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.

Influence of hunting strategy on foraging efficiency in Galapagos sea lions

The endangered Galapagos sea lion (GSL, Zalophus wollebaeki) exhibits a range of foraging strategies utilising various dive types including benthic, epipelagic and mesopelagic dives. In the present study, potential prey captures (PPC), prey energy consumption and energy expenditure in lactating adult female GSLs (n = 9) were examined to determine their foraging efficiency relative to the foraging strategy used. Individuals displayed four dive types: (a) epipelagic (<100 m; EP); or (b) mesopelagic (>100 m; MP) with a characteristic V-shape or U-shape diving profile; and (c) shallow benthic (<100 m; SB) or (d) deep benthic (>100 m; DB) with square or flat-bottom dive profiles. These dive types varied in the number of PPC, assumed prey types, and the energy expended. Prey items and their energetic value were assumed from previous GSL diet studies in combination with common habitat and depth ranges of the prey. In comparison to pelagic dives occurring at similar depths, when diving benthically, GSLs had both higher prey energy consumption and foraging energy expenditure whereas PPC rate was lower. Foraging efficiency varied across dive types, with benthic dives being more profitable than pelagic dives. Three foraging trip strategies were identified and varied relative to prey energy consumed, energy expended, and dive behaviour. Foraging efficiency did not significantly vary among the foraging trip strategies suggesting that, while individuals may diverge into different foraging habitats, they are optimal within them. These findings indicate that these three strategies will have different sensitivities to habitat-specific fluctuations due to environmental change.

First impressions: Use of the Azoth Systems O’Dive subclavian bubble monitor on a liveaboard dive vessel

Germonpré P, Van der Eecken P, Van Renterghem E, Germonpré F-L, Balestra C. First impressions: Use of the Azoth Systems O’Dive subclavian bubble monitor on a liveaboard dive vessel. Diving and Hyperbaric Medicine. 2020 December 20;50(4):405–412. doi: 10.28920/dhm50.4.405-412. PMID: 33325023.) Introduction: The Azoth Systems O’Dive bubble monitor is marketed at recreational and professional divers as a tool to improve personal diving decompression safety. We report the use of this tool during a 12-day dive trip aboard a liveaboard vessel. Methods: Six divers were consistently monitored according to the user manual of the O’Dive system. Data were synchronised with the Azoth server whenever possible (depending on cell phone data signal). Information regarding ease of use, diver acceptance and influence on dive behaviour were recorded. Results: In total, 157 dives were completely monitored over 11 diving days. Formal evaluations were only available after six days because of internet connection problems. Sixty-one dives resulted in the detection of bubbles, mostly in one diver, none of which produced any symptoms of decompression illness. Conclusions: The O’Dive system may contribute to increasing dive safety by making divers immediately aware of the potential consequences of certain types of diving behaviour. It was noted that bubble monitoring either reinforced divers in their safe diving habits or incited them to modify their dive planning. Whether this is a lasting effect is not known.

Narwhal Abundance in the Eastern Canadian High Arctic in 2013

In summer, narwhals (Monodon monoceros) migrate from Baffin Bay to northeastern Canada and northwest Greenland, where they are hunted by Inuit for subsistence. To prevent localized depletion, management of narwhals is based on summer stocks. The High Arctic Cetacean Survey (HACS), conducted in August 2013, was the first survey to estimate abundance of all 4 Canadian Baffin Bay narwhal summer stocks, as well as putative stocks in Jones Sound and Smith Sound, in the same summer. Narwhal abundance was estimated using a double-platform aerial survey. Distance sampling methods were used to estimate detection probability away from the track line. Mark-recapture methods were used to correct for the proportion of narwhals missed by visual observers on the track line (i.e., perception bias). We used a data-driven approach to identify single and duplicate sightings, using 4 covariates to compare differences in sightings made by front and rear observers based on: time of sighting, declination angle, group size, and species identity. Abundance in fjords was estimated using density surface modelling to account for their complex shape and uneven coverage. Estimates were corrected for availability bias (narwhals that are not available for detection because they are submerged when the aircraft passes overhead) using a new analysis of August dive behaviour data from narwhals equipped with satellite-linked time depth recorders. Corrected abundance estimates were 12,694 (95% CI: 6,324–25,481) for the Jones Sound stock; 16,360 (95% CI: 3,833–69,836) for the Smith Sound stock; 49,768 (95% CI: 32,945–75,182) for the Somerset Island stock; 35,043 (95% CI: 14,188–86,553) for the Admiralty Inlet stock; 10,489 (95% CI: 6,342–17,347) for the Eclipse Sound stock; and 17,555 (95% CI: 8,473–36,373) for the East Baffin Island stock. Total abundance for these 6 stocks was estimated at 141,908 (95% CI: 102,464–196,536). Sources of uncertainty arise from the high level of clustering observed, in particular in Admiralty Inlet, Eclipse Sound, and East Baffin Island, as well as the difficulty in identifying duplicate sightings between observers when large aggregations were encountered.

