Satellite Relay Data Loggers Research Articles

A lifetime at depth: vertical distribution of southern elephant seals in the water column

Although numerous studies have addressed the migration and dive behaviour of southern elephant seals (Mirounga leonina), questions remain about their habitat use in the marine environment. We report on the vertical use of the water column in the species and the potential lifetime implications for southern elephant seals from Marion Island. Long-term mark-resight data were used to complement vertical habitat use for 35 known individuals tagged with satellite-relay data loggers, resulting in cumulative depth use extrapolated for each individual over its estimated lifespan. Seals spent on average 77.59% of their lives diving at sea, 7.06% at the sea surface, and 15.35% hauled out on land. Some segregation was observed in maximum dive depths and depth use between male and female animals—males evidently being physiologically more capable of exploiting increased depths. Females and males spent 86.98 and 80.89% of their lives at sea, respectively. While at sea, all animals spent more time between 300 and 400 m depth, than any other depth category. Males and females spent comparable percentages of their lifetimes below 100 m depth (males: 65.54%; females: 68.92%), though males spent 8.98% of their lives at depths in excess of 700 m, compared to females’ 1.84% at such depths. Adult males often performed benthic dives in excess of 2,000 m, including the deepest known recorded dive of any air-breathing vertebrate (>2,133 m). Our results provide a close approximation of vertical habitat use by southern elephant seals, extrapolated over their lifespans, and we discuss some physiological and developmental implications of their variable depth use.

Foraging effort of juvenile Steller sea lions Eumetopias jubatus with respect to heterogeneity of sea surface temperature

Among many other factors, the decline of the western distinct population segment of Steller sea lions Eumetopias jubatus in Alaska (USA) has been attributed to changes in the distribu- tion or abundance of prey due to the cumulative effects of fisheries and large-scale climate change. However, the depletion of localized prey resources due to small-scale environmental variability and perturbations may be impeding recovery, resulting in the need to understand how the environment currently affects this species on smaller spatial and temporal scales. The objective of this study, there- fore, was to assess how Steller sea lions respond to changes in localized environmental features. Satellite-relayed data loggers were deployed on juvenile Steller sea lions (n = 24) from July 2002 to May 2004 in the Aleutian Islands and Gulf of Alaska. Weekly indices of foraging effort (mean and maximum trip duration, diving activity) of Steller sea lions were examined with respect to corre- sponding patterns of sea surface temperature (SST) data obtained from the moderate resolution imaging spectroradiometer. An assortment of landscape metrics was used to characterize the hetero- geneity of frontal features derived from SST gradients because it has been suggested that Steller sea lions depend on prey patches associated with these features. Multivariate analyses indicated that fractal dimension and patch density of frontal features were significant factors for predicting differ- ent aspects of foraging effort (p < 0.05; n = 6 models). Overall, results suggested that aggregated frontal features associated with small-scale temperature gradients were probably conducive to forag- ing effort of Steller sea lions, but additional mechanisms should be investigated further.

Goose barnacles hitchhike on satellite-tracked southern elephant seals

Goose barnacles (Lepas australis) attached to satellite-relay data loggers were carried by three southern elephant seals (Mirounga leonina) from Marion Island. Their movements across the Polar Frontal Zone are presented, providing further evidence that megafauna are potential vectors for the transport of species into the Southern Ocean.

Regional differences in the spatial and temporal heterogeneity of oceanographic habitat used by Steller sea lions

