Article

Identifying overlap between humpback whale foraging grounds and the Antarctic krill fishery

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Abstract

The Antarctic krill fishery is the largest in the southern ocean, but currently operates without fine-scale information on whale movement and behavior. Using a multi-year dataset of satellite-tagged whales, as well as information on krill catch levels, we analyzed the spatial distribution of whales and fisheries effort within the small-scale management units defined by the Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR). Using a Bayesian movement model to partition whale movement into traveling and area-restricted search states, we found that both whale behavior and krill catch effort were spatially clustered, with distinct hotspots of the whale activity in the Gerlache and southern Branfield Straits. These areas align with increases in krill fishing effort, and present potential areas of current and future conflict. We recommend that the Antarctic West and Bransfield Strait West management units merit particular attention when setting fine-scale catch limits and, more broadly, consideration as critical areas for krill predator foraging.

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... 48,50,51 These areas are used throughout the summer and become the exclusive feeding habitat in autumn as sea ice develops and krill move inshore in autumn. 46,47,52 The highest densities of humpback whales reported are from aggregations in autumn in the nearshore bays around the Gerlache and Bransfield Straits. 50,51 In one day, more than 500 humpback whales and 2.3 million tonnes of krill were measured in Wilhelmina in May 2009. ...
... 59 However, current management of the krill fishery has not considered or assessed the needs and behaviour of the largest krill predators in the Antarctic: baleen whales. 52 In Fine-scale information on humpback presence suggests that the uniform krill catch limit for all small-scale management units in the Antarctic Peninsula is overly broad and ignores the fact that whale behaviour and krill catch effort are spatially clustered. Resolving the disparity between the spatial and temporal preference for specific areas by humpback whales and fishery vessels and the uniform nature of the krill catch limits is critical in minimising the potential conflict between whales and the fishery. ...
... Resolving the disparity between the spatial and temporal preference for specific areas by humpback whales and fishery vessels and the uniform nature of the krill catch limits is critical in minimising the potential conflict between whales and the fishery. 52 In 2003, CCAMLR agreed to define a suite of small-scale management units (SSMUs) for this region throughout the entire Area 48, based on the distribution of krill, krill predator foraging range and the fishery. However, there has been no agreement on the allocation of catch limits at this scale. ...
Technical Report
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The Antarctic Peninsula and its whales are under increasing pressure from climate change, krill fishing and a growing tourism industry. New technologies such as digital tags, drones and satellite tracking are unlocking the mystery of exactly where baleen whales feed on krill, highlighting the need for increased protection of the Western Antarctic Peninsula – a feeding hotspot. Research reveals humpbacks rely heavily on the peninsula for feeding and resting. This information is part of a new WWF-University of California Santa Cruz report for policymakers entitled was presented at the 2018 Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) meeting.
... Humpbacks in these waters primarily feed on Antarctic krill (Euphausia superba), which form large aggregative swarms during the austral summer and fall [9,10]. At the broad scale, previous work has used two-dimensional visual observations to highlight areas of whale density [11][12][13], and satellite tag data to assess seasonal changes in movement [14]. Due to physiology and feeding mechanics, there is a minimal krill density at which foraging is energetically favorable for humpback whales, creating discrete bouts of feeding and traveling [15]. ...
... By refining spatial patterns of movement with nested foraging behaviors, we can connect seasonal changes in behavior with potential changes in foraging intensity. The seasonal demands in energy expenditure may be critical in understanding the rebound in humpback populations from historic declines [19,20], the effect of rapidly changing Antarctic marine environment [21,22], and the potential competition with the Antarctic Krill fishery [11,23]. ...
... Resting;Resting = (0.87,0.89)) ( Figs. 2 and 3). The spatial pattern of traveling and area-restricted search states largely matched previous work in [11,14], with the majority of area-restricted search events in the Gerlache and Bransfield straits (Fig. 4). Within area-restricted search, the mean percentage of time spent in foraging state (mean = 58.2%, ...
Article
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Background Matching animal movement with the behaviors that shape life history requires a rigorous connection between the observed patterns of space use and inferred behavioral states. As animal-borne dataloggers capture a greater diversity and frequency of three dimensional movements, we can increase the complexity of movement models describing animal behavior. One challenge in combining data streams is the different spatial and temporal frequency of observations. Nested movement models provide a flexible framework for gleaning data from long-duration, but temporally sparse, data sources. Results Using a two-layer nested model, we combined geographic and vertical movement to infer traveling, foraging and resting behaviors of Humpback whales off the West Antarctic Peninsula. This approach refined previous work using only geographic data to delineate coarser behavioral states. Our results showed increased intensity in foraging activity in late season animals as the whales prepared to migrate north to tropical calving grounds. Our model also suggests strong diel variation in movement states, likely linked to daily changes in prey distribution. Conclusions Using a combination of two-dimensional and three-dimensional movement data, we highlight the connection between whale movement and krill availability, as well as the complex spatial pattern of whale foraging in productive polar waters. Electronic supplementary material The online version of this article (10.1186/s40462-018-0134-4) contains supplementary material, which is available to authorized users.
... Humpback whales (Megaptera novaeangliae) are large marine vertebrates with a cosmopolitan distribution, which migrate seasonally between foraging and breeding areas [29]. In the Southern Hemisphere, seven breeding populations ("breeding stocks" A-G) [30] from discrete low-latitude winter breeding areas in the Atlantic, Indian, and Pacific Oceans migrate to summer foraging areas in the Southern Ocean around Antarctica. Published humpback whale tracking data for the Southern Ocean [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] (suggest that there is region-specific habitat selection in Southern Ocean humpback whales. This case thus presents a good scenario for testing how region-specific habitat selection patterns can be included in large-scale predictions. ...
... We compiled published and unpublished satellite tracking data from 378 individual humpback whales, totaling 291,628 location records. Argos satellite-linked telemetry tags were deployed on humpback whales in their breeding areas and Antarctic foraging areas from 2002-2018 [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] (Supplementary Table S1). Adult individuals were selected for tagging in these study areas indiscriminately; specific individuals were not targeted. ...
... Additionally, smaller important areas are highlighted in the Sub-Antarctic. The predictions also show that key humpback whale habitats are not homogeneously distributed around Antarctica-something already indicated by whaling records [87], sightings data (e.g., [99,100]), tracking data [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48], and other habitat modelling [99]. Similar to our validation approach, but excluding the whaling dataset, Bombosch et al. [99] used IWC sightings data corresponding with their study period as independent valuation of their predictions, achieving an AUC value of 0.877 (compared with our result of 0.821 for model M5). ...
Article
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Machine learning algorithms are often used to model and predict animal habitat selection the relationships between animal occurrences and habitat characteristics. For broadly distributed species, habitat selection often varies among populations and regions; thus, it would seem preferable to fit region- or population-specific models of habitat selection for more accurate inference and prediction, rather than fitting large-scale models using pooled data. However, where the aim is to make range-wide predictions, including areas for which there are no existing data or models of habitat selection, how can regional models best be combined? We propose that ensemble approaches commonly used to combine different algorithms for a single region can be reframed, treating regional habitat selection models as the candidate models. By doing so, we can incorporate regional variation when fitting predictive models of animal habitat selection across large ranges. We test this approach using satellite telemetry data from 168 humpback whales across five geographic regions in the Southern Ocean. Using random forests, we fitted a large-scale model relating humpback whale locations, versus background locations, to 10 environmental covariates, and made a circumpolar prediction of humpback whale habitat selection. We also fitted five regional models, the predictions of which we used as input features for four ensemble approaches: an unweighted ensemble, an ensemble weighted by environmental similarity in each cell, stacked generalization, and a hybrid approach wherein the environmental covariates and regional predictions were used as input features in a new model. We tested the predictive performance of these approaches on an independent validation dataset of humpback whale sightings and whaling catches. These multiregional ensemble approaches resulted in models with higher predictive performance than the circumpolar naive model. These approaches can be used to incorporate regional variation in animal habitat selection when fitting range-wide predictive models using machine learning algorithms. This can yield more accurate predictions across regions or populations of animals that may show variation in habitat selection.
... They often live in remote, inaccessible environments, can undertake long migrations, and spend the majority of their time underwater. Few studies have focused on the relationship between baleen whales and krill in the Antarctic, and most behavioural studies to date have taken place around the Antarctic Peninsula on humpback whales (Megaptera novaeangliae), minke whales (Balaenoptera bonaerensis), and fin whales (Balaenoptera physalus) over a variety of spatial scales (1-1000 s of kms) [23][24][25][26][27][28] . A variety of methods have been used in these studies to assess whale presence and behaviour, including visual surveys 25,26,29 , suction tags 23,24,27 and satellite tags 28 . ...
... Few studies have focused on the relationship between baleen whales and krill in the Antarctic, and most behavioural studies to date have taken place around the Antarctic Peninsula on humpback whales (Megaptera novaeangliae), minke whales (Balaenoptera bonaerensis), and fin whales (Balaenoptera physalus) over a variety of spatial scales (1-1000 s of kms) [23][24][25][26][27][28] . A variety of methods have been used in these studies to assess whale presence and behaviour, including visual surveys 25,26,29 , suction tags 23,24,27 and satellite tags 28 . Those that collected concurrent data on krill distribution did so using either active acoustics (scientific echosounders), allowing finer spatial sampling of individual swarms 24,26,29 or net hauls, resulting in coarser spatial sampling but direct measurements and identification of krill 25,26 . ...
... From these studies, several associations have been found between whales and krill around the Antarctic Peninsula, including spatial clustering with distinct hotspots at macro-and meso-scales 24,25,28 . At smaller scales, fin and humpback whales were associated with moderate 26 and high 24 levels of krill biomass respectively. ...
