Entanglement Of Pinnipeds At Marion Island, Southern Ocean: 1991-2001

2002 ◽  
Vol 24 (1) ◽  
pp. 141 ◽  
Author(s):  
G Hofmeyr ◽  
Maine M De ◽  
Mr Beste ◽  
S Kirkman ◽  
P Pistorius ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Fishing Industry ◽  
Marion Island ◽  
Mirounga Leonina ◽  
Elephant Seals ◽  
Small Impact ◽  
Fur Seals ◽  
Southern Elephant Seals ◽  
Longline Fisheries

Some 101 fur seals Arctocephalus spp. and five southern elephant seals Mirounga leonina were recorded entangled in anthropogenic debris over ten years at Marion Island, Southern Ocean. Approximately 67% of materials causing entanglement originated in the fishing industry. Polypropylene packaging straps were the most common entangling material, followed by trawl netting. Longline hooks embedded in animals, fishing line and portions of plastic were only encountered after the inception in 1996 of longline fishing in the waters around Marion Island. The incidence of entanglement of Arctocephalus spp. during the 1996-2001 longline fisheries period increased by more than 50% over that of the 1991-1996 pre-longline fisheries period. An estimated 0.24% of the populations of fur seals were entangled. The numbers of entangled M. leonina are very low. Longline fishing has had a direct, albeit small, impact on the pinniped populations

Movements of southern elephant seals

1996 ◽  
Vol 74 (8) ◽  
pp. 1485-1496 ◽  
Author(s):  
B. J. McConnell ◽  
M. A. Fedak
Keyword(s):  
Southern Ocean ◽  
Continental Shelf ◽  
Antarctic Peninsula ◽  
Average Rate ◽  
Stationary Phases ◽  
Mirounga Leonina ◽  
Elephant Seals ◽  
South Georgia ◽  
Southern Elephant Seals ◽  
The Antarctic

Twelve southern elephant seals (Mirounga leonina) were tracked for an average of 119 days as they left their breeding or moulting beaches on the island of South Georgia between 1990 and 1994. Females travelled either eastward up to 3000 km away to the open Southern Ocean or to the continental shelf on or near the Antarctic Peninsula. Males either stayed close to South Georgia or used South Georgia as a base for shorter trips. The females all left South Georgia in a directed manner at an average rate of 79.4 km/day over at least the first 15 days. Thereafter travel was interrupted by bouts of slower travel or stationary phases. The latter were localized at sites on the continental shelf or along its edge. Three seals that were tracked over more than one season repeated their outward direction of travel and used some of the same sites in subsequent years. The magnitude of the movements makes most of the Southern Ocean potentially available to elephant seals.

A longitudinal study of senescence in a pinniped

2002 ◽  
Vol 80 (3) ◽  
pp. 395-401 ◽  
Author(s):  
Pierre A Pistorius ◽  
Marthán N Bester
Keyword(s):  
Longitudinal Study ◽  
Adult Female ◽  
No Reduction ◽  
Marion Island ◽  
Mirounga Leonina ◽  
Elephant Seals ◽  
Reproductive Senescence ◽  
Southern Elephant Seals ◽  
Female Survival ◽  
Breeding Seasons

To measure the prevalence of senescence in southern elephant seals (Mirounga leonina Linn.) at Marion Island, changes in adult-female survival and breeding probabilities with age were quantified. Mark–recapture data that had been collected over a 17-year period were analysed using recently developed software to obtain likelihood estimates of survival and capture probabilities. With recapture effort constant over the study period, capture probabilities during the breeding seasons were used as indices of breeding probabilities. Longevity in the population was assessed from the resighting of tagged and hence known-age individuals. Less than a 1% difference between prime-age survival and post prime age survival was found over 8 cohorts of marked females. In addition, no reduction in survival of very old individuals was detected, suggesting the absence of senescence in terms of reduced survival in southern elephant seals. No evidence of reproductive senescence in terms of reduced breeding probability with age was detected. Mortality throughout the population therefore resulted in no individuals surviving to the age where physiological decline would become a mortality agent or result in failure to breed. Five percent of female southern elephant seals survived to age 10 and 0.5% to age 17.

scholarly journals Calibration procedures and first data set of Southern Ocean chlorophyll <i>a</i> profiles collected by elephant seal equipped with a newly developed CTD-fluorescence tags

2012 ◽  
Vol 5 (2) ◽  
pp. 853-891 ◽  
Author(s):  
C. Guinet ◽  
X. Xing ◽  
E. Walker ◽  
P. Monestiez ◽  
S. Marchand ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Elephant Seal ◽  
In Situ Observation ◽  
Mirounga Leonina ◽  
Data Set ◽  
Elephant Seals ◽  
Phytoplankton Concentration ◽  
Southern Elephant Seals ◽  
Indian Sector