Over the past three decades, the decline and altered spatial distribution of the western stock of Steller sea lions (Eumetopias jubatus) in Alaska have been attributed to changes in the distribution or abundance of their prey due to the cumulative effects of fisheries and environmental perturbations. During this period, dietary prey occurrence and diet diversity were related to population decline within metapopulation regions of the western stock of Steller sea lions, suggesting that environmental conditions may be variable among regions. The objective of this study, therefore, was to examine regional differences in the spatial and temporal heterogeneity of oceanographic habitat used by Steller sea lions within the context of recent measures of diet diversity and population trajectories. Habitat use was assessed by deploying satellite-depth recorders and satellite relay data loggers on juvenile Steller sea lions (n = 45) over a five-year period (2000-2004) within four regions of the western stock, including the western, central, and eastern Aleutian Islands, and central Gulf of Alaska. Areas used by sea lions during summer months (June, July, and August) were demarcated using satellite telemetry data and characterized by environmental variables (sea surface temperature [SST] and chlorophyll a [chl a]), which possibly serve as proxies for environmental processes or prey. Spatial patterns of SST diversity and Steller sea lion population trends among regions were fairly consistent with trends reported for diet studies, possibly indicating a link between environmental diversity, prey diversity, and distribution or abundance of Steller sea lions. Overall, maximum spatial heterogeneity coupled with minimal temporal variability of SST appeared to be beneficial for Steller sea lions. In contrast, these patterns were not consistent for chl a, and there appeared to be an ecological threshold. Understanding how Steller sea lions respond to measures of environmental heterogeneity will ultimately be useful for implementing ecosystem management approaches and developing additional conservation strategies.

Estimating the Number of Walruses in Svalbard from Aerial Surveys and Behavioural Data from Satellite Telemetry

All known terrestrial haul-out sites for walruses in Svalbard (n = 79) were surveyed during the period 1–3 August 2006, and sites that were in use (n = 17) were documented using digital photography. A total of 657 walruses were counted on land in the resultant images. An extensive behavioural data set from walruses equipped with satellite relay data loggers, covering August 2002 to August 2005, was used to account for walruses that were in the water. The proportion of walruses at sea during the survey was calculated to be 0.750 on the basis of 28 thirty-day periods from 23 male walruses. Time of day and wind chill did not significantly affect haul-out behaviour. However, a logistic regression model revealed both a correlation among haul-out patterns of individuals within years, and a year effect (chi-square = 6.42, df = 2, p = 0.04). Because the survey was not flown in a year when satellite tags were deployed, the interannual variance was retained in a model (with no other explanatory variables). The overdispersion parameter from this model was 2.02 (deviance = 28.33, df = 14). Thus, variance in proportions of time individuals spent at sea was multiplied by this parameter to achieve a corrected SE around the estimate. The 95% CI based on this SE corresponded to a proportion of walruses at sea during the survey between 0.717 and 0.781, resulting in an estimated total number of walruses in Svalbard in August 2006 of 2629 (95% CI: 2318– 2998).

Insights on leatherback turtle movements and high use areas in the Southwest Atlantic Ocean

Leatherback sea turtles, Dermochelys coriacea, undertake broad oceanic movements while traveling between breeding and foraging areas. While satellite telemetry has been used to investigate long-term movements and diving patterns of leatherback turtles around the world, behavioral information for this species in the South Atlantic Ocean is limited. Here we present the first data on movements, habitat use and diving behavior of leatherback turtles in the Southwest Atlantic Ocean (SWA). Four leatherback turtles (two females, one male and one subadult) were fitted with satellite relayed data loggers (SRDL) in 2005 and 2006 after being incidentally captured by industrial (high seas pelagic longlines) and artisanal (coastal bottom-set gillnets) Uruguayan fisheries. Turtles tended to remain in the western side of the South Atlantic Ocean where specific areas were frequented, in one instance showing a round-trip migration between temperate and tropical waters. Previously unidentified high use areas were recognized along continental shelf and break waters in the SWA, both in temperate and tropical regions. Leatherback turtles exhibited seasonal migration patterns and displayed marked changes in diving behavior between high use areas. Furthermore, our results highlight the importance of the Rio de la Plata estuary as a key foraging area for D. coriacea in the SWA which should be considered a central focus of attention for future research and conservation efforts.