Article
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We model the presence of rare Antarctic blue whales (Balaenoptera musculus intermedia) in relation to the swarm characteristics of their main prey species, Antarctic krill (Euphausia superba). A combination of visual observations and recent advances in passive acoustic technology were used to locate Antarctic blue whales, whilst simultaneously using active underwater acoustics to characterise the distribution, size, depth, composition and density of krill swarms. Krill swarm characteristics and blue whale presence were examined at a range of spatiotemporal scales to investigate sub meso-scale (i.e., <100 km) foraging behaviour. Results suggest that at all scales, Antarctic blue whales are more likely to be detected within the vicinity of krill swarms with a higher density of krill, those found shallower in the water column, and those of greater vertical height. These findings support hypotheses that as lunge-feeders of extreme size, Antarctic blue whales target shallow, dense krill swarms to maximise their energy intake. As both Antarctic krill and blue whales play a key role in the Southern Ocean ecosystem, the nature of their predator-prey dynamics is an important consideration, not only for the recovery of this endangered species in a changing environment, but for the future management of Antarctic krill fisheries.
... Here we applied a movement model to satellite tagging data of humpback whales on their Southern Ocean feeding grounds to infer underlying behavioral states: transiting and area restricted search (ARS), a behavior indicative of foraging (Weinstein et al., 2017;Andrews-Goff et al., 2018). We expected that aspects of whale foraging behavior would change throughout the feeding season. ...
... ARS is generally considered to be indicative of foraging, resting or breeding behavior (e.g. Weinstein et al., 2017;Andrews-Goff et al., 2018). Locations with a mean b estimate between 1.25 and 1.75 were treated as 'uncertain'. ...
... Although we were not able to confirm ARS behavior identified by our SSM as foraging, both previous studies and the general knowledge about humpback whale behavior south of 60°S suggest that ARS behavior identified by the SSM is largely foraging (Chittleborough, 1965;Weinstein et al., 2017;Andrews-Goff et al., 2018). With this assumption in mind, the high overall amount of transiting behavior south of 60°S might serve as an indicator of prey distribution, whereby whales may have to move quite long distances between prey patches. ...
Article
Satellite telemetry and animal movement models advance our ability to remotely monitor the behavior of wide-ranging species. Understanding how different behaviors (e.g. foraging) are shaped by dynamic environmental features is fundamental to understanding ecological interactions and the impact of variability. In this study we deployed satellite-linked tags on humpback whales (Megaptera novaeangliae) and used state-space models to estimate locations and to infer underlying behavioral states. We then modelled the association between whale behavior (e.g. foraging or transiting) and environmental variables using linear mixed-effect models. We identified the importance of two recently discovered Southern Ocean feeding areas for Oceania humpback whales as well as the key environmental drivers affecting whale behavior. We detected behavioral differences between whales utilizing the two adjacent feeding regions (~2000 km apart), which were likely caused by animals trying to efficiently locate prey in relation to the dynamic environmental characteristics of each habitat. We observed a seasonal pattern in foraging behavior, with the peak occurring in the middle of summer. Whales also foraged more intensively with increasing proximity to areas from which the ice edge had recently retreated, suggesting heightened productivity in these areas. The relationship between the animals and the physical features of the seascape, as well as the behavioral plasticity observed, could have implications for the future recovery of these whales in a changing Southern Ocean.
... 219 Growing commercial krill fishing Commercial krill fisheries that operate in the Antarctic Peninsula overlap with important humpback whale foraging areas, increasing risks of bycatch and competition for krill. 206,221 Photos: The Aker BioMarine krill fishing vessel -Antarctic Endurance, a Norweigan flagged ship -was photographed actively trawling towards and through a large group of fin whales 25 km north of Coronation Island on 13 January 2022. There were estimated to be between 500 and 1200 fin whales, with some blue and humpback whales in this aggregation. ...
... 224 Nonetheless, potential competition between fi sheries and krill predators, including baleen whales, is concerning. 221,[225][226][227][228] Krill catches have become more concentrated, 221,229 raising concerns about how local depletion of krill impacts predators. 221,228 CCAMLR recognized that this necessitates a smaller-scale management approach and designated "Small Scale Management Units" (16,000km 2 to 440,000km 2 ). ...
... 224 Nonetheless, potential competition between fi sheries and krill predators, including baleen whales, is concerning. 221,[225][226][227][228] Krill catches have become more concentrated, 221,229 raising concerns about how local depletion of krill impacts predators. 221,228 CCAMLR recognized that this necessitates a smaller-scale management approach and designated "Small Scale Management Units" (16,000km 2 to 440,000km 2 ). ...
Technical Report
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A new collaborative report from WWF and science partners provides the first comprehensive look at whale migrations and the threats they face across all oceans, highlighting how the cumulative impacts from industrial fishing, ship strikes, pollution, habitat loss, and climate change are creating a hazardous journey. Protecting Blue Corridors report visualises the satellite tracks of over 1000 migratory whales worldwide. The report outlines how whales are encountering multiple and growing threats in their critical ocean habitats – areas where they feed, mate, give birth, and nurse their young – and along their migration superhighways, or ‘blue corridors’. The report is a collaborative analysis of 30 years of scientific data contributed by more than 50 research groups, with leading marine scientists from Oregon State University, the University of California Santa Cruz, the University of Southampton and others. Case studies highlight hotspots and risks that whales navigate on their migrations, some of which can be thousands of kilometers each year. As a result of these hazards, six out of the 13 great whale species are now classified as endangered or vulnerable by the International Union for Conservation of Nature, even after decades of protection after commercial whaling. Among those populations most at risk is the critically endangered North Atlantic right whale, a species that migrates between Canada and the United States. It is at its lowest point in 20 years – numbering only 336 individuals. Protecting Blue Corridors calls for a new conservation approach to address these mounting threats and safeguard whales, through enhanced cooperation from local to regional to international levels. Of particular urgency is engagement with the United Nations, which is set to finalise negotiations on a new treaty for the high seas (Areas Beyond National Jurisdiction) in March 2022. The benefits from protected blue corridors extend far beyond whales. Growing evidence shows the critical role whales play maintaining ocean health and our global climate – with one whale capturing the same amount of carbon as thousands of trees. The International Monetary Fund estimates the value of a single great whale at more than US$2 million, which totals more than US$1 trillion for the current global population of great whales.
... A lack of updated estimates of krill biomass (the most recent data were collected in 2000 (Hewitt et al., 2004;Siegel et al., 2004)) and of predator demand for krill hinders the assessment of potential competition between the fishery and predators, but the likelihood of such competition is high (Watters et al., 2013). Given the absence of better information, the current CCAMLR catch allocation protocol is based on a fixed precautionary catch limit, allocated among four subareas (Weinstein et al., 2017), probably assuming that fishing effort will not focus on a specific area in view of the abundance of the resource. Despite these uncertainties, catches have increased steadily in the Western Antarctic Peninsula (WAP) region, which is recognized as a significant area for krill recruitment and sustains important foraging hotspots for krill predators, including marine birds and marine mammals (Alonzo et al., 2003;Hewitt et al., 2004;Santora et al., 2010;Santora and Veit, 2013;Hinke et al., 2014). ...
... The fishing fleet used to exploit the larger, more dispersed krill found in the Drake Passage area north of the South Shetland Islands in summer, but current efforts focus on the inner waters of the BS, mainly during the fall aggregation period, when krill are more vulnerable to fishing pressure, partly because of delayed winter sea ice formation (see above). Whales move into the BS and Gerlache Strait in fall and winter, potentially increasing competition between the fishery and whales in smaller areas (Curtice et al., 2015;Weinstein et al., 2017), where the disruptive effect of the fleet on krill swarms is accentuated. ...
... Once a profitable krill swarm is found, whales tend to remain in the area, feeding for several days until the krill are consumed and/or dispersed, then move to seek another swarm (Nowacek et al., 2011;Curtice et al., 2015). Whale distribution patterns have therefore been proposed as indicators of the overall distribution of krill swarms (Curtice et al., 2015;Weinstein et al., 2017), as has the aggregated behavior of the fleet. ...
Article
Antarctic krill is a vital part of the food web and supports a significant fishery in the Southern Ocean. Shifts in historical fishing grounds and spatial distribution of catches have occurred as a result of recent changes in fishery practices. To understand these shifts, fishery spatial dynamics and fishing fleet behavior evaluated on different spatial and temporal scales are critical. We examine the catch distribution on three spatial-temporal scales. At the Western Antarctic Peninsula (WAP) scale, we assessed the fleet’s southward expansion, identifying the Bransfield Strait (BS) as the main current fishing ground, replacing the historical Drake sector. At the BS scale, we identified fishing hotspots (FHs) that concentrated 48%–57% of the total catch over a period of 2–6 months and had high catch densities (2.2–30.3 ton km−2). At the FH scale, we tracked the spatial distribution of the fleet within FHs, demonstrating a shift of fishing vessels to contiguous zones as a result of a decrease in daily catch rates (CPUE). Such shifts (allowing the fleet to increase CPUE) occurred every 4–17 days. Previously exploited fishing grounds were revisited based on FH persistence and sea ice conditions. This paper concludes with a discussion of the potential impact of fishing fleet behavior and catch concentration, considering the recent spatial shift towards less-exploited areas, the overlap with critical zones for predator feeding, and several implications for fisheries management.
... Among humpback whales migrating from Central and South America the arrival time at the Antarctic peninsula has advanced by nearly 30 days in 30 years (Avila et al., 2020). Meanwhile, tracking reveals whales are remaining in ice-free Antarctic Peninsula waters well into winter (Weinstein et al., 2017), leading to longer regional residence times. More detailed investigation may reveal that climate change is differentially affecting population components. ...
... comm.). In this region, the fishery is extending its activities until the beginning of winter, thus overlapping with the fledging period of three pygoscelid species (during summer, Hinke et al., 2017) as well as with feeding activities of large numbers of humpback whales present in the area until winter (Weinstein et al., 2017). ...
... However, in recent years the fishery has concentrated over specific hotspots where krill dependent predators forage (Santa Cruz et al., 2018). While spatial and temporal overlap has been demonstrated (Santora et al., 2010;Ratcliffe et al., 2015;Hinke et al., 2017;Weinstein et al., 2017) direct evidence that current levels of biomass extraction alter life histories of predators has not been clearly demonstrated. Conversely, Watters et al. (2020) argue there is no evidence that simply having a small catch relative to estimated krill biomass indicates precaution (see section "Integrated Conservation Under Uncertainty and Change"). ...