Abstract. In-situ observation of the marine environment has traditionally relied on ship-based platforms. The obvious consequence is that physical and biogeochemical properties have been dramatically undersampled, especially in the remote Southern Ocean (SO). The difficulty in obtaining in situ data represents the major limitations to our understanding, and interpretation of the coupling between physical forcing and the biogeochemical response. Southern elephant seals (Mirounga leonina) equipped with a new generation of oceanographic sensors can measure ocean structure in regions and seasons rarely observed with traditional oceanographic platforms. Over the last few years, seals have allowed for a considerable increase in temperature and salinity profiles from the SO. However we were still lacking information on the spatio-temporal variation of phytoplankton concentration. This information is critical to assess how the biological productivity of the SO, with direct consequences on the amount of CO2 "fixed" by the biological pump, will respond to global warming. In this research program, we use an innovative sampling fluorescence approach to quantify phytoplankton concentration at sea. For the first time, a low energy consumption fluorometer was added to Argos CTD-SRDL tags, and these novel instruments were deployed on 27 southern elephant seals between 25 December 2007 and the 4 February 2011. As many as 3388 fluorescence profiles associated with temperature and salinity measurements were thereby collected from a vast sector of the Southern Indian Ocean. This paper address the calibration issue of the fluorometer before being deployed on elephant seals and present the first results obtained for the Indian Sector of the Southern Ocean. This in situ system is implemented in synergy with satellite ocean colour radiometry. Satellite-derived data is limited to the surface layer and is restricted over the SO by extensive cloud cover. However, with the addition of these new tags, we're able to assess the 3 dimension distribution of phytoplankton concentration by foraging southern elephant seals. This approach reveals that for the Indian sector of the SO, the surface chlorophyll a (chl a) concentrations provided by MODIS were underestimated by a factor of the order of 2–3 compared to in situ measurements. The scientific outcomes of this program include an improved understanding of both the present state and variability in ocean biology, and the accompanying biogeochemistry, as well as the delivery of real-time and open-access data to scientists (doi:10.7491/MEMO.1x).

Deep divers in even deeper seas: habitat use of male southern elephant seals from Marion Island

2012 ◽  
Vol 24 (6) ◽  
pp. 561-570 ◽  
Author(s):  
Trevor Mcintyre ◽  
Horst Bornemann ◽  
Joachim Plötz ◽  
Cheryl A. Tosh ◽  
Marthán N. Bester
Keyword(s):  
Habitat Use ◽  
Mixed Model ◽  
Marion Island ◽  
Mirounga Leonina ◽  
Fracture Zones ◽  
Elephant Seals ◽  
Sea Floor ◽  
Close Proximity ◽  
Southern Elephant Seals ◽  
Migration Strategies

AbstractWe describe the habitat use of 22 male southern elephant seals (Mirounga leonina) satellite tagged at Marion Island between 2004 and 2008. While a few areas of increased utilization appeared to be associated with areas of shallower bathymetry (such as sea-floor ridges and fracture zones), seals in our study did not target other areas of shallow bathymetry within close proximity to Marion Island. Rather, most elephant seals foraged pelagically over very deep water where much variation was evident in diel vertical migration strategies. These strategies resulted in generally deeper and longer dives than what has been reported for male elephant seals from other colonies. No significant differences were recorded for dive durations or dive depths between adults and sub-adults. However, younger animals displayed a positive relationship between dive durations and age, as well as between dive depths and age, while these relationships became negative for older animals. Mixed model outputs suggested that seals increased their aerobic fitness as migrations progressed, enabling them to undertake longer dives. We conclude that Marion Island male elephant seals exhibit much variability in dive strategy and are seemingly capable of exploiting a range of different prey types occurring in various depth layers.

scholarly journals Calibration procedures and first dataset of Southern Ocean chlorophyll <i>a</i> profiles collected by elephant seals equipped with a newly developed CTD-fluorescence tags

2013 ◽  
Vol 5 (1) ◽  
pp. 15-29 ◽  
Author(s):  
C. Guinet ◽  
X. Xing ◽  
E. Walker ◽  
P. Monestiez ◽  
S. Marchand ◽  
...  
Keyword(s):  
Southern Ocean ◽  
In Situ Observation ◽  
Mirounga Leonina ◽  
Elephant Seals ◽  
Chl A ◽  
Phytoplankton Concentration ◽  
Fluorescence Measurements ◽  
Southern Elephant Seals ◽  
Indian Sector