Seasonal diving and foraging behaviour of Eastern Canada-West Greenland bowhead whales

Climate change may affect the foraging success of bowhead whales Balaena mysticetus by altering the diversity and abundance of zooplankton species available as food. However, assessing climate-induced impacts first requires documenting feeding conditions under current environmental conditions. We collected seasonal movement and dive-behaviour data from 25 Eastern Canada-West Greenland bowheads instrumented with time-depth telemetry tags and used state-space models to examine whale movements and dive behaviours. Zooplankton samples were also collected in Cumberland Sound (CS) to determine species composition and biomass. We found that CS was used seasonally by 14 of the 25 tagged whales. Area-restricted movement was the dominant behaviour in CS, suggesting that the tagged whales allocated considerable time to feeding. Prey sampling data suggested that bowheads were exploiting energy-rich Arctic copepods such as Calanus glacialis and C. hyperboreus during summer. Dive behaviour changed seasonally in CS. Most notably, probable feeding dives were substantially shallower during spring and summer compared to fall and winter. These seasonal changes in dive depths likely reflect changes in the vertical distribution of calanoid copepods, which are known to suspend development and overwinter at depth during fall and winter when availability of their phytoplankton prey is presumed to be lower. Overall, CS appears to be an important year-round foraging habitat for bowheads, but is particularly important during the late summer and fall. Whether CS will remain a reliable feeding area for bowhead whales under climate change is not yet known.

Dive behaviour and foraging effort of female Cape fur seals Arctocephalus pusillus pusillus

While marine top predators can play a critical role in ecosystem structure and dynamics through their effects on prey populations, how the predators function in this role is often not well understood. In the Benguela region of southern Africa, the Cape fur seal ( Arctocephalus pusillus pusillus ) population constitutes the largest marine top predator biomass, but little is known of its foraging ecology other than its diet and some preliminary dive records. Dive information was obtained from 32 adult females instrumented with dive recorders at the Kleinsee colony (29°34.17′ S, 16°59.80′ E) in South Africa during 2006–2008. Most dives were in the depth range of epipelagic prey species (less than 50 m deep) and at night, reflecting the reliance of Cape fur seals on small, vertically migrating, schooling prey. However, most females also performed benthic dives, and benthic diving was prevalent in some individuals. Benthic diving was significantly associated with the frequency with which females exceeded their aerobic dive limit. The greater putative costs of benthic diving highlight the potential detrimental effects to Cape fur seals of well-documented changes in the availability of epipelagic prey species in the Benguela.

Movements and dive behaviour of a toothfish-depredating killer and sperm whale

Depredation of demersal longlines by killer and sperm whales is a widespread behaviour that impacts fisheries and whale populations. To better understand how depredating whales behave in response to fishing activity, we deployed satellite-linked location and dive-profile tags on a sperm and killer whale that were depredating Patagonian toothfish from commercial longlines off South Georgia. The sperm and killer whale followed one fishing vessel for &gt;180 km and &gt;300 km and repeatedly depredated when longlines were being retrieved over periods of 6 and 7 d, respectively. Their behaviours were also sometimes correlated with the depths and locations of deployed gear. They both dove significantly deeper and faster when depredating compared with when foraging naturally. The killer whale dove &gt;750 m on five occasions while depredating (maximum: 1087 m), but these deep dives were always followed by long periods (3.9–4.6 h) of shallow (&lt;100 m) diving. We hypothesize that energetically and physiologically costly dive behaviour while depredating is driven by intra- and inter-specific competition due to the limited availability of this abundant resource.