Tracking leatherback turtles ( Dermochelys coriacea) during consecutive inter-nesting intervals: Further support for direct transmitter attachment

Over recent years there have been substantial efforts to record and interpret the post-nesting movements of leatherback turtles ( Dermochelys coriacea) breeding in tropical regions. Less well documented are the movements undertaken by individual turtles during the breeding season itself, or more specifically between sequential nesting events. Such movements are of interest for two reasons: (1) gravid female leatherbacks may range extensively into the territorial waters and nesting beaches of neighbouring countries, raising questions for conservationists and population ecologists; and (2) the magnitude of movements themselves help elucidate underlying reproductive strategies (e.g. whether to rest near to the nesting or forage extensively). Here, satellite relay data loggers are used (SRDLs) to detail the movements and behaviour of two female leatherback turtles throughout three consecutive inter-nesting intervals in the Commonwealth of Dominica, West Indies. Both near-shore residence and extensive inter-nesting movements were recorded, contrasting previous studies, with movements away from the nesting beach increasing towards the end of the nesting season. Using this behavioural study as a backdrop, the suitability of attaching satellite transmitters directly to the carapace was additionally explored as an alternative approach to conventional harness deployments. Specifically, the principal aims were to (1) gather empirical data on speed of travel and (2) assess dive performance (aerobic dive limit) to enable comparisons with turtles previously fitted with harnesses elsewhere in the Caribbean ( n = 6 turtles; Grenada, WI). This produced mixed results with animals bearing directly attached transmitters travelling significantly faster (55.21 km day − 1 ; SD 6.68) than harnessed individuals (39.80 km day − 1 ; SD 6.19); whilst no discernable difference in dive performance could be found between the two groups of study animals.

Time budgets and at-sea behaviour of lactating female Antarctic fur seals Arctocephalus gazella at Bouvetøya

We present the first data on attendance patterns, at-sea movements and diving behaviour of Antarctic fur seals breeding at Bouvetoya (Bouvet Island), Southern Ocean. While other colonies have been extensively studied, this remote and second largest global population remains relatively unknown. Time depth recorders and satellite relay data loggers were deployed on breeding females during the 2000-2001 and 2001-2002 summers. Attendance and foraging patterns were similar to those observed at colonies in the Scotia Sea region where Antarctic krill Euphausia superba is the pre- dominant prey. Early to mid-lactation trips ranged within ~100 km of the island, usually towards the west; the dominant direction shifted later in the season and the range also increased markedly to a peak between early February and early March. Solar elevation influenced arrivals and departures from the island, with most departures occurring around sunset. Diurnal variations in diving behaviour were consistent with the vertical migration of krill. Diving frequency was higher at night and diving effort peaked around morning twilight. Afternoon deep diving was common, suggesting that females might target dense daytime krill aggregations between the photic zone and the thermocline. Trip durations increased throughout early to mid-lactation, peaking in late January to early March, before again decreasing towards the end of lactation. Our results illustrate the substantial variability, both between individuals and within individuals over time, that is likely to reflect variations in prey distrib- ution and in the growth requirements of pups. Such variations need to be taken into account when estimating habitat use and resource utilisation in marine top predators.

Estimating seasonal abundance of a central place forager using counts and telemetry data

Obtaining population estimates of species that are not easily observed directly can be problematic. However, central place foragers can often be observed some of the time, e.g. when seals are hauled out. In these instances, population estimates can be derived from counts, combined with information on the proportion of time that animals can be observed. We present a modelling frame- work to estimate seasonal absolute abundance using counts and information from satellite telemetry data. The method was tested on a harbour seal population in an area of southeast Scotland. Counts were made monthly, between November 2001 and June 2003, when seals were hauled out on land and were corrected for the proportion of time the seals were at sea using satellite telemetry. Harbour seals (n = 25) were tagged with satellite relay data loggers between November 2001 and March 2003. To estimate the proportion of time spent hauled out, time at sea on foraging trips was modelled sep- arately from haul-out behaviour close to haul-out sites because of the different factors affecting these processes. A generalised linear mixed model framework was developed to capture the longitudinal nature of the data and the repeated measures across individuals. Despite seasonal variability in the number of seals counted at haul-out sites, the model generated estimates of abundance, with an over- all mean of 846 (95% CI: 767 to 979). The methodology shows the value of using count and telemetry data collected concurrently for estimating absolute abundance, information that is essential to assess interactions between predators, fish stocks and fisheries.