Article
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The massive number of seabirds (penguins and procellariiformes) and marine mammals (cetaceans and pinnipeds) – referred to here as top predators – is one of the most iconic components of the Antarctic and Southern Ocean. They play an important role as highly mobile consumers, structuring and connecting pelagic marine food webs and are widely studied relative to other taxa. Many birds and mammals establish dense breeding colonies or use haul-out sites, making them relatively easy to study. Cetaceans, however, spend their lives at sea and thus aspects of their life cycle are more complicated to monitor and study. Nevertheless, they all feed at sea and their reproductive success depends on the food availability in the marine environment, hence they are considered useful indicators of the state of the marine resources. In general, top predators have large body sizes that allow for instrumentation with miniature data-recording or transmitting devices to monitor their activities at sea. Development of scientific techniques to study reproduction and foraging of top predators has led to substantial scientific literature on their population trends, key biological parameters, migratory patterns, foraging and feeding ecology, and linkages with atmospheric or oceanographic dynamics, for a number of species and regions. We briefly summarize the vast literature on Southern Ocean top predators, focusing on the most recent syntheses. We also provide an overview on the key current and emerging pressures faced by these animals as a result of both natural and human causes. We recognize the overarching impact that environmental changes driven by climate change have on the ecology of these species. We also evaluate direct and indirect interactions between marine predators and other factors such as disease, pollution, land disturbance and the increasing pressure from global fisheries in the Southern Ocean. Where possible we consider the data availability for assessing the status and trends for each of these components, their capacity for resilience or recovery, effectiveness of management responses, risk likelihood of key impacts and future outlook.
... For example, though most species of baleen whale that occur in the Scotia Sea and Antarctic Peninsula region remain depleted to some extent (Reilly et al. 2004), humpback whales (Megaptera novaeangliae) have recovered more rapidly than others (Clapham et al. 1999, Matsuoka et al. 2006, Herr et al. 2016 and could now represent competition to penguins in coastal areas. Humpback distribution appears to be related to the distribution and abundance of krill, particularly in nearshore locations (Friedlaender et al. 2006, Nowacek et al. 2011, Weinstein et al. 2017. It is interesting that one of the most rapidly recovering whale species apparently occupies habitats analogous to those used by chinstrap penguins. ...
... Our results highlight the importance of managing krill fishing activities at temporal and spatial scales relevant to the population processes of predators. Evidence is now accumulating that krill predators preferentially occupy habitats that are also important to the krill fishery (e.g., Hinke et al. 2017, Weinstein et al. 2017, but for which we have no understanding in terms of krill retention, depletion, or replenishment. These processes are key to understanding both the future recovery of baleen whale stocks and the future sustainability of penguin populations and the krill fishery. ...
... We show that in the case of chinstrap penguins during their breeding season, habitat models can, with some confidence, be extrapolated to predict the at-sea locations where animals from untracked colonies probably forage, even in different regions and across different archipelagos. We show that chinstrap penguins prefer nearshore habitats over shallow bathymetry with slow-flowing water, habitats similar to those used by krill-eating humpback whales (Weinstein et al. 2017), offering insights into the plausibility of the krill surplus hypothesis (Sladen 1964, Laws 1977. These habitats can have elevated levels of krill biomass (Warren and Demer 2010), which reinforces the need to better understand bottom-up and top-down forcing in the Antarctic. ...
Article
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In the Southern Ocean, the at-sea distributions of most predators of Antarctic krill are poorly known, primarily because tracking studies have only been undertaken on a restricted set of species, and then only at a limited number of sites. For chinstrap penguins, one of the most abundant krill predators breeding across the Antarctic Peninsula, we show that habitat models developed utilizing the distance from the colony and the bearing to the shelf-edge, adjusting for the at-sea density of Pygoscelis penguins from other colonies, can be used to predict, with a high level of confidence, the at-sea distribution of chinstrap penguins from untracked colonies during the breeding season. Comparison of predicted penguin distributions with outputs from a high-resolution oceanographic model shows that chinstrap penguins prefer nearshore habitats, over shallow bathymetry, with slow-flowing waters, but that they sometimes also travel to areas beyond the edge of the continental shelf where the faster-flowing waters of the Coastal Current or the fronts of the Antarctic Circumpolar Current occur. In the slow-moving shelf waters, large penguin colonies may lead to krill depletion during incubation and chick-rearing periods when penguins are acting as central place foragers. The habitats used by chinstrap penguins are also locations preferentially used by the commercial krill fishery, one of the last under-developed marine capture fisheries any- where on the planet. As it develops, this fishery has the potential to compete with chinstrap penguins and other natural krill predators. Scaling our habitat models by chinstrap penguin population data demonstrates where overlap with the fishery is likely to be most important. Our results suggest that a better understanding of krill retention and krill depletion in areas used by natural predators and by the krill fishery are needed, and that risk management strategies for the fishery should include assessment of how krill movement can satisfy the demands of both natural predators and the fishery across a range of spatial and temporal scales. Such information will help regional management authorities better understand how plausible ecosystem-based management frameworks could be developed to ensure sustainable co-existence of the fishery and competing natural predators.
... These breeding stocks are distributed around lower latitude coastal regions in the Atlantic, Indian, and Pacific Ocean and rely on highly productive seasonal habitats in the Antarctic. Breeding stock G, whose calving ground is associated with the western coast of South America, utilizes the Western Antarctic Peninsula (WAP), one of the most rapidly warming areas in the world, as its foraging ground [6][7][8]. ...
... However, this can make the model so computationally complex that it cannot converge. This occurred with our model, and to counter this we ran the observation model with a multivariate normal distribution as done in Weinstein et al. [6,7] and used the package Argosfilter in R [64,66] to filter out implausible points that indicated speeds higher than ~ 20 km hr-1 (vmax = 6) [6,7]. We used a timestep of 12 h, which we deemed to be a conservative balance between taking into account gaps in the data as well as ensuring behaviors did not change between locations. ...
... However, this can make the model so computationally complex that it cannot converge. This occurred with our model, and to counter this we ran the observation model with a multivariate normal distribution as done in Weinstein et al. [6,7] and used the package Argosfilter in R [64,66] to filter out implausible points that indicated speeds higher than ~ 20 km hr-1 (vmax = 6) [6,7]. We used a timestep of 12 h, which we deemed to be a conservative balance between taking into account gaps in the data as well as ensuring behaviors did not change between locations. ...
Article
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Background Despite exhibiting one of the longest migrations in the world, half of the humpback whale migratory cycle has remained unexamined. Until now, no study has provided a continuous description of humpback whale migratory behavior from a feeding ground to a calving ground. We present new information on satellite-derived offshore migratory movements of 16 Breeding Stock G humpback whales from Antarctic feeding grounds to South American calving grounds. Satellite locations were used to demonstrate migratory corridors, while the impact of departure date on migration speed was assessed using a linear regression. A Bayesian hierarchical state–space animal movement model (HSSM) was utilized to investigate the presence of Area Restricted Search (ARS) en route. Results 35,642 Argos locations from 16 tagged whales from 2012 to 2017 were collected. The 16 whales were tracked for a mean of 38.5 days of migration (range 10–151 days). The length of individually derived tracks ranged from 645 to 6381 km. Humpbacks were widely dispersed geographically during the initial and middle stages of their migration, but convened in two convergence regions near the southernmost point of Chile as well as Peru’s Illescas Peninsula. The state–space model showed almost no instances of ARS along the migratory route. The linear regression assessing whether departure date affected migration speed showed suggestive but inconclusive support for a positive trend between the two variables. Results suggestive of stratification by sex and reproductive status were found for departure date and route choice. Conclusions This multi-year study sets a baseline against which the effects of climate change on humpback whales can be studied across years and conditions and provides an excellent starting point for the investigation into humpback whale migration.
... Atlantic, Indian, and Pacific Ocean and rely on highly productive seasonal habitats in the 59 Antarctic, with several populations utilizing the Western Antarctic Peninsula, one of the most 60 rapidly warming areas in the world, as their foraging ground (4)(5)(6). 61 ...
... However, this can make the model so computationally complex that it cannot 288 converge. This occurred with our models, and to counter this we removed any extreme and 289 implausible locations from our data using the Argosfilter package in R (Freitas 2012, R Core 290 Team 2017), and then ran the observation model with a multivariate normal distribution as done 291 in Weinstein et al. (2017a, 2017b)(4,5). We used a timestep of 12 hours, which we deemed to be 292 behaviors did not change between locations. ...
Preprint
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Background: Despite exhibiting one of the longest migrations in the world, half of the humpback whale migratory cycle has remained unexamined; until this point, no study has provided a continuous description of humpback whale migratory behavior from a feeding ground to a breeding ground. We present new information on the satellite derived offshore migratory movements of 16 humpback whales from Antarctic feeding grounds to South American breeding grounds. Satellite locations were used to demonstrate migratory corridors, while the impact of departure date on migration speed was assessed using a linear regression, and a Bayesian hierarchical state-space animal movement model was utilized to investigate the presence of feeding behavior en route. Results: 35,642 Argos locations from 16 tagged whales from 2012-2017 were collected. The 16 whales were tracked for an average of 38.5 days of migration (range 10-151 days). The length of individually derived tracks ranged from 645–6,381 km. Humpbacks were widely dispersed geographically during the initial and middle stages of their migration but convened in two bottleneck regions near the southernmost point of Chile as well as Peru’s Illescas Peninsula. The state space model found almost no instances of ARS, a proxy for feeding behavior, along the migratory route. The linear regression assessing whether departure date affected migration speed found suggestive but inconclusive support for a positive trend between the two variables. No clear stratification by sex or reproductive status, either in migration speed, departure date, or route choice, was found. Conclusions: Southern hemisphere humpback whale populations are recovering quickly from intense commercial whaling and, around the Antarctic Peninsula, are doing so in the face of a rapidly changing environment. The current lack of scientific knowledge on marine mammal migration is a major barrier to cetacean conservation. This multi-year study sets a baseline against which the effects of climate change on humpback whales can be studied across years and conditions and provides an excellent starting point for the investigation into humpback whale migration.