Like clockwork - nest attendance patterns and foraging behaviour of Snares penguins Eudyptes robustus as a function of daylength and oceanography

The breeding routines and foraging behaviour of many pelagic seabird species is influenced by environmental factors. Seasonality greatly affects the temporal prey availability for many marine species while the spatial distribution of prey often correlates to oceanographic features. We examined the influence of such environmental factors on the nesting routines and the foraging behaviour of Snares penguins Eudyptes robustus that is endemic to the Snares island group south of New Zealand. Nest attendance and foraging patterns were studied during the incubation stage of three consecutive breeding seasons (2002-2004). Nesting patterns observed in one of the biggest colonies (ca 1200 nest) were highly synchronised, with male penguins leaving the colony to forage within a five-day period around 13 October each year. The males stayed at sea for a mean 11 days before most males returned within a 7-day period around 24-26 October which also marked the main departure period of the females. The females’ foraging trips were considerably shorter and ranged from 5-8 days. The females’ return occurred around the same dates in 2002 and 2003 (late October) but was markedly later in 2004 (early November). Nevertheless, the female’s return was always in sync with egg hatching. Foraging ranges and dive behaviour of six male and two female penguins was examined with GPS dive loggers and time depth recorders. Four of the six males foraged mainly in the cooler waters south of the subtropical front (STF), some 200 km east of the Snares. Dive behaviour of all males indicates primarily travelling behaviour during the first two days at sea. Two males remained in warmer Central Tasman Water (CTW). Movements of three birds determined from GPS suggest that the penguins targeted sea areas with elevated chlorophyll a concentration. Dive behaviour was also related to water mass with dive depths being on average deeper in the cooler waters of the STF. Both females remained only within warmer CTW; temperature data suggests that both birds foraged north to north-east of the island. Dive data indicates that females travelled continuously throughout their trips. The Snares penguin’s foraging behaviour is dictated by oceanic productivity which in turn depends on environmental factors such as day length. Thus, foraging and, consequently, nesting patterns of incubating Snares penguins are also to a great extent a product these factors.

Like clockwork - nest attendance patterns and foraging behaviour of Snares penguins Eudyptes robustus as a function of daylength and oceanography

The breeding routines and foraging behaviour of many pelagic seabird species is influenced by environmental factors. Seasonality greatly affects the temporal prey availability for many marine species while the spatial distribution of prey often correlates to oceanographic features. We examined the influence of such environmental factors on the nesting routines and the foraging behaviour of Snares penguins Eudyptes robustus that is endemic to the Snares island group south of New Zealand. Nest attendance and foraging patterns were studied during the incubation stage of three consecutive breeding seasons (2002-2004). Nesting patterns observed in one of the biggest colonies (ca 1200 nest) were highly synchronised, with male penguins leaving the colony to forage within a five-day period around 13 October each year. The males stayed at sea for a mean 11 days before most males returned within a 7-day period around 24-26 October which also marked the main departure period of the females. The females’ foraging trips were considerably shorter and ranged from 5-8 days. The females’ return occurred around the same dates in 2002 and 2003 (late October) but was markedly later in 2004 (early November). Nevertheless, the female’s return was always in sync with egg hatching. Foraging ranges and dive behaviour of six male and two female penguins was examined with GPS dive loggers and time depth recorders. Four of the six males foraged mainly in the cooler waters south of the subtropical front (STF), some 200 km east of the Snares. Dive behaviour of all males indicates primarily travelling behaviour during the first two days at sea. Two males remained in warmer Central Tasman Water (CTW). Movements of three birds determined from GPS suggest that the penguins targeted sea areas with elevated chlorophyll a concentration. Dive behaviour was also related to water mass with dive depths being on average deeper in the cooler waters of the STF. Both females remained only within warmer CTW; temperature data suggests that both birds foraged north to north-east of the island. Dive data indicates that females travelled continuously throughout their trips. The Snares penguin’s foraging behaviour is dictated by oceanic productivity which in turn depends on environmental factors such as day length. Thus, foraging and, consequently, nesting patterns of incubating Snares penguins are also to a great extent a product these factors.