Monitoring Drake Passage with elephant seals: Frontal structures and snapshots of transport

Conductivity‐temperature‐pressure satellite relay data loggers (CTD‐SRDLs) were attached to southern elephant seals (Mirounga leonina) on the island of South Georgia. During the animals' migration the CTDSRDLs recorded and transmitted hydrographic profiles at a rate of approximately two profiles per day to an average depth of about 547 m, representing transect‐type sections with a spatial resolution of 16‐47 km along the migratory routes of the seals. Two sections are used to clearly identify the locations of the Antarctic Circumpolar Current fronts across Drake Passage, providing in situ data complementary to satellite and other techniques. An empirical relationship between upper ocean temperature and baroclinic mass transport is used to determine the transport through Drake Passage at the times of the sections, and these transports are compared with estimates derived by other techniques. An absolute geostrophic velocity section across Drake Passage is calculated using CTD‐SRDL data and data of absolute geostrophic surface velocities from altimetry. The mean total baroclinic transports in June 2004 and April 2005 are estimated to be 124 × 106 ± 14 × 106 m3 s−1 and 112 × 106 ± 14 × 106 m3 s−1 respectively.

The role of infrequent and extraordinary deep dives in leatherback turtles (Dermochelys coriacea)

Infrequent and exceptional behaviours can provide insight into the ecology and physiology of a particular species. Here we examined extraordinarily deep (300-1250 m) and protracted (>1h) dives made by critically endangered leatherback turtles (Dermochelys coriacea) in the context of three previously suggested hypotheses: predator evasion, thermoregulation and exploration for gelatinous prey. Data were obtained via satellite relay data loggers attached to adult turtles at nesting beaches (N=11) and temperate foraging grounds (N=2), constituting a combined tracking period of 9.6 years (N=26,146 dives) and spanning the entire North Atlantic Ocean. Of the dives, 99.6% (N=26,051) were to depths <300 m with only 0.4% (N=95) extending to greater depths (subsequently termed ;deep dives'). Analysis suggested that deep dives: (1) were normally distributed around midday; (2) may exceed the inferred aerobic dive limit for the species; (3) displayed slow vertical descent rates and protracted durations; (4) were much deeper than the thermocline; and (5) occurred predominantly during transit, yet ceased once seasonal residence on foraging grounds began. These findings support the hypothesis that deep dives are periodically employed to survey the water column for diurnally descending gelatinous prey. If a suitable patch is encountered then the turtle may cease transit and remain within that area, waiting for prey to approach the surface at night. If unsuccessful, then migration may continue until a more suitable site is encountered. Additional studies using a meta-analytical approach are nonetheless recommended to further resolve this matter.

Assessment of scale‐dependent foraging behaviour in southern elephant seals incorporating the vertical dimension: a development of the First Passage Time method

1. Identifying the spatial scales at which top marine predators forage is important for understanding oceanic ecosystems. Several methods quantify how individuals concentrate their search effort along a given path. Among these, First-Passage Time (FPT) analysis is particularly useful to identify transitions in movement patterns (e.g. between searching and feeding). This method has mainly been applied to terrestrial animals or flying seabirds that have little or no vertical component to their foraging, so we examined the differences between classic FPT and a modification of this approach using the time spent at the bottom of a dive for characterizing the foraging activity of a diving predator: the southern elephant seal. 2. Satellite relayed data loggers were deployed on 20 individuals during three successive summers at the Kerguelen Islands, providing a total of 72 978 dives from eight juvenile males and nine adult females. 3. Spatial scales identified using the time spent at the bottom of a dive ( = 68.2 +/- 42.1 km) were smaller than those obtained by the classic FPT analysis ( = 104.7 +/- 67.3 km). Moreover, foraging areas identified using the new approach clearly overlapped areas where individuals increased their body condition, indicating that it accurately reflected the foraging activity of the seals. 4. These results suggest that incorporating the vertical dimension into FPT provides a different result to the surface path alone. Close to the Antarctic continent, within the pack-ice, sinuosity of the path could be explained by a high sea-ice concentration (restricting elephant seal movements), and was not necessarily related to foraging activity. 5. Our approach distinguished between actual foraging activity and changes in behaviour induced by the physical environment like sea ice, and could be applied to other diving predators. Inclusion of diving parameters appears to be essential to identify the spatial scale of foraging areas of diving animals.