... Antarctic krill (Euphausia superba) dominates the main flow of energy in food webs along the Western Antarctic Peninsula (Ducklow et al. 2006). However, krill is also the target of commercial exploitation from the Mar de la Flota/Bransfield Strait off the Antarctic Peninsula to the northwest of South Orkney Islands, and this activity overlaps with foraging areas of some krill-dependent predators, such as penguins, seals, and whales (Hinke et al. 2017;Weinstein et al. 2017). ...
... Fraser et al. 2013;Juáres et al. 2015). Hinke et al. (2017) and Weinstein et al. (2017) have demonstrated that there is a spatio-temporal overlap between krill fishery and krill-dependent predators in the Scotia Sea, suggesting a competition between them for the resource. Management strategies require expanding our knowledge on the trophic ecology of predators in a larger number of breeding sites. ...
Article
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Knowledge of the feeding ecology of a species at local level is fundamental to determine the relationship between the fluctuations in local marine resources and population dynamics of predators. In this study, we examined the diet of Adélie penguins (Pygoscelis adeliae) during the crèche stage at the Stranger Point colony, South Shetland Islands, Antarctica, over a 13-year period (2002/2003–2014/2015). Antarctic krill (Euphausia superba) was the dominant prey for Adélie penguins during the crèche period (contribution: 100% of occurrence and >99.7% by mass). The fish component in the diet represented a small proportion of the total prey (contribution: from 4 to 24% of occurrence but <0.15% by mass). A marked inter-annual variability in the mass of stomach contents, the krill size consumed and the proportion of juvenile krill was observed. Moreover, a possible recruitment event of krill was recorded. A negative relationship between the size of krill in the diet and breeding success was found, suggesting that population dynamics of krill also reflected changes in the local availability of this crustacean. This work is the first long-term study of dietary parameters of Adélie penguins for the Stranger Point colony.
... We acknowledge the existence of other critical sources of uncertainty around the spatial krill abundance and depletion that could challenge our CPUE-based approach. Cetaceans are predators that, similarly to the fishing fleet, search for large krill swarms using much of the same fishery exploited areas (Weinstein et al., 2017;Friedlaender et al., 2021). Since some species such as humpback and minke whales are showing significant population recovery and considering they elevated daily consumption rates (Nowacek et al., 2011), this would likely have important implications across the Antarctic pelagic ecosystem, particularly within their feeding grounds (Zerbini et al., 2019). ...
... It is worth mentioning that while some fishing sectors such as the Bransfield Strait or SOI are regularly monitored acoustically by the U.S. AMLR and Norwegian programs (Krafft et al., 2018) respectively, other sectors such as Gerlache Strait do not have regular monitoring. The latter is a highly important feeding area for predators (Weinstein et al., 2017(Weinstein et al., , 2018 and should be monitored to better understand the relationship between negative CPUE trend with potential local fishing depletion and other sources of environmental variability. ...
Article
The undergoing rapid climate changes recorded along the Western Antarctic Peninsula (WAP) in combination with the increasing seasonal catches reported by the krill fishery have raised concerns as to whether the management strategy established by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) is effectively avoiding impacts on the krill stock and related ecosystem. Despite the current fixed catch limit being spread across fishing areas to reduce spatial catches concentrations, our 38-year analysis revealed the highest historical spatial (ton/km²) and temporal (ton/day) fishing concentration levels across the WAP and South Orkney Islands. Higher seasonal catches in recent decades removed persistently within the same small fishing areas and during shorter fishing seasons are key factors influencing this situation. We used the catch per unit effort (CPUE) as a measure of fishing performance. CPUE was standardized using a GAMM model taking into account operational factors such as fleet composition, trawling methods, seasonality and daily catches, and we detected negative CPUE trends over time and across the different fishing areas. Our results suggest that the fishing performance have responded to the elevated spatio-temporal fishing concentration and changes in sea-ice. We discuss whether the negative CPUE trends are caused by fishing-induced depletion or driven by other factors such as krill flux, reduction and contraction of krill abundance and increased cetacean foraging (due recovery of whale populations). Finally, we also highlight the need to expand the survey's coverage (by acoustic or net-based methods) to the new, highly fished, and non-monitored areas such as Gerlache Strait, which is an important area for krill and dependent predators.
... blue whales (Balaenoptera musculus brevicauda) migrate between Australia and Indonesia along Australia's western coastline -a migratory path which has since been confirmed using satellite telemetry 10 . In these and other cases (for example 11 ), satellite telemetry provided new detailed movement information and identified habitat important to the conservation and management of whale species. Improvements in tagging technology, particularly advances in sensor, storage and transmission capabilities, have brought improvements in the amount and quality of data received 12,13 . ...
... The capability of satellite tags to detail whale movements is markedly building our understanding of how whales move and interact with their environment throughout important migration pathways 22,28 . This novel information ultimately plays an important role in conservation and management 11,29 . The tag-derived movements reported here substantially increase our current knowledge of the east Australian humpback whale population by revealing new movement patterns, unidentified temperate feeding locations and providing the first description of the environmental predictors that characterise key foraging habitat in Antarctica. ...
Article
Full-text available
Humpback whale (Megaptera novaeangliae) populations typically undertake seasonal migrations, spending winters in low latitude breeding grounds and summers foraging in high latitude feeding grounds. Until recently, a broad scale understanding of whale movement has been derived from whaling records, Discovery marks, photo identification and genetic analyses. However, with advances in satellite tagging technology and concurrent development of analytical methodologies we can now detail finer scale humpback whale movement, infer behavioural context and examine how these animals interact with their physical environment. Here we describe the temporal and spatial characteristics of migration along the east Australian seaboard and into the Southern Ocean by 30 humpback whales satellite tagged over three consecutive austral summers. We characterise the putative Antarctic feeding grounds and identify supplemental foraging within temperate, migratory corridors. We demonstrate that Antarctic foraging habitat is associated with the marginal ice zone, with key predictors of inferred foraging behaviour including distance from the ice edge, ice melt rate and variability in ice concentration two months prior to arrival. We discuss the highly variable ice season within the putative foraging habitat and the implications that this and other environmental factors may have on the continued strong recovery of this humpback whale population.
... Humpback whales in the Southern Hemisphere migrate from several low latitude breeding areas to areas in the Southern Ocean where they forage on Antarctic krill (Euphausia superba) (Reisinger et al. 2021). In their breeding areas and along their migratory routes, they are exposed to anthropogenic stressors including shipping and oil and gas development (Rosenbaum et al. 2014;Chou et al. 2020;Guzman et al. 2020) but once they reach their feeding areas these stressors are all but absent and whales instead contend with rapidly changing environmental conditions and shifting prey distributions (Tulloch et al. 2019) as well as fisheries for Antarctic krill in some areas (Weinstein and Friedlaender 2017) (Fig. 5.6). In another example, the vulnerability of Arctic marine mammals to shipping traffic is higher in geographic bottlenecks through which both ships and marine mammals are obliged to pass, such as the Bering Strait and parts of the eastern Canadian Arctic (e.g., Lancaster Sound) (Hauser et al. 2018). ...
... Oil rig data fromHalpern et al. (2015). c Depicts satellite tracking location estimates of humpback whales in the Antarctic Peninsula region (left panel), where they aggregate to feed on Antarctic krill (Euphausia superba) that are also the subject of commercial fisheries(Weinstein et al. 2017), the effort of which (hours of fishing effort 2012-2016) are shown in the right panel (fishing data from Global Fishing Watch/Kroodsma et al. 2018) ...
Chapter
Marine mammalsMarine mammals move through dynamic and heterogeneous environments to fulfill maintenance functions. These movements can be studied with various techniques that yield different types of information, and this is increasingly revealing the diversity of movement behaviors among marine mammals. These behaviors vary extensively in their characteristics, from the restricted ranging of some dolphinDolphin species to long-distance seasonal migrationsMigration by species such as humpback and gray whalesGray whale, some of the longest migrations of any animal. As such, movements link places and processes across space and time and are therefore key to understanding the ecology of marine mammals. Given these connections, movement also exposes marine mammals to various natural and anthropogenic threatsAnthropogenic threats and a layer of conservationConservation, management,Management and policy actions across national and international jurisdictions. We review marine mammal movement ecologyMovement ecology in this context, using diverse examples to illustrate the implications of marine mammals’ movements for their conservationConservation and management as well as identifying opportunities therefore. Movement behaviors across different spatiotemporal scales present a difficult challenge for the conservationConservationof marine mammalsMarine mammals, since marine mammals are exposed to pressures and threatsThreats varying from localized effects to global effects such as climate changeClimate change, which are set within—but often beyond—the jurisdiction of many states. For example, species such as blue and humpback whalesHumpback whale migrate through the waters of several nations, and the critical habitatsCritical habitat of pelagic species such as elephant sealsSeal lie in Areas Beyond National Jurisdiction. However, both place-based conservationConservation approaches (such as Marine Protected AreasMarine Protected Area (MPA)) and pressure-based conservationConservation approaches (such as those promoted by multilateral agreementsAgreementsincluding the Convention on the Conservation of Migratory Species of Wild AnimalsConvention on the Conservation of Migratory Species of Wild Animals (CMS)) can integrate information on the movement ecologyMovement ecology of marine mammals, in increasingly dynamic ways. It is clear that “movescapesMovescapes” (the functional value of land- and seascapes to animals over space and time) are essential conservationConservation features, as recognized by Important Marine Mammal AreasImportant Marine Mammal Area (IMMA), for example. Further, as the patterns and consequences of connectivityConnectivity among discrete sites are elucidated, the preservation of connectivity is emerging as a key challenge and opportunity for the conservationConservationand managementManagementof marine mammalsMarine mammals. However, to achieve effective conservationConservation outcomes to so many pressing threatsThreats, marine mammal movescapeMovescapes data needs to be open, accessible, and actionable to inform design and implementation of conservationConservation measures connecting critical habitatsCritical habitatand migration corridorsMigration corridors to mitigate threats. To achieve success, an improved understanding of the needs of managers, policymakers, and governments on a national and international level is required from the start and needs to be championed by the data producers with relevant stakeholdersStakeholders along the way.
