Dive Time Research Articles

Determining standards for professional divers diving in benzene polluted waters

The main objective of this study is to calculate the hours of diving in benzene-polluted waters acceptable for professional divers. We considered recommended absorption limit as that from pulmonary workplace absorption during an 8-h workday at recommended exposure limits set by the National Institute of Occupational Safety and Health, and developed a formula to determine recommended limits for diving time based on actual water and sediment concentrations and exposure conditions. The recommended absorption limit is 1.6 mg of benzene per workday. This is equivalent to total body dermal absorption over a 1-h dive at water concentration of 7.6 mg/L, or absorption from drinking 0.1 L of water with a concentration of 16.5 mg/L, or dermal absorption with 50% of the body covered in sediment with a concentration of 18,851 mg/kg. A formula that calculates allowable diving time considering benzene water and sediment concentrations, and gastrointestinal and dermal exposures is presented. Water concentrations and not exposure to sediment limit recommended diving time, and unlimited diving in areas with sediment and water concentrations thought to pose a serious human health hazard would not surpass the recommended amount of benzene absorbed in the workplace. We conclude that allowable diving time in polluted waters can be calculated resulting in absorption equivalent to recommended limits for pulmonary absorption in the workplace. Our results suggest that agencies determining significant health risk levels of chemical concentrations in sediment and water should consider our findings.

To breathe or not to breathe? Optimal breathing, aerobic dive limit and oxygen stores in deep-diving blue-eyed shags

Optimality models exist for diving endotherms, but are rarely tested with behavioural data or used to estimate oxygen reserves. We used a model for avian divers to study the extreme diving performances of blue-eyed shags. Time–depth recorders were deployed on 15 breeding Kerguelen shags, Phalacrocorax verrucosus. The shags regularly dived deeper than 100 m and longer than their behavioural aerobic dive limit (4 min). The dive duration to postdive interval ratio peaked for dives lasting 1 min, the dive time theoretically necessary to deplete oxygen reserves from the respiratory tract. Most dive parameters of the Kerguelen shag converged with those known for the Crozet shag, Phalacrocorax melanogenis. Yet, whereas the distribution of dive durations matched optimal breathing for the Crozet shag (shallow diving), this was not true for the Kerguelen shag which made mostly deep dives. Thus, regardless of how similar the physiologies of blue-eyed shag species may be, they can adapt their diving behaviour to different environmental conditions, in this case resource distribution. From the model, the volume of body oxygen reserves for blue-eyed shags was calculated as 264 ml/kg, which is significantly higher than values found in the literature for avian divers. The volume of the respiratory tract obtained with the model (830 ml), however, was realistic. We suggest the model overestimated body oxygen stores because blue-eyed shags have numerous means for reducing their deep-diving metabolism, such as bradycardia, hypothermia or anaerobic metabolism.

Fine-scale analyses of diving energetics in king penguins Aptenodytes patagonicus: how behaviour affects costs of a foraging dive

