Dive characteristics can predict foraging success in Australian fur seals (arctocephalus pusillus doriferus) as validated by animal-borne video

Dive characteristics and dive shape are often used to infer foraging success in pinnipeds. However, these inferences have not been directly validated in the field with video, and it remains unclear if this method can be applied to benthic foraging animals. This study assessed the ability of dive characteristics from time-depth recorders (TDR) to predict attempted prey capture events (APC) that were directly observed on animal-borne video in Australian fur seals (Arctocephalus pusillus doriferus, n=11). The most parsimonious model predicting the probability of a dive with ≥1 APC on video included only descent rate as a predictor variable. The majority (94%) of the 389 total APC were successful, and the majority of the dives (68%) contained at least one successful APC. The best model predicting these successful dives included descent rate as a predictor. Comparisons of the TDR model predictions to video yielded a maximum accuracy of 77.5% in classifying dives as either APC or non-APC or 77.1% in classifying dives as successful verses unsuccessful. Foraging intensity, measured as either total APC per dive or total successful APC per dive, was best predicted by bottom duration and ascent rate. The accuracy in predicting total APC per dive varied based on the number of APC per dive with maximum accuracy occurring at 1 APC for both total (54%) and only successful APC (52%). Results from this study linking verified foraging dives to dive characteristics potentially opens the door to decades of historical TDR datasets across several otariid species.

New insights into the cardiorespiratory physiology of weaned southern elephant seals (Mirounga leonina)

Southern elephant seal (Mirounga leonina) pups must strike a balance between conserving energy during their post-weaning fast and simultaneously developing diving abilities to attain nutritional independence. Little is known about environmental influences on cardiorespiratory patterns, hence energy use, throughout the 6 week fast. Continuous heart rates were recorded for free-ranging, newly weaned southern elephant seals using heart rate time-depth recorders for 5-9 days at Sub-Antarctic Macquarie Island, during October 1994 (n = 1), 1995 (n = 4) and 1996 (n = 1). Daytime observations of respiration and behaviour were made throughout. We present the first instance of synchronous heart rate traces recorded simultaneously for individual weaners. Generalized additive models revealed that a sinusoidal pattern of diurnal heart rate elevation and nocturnal depression was evident in all seals and, on at least one occasion, a conspicuous break in this pattern coincided with an extreme cold weather event. Seals in this study were capable of considerable cardiorespiratory control and regularly demonstrated bradycardia during periods of resting apnoea. Apnoeic duration ranged from 33 to 291 s (mean 134 s). Apnoeic heart rates (mean 67 ± 15 beats min(-1), range 40-114 beats min(-1)) were on average 19.7% lower than those exhibited during periods of eupnoea (mean 83 ± 15 beats min(-1), range 44-124 beats min(-1)). The early development of the cardiorespiratory response is characterized by arrhythmic heart and respiration rates. The strong temporal patterns observed are being driven by the opposing requirements of maximizing time spent fasting in order to develop diving capabilities and of maximizing departure mass. This pilot study has highlighted a potentially large effect of ambient weather conditions on newly weaned southern elephant seal cardiorespiratory activity. Given the increasing westerlies and more erratic and increasing storminess associated with the Southern Annular Mode predicted in the Southern Ocean, the patterns observed here warrant further investigation.

Physiological and behavioural factors influencing foraging success in otariid seals

 This thesis directly validated methods of estimating energetic gain and energetic expenditure in diving seals and sea lions. Results showed that head-mounted accelerometers and dive behaviour can predict foraging behaviour and energetic gain. In contrast, 3-dimensional body movement was unable to reliably predict energetic expenditure of diving pinnipeds.

Early-life sexual segregation: ontogeny of isotopic niche differentiation in the Antarctic fur seal

Investigating the ontogeny of niche differentiation enables to determine at which life-stages sexual segregation arises, providing insights into the main factors driving resource partitioning. We investigated the ontogeny of foraging ecology in Antarctic fur seals (Arctocephalus gazella), a highly dimorphic species with contrasting breeding strategies between sexes. Sequential δ(13)C and δ(15)N values of whiskers provided a longitudinal proxy of the foraging niche throughout the whole life of seals, from weaning, when size dimorphism is minimal to the age of 5. Females exhibited an early-life ontogenetic shift, from a total segregation during their first year at-sea, to a similar isotopic niche as breeding females as early as age 2. In contrast, males showed a progressive change in isotopic niche throughout their development such that 5-year-old males did not share the same niche as territorial bulls. Interestingly, males and females segregated straight after weaning with males appearing to feed in more southerly habitats than females. This spatial segregation was of similar amplitude as observed in breeding adults and was maintained throughout development. Such early-life niche differentiation is an unusual pattern and indicates size dimorphism and breeding constraints do not directly drive sexual segregation contrary to what has been assumed in otariid seals.

Testing optimal foraging theory models on benthic divers

Empirical testing of optimal foraging models on diving air-breathing animals is limited due to difficulties in quantifying the prey field through direct observations. Here we used accelerometers to detect rapid head movements during prey encounter events (PEE) of free-ranging benthic-divers, Australian fur seals, Arctocephalus pusillus doriferus. PEE signals from accelerometer data were validated by simultaneous video data. We then used PEEs as a measure of patch quality to test several optimal foraging model predictions. Seals had longer bottom durations in unfruitful dives (no PEE) than those with some foraging success (PEE. ≥. 1). However, when examined in greater detail, seals had longer bottom durations in dives with more PEEs, but shorter bottom durations in bouts (sequences of dives) with more PEEs. Our results suggest that seals were generally maximizing bottom durations in all foraging dives, characteristic of benthic divers. However, successful foraging dives might be more energetically costly (e.g. digestive costs), thus resulting in shorter bottom durations at the larger scale of bouts. Our study provides a case study of how the foraging behaviour of a central place forager foraging in a fairly homogeneous environment, with relatively high travel costs, may deviate from current foraging models under different situations. Future foraging models should aim to integrate other aspects (e.g. diet) of the foraging process for more accurate predictions.