... describing migration routes and destinations (e.g. Félix & Guzmán, 2014;Garrigue et al., 2010;Zerbini et al., 2006Zerbini et al., , 2011, behaviour and habitat use patterns (Curtice et al., 2015;Kennedy et al., 2014;Weinstein et al., 2017), and for discovering novel habitats (Garrigue et al., 2015;Zerbini et al., 2006). However, most tag deployments on Oceania humpbacks have occurred on the breeding grounds (Garrigue et al., 2010(Garrigue et al., , 2015Hauser et al., 2010) and have not been fully integrated with other research tools. ...
Article
Obtaining direct measurements to characterise ecosystem function can be hindered by remote or inaccessible regions. Next-generation satellite tags that inform increasingly sophisticated movement models, and the min-iaturisation of animal-borne loggers, have enabled the use of animals as tools to collect habitat data in remote environments, such as the Southern Ocean. Research on the distribution, habitat use and recovery of Oceania's humpback whales (Megaptera novaeangliae) has been constrained by the inaccessibility to their Antarctic feeding grounds and the limitations of technology. In this multidisciplinary study, we combine innovative analytical tools to comprehensively assess the distribution and population structure of this marine predator throughout their entire migratory range. We used genotype and photo-identification matches and conducted a genetic mixed-stock analysis to identify the breeding ground origins of humpback whales migrating past the Kermadec Islands, New Zealand. Satellite tracking data and a state-space model were then used to identify the migratory paths and behaviour of 18 whales, and to reveal their Antarctic feeding ground destinations. Additionally, we conducted progesterone assays and epigenetic aging to determine the pregnancy rate and age-profile of the population. Humpback whales passing the Kermadec Islands did not assign to a single breeding ground origin, but instead came from a range of breeding grounds spanning ∼3500 km of ocean. Sampled whales ranged from calves to adults of up to 67 years of age, and a pregnancy rate of 57% was estimated from 30 adult females. The whales migrated to the Southern Ocean (straight-line distances of up to 7000 km) and spanned ∼4500 km across their Antarctic feeding grounds. All fully tracked females with a dependent calf (n = 4) migrated to the Ross Sea region, while 70% of adults without calves (n = 7) travelled further east to the Amundsen and Bellingshausen Seas region. By combining multiple research and analytical tools we obtained a comprehensive understanding of this wide-ranging, remote population of whales. Our results indicate a population recovering from exploitation, https://doi. T and their feeding ground distribution serves as an indicator of the resources available in these environments. The unexpected Kermadec Islands migratory bottleneck of whales from several breeding grounds, variable distribution patterns by life history stage and high pregnancy rates will be important in informing conservation and management planning, and for understanding how this, as well as other whale populations, might respond to emerging threats such as climate change.
... The largest historical catch was 528,000 tons in 1982, and under CCAMLR management this declined to an annual average catch of 388,000 tons between 1986 -1991 Concerns have been raised about the effects of fishing on krill predators, and studies have been conducted to assess the impact of the fishery on higher trophic levels (Butterworth & Thomson 1995;Mangel & Switzer 1998;Plagányi & Butterworth 2012;Weinstein et al. 2017). Current low levels of fishing pressure are unlikely to have a significant impact on the krill population, but the fishery needs to be carefully managed into the future if the fishery expands . ...
Thesis
Antarctic krill (Euphausia superba, hereafter ‘krill’) are lipid-rich euphausiids with an important role in the Southern Ocean, including as the primary prey of Antarctic megafauna (whales, seals, penguins), fish, squid and seabirds. They contain high levels of nutritious long-chain (≥C20) polyunsaturated fatty acids (LC-PUFA), specifically eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3). The sheer abundance of krill in the Southern Ocean means that the ecosystem is largely driven by energy derived from krill lipids. In addition to their ecological importance, a Scotia Sea krill fishery harvests krill, including for commercial use of their LC-PUFA. The existence of this year-round krill fishery provides a unique opportunity to collect krill samples for research over large spatial and temporal scales, which is unfeasible using scientific research vessels. In this thesis, fishery caught krill samples were used to investigate the fatty acid content and composition of krill, during all seasons and over consecutive years (2013 – 2016). This research (presented in Chapter 2) aimed to fill knowledge gaps on the seasonal diet of krill (particularly in winter) in the Scotia Sea region, using fatty acids as dietary biomarkers. Krill were primarily herbivorous in summer (higher levels of 20:5n-3 and 22:6n-3, and low 18:1n-9c/18:1n-7c ratios) and became more omnivorous from autumn to spring (increasing ratios of 18:1n-9c/18:1n-7c and percentages of Σ 20:1 + 22:1 isomers). Seasonal proportions of herbivory and omnivory differed between years, and fatty acid composition differed between fishing locations. Selected samples were also used to investigate the composition of fatty acids in the structural (phospholipids) and storage lipids (triacylglycerols) of krill (Chapter 3). Triacylglycerol fatty acids (thought to better represent recent diet), reflected omnivorous feeding with highest percentages of flagellate biomarkers (18:4n-3) occurring in summer, diatom biomarkers (16:1n-7c) from autumn-spring, and greater carnivory (higher Σ 20:1 + 22:1 and 18:1n-9c/18:1n-7c ratios) in autumn. Phospholipid fatty acids were less variable and were higher in the essential membrane fatty acids 20:5n-3 and 22:6n-3. Percentages of the major krill sterol, cholesterol, were significantly higher in winter and spring compared with summer and autumn. Results presented in Chapters 2 and 3 highlighted the dynamic nature of krill lipids, and the flexible diet of krill, which likely contributes to their huge biomass and success as one of the most abundant organisms on Earth. Because krill are so important in the Southern Ocean food web, any decreases in krill biomass could result in a major ecological regime shift. Very little is known about how climate change will affect krill. Increasing anthropogenic carbon dioxide (CO2) emissions are causing ocean acidification, as absorption of atmospheric CO2 in seawater alters ocean chemistry. Ocean acidification increases mortality and negatively affects physiological functioning in some marine invertebrates, and is predicted to occur most rapidly at high latitudes. Long-term laboratory studies are needed to understand how keystone species such as krill may respond to predicted future pCO2 levels. A long term experiment was conducted to test whether rising ocean pCO2 is likely to impact krill physiology and biochemistry (Chapters 4 and 5). Adult krill were exposed to near-future ocean acidification (1000 – 2000 μatm pCO2) for one year in the laboratory. Krill reared in near-future pCO2 conditions were able to survive, grow, store fat, mature, and maintain normal respiration rates. Haemolymph pH, lipid and fatty acid composition were also maintained at the same levels as krill in ambient pCO2 (400 μatm). Negative effects on physiology and lipid biochemistry were only observed in extreme pCO2 conditions (4000 μatm), which krill will not experience in the wild. These results place adult krill among the most resilient species in ocean acidification studies to date. In summary, results in this thesis highlight the remarkable adaptability of krill in a changing environment, from short-term seasonal or annual scales, to longer-term decadal scales. Their flexible phenotype may aid their survival in an ocean that is rapidly changing with increasing anthropogenic CO2 emissions. The data obtained in this thesis can be used for fisheries management to guide fishing activities, and in fisheries models to predict how krill biomass may be affected by climate change. Krill lipid energy fuels the Southern Ocean ecosystem and to date, lipid data has not been included in Antarctic ecosystem models. The large scale of lipid data in this study makes it ideal for inclusion in such models, and it has important implications for the health of the wider Southern Ocean ecosystem.
... 12,22 ). Satellite telemetry is helping to clarify migratory routes, providing detailed information about key corridors, important habitats and potential for overlap with human activities [26][27][28][29][30][31][32][33] . Here, we present the first high-resolution migratory pathways to Southern Ocean summer forage grounds for the WA HBW population. ...
Article
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Humpback whale populations migrate extensively between winter breeding grounds and summer feeding grounds, however known links to remote Antarctic feeding grounds remain limited in many cases. New satellite tracks detail humpback whale migration pathways from Western Australia into the Southern Ocean. These highlight a focal feeding area during austral spring and early summer at the southern Kerguelen plateau, in a western boundary current where a sharp northward turn and retroflection of ocean fronts occurs along the eastern plateau edge. The topographic steering of oceanographic features here likely supports a predictable, productive and persistent forage ground. The spatial distribution of whaling catches and Discovery era mark-recaptures confirms the importance of this region to Western Australian humpback whales since at least historical times. Movement modelling discriminates sex-related behaviours, with females moving faster during both transit and resident periods, which may be a consequence of size or indicate differential energetic requirements. Relatively short and directed migratory pathways overall, together with high-quality, reliable forage resources may provide a partial explanation for the ongoing strong recovery demonstrated by this population. The combination of new oceanographic information and movement data provides enhanced understanding of important biological processes, which are relevant within the context of the current spatial management and conservation efforts in the Southern Ocean.
... Currently, an industrial fishery for Antarctic krill operates throughout the Antarctic Peninsula region. The fishery has grown [to 300,000 tonnes (63)], and grown more concentrated in recent years, with increasing encroachment upon penguin and whale foraging grounds (113)(114)(115)(116). Fisheries for Patagonian and Antarctic toothfish, the top fish predators in the Southern Ocean, are scattered throughout the CAMLR Convention area and are contentious. ...
Article
Antarctica and the Southern Ocean comprise a critical part of the Earth System. Their environments are better understood than ever before, yet the region remains poorly considered among international agreements to improve the state of the global environment. In part the situation owes to isolated regional regulation within the Antarctic Treaty System, and in part to the dated notion that Antarctica and the Southern Ocean are well conserved and relatively free from human impact. Here we review growth in knowledge of Antarctic environments and anthropogenic pressures on them. We show that the region's unusual diversity is facing substantial local and globally mediated anthropogenic pressure, on a par with environments globally. Antarctic environmental management and regulation is being challenged to keep pace with the change. Much benefit can be derived from consideration of Antarctic environmental and resource management in the context of global agreements.
... Previous studies have found that humpback whales in the Antarctic follow krill patches over large distances (Friedlaender et al. 2006(Friedlaender et al. , 2013Dalla Rosa et al. 2008;Curtice et al. 2015), and it is well known that the WAP has one of the highest concentrations of krill in the Southern Ocean (Quetin and Ross 2003). Moreover, it was recently found that the direct hotspots of humpback whale activity are the same areas targeted for the most intense krill fishing effort (Weinstein et al. 2017). The authors suggested the krill fishery be reevaluated to take into consideration humpback whale foraging and climate change. ...