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 344:299-309 (2007) - DOI: https://doi.org/10.3354/meps06896 Fine-scale analyses of diving energetics in king penguins Aptenodytes patagonicus: how behaviour affects costs of a foraging dive L. G. Halsey1,*, Y. Handrich2, A. Fahlman3, A. Schmidt4, C.-A. Bost2, R. L. Holder5, A. J. Woakes1, P. J. Butler1 1Centre for Ornithology, School of Biosciences, University of Birmingham, Edgbaston B15 2TT, UK 2Institut Pluridisciplinaire Hubert Curien (IPHC), UMR 7178 CNRS-ULP, Département Ecologie, Physiologie et Ethologie (DEPE), 23 rue Becquerel, 67087 Strasbourg Cedex 02, France 3North Pacific Universities Marine Mammal Research Consortium, UBC Marine Mammal Research Unit, 2202 Main Hall, V6T 1Z4 Vancouver, British Columbia, Canada 4Centre d'Etudes Biologiques de Chizé-Centre National de la Recherche Scientifique, Villiers en Bois, 79360 Beauvoir Sur Niort Cedex, France 5Department of Primary Care and General Practice, University of Birmingham, Edgbaston B15 2TT, UK *Email: l.g.halsey@bham.ac.uk ABSTRACT: Heart rate data loggers were implanted into king penguins Aptenodytes patagonicus undertaking foraging trips at sea during three austral summers. Data were obtained from a total of 20 king penguins. Our aim was to investigate variations in mean heart rate over the dive cycle (i.e. dive plus the subsequent surface period) with changes in diving behaviour, at the scale of the individual foraging dive. From these heart rate values, energetic costs were estimated in terms of rate of oxygen consumption. Shorter dive durations and longer surface durations were associated with statistically significantly higher mean heart rates, and hence energetic costs, over the dive cycle. A decrease in the duration of the bottom period of dives was also associated with an increase in heart rate and energetic costs. In contrast to model predictions that power requirements of swimming in penguins increase rapidly with increasing speed, in the main, the number of wiggles (i.e. intensive prey pursuits lasting several seconds) in a dive did not affect mean heart rate. Furthermore, the shape of the dive did not affect mean heart rate. Diving behaviour and mean heart rates over the dive cycle of birds during 2 austral summers was compared. While the birds in the earlier austral summer undertook considerably longer foraging trips than did the birds in the latter summer, mean mass gain while at sea was similar. Birds during the latter summer exhibited statistically significantly longer dive durations and bottom durations and dived to statistically significantly shallower depths than birds during the earlier summer. However, this did not translate into a statistically significantly lower mean heart rate over the dive cycle in these birds. This suggests that the differences in dive time budgeting between the two summers had only a relatively subtle effect on mean heart rate. In turn the relationship between diving behaviour and foraging success in king penguins may be more obvious than that between diving behaviour and mean heart rate over the dive cycle. KEY WORDS: Diving behaviour · Energetics · King penguin · Oxygen consumption · Foraging behaviour Full text in pdf format PreviousCite this article as: Halsey LG, Handrich Y, Fahlman A, Schmidt A and others (2007) Fine-scale analyses of diving energetics in king penguins Aptenodytes patagonicus: how behaviour affects costs of a foraging dive. Mar Ecol Prog Ser 344:299-309. https://doi.org/10.3354/meps06896Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 344. Online publication date: August 23, 2007 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2007 Inter-Research.

Abundance, behavior, and movement patterns of western gray whales in relation to a 3-D seismic survey, Northeast Sakhalin Island, Russia.

A geophysical seismic survey was conducted in the summer of 2001 off the northeastern coast of Sakhalin Island, Russia. The area of seismic exploration was immediately adjacent to the Piltun feeding grounds of the endangered western gray whale (Eschrichtius robustus). This study investigates relative abundance, behavior, and movement patterns of gray whales in relation to occurrence and proximity to the seismic survey by employing scan sampling, focal follow, and theodolite tracking methodologies. These data were analyzed in relation to temporal, environmental, and seismic related variables to evaluate potential disturbance reactions of gray whales to the seismic survey. The relative numbers of whales and pods recorded from five shore-based stations were not significantly different during periods when seismic surveys were occurring compared to periods when no seismic surveys were occurring and to the post-seismic period. Univariate analyses indicated no significant statistical correlation between seismic survey variables and any of the eleven movement and behavior variables. Multiple regression analyses indicated that, after accounting for temporal and environmental variables, 6 of 11 movement and behavior variables (linearity, acceleration, mean direction, blows per surfacing, and surface-dive blow rate) were not significantly associated with seismic survey variables, and 5 of 11 variables (leg speed, reorientation rate, distance-from-shore, blow interval, and dive time) were significantly associated with seismic survey variables. In summary, after accounting for environmental variables, no correlation was found between seismic survey variables and the linearity of whale movements, changes in whale swimming speed between theodolite fixes, mean direction of whale movement, mean number of whale exhalations per minute at the surface, mean time at the surface, and mean number of exhalations per minute during a whales surface-to-dive cycle. In contrast, at higher received sound energy exposure levels, whales traveled faster, changed directions of movement less, were recorded further from shore, and stayed under water longer between respirations.