Flexible inter-nesting behaviour of generalist olive ridley turtles in Australia

While olive ridley turtles ( Lepidochelys olivacea) occur throughout tropical oceans their physiological ecology has been poorly documented. In May 2005, satellite-relayed data loggers (SRDLs) were attached during oviposition to four adult female olive ridley turtles on the Wessell Islands, northern Australia. Subsequent nesting haul-outs were determined for two of these turtles using a combination of movement and diving data. Internesting intervals were relatively long (27 and 18 days, respectively) for hard-shelled turtles given the warm (27–28 °C) water temperatures, possibly due to a low metabolic rate for this species. Turtles travelled considerable distances during the internesting interval (200 and 125 km respectively), possibly associated with a search for food or alternative nesting sites. Changes in dive behaviour suggest that olive ridleys prepare for oviposition by searching for an appropriate beach over several days.

Fine-scale habitat selection of crabeater seals as determined by diving behavior

Abstract Previous studies within the Marguerite Bay region of the Antarctic Peninsula (∼67°S, ∼67°W) demonstrated that during winter, crabeater seals (Lobodon carcinophagus) were not randomly distributed across available habitat, but instead were more likely to be located in nearshore waters where bathymetric gradients and ice concentrations were high. Here, we investigate how the diving patterns of crabeater seals vary in response to these habitat characteristics, and interpret seal behaviors in light of information on the distribution of their primary prey, krill (Euphausia superba or Euphausia crystallorophias). Diving and movement patterns were obtained from 34 seals (16 male, 18 female) fitted with satellite-relayed data loggers (SRDLs) during the 2001 and 2002 Southern Ocean GLOBEC cruises. Tags transmitted position and dive information for 4–174 days, during which time we received an average of 21 positions/day, and information on a total of 124,681 dives. A series of generalized linear mixed-effect models (GLMM) were used to evaluate the relationship between diving behavior and temporal and physical features of the habitat, and models contrasted using AICc and BIC weights. Overall, we found that the most parsimonious models included year, month, and period (day, dusk, night). In general, seals dived deeper (158 vs. 73 m) and longer (432 vs. 360 s) during the day than at night. In addition, daytime dives included slightly more time at the foraging depths (142 vs. 102 s), and were slightly more efficient (24% vs. 21% of the dive cycle spent at the bottom). When dive patterns were examined with respect to bathymetry, models indicated that seals were foraging in shallower waters (366 vs. 410 m) and closer to the bottom (dives were 50.3% vs. 26.3% of bathymetric depth) during the day than at night. In combination, these findings suggest that crabeater seals foraging during the day exploited zooplankton schools compressed along the bottom. At night, when zooplankton were dispersed and light levels low, foraging activity was less frequent and seals concentrated their diving closer to the surface over a broader range of habitat depths. As individual seals moved an average of only 4.1±1.4 km between daytime and nighttime positions, these results suggest that crabeater seals diving along the Western Antarctic Peninsula select areas of high bathymetric gradients so that they can maximize foraging success over a 24-h cycle without the need to travel long distances. However, annual differences in behavior and the generally low amount of deviation explained by models also suggests that seals vary their diving behavior in response to finer-scale biological, temporal, and/or physical features that were not monitored as part of this study.