Flipper strokes can predict energy expenditure and locomotion costs in free-ranging northern and Antarctic fur seals

Flipper strokes have been proposed as proxies to estimate the energy expended by marine vertebrates while foraging at sea, but this has never been validated on free-ranging otariids (fur seals and sea lions). Our goal was to investigate how well flipper strokes correlate with energy expenditure in 33 foraging northern and Antarctic fur seals equipped with accelerometers, GPS, and time-depth recorders. We concomitantly measured field metabolic rates with the doubly-labelled water method and derived activity-specific energy expenditures using fine-scale time-activity budgets for each seal. Flipper strokes were detected while diving or surface transiting using dynamic acceleration. Despite some inter-species differences in flipper stroke dynamics or frequencies, both species of fur seals spent 3.79 ± 0.39 J/kg per stroke and had a cost of transport of ~1.6-1.9 J/kg/m while diving. Also, flipper stroke counts were good predictors of energy spent while diving (R(2) = 0.76) and to a lesser extent while transiting (R(2) = 0.63). However, flipper stroke count was a poor predictor overall of total energy spent during a full foraging trip (R(2) = 0.50). Amplitude of flipper strokes (i.e., acceleration amplitude × number of strokes) predicted total energy expenditure (R(2) = 0.63) better than flipper stroke counts, but was not as accurate as other acceleration-based proxies, i.e. Overall Dynamic Body Acceleration.

Acknowledging long-term ecological change: the problem of shifting baselines

Shifting baselines describes the phenomenon where long-term changes to an environment go unrecognized because what is perceived as natural shifts with succeeding generations of scientists and other observers. This is a particular problem for the oceans because we are rarely able to directly observe the consequences of human activities. In the absence of data to track these consequences, a common assumption has been that the communities we observe today using SCUBA or other technology, are similar to the communities that existed 10, 100, or even 1000 years ago. Research is increasingly demonstrating this is not the case. Instead, marine ecosystems may have been vastly different in the past, and we have succumbed to the shifting baselines syndrome. This has significant implications for scientific study, management, and for human communities more broadly. We discuss these implications, and how we might address the shifting baseline syndrome in the oceans to confront its repercussions. In a world where environmental degradation is accelerating, doing so is critical to avoid further ratcheting down of our expectations of ecosystem health and productivity, and to ensure that we have the information necessary to implement appropriate recovery and management goals.

Ecotourism snorkelling routes at Marinha Beach (Algarve)

Coastal ecotourism is one of the fastest growing leisure industries in the world and snorkelling is emerging as an important beach-based activity. Snorkelling has the potential to enhance biodiversity conservation when developed within environmental education framework. The aim of this study was to implement and evaluate snorkelling routes, in the Algarve (South Portugal), as a sustainable ecotourism offer. To achieve these objectives, three snorkelling routes were established at the pristine Marinha beach. After the diving experience, a face-to-face questionnaire survey was conducted to collect information about individuals' opinions regarding the underwater routes, their social demographic characteristics, ecological appreciation, opinions about beach facilities and trip expenditures. The survey was undertaken during the summer months of 2008 and 2009, and 202 people were interviewed. Data was analysed using univariate and multivariate statistic methods. Most respondents perceived the existence of routes to be good for the preservation of the local biodiversity and reported this experience as "good" or "excellent". The only difference in perceptions was observed by visitor snorkelling in groups of more than two people. Interviewers consider that emergency support and sanitary facilities are the most important beach support infrastructures. Overall, these routes seem to be an effective tool for developing ecological awareness in tourists, as they enhance the preservation and the understanding of the marine coastal environment.

First record of Calcinus tubularis on the southern coast of Portugal (Crustacea: Decapoda: Anomura: Diogenidae)

Twenty-five specimens of the hermit crab Calcinus tubularis were observed during SCUBA dives for fauna and flora assessment in the shallow rocky reefs of the southern coast of Portugal between 2003 and 2008. Of the specimens observed, only one specimen used a tube gallery, while the others occupied unidentified gastropod shells with strong bio-cover. Calcinus tubularis is here recorded from the mainland Portuguese coast for the first time. This is the first record of the species in European coastal waters outside the Mediterranean Sea (excluding the Atlantic Islands) and extends the known geographical distribution of the species further north in the north-eastern Atlantic.

Underwater survey of ichthyofauna of eastern Atlantic seamounts: Gettysburg and Ormond (Gorringe Bank)

Gettysburg and Ormond are seamounts belonging to the Gorringe Bank, which is located on the Europen-African plate boundary. Given the importance of these oceanic features for understanding marine biodiversity patterns, two surveys were carried out in 1998 (Gettysburg) and 1999 (Ormond) using diving, photography and video for species identification and abundance evaluation. Of the 9 fish species found at Gettysburg and 11 at Ormond, 6 were common to both sites and these included the dominant species: the oceanic and commercially important, Seriola rivoliana, and the coastal, typically Atlantic-Mediterranean Coris julis and Anthias anthias. The strong representation of coastal, demersal and Atlantic-Mediterranean species in the Gorringe Bank region and the presence of Abudefduf luridus, an endemic Macaronesian species, at Gettysburg suggests that the upper part of these seamounts may have acted and still act as “stepping stones” for the dispersal of coastal species.