Diving behaviour of Elseya albagula from a naturally flowing and hydrologically altered habitat

AbstractThis study investigated the diving behaviour and performance of the bimodally respiring turtle Elseya albagula within the Burnett River, central Qld, Australia. Diving parameters were recorded using pressure‐sensitive time‐depth recorders for turtles residing within a free flowing versus regulated reach. Maximum submergence time recorded for El. albagula (greater than 3 hours) is among the longest recorded for a voluntarily diving vertebrate, and is attributed to the turtle's ability to respire aquatically. Median dive times logged for El. albagula within the regulated reach (6.7 min) were threefold longer than values recorded for turtles residing within a naturally flowing creek (1.9 min), with discrepancies in dive duration possibly due to the variable hydrologic flows recorded below the weir. No correlation was observed between dive duration and subsequent surfacing intervals, suggesting that dives remained aerobic throughout the study. Despite considerable differences in the magnitude and daily variation of water flow between the two locations, similar diel activity and surfacing trends were recorded for El. albagula. Turtles undertook deep resting dives (>1.5 m) during the day before moving into shallower habitats (<1.0 m) for the night, while the crepuscular hours were characterized by elevated surfacing frequencies attributed to periods of increased activity possibly associated with foraging.

A Biology Laboratory on the Seafloor

Although occupied submersibles have played an essential role in the discovery and study of hydrothermal ecosystems at depths ranging from 1500–3500 m, operational constraints at great depths have meant that the wide chemical and thermal diversity of the hydrothermal environments have long remained poorly defi ned. In the last decade, use of remotely operated vehicles (ROVs) to substantially extend dive time and development of a new set of dedicated instruments have greatly expanded our capacity to characterize seafl oor hydrothermal habitats at the interface between hydrothermal fl uid and seawater. In particular, major breakthroughs in the fi eld of in situ chemical sensing and highpressure experimentation have led to a much better understanding of the adaptation of invertebrate species to their extreme environment.

Observations of Longman's Beaked Whale (<I>Indopacetus pacificus</I>) in the Western Indian Ocean

Seventeen new sightings, and a total of 32 records, of the little-known Longman’s beaked whale, (Indopacetus pacificus) (also called tropical bottlenose whale or Indo-pacific beaked whale) are reported from the western Indian Ocean. Field identification features are reviewed, and the possibilities of confusion with other beaked whales are noted. Mean group size for the western Indian Ocean sightings was 7.2 individuals (n = 22, SD = 10.9, range = 1 to 40). This is smaller than previously published estimates from the Pacific, reflecting a relatively large number of new sightings of individuals and small groups, which, in turn, reflect the recent description of the external appearance of this species. Recorded dive times were either short (mean = 14 min, range = 11 to 18 min, n = 5) or long (mean = 26 min, range = 20 to 33 min, n = 19). Longman’s beaked whales appear to be widely distributed in the warmer (> 27o C) waters of the western Indian Ocean, but most sightings were over or adjacent to deep slopes (depths 250 to 2,000+ m). Mean sighting rates were much higher in the western Indian Ocean (1 sighting per 31 sea days for visual surveys) and particularly around the Maldives (1 sighting per 21 sea days) than have been reported from the Pacific (1 sighting per 200 sea days). Longman’s beaked whales may therefore be more common in the western Indian Ocean than in the Pacific, although survey methodologies used in the two oceans were not identical. Widespread gillnet fisheries may pose a potential threat to this species in the Indian Ocean.

Mechanical disruption of seagrass in the digestive tract of the dugong

AbstractThe cheek teeth in dugongs are considered to be largely non‐functional whereas the oral horny pads are important both in mechanical disruption of the diet and in conveying seagrass through the mouth. Particle size distributions of digesta from 41 dead stranded dugongs were examined to investigate the relationship between degree of food breakdown, gut region and functional surface area of the mouthparts. The in vitro ease of fracture of major dietary seagrass species were compared. The rate of food breakdown through the gut appears to be more closely linked to fibre level of the diet than to size or age of the dugong and its mouthparts. Low fibre seagrass, for example Halophila ovalis, breaks down at a faster rate than high fibre seagrass, for example Zostera capricorni both in dugong guts and in vitro. Several structural characteristics of seagrass, including level and arrangement of fibre, and water content, make it particularly amenable to mechanical breakdown. The soft mouthparts of the dugong are highly modified so that the entire oral cavity functions to crush low fibre seagrasses. Thus, the dugong has developed an efficient method of food ingestion and mastication that is suited to processing large quantities of soft seagrass during short dive times. The potential cost to the dugong in having lost its hard dental surfaces is that it has become restricted to a low fibre diet.

