Flying after diving: a questionnaire-based evaluation of pre-flight diving behaviour in a recreational diving cohort

Introduction: Divers are recommended to observe a pre-flight surface interval (PFSI) ≥ 24 hours before boarding a plane following a diving vacation. Decompression sickness (DCS) symptoms may occur during or post-flight. This study aimed to examine the adherence of PFSI ≥ 24 in vacationing divers, and if any perceived signs and symptoms of DCS during or after flight were experienced. Methods: An anonymous online survey was publicised through diving exhibitions and social media. Data included diver/diving demographics, PFSI before flight, flight details, and perceived signs and symptoms of DCS during or after flight. Results: Data from 316 divers were examined (31% female) with the age range 1-75 years (median 49). Divers recorded 4,356 dives in the week preceding the flight, range 1-36 (median 14). Overall, 251/316 (79%) respondents reported a PFSI of ≥ 24 hours. PFSIs of < 12 hours were reported by 6 respondents. Diagnosed and treated DCS developing during, and post flight was reported by 4 divers with PFSIs ≥ 24 hours and by 2 divers with PFSIs < 24 hours. Fifteen divers boarded a plane with perceived symptoms of DCS. Conclusions: These data suggest that most divers in this study observed the recommendations of a ≥ 24 hour PFSI with safe outcomes.

The immune response and diving: conservation considerations for belugas (Delphinapterus leucas) in a changing Arctic environment

Diving is a critical behaviour of marine mammals, including belugas, which dive to forage and travel under Arctic sea ice. While the limitations of dive behaviour and physiological dive adaptations have been the focus of several studies, cellular adaptations, particularly those of the immune system, have been little considered. However, diving itself presents several challenges that can impact immune responses, leading to disease or injury. As beluga dive their behaviour changes in response to human activity or environmental shifts. It is necessary to better understand how the beluga’s immune system functions during diving. This review provides a brief overview of what is known about beluga’s diving behaviour and physiology and discusses the first efforts to understand the link between diving and health via immune function in belugas. This new area of research is an important consideration regarding potential sub-lethal impacts of a rapidly changing Arctic environment on beluga’s diving behaviour, health and disease susceptibility.

Seasonal resource pulses and the foraging depth of a Southern Ocean top predator

Seasonal resource pulses can have enormous impacts on species interactions. In marine ecosystems, air-breathing predators often drive their prey to deeper waters. However, it is unclear how ephemeral resource pulses such as near-surface phytoplankton blooms alter the vertical trade-off between predation avoidance and resource availability in consumers, and how these changes cascade to the diving behaviour of top predators. We integrated data on Weddell seal diving behaviour, diet stable isotopes, feeding success and mass gain to examine shifts in vertical foraging throughout ice break-out and the resulting phytoplankton bloom each year. We also tested hypotheses about the likely location of phytoplankton bloom origination (advected or produced in situ where seals foraged) based on sea ice break-out phenology and advection rates from several locations within 150 km of the seal colony. In early summer, seals foraged at deeper depths resulting in lower feeding rates and mass gain. As sea ice extent decreased throughout the summer, seals foraged at shallower depths and benefited from more efficient energy intake. Changes in diving depth were not due to seasonal shifts in seal diets or horizontal space use and instead may reflect a change in the vertical distribution of prey. Correspondence between the timing of seal shallowing and the resource pulse was variable from year to year and could not be readily explained by our existing understanding of the ocean and ice dynamics. Phytoplankton advection occurred faster than ice break-out, and seal dive shallowing occurred substantially earlier than local break-out. While there remains much to be learned about the marine ecosystem, it appears that an increase in prey abundance and accessibility via shallower distributions during the resource pulse could synchronize life-history phenology across trophic levels in this high-latitude ecosystem.

Diving behaviour of albatrosses: implications for foraging ecology and bycatch susceptibility

Diving is an ecologically important behaviour that provides air-breathing predators with opportunities to capture prey, but that also increases their exposure to incidental mortality (bycatch) in commercial fisheries. In this study, we characterised the diving behaviour of 26 individuals of three species, the black-browed albatross Thalassarche melanophris, grey-headed albatross T. chrysostoma and light-mantled albatross Phoebetria palpebrata, breeding at Bird Island, South Georgia. Individuals were tracked using Global Location Sensor (GLS)-immersion loggers and time-depth recorders (TDRs) and, for two species, Global Positioning System (GPS) loggers. Although the TDRs recorded 589 dives (defined in this paper as submersion > 1 m), average dive depths and durations were just 1.30–1.49 m and 2.5–3.3 s, respectively, for the three species. In addition, many individuals (22% of black-browed, 20% of grey-headed, and 57% of light-mantled albatrosses; total n = 9, 10 and 7 individuals, respectively) did not dive at all. Most dives occurred at the distal end of foraging trips and were rare during the commuting phase. No dives took place in darkness, despite long periods spent on water at night. The limited and shallow dive activity contrasts with impressions from a previous study using capillary-tube depth gauges (which are less accurate than TDRs) and has implications for the susceptibility of albatrosses to bycatch on longlines. This study provides further support for regulations requiring night setting and increased sink rates of baited hooks to help mitigate albatross bycatch.