Abstract. In situ observation of the marine environment has traditionally relied on ship-based platforms. The obvious consequence is that physical and biogeochemical properties have been dramatically undersampled, especially in the remote Southern Ocean (SO). The difficulty in obtaining in situ data represents the major limitations to our understanding, and interpretation of the coupling between physical forcing and the biogeochemical response. Southern elephant seals (Mirounga leonina) equipped with a new generation of oceanographic sensors can measure ocean structure in regions and seasons rarely observed with traditional oceanographic platforms. Over the last few years, seals have allowed for a considerable increase in temperature and salinity profiles from the SO, but we were still lacking information on the spatiotemporal variation of phytoplankton concentration. This information is critical to assess how the biological productivity of the SO, with direct consequences on the amount of CO2 "fixed'' by the biological pump, will respond to global warming. In this research programme, we use an innovative sampling fluorescence approach to quantify phytoplankton concentration at sea. For the first time, a low energy consumption fluorometer was added to Argos CTD-SRDL tags, and these novel instruments were deployed on 27 southern elephant seals between 25 December 2007 and the 4 February 2011. As many as 3388 fluorescence profiles associated with temperature and salinity measurements were thereby collected from a vast sector of the Southern Indian Ocean. This paper addresses the calibration issue of the fluorometer before being deployed on elephant seals and presents the first results obtained for the Indian sector of the Southern Ocean. This in situ system is implemented in synergy with satellite ocean colour radiometry. Satellite-derived data is limited to the surface layer and is restricted over the SO by extensive cloud cover. However, with the addition of these new tags, we are able to assess the 3-dimension distribution of phytoplankton concentration by foraging southern elephant seals. This approach reveals that for the Indian sector of the SO, the surface chlorophyll a (chl a) concentrations provided by MODIS were underestimated by a factor 2 compared to chl a concentrations estimated from HPLC corrected in situ fluorescence measurements. The scientific outcomes of this programme include an improved understanding of both the present state and variability in ocean biology, and the accompanying biogeochemistry, as well as the delivery of real-time and open-access data to scientists (doi:10.7491/MEMO.1).

Spatial and temporal patterns of changes in condition of southern elephant seals

2015 ◽  
Vol 28 (2) ◽  
pp. 81-90 ◽  
Author(s):  
Trevor McIntyre ◽  
Ashleigh Donaldson ◽  
Marthán N. Bester
Keyword(s):  
Temporal Patterns ◽  
Polar Front ◽  
Antarctic Polar Front ◽  
Marion Island ◽  
Mirounga Leonina ◽  
Foraging Success ◽  
Spatial And Temporal Patterns ◽  
Elephant Seals ◽  
Southern Elephant Seals ◽  
Gains And Losses

AbstractThe study of foraging success in marine predators is complicated by a lack of direct observations and relies mostly on proxy measures of foraging success. This study assessed spatial and temporal patterns of changes in body condition of southern elephant seals (Mirounga leonina) from Marion Island, based on changes in drift rates (which are related to gains and losses of blubber). Seals showed substantial individual variation in condition changes throughout migrations, which was not explained by age-, sex- or reproductive stages. Substantial variation was also evident in the spatial patterns of condition changes, although an area south of the Antarctic Polar Front (APF) between 10°E and 35°E was evidently associated with moderate, yet consistent gains in condition. Seals that foraged more distantly from Marion Island displayed more extreme gains and losses in condition, suggesting a possible risk/reward trade-off associated with foraging further afield versus closer to the island. Increased condition was consistently negatively related to sea surface temperature, suggesting that seals were generally improving their condition faster in cooler water masses. These results support previous studies predicting that continued warming of the Southern Ocean will result in changes to the habitat use patterns exhibited by southern elephant seals at sea.

Tag-loss in southern elephant seals, Mirounga leonina, at Marion Island

1997 ◽  
Vol 9 (2) ◽  
pp. 162-167 ◽  
Author(s):  
I.S. Wilkinson ◽  
M.N. Bester
Keyword(s):  
Elephant Seal ◽  
Southern Elephant Seal ◽  
Island Population ◽  
Marion Island ◽  
Mirounga Leonina ◽  
Elephant Seals ◽  
Tag Loss ◽  
Southern Elephant Seals ◽  
Marking Technique ◽  
Loss Rates

Rates of tag-loss are determined for Dalton Jumbo Rototags applied to the hind flippers of 4343 (2208 males, 2135 females) southern elephant seal (Mirounga leonina) pups at Marion Island over an eight year period from 1983–1990 as part of a demographic study of the species. Loss rates were the lowest recorded to date for this species (range 0.0–9.1%). No significant relationship existed between age and rate of tag-loss, neither was there any sex or year related differences in age-specific tag-loss rates. The low rates of loss highlight the value of tagging as a marking technique, and allow for high levels of confidence in the reliability of the population parameters that are derived from the tagging data collected for the Marion Island population.

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