Article
Full-text available
Southern Hemisphere humpback whales breed in tropical waters and migrate to Antarctica to forage. While the breeding grounds are well defined, the population structure on Antarctic feeding grounds is poorly described. The Western Antarctic Peninsula (WAP) is of particular interest, where rapidly changing environmental conditions could alter prey distribution or migration pathways. To examine changes in the population of whales around the WAP, we used mitochondrial DNA (mtDNA) and 15 microsatellite loci. We compared our WAP dataset to a dataset collected 18 years earlier, and identified new haplotypes for the region, but found no significant difference between the datasets. We compared whales from the WAP to breeding populations in Oceania, Colombia, and Brazil. We used an Analysis of Molecular Variance to confirm significant genetic differentiation between the WAP and each breeding ground (overall FST = 0.035/0.007 mtDNA/microsatellite, p < 0.001) except Colombia. Bayesian mixed-stock analyses showed a large apportionment to Colombia (mtDNA 93.0%; CL 91–99%; microsatellites 86%; CL 72–93%) and a small apportionment to French Polynesia/Samoan Islands (mtDNA 2.9%; CL 0.0–11.5%; microsatellites 8.9%; CL 0–22%), supporting the strong connection between Colombia and the WAP. Assignment tests allocated 81 individuals to Colombia and two to French Polynesia/Samoan Islands. No other breeding grounds had significant apportionments. Direct connectivity of French Polynesia to the WAP was confirmed with the first genotype match of French Polynesia to a feeding area. Continued genetic monitoring will highlight the complex patterns of humpbacks in this rapidly changing climate. Our results serve as a baseline for humpback whale population structure, illustrate mixed-stock analysis as a useful tool for migrating wildlife, and aid in future management considerations for humpbacks.
... Alternatively, increased krill consumption by whales may fertilize surface waters and increase the productivity of the ecosystem 36,37 . Cetaceans forage in areas where our study penguins overlap with the krill fishery 38 , and the effects of increasing cetacean populations on the structure and function of the ecosystem may affect penguin performance. Determining whether future management of the krill fishery is precautionary will benefit from consideration of such ecosystem perspectives by effectively improving estimates of LKB, and thus LHR. ...
Article
Full-text available
Low catch limits for forage species are often considered to be precautionary measures that can help conserve marine predators. Difficulties measuring the impacts of fisheries removals on dependent predators maintain this perspective, but consideration of the spatio-temporal scales over which forage species, their predators, and fisheries interact can aid assessment of whether low catch limits are as precautionary as presumed. Antarctic krill are targeted by the largest fishery in the Southern Ocean and are key forage for numerous predators. Current krill removals are considered precautionary and have not been previously observed to affect krill-dependent predators, like penguins. Using a hierarchical model and 30+ years of monitoring data, we show that expected penguin performance was reduced when local harvest rates of krill were ≥0.1, and this effect was similar in magnitude to that of poor environmental conditions. With continued climate warming and high local harvest rates, future observations of penguin performance are predicted to be below the long-term mean with a probability of 0.77. Catch limits that are considered precautionary for forage species simply because the limit is a small proportion of the species’ standing biomass may not be precautionary for their predators.
... Antarctic krill fishery has grown in the recent decade (Commission for the Conservation of Antarctic Marine Living Resources, 2018), and there are concerns regarding how the spatial overlap between fishery efforts and Antarctic krill predators might negatively impact these species and the marine ecosystem (Smith et al., 2011;Weinstein, Double, Gales, Johnston, & Friedlaender, 2017). However, the Antarctic krill fishery is currently focused on the South Atlantic sector and around the Antarctic Peninsula and is therefore not a primary concern for the Oceania humpback whale population. ...
Article
Long‐distance migration is a demanding physical activity, and how well animals manage the associated costs will have important implications for their fitness. The Oceania humpback whale (Megaptera novaeangliae) population is recovering from past exploitation markedly slower than the neighbouring east Australian whales. The reasons for this are unknown, although higher energetic costs of longer migratory distances could be a possible explanation. Due to their fully aquatic lives, studying the energy expenditure of these large animals requires methods that do not rely on capturing the animal, such as bioenergetic models. A state‐space model was fitted to satellite data to infer behavioural states for southern migrating whales. Travel speeds and behavioural states were used in a bioenergetic model to estimate the energetic cost of the migration phase. Relative differences in average duration, distance, and energetic costs were compared between migratory routes and distances. Total energy used during migration was a trade‐off between cost of transport (determined by travel speed) and daily maintenance (determined by daily basal metabolic costs). Oceania whales migrating to the Amundsen and Bellingshausen Seas travelled fastest and furthest, 15 and 21% further than whales migrating to the d'Urville Sea (east Australian whales) and Ross Sea, respectively. Therefore, they had the highest cost of transport, 25 and 85% higher than for d'Urville Sea and Ross Sea whales, respectively. However, energy saved in terms of daily maintenance by using fewer days to complete a longer migration resulted in only a 6–7% increase in total energetic cost. The results highlight that travelling further does not necessarily translate into an increase in total energy expenditure for migratory whales, since they can compensate for longer distance by travelling faster. Further research on the energetics of different whale populations could provide insight into the productivity of Southern Ocean feeding regions and help understand the environmental and anthropogenic effects on the whales' energy budgets.
... These overlaps may increase the likelihood of mortality from prey competition, entanglement and vessel strikes. 25 For whale species feeding almost exclusively on krill-such as Antarctic blue (Balaenoptera musculus intermedia), humpback (Megaptera novaengliae) and Antarctic minke whales-these southward shifts in krill distribution are likely to impose high energetic costs on migrating whales, with effects on body condition, reproductive fitness and population abundance. 26 WWF collaborators are developing biochemical tools to more accurately track whale population growth (see case study, p.35) in an effort to detect potential declines as the ocean warms. ...
Technical Report
Full-text available
Tracking Antarctica - Responding to the Climate Crisis is an WWF policy report synthesizing latest climate science and technical reports related to the Southern Ocean. It was presented at the 2019 meeting by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) which currently does not include climate change information or modelling in their ecosystem-based management of fisheries.
... Outcomes at the scale of the model arena effectively masked important impacts of the MPAs at smaller spatial scales. This is especially pertinent given the potential for overlap with human use [38,39] and the consequences of climate change [42] at finer spatial scales. Overall changes in species abundance may not signal local declines in areas more vulnerable to the effects of climate change [42]. ...
Article
Full-text available
Both costs and benefits must be considered when implementing marine protected areas (MPAs), particularly those associated with fishing effort displaced by potential closures. The Southern Ocean offers a case study in understanding such tradeoffs, where MPAs are actively being discussed to achieve a range of protection and sustainable use objectives. Here, we evaluated the possible impacts of two MPA scenarios on the Antarctic krill (Euphausia superba) fishery and krill-dependent predators in the Scotia Sea, explicitly addressing the displacement of fishing from closed areas. For both scenarios, we employed a minimally realistic, spatially explicit ecosystem model and considered three alternative redistributions of displaced fishing. We projected both MPAs to provide positive outcomes for many krill-dependent predators, especially when closed areas included at least 50–75% of their foraging distributions. Further, differences between the scenarios suggest ways to improve seal and penguin protection in the Scotia Sea. MPA scenarios also projected increases in total fishery yields, but alongside risks of fishing in areas where relatively low krill densities could cause the fishery to suspend operations. The three alternatives for redistributing displaced fishing had little effect on benefits to predators, but did matter for the fishery, with greater differences in overall catch and risk of fishing in areas of low krill density when displaced fishing was redistributed evenly among the open areas. Collectively, results suggest a well-designed MPA in the Scotia Sea may protect krill-dependent predators, even with displaced fishing, and preclude further spatial management of the krill fishery outside the MPA. More broadly, outcomes denote the importance of delineating fishing and predator habitat, spatial scales, and the critical trade-offs inherent in MPA development.
... Moreover, impact of regional anthropogenic climate change on sea surface temperature and the stratification layer change nutrient cycle and primary production leading to ecological changes such as shift in temporal and spatial distribution of marine species (Findlay et al., 2017;Fleming et al., 2016). Ecological changes combined with impact of commercial fishing (Weinstein et al., 2017) could affect foraging behavior of baleen whales and (Briscoe et al., 2017) result in a change in δ 15 N and/or δ 13 C values of earwax. In addition, previous studies have indicated that exposure to anthropogenic noises may impact baleen whale foraging efficiency as well as prey patch displacement (Goldbogen et al., 2013;Blair et al., 2016;Trumble et al., 2018;Melcon et al., 2012). ...
Article
Biological time series datasets provide an unparalleled opportunity to investigate regional and global changes in the marine environment. Baleen whales are long-lived sentinel species and an integral part of the marine ecosystem. Increasing anthropogenic terrestrial and marine activities alter ocean systems, and such alterations could change foraging and feeding behavior of baleen whales. In this study, we analyzed δ¹³C and δ¹⁵N of baleen whale earplugs from three different species (N = 6 earplugs, n = 337 laminae) to reconstruct the first continuous stable isotope profiles with a six-month resolution. Results of our study provide an unprecedented opportunity to assess behavioral as well as ecological changes. Abrupt shifts and temporal variability observed in δ¹³C and δ¹⁵N profiles could be indicative of behavior change such as shift in foraging location and/or trophic level in response to natural or anthropogenic disturbances. Additionally, five out of six individuals demonstrated long-term declining trends in δ¹³C profiles, which could suggest influence of emission of depleted ¹³CO2 from fossil fuel combustion referred to as the Suess effect. After adjusting the δ¹³C values of earplugs for the estimated Suess effect and re-evaluating δ¹³C profiles, significant decline in δ¹³C values as well as different rate of depletion suggest contribution of other sources that could impact δ¹³C values at the base of the food web.
... Strycker et al., 2020). The implementation of the voluntary restriction on fishing linked to the breeding season of penguins (see Black, 2016), such that: In addition to protecting the foraging habitat of large numbers of breeding penguins, the ARK VBZ also protect areas where pelagic predators such as cetaceans feed on krill (see Friedlaender et al., 2006;Nowacek et al., 2011;Weinstein et al., 2017;Trathan et al., 2022). ...