Body cooling and the diving capabilities of muskrats ( Ondatra zibethicus): A test of the adaptive hypothermia hypothesis

We tested the hypothesis that immersion hypothermia enhances the diving capabilities of adult and juvenile muskrats by reducing rates of oxygen consumption (V˙O 2). Declines in abdominal body temperature ( T b) comparable to those observed in nature (0.5–3.5 °C) were induced by pre-chilling animals in 6 °C water. Pre-chilling did not reduce diving V˙O 2 of any animal tested in 10 °C or 30 °C water, irrespective of the nature of the dive. Most behavioural indices of dive performance, including average and cumulative dive times, were unaffected by T b reduction in adults, but depressed in hypothermic juveniles (200–400 g). Hypothermia reduced diving heart rate only on short (< 25 s) dives (16% reduction, P = 0.01), but did not affect the temporal onset of diving bradycardia. Post-immersion V˙O 2 was higher for pre-chilled than for normothermic muskrats, but the difference became insignificant on longer (> 90 s) dives. Our findings suggest that the mild hypothermia experienced by muskrats in nature has minimal effect on diving and post-immersion metabolic costs, and thus has little impact on the dive performance of this northern semi-aquatic mammal.

Diving to extremes: are New Zealand sea lions (Phocarctos hookeri) pushing their limits in a marginal habitat?

AbstractWhen studying diving behaviour, it is important to know whether a species is operating at or close to its maximum physiological capacity, because if it is, it will be less capable of compensating for normal environmental or human‐induced fluctuations in its environment. New Zealand (NZ) sea lions Phocarctos hookeri are among the world's rarest pinnipeds with a restricted distribution and abundance to the most southerly limit of their known range, NZ's sub‐Antarctic. Female NZ sea lions are the deepest and longest diving of the otariids, foraging further from their breeding rookeries than any other sea lion. In this study, the diving behaviours of 18 female NZ sea lions from Enderby Island, Auckland Islands, were recorded during early lactation over two austral summers, 2003 and 2004. While at sea, sea lions dived almost continuously, spending on average 52.7% of their time submerged (&gt;6 m). The mean dive depth (±se) for all dives was 129.5±5.3 m (range 94.6±1.1 to 178.9±1.6 m). The mean duration of dives was 4.0±0.1 min with an average of 40±2.9% of all dive times spent in the deepest 85% of the dive. Although there was high variation in diving behaviour among individuals, overall, animals were found to be diving beyond their estimated aerobic dive limits on 68% of all dives. Given that female NZ sea lions have a high percentage of dives that are beyond their theoretical aerobic limits, we ask whether this represents a miscalculation in aerobic limits, is it a species highly adapted to carry an anaerobic load or a species that is physically stretched to their limits? A species that is presumably under physiological stress just to maintain its current low static population numbers is also likely to be more susceptible to external impacts and this needs consideration for their management.

Diving behaviour of Mediterranean monk seal pups during lactation and post weaning

Time depth recorders (TDRs) were attached to 3 Mediterranean monk seal pups during a range of periods around weaning, providing a composite picture of activity from the first weeks of life until nutritional independence. The pups entered the water during their first week of life and their diving performance increase progressively with age. All pups spent most of their time at sea (55 to 74%), and their swimming activity was greater at nighttime compared with daytime. Dive per- formance in relation to pup age was poorer compared with other phocid seal species. Dive types were classified using a combination of hierarchical and k-mean clustering. We found 3 dive types: 1 V- shaped and 2 U-shaped. The most common type was U1-dives, mainly used by older pups during 44 to 48% of their total dive time. These dives were relatively deep and long (mean depth = 11.6 ± 9.5 m, mean duration = 149.1 ± 80.6 s). They had long bottom times (100 ± 67 s), suggesting that pups were foraging. Pups appeared to start feeding at the end of lactation.