Overwintering behaviour in sea turtles: dormancy is optional

Thirteen loggerhead turtles Caretta caretta were released (10 from Naples, Italy, 2 from Monastir, Tunisia, 1 from Gallipoli, South Italy) with satellite relay data loggers (SRDL) to elucidate their overwintering behaviour. Nine turtles were successfully tracked throughout the winter, while 4 SRDLs failed to transmit after short deployment periods. Of these 9, 4 remained within 80 km of the release site, 3 travelled to a distant overwintering site, and 2 continued to move and did not remain within 80 km of a specific site. Apart from these differences, all turtles stayed near the coast and ded- icated most of their time to dives lasting 3 h and longer. Maximum dive durations ranged from 270 to 480 min and were highly correlated with water temperatures, which fell below the supposed 15°C threshold for sea turtle hibernation in all overwintering sites. Median dive depths were between 4 and 24 m and were, thus, well within the mixed layer, as revealed by temperature profiles, which also were relayed by the SRDLs. No evidence was found that the turtles preferred warmer temperatures to overwinter in, because the range of temperature was very narrow on both the horizontal and the vertical scale of their movements. Despite the long resting phases and the low temperatures (mini- mum = 11.8°C) all turtles retained activity to some degree, at least to commute between the depth of resting and the surface to breathe. While the degree of winter dormancy is certainly affected by temperature, turtles were by no means obligatory hibernators, and their ability to move and even forage during the winter may be important for their growth and maturation rates, as well as their reproductive output.

Satellite tracking and diving behaviour of sub-adult narwhals (Monodon monoceros) in Svalbard, Norway

Three juvenile narwhals captured during August 1998 in the northeast of Svalbard, Norway, were equipped with satellite-relayed data loggers (SRDLs) that transmitted diving and swim-speed data, in addition to location, for up to 46 days. A total of 1,354 complete dive cycles were recorded. Most of the diving was shallow and of short duration. Maximum recorded dive depth was 546 m, maximum recorded dive duration was 24.8 min, and maximum recorded swim-speed was 4.7 ms−1. Ascent speed, vertical ascent speed, descent speed and vertical descent speed were all significantly higher during deep dives (>200 m) than for shallow dives (<200 m). In addition both ascent and descent angles were much steeper for deep dives than during shallow dives. Most of the shallow diving seemed to be associated with travelling, with the animal shifting between various locations, while the deep diving (often to the bottom) for extended periods in some specific areas might have been associated with foraging. Even though the sample size in this study is small, the data are the first information available for movements and diving behaviour of narwhals near Svalbard.

Status and conservation of the grey seal, Halichœ rus grypus, in France

We investigated the status of the grey seal in the Molène archipelago, western Brittany, where a Marine National Park is planned. We combined regular censuses, photo-identification and satellite telemetry to investigate trends in grey seal abundance, site fidelity, individual movements and haulout site use. Individual movements and seasonal variations in abundance suggest that the seals used the Molène archipelago alternatively with other haulout sites of the South-west British Isles during their annual cycle. Nine out of 16 seals fitted with Satellite Relay Data Loggers (SRDLs) moved to the Isles of Scilly, English Cornwall, Wales or the Channel islands. On average the seals spent 85% of their time Near Haulout, 56.8% of which in the Molène archipelago. Overall the seals spent 66% of their tracking time within the boundaries of the Marine National Park. From 1997 to 2000 in the Molène archipelago, we observed a peak in number during the moulting season (mean = 49.8 seals) and a lower abundance during the breeding season (mean = 38.3 seals). The sex ratio was strongly skewed towards males during the moult (between 3.1 and 5.3–1), and was close to 1:1 during the summer. Inter-annual site fidelity outside the breeding season was very high, varying from 70% to 95% of identified seals, suggesting that the observed movements constitute rotations rather than random dispersion. From 1991/1994 to 1997/2000, the mean number of seals counted at haulout sites increased by 7%, close to the rates of increase observed in the core population of the British Isles at the same period. The Marine National Park may be too restricted for the overall conservation of the population but management plans should be aimed at preserving the characteristics of the habitat for the grey seal.

