est du golfe Amundsen et dans l'ouest du détroit de Prince-Albert n'a affiché qu'une petite tendance vers une débâcle printanière plus hâtive (de 3 à 7 jours par décennie) (p < 0,10) et aucune tendance vers un englacement plus tardif ou une variabilité accrue caractérisant la période de la débâcle du printemps. Un échantillon recueilli à partir de 2 281 phoques annelés ayant fait l'objet d'une récolte de subs...

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“…To provide short-term pain relief, a local anaesthetic (0.7 ml, Lignocaine, AustraZeneca) was injected in the gum beside the post-canine. Ages were estimated by counting growth layer groups in the cementum of decalcified and stained longitudinal sections of post canines, using methods adapted from Stewart et al (1996). The aging technique was validated on post-canine teeth that were collected from 22 known-age NZ fur seals.…”

Section: Methodsmentioning

confidence: 99%

Spatial separation of foraging habitats among New Zealand fur seals

Page¹,

McKenzie²,

Sumner³

et al. 2006

Mar. Ecol. Prog. Ser.

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We studied the foraging behaviour of lactating female, adult male and juvenile New Zealand (NZ) fur seals to compare and contrast their foraging strategies and assess the degree of spatial separation of their foraging habitats. Adult male fur seals are longer and heavier than lactating females, which are longer and heavier than juveniles. Trip duration was positively correlated with the distance travelled by all age/sex groups. Juveniles conducted longer trips and travelled further from the colony than males. Both juveniles and males conducted longer trips and travelled further than females, which made brief trips because they were provisioning pups. There were no seasonal differences in the behaviour of males, but females and juveniles foraged closer to the colony in summer when they were moulting and females had younger pups. Behavioural differences were recorded between lactating female, male and juvenile seals in the directional bearing from the colony, the distance travelled, the minimum size of the area that was potentially visited and the horizontal swim speed. Intra-specific foraging competition among these age/sex groups was minimal because lactating females typically used continental shelf waters and males utilised deeper waters over the shelf break, adjacent to female foraging grounds. Furthermore, juveniles used pelagic waters, up to 1000 km south of the habitats used by adults. Differences in the habitats used by females, males and juveniles were also apparent in the seafloor gradient, the SST and the surface chl a concentration, with females using regions with the highest chl a concentrations. Results from this study suggest that smaller seals cannot efficiently utilise prey in the same habitats as larger seals because smaller seals do not have the capacity to spend enough time underwater at the greater depths.

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COUNTS OF GROWTH LAYER GROUPS IN CEMENTUM AND DENTINE IN RINGED SEALS (PHOCA HISPIDA)

Cited by 111 publications

References 21 publications

Variation in Reproduction and Body Condition of the Ringed Seal (<i>Phoca hispida</i>) in Western Prince Albert Sound, NT, Canada, as Assessed Through a Harvest-based Sampling Program

Variation in Reproduction and Body Condition of the Ringed Seal (<i>Phoca hispida</i>) in Western Prince Albert Sound, NT, Canada, as Assessed Through a Harvest-based Sampling Program

Ringed Seals and Sea Ice in Canada’s Western Arctic: Harvest-Based Monitoring 1992–2011

Spatial separation of foraging habitats among New Zealand fur seals

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