FORAGING PATTERNS AND PREY SELECTION IN AN INCREASING AND EXPANDING SEA OTTER POPULATION

Focal observations of sea otter (Enhydra lutris kenyoni) foraging patterns and prey selection were collected in coastal Washington between 1993 and 1999. Records consisted of 13,847 individual dives from 841 feeding bouts ranging from 1 min to >4 h. Average dive time was 55 s ± 0.9 SE and average surface time was 45 s ± 2.3 SE, irrespective of dive success. At least 77% of all dives (n = 10,636) were successful prey captures (dives in low light or of undetermined success were excluded). Prey capture success was significantly lower for subadults (63% ± 5 SE) than adults (82% ± 1 SE; P < 0.001). Sea otters occupying the established population range on the outer coast of Washington fed heavily on bivalves (63%) and had a diverse diet consisting of several prey groups (n = 10). In contrast, sea otters occupying new habitat in the Strait of Juan de Fuca had a restricted diet dominated by >60% red urchins (Strongylocentrotus franciscanus), with only 2 other prey species comprising >10% of their diet. Prey size and prey category were dominant predictor variables in generalized linear models of dive duration and postdive surface duration on successful dives. Significant increases in areal extent of surface canopy of giant kelp (Macrocystis integrifolid) and bull kelp (Nereocystis leutkeana) were found both in the outer coast and the Strait of Juan de Fuca (0.4–0.5 km2 per year, P < 0.05) and suggest increasing suitable habitat for a growing population. The growth and expansion of a small and isolated sea otter population provides a unique opportunity to examine the relationship between dietary diversity and population status and explore similarities and differences between trophic paradigms established for sea otter populations at other localities.

An Advanced Method to Estimate Deep Currents from Profiling Floats

Abstract Subsurface ocean currents can be estimated from the positions of drifting profiling floats that are being widely deployed for the international Argo program. The calculation of subsurface velocity depends on how the trajectory of the float while on the surface is treated. The following three aspects of the calculation of drift velocities are addressed: the accurate determination of surfacing and dive times, a new method for extrapolating surface and dive positions from the set of discrete Argos position fixes, and a discussion of the errors in the method. In the new method described herein, the mean drift velocity and the phase and amplitude of inertial motions are derived explicitly from a least squares fit to the set of Argos position fixes for each surface cycle separately. The new method differs from previous methods that include prior assumptions about the statistics of inertial motions. It is concluded that the endpoints of the subsurface trajectory can be estimated with accuracy better than 1.7 km (East Sea/Sea of Japan) and 0.8 km (Indian Ocean). All errors, combined with the error that results from geostrophic shear and extrapolation, should result in individual subsurface velocity estimates with uncertainty of the order of 0.2 cm s−1.

A Theoretical Analysis of Diving Performance in the Weddell Seal (Leptonychotes weddelli)

Marine mammals are constrained in their foraging behaviour because, as obligate air breathers, they must undertake regular trips to the water surface to satisfy the need for respiratory gas exchange. Maximum underwater endurance time is determined by O2 supply and demand, but this does not necessarily imply that O2 is the main factor regulating individual dive and surface times. This study presents a theoretical analysis of diving performance that emphasizes a key role for CO2 in the proximate control of diving behaviour. Computer simulations, based on a mathematical model of the mammalian cardiorespiratory control system, are used to investigate the influence of swimming to depth and other energetic stresses (feeding, thermogenesis, sleep) on predicted diving behaviour in an average adult Weddell seal. The plausibility of the proposed model is supported by the study, which replicated published observations of natural diving behaviour in this species. It is suggested that diving behaviour is tuned to oscillations in respiratory drive and that behavioural and physiological factors can alter the dynamic characteristics of the system to achieve a highly adaptable reciprocal interaction that blurs the boundary between physiology and behaviour.