Article
Full-text available
The Commission for the Conservation of Antarctic Marine Living Resources is responsible for management of the Antarctic marine ecosystem, including its living resources. The Commission has yet to implement precautionary measures that protect predators dependent upon Antarctic krill from potential food competition with fisheries where these now increasingly spatially aggregate. Here, we describe voluntary buffer zones (VBZ) implemented in 2018 by the Association of Responsible Krill harvesting companies (ARK) following negotiations with environmental NGOs. The VBZ now prohibit krill fishing during the penguin-breeding season around important penguin colonies along the Antarctic Peninsula. We describe the background of the VBZ and further actions that would ensure ongoing ecological benefits. Lack of data and delays in the implementation of the Commission's revised krill fishery management framework continue to concern NGOs and other stakeholders, especially as part of the management framework will expire in November 2022. Without action by CCAMLR, the ARK VBZ will be the only regulation providing precautionary protection at relevant spatial and temporal scales. The VBZ are an example of how responsible industry can help to protect marine ecosystems when regional management is unable to act given lack of data, and/or associated legal and political constraints.
... For example, a spatial study of multiple krill predators, using canyon waters near Livingstone Island, suggested an overlap between humpback whales and penguins which would support this idea (Santora and Reiss, 2011). Any reductions may be compounded by local krill fishing, particularly in the Antarctic Peninsula region where this activity is concentrated (Kawaguchi and Nicol, 2020) and partially coincident with the peak period when whales visit (Weinstein et al., 2017). However, prey competition is not necessarily the obvious outcome of whale presence, as whales are less spatially restricted than the central place foragers, may have differing krill swarm preferences (Friedlaender et al., 2009(Friedlaender et al., , 2016 and may even modify krill swarm behaviour (e.g., Cox et al., 2009). ...
Article
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Local drivers are human activities or processes that occur in specific locations, and cause physical or ecological change at the local or regional scale. Here, we consider marine and land-derived pollution, non-indigenous species, tourism and other human visits, exploitation of marine resources, recovery of marine mammals, and coastal change as a result of ice loss, in terms of their historic and current extent, and their interactions with the Southern Ocean environment. We summarise projected increases or decreases in the influence of local drivers, and projected changes to their geographic range, concluding that the influence of non-indigenous species, fishing, and the recovery of marine mammals are predicted to increase in the future across the Southern Ocean. Local drivers can be managed regionally, and we identify existing governance frameworks as part of the Antarctic Treaty System and other instruments which may be employed to mitigate or limit their impacts on Southern Ocean ecosystems.
... The pressures exerted by fisheries on marine mammal energy intake and predation are orders of magnitude higher than the e ect of marine mammal predation on the fish catch of commercial and small-scale fisheries (Croll and Tershy, 1998;Weinstein et al., 2017). An indirect e ect of this trophic competition also leads to the shift of marine mammal diet from higher to lower trophic level species. ...
Article
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Marine mammal interactions with fisheries, such as bycatch and depredation, are a common occurrence across commercial and small-scale fisheries. We conducted a systematic review to assess the management responses to marine mammal interactions with fisheries. We analyzed literature between 1995 and 2021 to measure research trends in studies on direct and indirect interactions for: (i) high and low to middle-income countries, (ii) fishery operations (commercial and small-scale), and (iii) taxonomic groups. Management responses were categorized using the framework described previously in peer-reviewed studies. Marine mammal bycatch remains a major conservation concern, followed by marine mammal depredation of fishing gear. A high proportion of studies concentrated on commercial fisheries in high-income countries, with an increase in small-scale fisheries in low to middle-income countries between 1999 and 2020. The insufficient understanding of the social dimensions of interactions and the inevitable uncertainties concerning animal and human behaviors are major challenges to effective management. Despite the key role of human behavior and socioeconomics, we found only eight articles that incorporate human dimensions in the management context. Integrating social dimensions of marine mammal interactions with fisheries could help in setting pragmatic conservation priorities based on enhanced understanding of critical knowledge gaps. An area-specific adaptive management framework could be an effective tool in reducing the risk to marine mammals from fisheries by coupling technical solutions with socio-economic and political interventions. We conclude that despite the vast body of literature on this subject, a “silver bullet” management solution to marine mammal interactions with fisheries does not yet exist.
... This study also suggests that CCAMLR, which aims to take the requirements and conservation status of krill predators into account while managing the krill fishery, may need to consider data collected outside the Southern Ocean. As suggested in previous studies (e.g., Hinke et al., 2017;Weinstein et al., 2017), the overlap of krill predators and krill fisheries can pose risks to predator populations that rely on krill as their main food resource. We have shown that the outcomes of changes in krill availability may not be apparent in the Antarctic since many predators leave the Southern Ocean during the austral winter and thus data from the whole home range of such species might be needed. ...
... Our ultimate goal is to replace the ship-based krill surveys historically conducted by the U.S. AMLR Program with gliderbased surveys. We aim to implement glider surveys that (1) provide management-relevant indices of krill biomass in smaller areas around the northern Antarctic Peninsula, (2) increase data collected from locations where the krill fishery and foraging krill predators (seabirds, pinnipeds, and cetaceans) overlap (see Hinke et al., 2017;Weinstein et al., 2017), and (3) expand the temporal extent of our krill-centric observations. ...
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We compare estimates of krill density derived from gliders to those from contemporaneous and previous ship-based surveys. Our comparisons cover several temporal and spatial scales within two strata around the northern Antarctic Peninsula (off Cape Shirreff on the north side of Livingston Island and in the Bransfield Strait). Our objective is to explore the feasibility of using gliders to supplement or replace vessel-based surveys of fishery resources. We deployed two long-duration Slocum G3 gliders manufactured by Teledyne Webb Research (TWR), each equipped with a suite of oceanographic sensors and a three-frequency (38, 67.5, and 125 kHz, each single-beam) Acoustic Zooplankton Fish Profiler. We used the acoustic data collected by these gliders to estimate biomass densities (g·m −2) of Antarctic krill (Euphausia superba). The two gliders were, respectively, deployed for 82 and 88 days from mid-December 2018 through mid-March 2019. Off Cape Shirreff, glider-based densities estimated from two repeat small-scale surveys during mid-December and January were 110.6 and 55.7 g·m −2 , respectively. In Bransfield Strait, the glider-based estimate of biomass density was 106.7 g·m −2 during December-January. Contemporaneous ship-based estimates of biomass density, from a multi-ship broad-scale krill survey (Macaulay et al., 2019) restricted to the areas sampled by the gliders, were 84.6 g·m −2 off Cape Shirreff and 79.7 g·m −2 in Bransfield Strait during January. We compared two alternative krill-delineation algorithms (dB differencing and SHAPES); differences between biomass densities estimated by applying these algorithms were small and ranged between 4 and 7%. Alternative methods of sampling krill length-frequency distributions (LFDs) (nets or predator diets), which are required to convert acoustic energy to biomass density, also influenced the glider-based results. In Bransfield Strait, net-based estimates of biomass density were 6% less than those based on predator diets. Off Cape Shirreff the biomass density of krill estimated from a net-based LFD was 20% greater than that based on predator diets. Development of a variance estimator Frontiers in Marine Science | www.frontiersin.org 1 March 2021 | Volume 8 | Article 604043 Reiss et al. Glider-Based Acoustic Meso-Zooplankton Fisheries Surveys for glider-based biomass surveys is ongoing, but our results demonstrate that fisheries surveys using acoustically-equipped gliders are feasible, can provide density estimates to inform management, and may be conducted at lower cost than ship surveys in some cases.
... The WAP is a well-known HW hotspot area in summer and autumn (Stone and Hamner, 1988;Thiele et al., 2004;Nowacek et al., 2011;Johnston et al., 2012;Friedlaender et al., 2013;Bester et al., 2017;Reisinger et al., 2021). Krill is the primary food source of HWs, and the distribution and movement of HWs are highly associated with the distribution and abundance of krill (Murase et al., 2002;Nowacek et al., 2011;Curtice et al., 2015;Weinstein et al., 2017;Friedlaender et al., 2021). The WAP area is known to support large populations of krill and their predators (Friedlaender et al., 2006(Friedlaender et al., , 2013Nowacek et al., 2011;Atkinson et al., 2017) because of the nutrient-rich and phytoplankton-laden water near the surface advected along the WAP by the Antarctic Circumpolar Current and nutrient-rich Circumpolar Deep Water being upwelled in the cross-shelf deep water canyons (Curtice et al., 2015) along the WAP's northern shelf break. ...
Presentation
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These animated videos represent daily and weekly mean habitat suitability from dynamic species distribution models on four baleen whale species in the Southern Ocean: Antarctic minke (Balaenoptera bonaerensis), Antarctic blue (Balaenoptera musculus intermedia), fin (Balaenoptera physalus), and humpback (Megaptera novaeangliae) whales. For more information, see the full manuscript: > El-Gabbas et al. (2021) Dynamic species distribution models in the marine realm: predicting year-round habitat suitability of baleen whales in the Southern Ocean. Frontiers in Marine Science 8:802276. DOI: https://doi.org/10.3389/fmars.2021.802276 The same content is also available as a YouTube playlist: https://www.youtube.com/playlist?list=PLdpRuazqmy6Es97xn0TbWi91XtLd8Wf5i
... For example, telemetry studies have been undertaken to assess humpback whale residency [17], feeding and breeding behavior [18,19], movement patterns [20], energy budgets [21], health or vessel strike risks [22] and population connectivity [23,24]. Predominantly, tagging studies have focused on breeding grounds [16], feeding grounds [25] and large scale migration [26]. Very few studies have investigated resting areas where humpback whales display prolonged surface time and reduced swim speed and fine scale migratory behavior [27]. ...