First records of dive durations for a hibernating sea turtle

The first published record, from the early 1970s, of hibernation in sea turtles is based on the reports of the indigenous Indians and fishermen from Mexico, who hunted dormant green turtles (Chelonia mydas) in the Gulf of California. However, there were no successful attempts to investigate the biology of this particular behaviour further. Hence, data such as the exact duration and energetic requirements of dormant winter submergences are lacking. We used new satellite relay data loggers to obtain the first records of up to 7h long dives of a loggerhead turtle (Caretta caretta) overwintering in Greek waters. These represent the longest dives ever reported for a diving marine vertebrate. There is strong evidence that the dives were aerobic, because the turtle surfaced only for short intervals and before the calculated oxygen stores were depleted. This evidence suggests that the common belief that sea turtles hibernate underwater, as some freshwater turtles do, is incorrect.

Winter habitat use and foraging behavior of crabeater seals along the Western Antarctic Peninsula

We quantified the winter and spring movement patterns and foraging behavior of adult crabeater seals (Lobodon carcinophagus), and the influence of sea ice and bathymetry on their foraging behavior. Thirty-four seals (16 M 18 F) were outfitted with Satellite Relay Data Loggers (SRDLs) in the Marguerite Bay Region of the Antarctic Peninsula (� 671S, 671W) during the austral winters of 2001 and 2002. Tags transmitted position and dive information for between 4 and 174 days. Overall, winter activity patterns differed significantly from previously reported data collected during the summer: seals in this study dived deeper (9270.2 m, range 6–713 m) and longer (5.26 min70.6, range 0.2–23.6 min), hauled out during the night rather than the day, and showed seasonal shifts in foraging patterns consistent with foraging on vertically migrating prey. While these patterns were more pronounced in 2001 than in 2002, there were no strong differences in patterns of habitat use between the 2 years. Some animals made long distance movements (furthest movements 664 km to northeast, 1147 km to southwest), but most seals remained within 300 km of their tagging location. Within the Marguerite Bay/Crystal Sound region, seals appeared to favor foraging locations on the continental shelf within the 50 to 450 m depth range, with a tendency to avoid depths of 600 m or greater. In both years, seals remained deep within the pack ice throughout the winter, and did not move into regions with less ice cover. Seals were more likely to be located in shallow water where the bathymetric gradients were greatest, and in areas of higher

Temperature data from Norwegian and Russian waters of the northern Barents Sea collected by free-living ringed seals

Free-living ringed seals ( N=11) equipped with satellite-relayed data loggers (SRDLs) with incorporated oceanographic-quality temperature sensors were used to collect data from a large sector of the northern Barents Sea during the autumn and early winter. A total of 2346 temperature profiles were collected over a 4-month period from Norwegian and Russian arctic waters in areas that were at times 90–100% ice-covered. Temperature distributions at different depths from northeastern parts of Svalbard, Norway show warm North Atlantic water (NAW) flowing along the continental slope and gradually cooling at all depths as it flows eastwards. The data suggest that most of the cooling takes place west of 30°E. Vertical temperature profiles from the area between Svalbard and Franz Josef Land, Russia show how the surface water cools during freeze-up and demonstrate a warm water flow, which is probably NAW, coming in from the north through a deep trench west of Franz Josef Land. Global oceanographic and climate models require improved oceanographic databases from crucial areas where important hydrological phenomena occur. Such areas in arctic waters are often inaccessible during winter and logistically difficult to reach even in summer. The present study demonstrates how large amounts of oceanographic information can be collected and retrieved in a cost-efficient manner using ice-associated marine mammals as carrier of oceanographic sampling equipment. In addition to the oceanographic value of the data collected by marine mammals in this manner, a vast amount of information regarding the habitat of these animals is concomitantly sampled.