Tufted ducks Aythya fuligula do not control buoyancy during diving

Work against buoyancy during submergence is a large component of the energy costs for shallow diving ducks. For penguins, buoyancy is less of a problem, however they still seem to trade‐off levels of oxygen stores against the costs and benefits of buoyant force during descent and ascent. This trade‐off is presumably achieved by increasing air sac volume and hence pre‐dive buoyancy (Bpre) when diving deeper. Tufted ducks, Aythya fuligula, almost always dive with nearly full oxygen stores so these cannot be increased. However, the high natural buoyancy of tufted ducks guarantees a passive ascent, so they might be expected to decrease Bpre before particularly deep, long dives to reduce the energy costs of diving. Body heat lost to the water can also be a cause of substantial energy expenditure during a dive, both through dissipation to the ambient environment and through the heating of ingested food and water. Thus dive depth (dd), duration and food type can influence how much heat energy is lost during a dive. The present study investigated the relationship between certain physiological and behavioural adjustments by tufted ducks to dd and food type. Changes in Bpre, deep body temperature (Tb) and dive time budgeting of four ducks were measured when diving to two different depths (1.5 and 5.7 m), and for two types of food (mussels and mealworms). The hypothesis was that in tufted ducks, Bpre decreases as dd increases. The ducks did not change Bpre in response to different diving depths, and thus the hypothesis was rejected. Tb was largely unaffected by dives to either depth. However, diving behaviour changed at the greater dd, including an increase in dive duration and vertical descent speed. Behaviour also changed depending on the food type, including an increase in foraging duration and vertical descent speed when mussels were present. Behavioural changes seem to represent the major adjustment made by tufted ducks in response to changes in their diving environment.

Effects of Diving and Swimming Behavior on Body Temperatures of Pacific Leatherback Turtles in Tropical Seas

Mathematical models and recordings of cloacal temperature suggest that leatherback turtles (Dermochelys coriacea) maintain core body temperature higher than ambient water temperature (T(W)) while freely swimming at sea. We investigated the thermoregulatory capabilities of free-ranging leatherbacks and, specifically, the effect that changes in diving patterns and ambient temperatures have on leatherback body temperatures (T(B)). Data loggers were used to record subcarapace and gastrointestinal tract temperatures (T(SC) and T(GT), respectively), T(W), swim speed, dive depth, and dive times of female leatherback turtles during internesting intervals off the coast of Guanacaste, Costa Rica. Mean T(SC) (28.7 degrees -29.0 degrees C) was significantly higher than mean T(W) (25.0 degrees -27.5 degrees C). There was a significant positive relationship between T(SC) and T(W) and a significant negative correlation between T(SC) and dive depth and T(GT) and dive depth. Rapid fluctuations in T(GT) occurred during the first several days of the internesting interval, which suggests that turtles were ingesting prey or water during this time. Turtles spent 79%-91% of the time at sea swimming at speeds greater than 0.2 m s(-1), and the average swim speed was 0.7 +/- 0.2 m s(-1). Results from this study show that alterations in diving behavior and T(W) affect T(B) of leatherback turtles in the tropics. Body temperatures of free-ranging leatherback turtles correspond well with values for T(B) predicted by mathematical models for tropical conditions.

Diving Heart Rate Development in Postnatal Harbour Seals,Phoca vitulina

Harbour seals, Phoca vitulina, dive from birth, providing a means of mapping the development of the diving response, and so our objective was to investigate the postpartum development of diving bradycardia. The study was conducted May-July 2000 and 2001 in the St. Lawrence River Estuary (48 degrees 41'N, 68 degrees 01'W). Both depth and heart rate (HR) were remotely recorded during 86,931 dives (ages 2-42 d, n = 15) and only depth for an additional 20,300 dives (combined data covered newborn to 60 d, n = 20). The mean dive depth and mean dive durations were conservative during nursing (2.1 +/- 0.1 m and 0.57 +/- 0.01 min, range = 0-30.9 m and 0-5.9 min, respectively). The HR of neonatal pups during submersion was bimodal, but as days passed, the milder of the two diving HRs disappeared from their diving HR record. By 15 d of age, most of the dive time was spent at the lower diving bradycardia rate. Additionally, this study shows that pups are born with the ability to maintain the lower, more fully developed dive bradycardia during focused diving but do not do so during shorter routine dives.