Long-distance movements and associated diving behaviour of ringed seals (Pusa hispida) in the eastern Canadian Arctic

Animal distribution and movement facilitate energy and nutrient transfer within and between regions, thus influencing ecosystem structure and function. Ringed seals (Pusa hispida (Schreber, 1775)) have been observed making sustained, extensive migrations (>1000 km) in the western Canadian Arctic, but observations of their movements from the eastern Canadian Arctic are limited. We equipped 12 ringed seals with satellite telemetry tags in Resolute Bay (n = 7; 2012, 2013) and Tremblay Sound (n = 5; 2017, 2018), Nunavut, to monitor their movements, behavioural states, and diving behaviour from late summer until their spring moult. Six tags transmitted into winter and recorded long-distance movements to southeastern Baffin Island, with three seals travelling through central Baffin Bay (3608 ± 315 km; maximum 4226 km), whereas three travelled along the Baffin Island coastline (3674 ± 655 km; maximum 4872 km). Seals that travelled through central Baffin Bay made shallower dives (25.4 ± 1.1 m) than those that travelled near the coast (100.0 ± 4.1 m). Results provide new information on the variability, scales, and pathways of movement and diving behaviour of eastern Canadian Arctic ringed seals. This new knowledge can be used to inform spatial conservation and management priorities of this ecologically and culturally important species.

Distribution and Abundance of the Eastern Canada – West Greenland Bowhead Whale Population Based on the 2013 High Arctic Cetacean Survey

The hunting of bowhead whales (Balaena mysticetus) is an integral part of Inuit culture. An up-to-date abundance estimate of the entire Eastern Canada – West Greenland (EC-WG) bowhead population is necessary to support sustainable management of this harvest. The High Arctic Cetacean Survey (HACS) was conducted in August 2013, primarily to update abundance estimates for known stocks of Baffin Bay narwhal (Monodon monoceros). As the ranges of narwhal and bowhead largely overlap, the survey area was expanded to cover the summer range of bowhead whales. Bowhead whale abundance was estimated using 3 aircraft to cover the large survey area within a short time frame. Distance sampling methods were used to estimate detection probability away from the track line. Double platform with mark-recapture methods were used to correct for the proportion of whales missed by visual observers on the track line (perception bias). Abundance in Isabella Bay, an area known for high bowhead density, was estimated using density surface modelling to account for its complex shape and uneven coverage. Estimates were corrected for availability bias (whales that were not available for detection because they were submerged when the aircraft passed overhead) using a recent analysis of satellite-linked time depth recorders transmitting information on the diving behaviour of bowhead whales in the study area in August of the same survey year. The fully corrected abundance estimate for the EC-WG bowhead whale population was 6,446 (95% CI: 3,838–10,827). Possible sources of uncertainty include incomplete coverage and the diving behaviour of bowhead whales. These results confirm earlier indications that the EC-WG stock is continuing to recover from past overexploitation.

Changes in diving behaviour and habitat use of provisioned whale sharks: implications for management

Whale shark (Rhincodon typus) tourism is increasingly popular at predictable aggregations around the world, but only a few use provisioning to ensure close interactions. Understanding the effects of provisioning on the behaviour of this endangered species is critical to manage this growing industry. We recorded the diving behaviour and habitat use of juvenile whale sharks (n = 4) for a mean of 49.5 provisioned and 33.8 non-provisioned days using temperature-depth-recorders. We found that time spent at the surface (< 2 m) between 6 am and 1 pm increased ~ sixfold, while timing of deep dives shifted from 4–10 am to 10 am–2 pm, i.e. near or at the end of the provisioning activities. The shift might be related to a need to thermoregulate following a prolonged period of time in warmer water. These changes could have fitness implications for individuals frequently visiting the provisioning site. Based on recorded amount of time spent in warm waters and published Q10 values for ectotherms, we estimate a 7.2 ± 3.7% (range 1.3–17.8%) higher metabolic rate when sharks frequent the provisioning site. The observed behavioural, habitat use, and potential fitness shifts should be considered when developing guidelines for sustainable tourism, particularly in light of new provisioning sites developing elsewhere.

Hereditary determined diving behaviour in rats as a factor of fitness

Background. Rats natural ability to swim and dive provides adaptation in the wildlife and is widely applied as an instrument in experimental physiology. Nevertheless theres little scientific evidence on diving behaviour in rats itself. Meanwhile this behavioural pattern might be a notable trait to shed light on functional features of the nervous system, the higher nervous activity structure and evolutional adaptability in animals, including inherited ones. Materials and methods. In the present work we compared the performance of the spontaneous diving behaviour in the Morris water maze and forced diving behaviour in the Extrapolation escape task in two selected rat strains genetically differing in the nervous system excitability threshold. Results. We found a greater extent and adaptive pattern of both types of the diving behaviour in the high-excitable LT strain. This may be due to such basic features of this strain as high exploratory activity and an increased level of fear reactions. It was also shown that the second, low-excitable HT rat strain, demonstrates maladaptive jumping behaviour in the Extrapolation escape task due to higher anxiety level in the stress conditions. Conclusion. Observed differences between two strains allow us to consider the diving behaviour performed by high-excitable rats an inherited strain characteristic resembling adaptive rat behaviours in the wild and look forward to investigate its genetic mechanisms.