Diving and Feeding Behaviour of Sperm Whales (&lt;I&gt;Physeter macrocephalus&lt;/I&gt;) in the Northwestern Mediterranean Sea

Sperm whale (Physeter macrocephalus) is one of the common cetacean species inhabiting the western Mediterranean Sea. The aim of this study was to describe the dive cycle of sperm whales in this region and gain insight into their foraging activity. Dedicated summer field seasons were conducted from 2001-2003. Visual and acoustic measures were undertaken and their relationships analyzed. The measures included surface/dive periods, blow rate, distance traveled, timing of clicks & creak activity, and inter-pulse interval measurements of sperm whale clicks. The whales exhibited dive cycle parameters consistent with those measured in other parts of the world: approximately 45 min dive duration, 9 min surface period (i.e., inter-dive interval), with 5 blows/min, and 1.3 nmi horizontal displacement between dives. An average of 25 creaks per dive were registered. Whale body size appeared to be significantly related with both the number of creaks per dive and the dive time at which the first creak occurred, suggesting that larger whales may increase their prey intake and use deeper water layers than smaller whales. The timing of the first creak and the last click of the dive (around 6 min after fluke-up, and just before the surfacing, respectively) suggest a foraging depth of between 500 and 800 m, based on known descent and ascent rates.

Respiratory frequency, dive behaviour and social interactions of leatherback turtles, Dermochelys coriacea during the inter-nesting interval

We collected simultaneous dive Time Depth Recorder (TDR) data and video images from free swimming adult female leatherback turtles, Dermochelys coriacea, during the first 24 h after nesting on the beach, in order to determine relationships between dive parameters, activity, overall respiratory frequency and behaviour. We identified three different underwater locomotory activities (subsurface swimming, V-shaped dives and U-shaped dives) from video and TDR data that varied in their mean depth, duration and a number of other parameters. Overall respiratory frequency (overall f R) was significantly different between all locomotory activities, with turtles taking 1.7±0.1 breaths min −1 while subsurface swimming, 0.78 breaths min −1 after V-shaped dives and 0.57 breaths min −1 after U-shaped dives. Descent rates and ascent rates were significantly faster in U-shaped dives (descent 0.19±0.010 m s −1, ascent 0.28±0.015 m s −1) than in V-shaped dives (descent 0.10±0.008 m s −1, ascent 0.12±0.012 m s −1). Flipper stroke rates were significantly lower during the bottom component of U-shaped dives (0.18±0.02 strokes s −1) than during the descent (0.29±0.03 strokes s −1) or ascent (0.29±0.03 strokes s −1). From overall f R and flipper stroke rate data, we inferred that turtles used less energy during U-shaped dives than the other activity types. We recorded interactions between male turtles and the study females that lasted up to 11 min, during which male turtles displayed the characteristic courtship behaviour of sea turtles. It appeared that females attempted to avoid males by aborting ascent and extending dive duration to swim to the sea floor when males were present.

AERIAL SURVEYS FOR COASTAL DOLPHINS: ABUNDANCE OF HECTOR'S DOLPHINS OFF THE SOUTH ISLAND WEST COAST, NEW ZEALAND

AbstractLine‐transect surveys of abundance depend critically on the estimation of detection probability, which includes corrections for availability and visibility. In this aerial line‐transect survey for Hector's dolphin (Cephalorhynchus hectori) we recorded dive times from a helicopter to estimate the proportion of time that dolphins could be seen at or near the water surface and were therefore “available” to be counted. The proportion of available sightings that were counted on transect lines was estimated by comparing sightings by two independent teams of two observers in the fixed‐wing plane. The survey covered the area between Farewell Spit and Milford Sound, off the west coast of the South Island of New Zealand. Survey effort was stratified according to existing distribution data. A total of 142 separate sightings was made on 1,355 km of trackline. Average availability for fifty Hector's dolphin groups observed from the helicopter (161 dive/surface cycles) was 46.3% (CV = 4.2%). Data from the two independent observer teams indicated that 96.2% (CV = 2.3%) of the dolphin groups that were at the surface and on the trackline were seen. The abundance estimate for the South Island west coast, corrected for visibility and availability, was 5,388 Hector's dolphins (CV = 20.6%). The total population estimate for South Island Hector's dolphins is 7,270 (CV = 16.2%).