Article
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The study of marine mammals is greatly enhanced through fine scale data on habitat use. Here we used a commonly available asset tracker Global Positioning System/Global Systems for Mobile Communication (GPS/GSM) integrated into a CATS suction cup tag to test its feasibility in providing real time location position on migrating humpback whales in coastal waters of eastern Australia. During two deployments—one on a suspected male and another on a female humpback whale—the tags provided location points with relatively high accuracy for both individuals albeit different swim behavior and surface intervals. In combination with an integrated archival data logger, the tag also provided detailed information on fine scale habitat use such as dive profiles. However, surface intervals were too short to allow for an upload of location data during deployment. Further improvements of the tag design will allow remote access to location data after deployment. Preliminary results suggested location acquisition was better when the tag was positioned well above the midline of the whale body. The technology promises less expensive, more reliable and more accurate short-term tracking of humpback whales compared to satellite relay tags, and it has the potential to be deployed on other marine mammals in coastal waters.
... Both time series are represented as anomalies scaled between −1 and 1. See Text S2 for methods. and marine predators within SSMUs (e.g., Plagányi & Butterworth, 2012;Watters et al., 2020;Weinstein et al., 2017), these results lend support to the idea of concentrated extraction around the AP having downstream consequences for the regional krill population. ...
Article
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Plain Language Summary Antarctic krill (krill) are a key prey item for many Southern Ocean marine predators and also support an expanding commercial fishery. However, there is a need to identify areas of the Southern Ocean that are best for both the production of eggs, and subsequent survival until free‐swimming larvae. We create a model for spawning habitat which considers the temperature and food conditions that adult female krill need to successfully produce eggs, as well as the density of predators feeding on spawned eggs. We optimize our model using existing regional‐scale data of krill eggs and larvae and use this to predict where good spawning habitat may exist around the whole Southern Ocean. Our model found that nearly half of the best spawning habitat occurs in the southwest Atlantic. Within this area, small‐scale krill fishing management areas around the Antarctic Peninsula contain good‐quality spawning habitat. Krill fished here are likely to be locally produced. But, other small‐scale management areas contain little good‐quality spawning habitat (except around South Georgia) and probably rely on krill being imported by ocean currents. This is important for understanding how fishing may impact both local ecosystems and those that are downstream.
... The WAP is a well-known HW hotspot area in summer and autumn (Stone and Hamner, 1988;Thiele et al., 2004;Nowacek et al., 2011;Johnston et al., 2012;Friedlaender et al., 2013;Bester et al., 2017;Reisinger et al., 2021). Krill is the primary food source of HWs, and the distribution and movement of HWs are highly associated with the distribution and abundance of krill (Murase et al., 2002;Nowacek et al., 2011;Curtice et al., 2015;Weinstein et al., 2017;Friedlaender et al., 2021). The WAP area is known to support large populations of krill and their predators (Friedlaender et al., 2006(Friedlaender et al., , 2013Nowacek et al., 2011;Atkinson et al., 2017) because of the nutrient-rich and phytoplankton-laden water near the surface advected along the WAP by the Antarctic Circumpolar Current and nutrient-rich Circumpolar Deep Water being upwelled in the cross-shelf deep water canyons (Curtice et al., 2015) along the WAP's northern shelf break. ...
Article
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Species distribution models (SDMs) relate species information to environmental conditions to predict potential species distributions. The majority of SDMs are static, relating species presence information to long-term average environmental conditions. The resulting temporal mismatch between species information and environmental conditions can increase model inference’s uncertainty. For SDMs to capture the dynamic species-environment relationships and predict near-real-time habitat suitability, species information needs to be spatiotemporally matched with environmental conditions contemporaneous to the species’ presence (dynamic SDMs). Implementing dynamic SDMs in the marine realm is highly challenging, particularly due to species and environmental data paucity and spatiotemporally biases. Here, we implemented presence-only dynamic SDMs for four migratory baleen whale species in the Southern Ocean (SO): Antarctic minke, Antarctic blue, fin, and humpback whales. Sightings were spatiotemporally matched with their respective daily environmental predictors. Background information was sampled daily to describe the dynamic environmental conditions in the highly dynamic SO. We corrected for spatial sampling bias by sampling background information respective to the seasonal research efforts. Independent model evaluation was performed on spatial and temporal cross-validation. We predicted the circumantarctic year-round habitat suitability of each species. Daily predictions were also summarized into bi-weekly and monthly habitat suitability. We identified important predictors and species suitability responses to environmental changes. Our results support the propitious use of dynamic SDMs to fill species information gaps and improve conservation planning strategies. Near-real-time predictions can be used for dynamic ocean management, e.g., to examine the overlap between habitat suitability and human activities. Nevertheless, the inevitable spatiotemporal biases in sighting data from the SO call for the need for improving sampling effort in the SO and using alternative data sources (e.g., passive acoustic monitoring) in future SDMs. We further discuss challenges of calibrating dynamic SDMs on baleen whale species in the SO, with a particular focus on spatiotemporal sampling bias issues and how background information should be sampled in presence-only dynamic SDMs. We also highlight the need to integrate visual and acoustic data in future SDMs on baleen whales for better coverage of environmental conditions suitable for the species and avoid constraints of using either data type alone.
... The preferences for resting areas are similar to those of breeding areas, with resting mother-calf pairs found in 30 m or less depth of water (Valani et al., 2020) and in close proximity to shore often in open or closed embayments Bruce et al., 2014). Short periods of resting may also occur during offshore migration and feeding but limited information is available, with information mainly coming from direct observation or tagging (Weinstein et al., 2017). Lower SST (relative to surrounding waters) may be preferred during resting along the migratory corridor (Reinke et al., 2016;Tardin et al., 2019). ...
Article
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Humpback whales, Megaptera novaeangliae , are a highly migratory species exposed to a wide range of environmental factors during their lifetime. The spatial and temporal characteristics of such factors play a significant role in determining suitable habitats for breeding, feeding and resting. The existing studies of the relationship between oceanic conditions and humpback whale ecology provide the basis for understanding impacts on this species. Here we have determined the most relevant environmental drivers identified in peer-reviewed literature published over the last four decades, and assessed the methods used to identify relationships. A total of 148 studies were extracted through an online literature search. These studies used a combined estimated 105,000 humpback whale observations over 1,216 accumulated study years investigating the relationship between humpback whales and environmental drivers in both Northern and Southern Hemispheres. Studies focusing on humpback whales in feeding areas found preferences for areas of upwelling, high chlorophyll-a concentration and frontal areas with changes in temperature, depth and currents, where prey can be found in high concentration. Preferred calving grounds were identified as shallow, warm and with slow water movement to aid the survival of calves. The few studies of migration routes have found preferences for shallow waters close to shorelines with moderate temperature and chlorophyll-a concentration. Extracting information and understanding the influence of key drivers of humpback whale behavioral modes are important for conservation, particularly in regard to expected changes of environmental conditions under climate change.
... ARS behavior has also been observed in other baleen whale species [e.g., blue whales (Balaenoptera musculus) and humpback whales (Megaptera novaeangliae)]. ARS behavior has been interpretted as feeding behavior when these species are in known feeding areas, but may also be indicative of mating or social behavior in lower-latitude breeding areas (e.g., Bailey et al., 2009;Weinstein et al., 2017). ...
Article
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Male fin whales sing using 20 Hz pulses produced in regular patterns of inter-note intervals, but little is known about fin whale swimming behavior while they are singing. Even less is known about fin whales in Hawaiian waters because they have rarely been sighted during surveys and passive acoustic monitoring has been limited to sparse hydrophone systems that do not have localization capabilities. We hypothesized that fin whale kinematics may be related to their singing behavior, or external variables such as time and sea state. To investigate this hypothesis, we analyzed 115 tracks containing 50,034 unique notes generated from passive acoustic recordings on an array of 14 hydrophones from 2011 to 2017 at the U.S. Navy Pacific Missile Range Facility off Kauai, Hawaii. Fin whales swam at an average speed of 1.1 m/s over relatively direct paths. We incorporated the whales' speed and turning angle into hidden Markov models to identify different behavioral states based on the whales' movements. We found that fin whale kinematic behavioral state was related to the vocalization rate (also known as cue rate) and time of day. When cue rate was higher, fin whales were more likely to swim slower and turn more than when cue rate was lower. During the night, fin whales were also more likely to swim slower and turn more than during the day. In addition, we examined whether the presence of singing fin whales was related to time and sea state using generalized additive models. Fin whale track presence was affected by day of the year and song season, and possibly also wind speed and wave height. Although the track kinematics from the fin whale tracks presented here are limited to a subset of whales that are acoustically active, they provide some of the only detailed movements of fin whales in the region and can be compared against fin whale swim speeds in other regions. Understanding how fin whale swimming behavior varies based on their vocalization patterns, time, and environmental factors will help us to contextualize potential changes in whale behavior during Navy training and testing on the range.
... [131] These risks are likely to be exacerbated in climate adverse conditions (e.g. [117,[131][132][133] ), and challenge the precautionary approach as it stands. ...
Technical Report
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The Antarctic has long been seen as an untouchable wilderness where few venture beyond scientists at remote research bases, scattered fishing vessels, and a limited number of well-heeled tourists. Yet shifts in Antarctic processes, driven by human-caused climate change, are impacting wider earth systems, with profound implications for human and ecological communities far from the icy continent. The Wilson Center’s Polar Institute and The Pew Charitable Trusts co-convened an ad hoc Expert Working Group of leading Antarctic scientists globally to discuss climate-driven changes to the Southern Ocean around Antarctica. Key considerations were how these changes impact global marine, climate, and human systems, and how management actions taken through the Antarctic Treaty System, in particular CCAMLR, can build resilience to these changes in the Southern Ocean.
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Marine mammal strandings provide vital information on species’ life histories, population health and status of marine ecosystems. Opportunistic reporting of strandings also serve as a powerful low-cost tool for monitoring these elusive mammals. We collated data over ~ 270 years available through various open access databases, reports and publications. Annual strandings along the Indian coast (mean = 11.25 ± SE 9.1) increased in the last two years of the study (2015–2017, mean = 27.66 ± SE 8.5 strandings /year). We found that stranding events spike during June—September along the west coast and during December–January along the east coast. We identified several sections of the coastline, such as Mumbai (0.38 strandings/km), Kozhikode (0.28 strandings/km), Tuticorin (0.4 strandings/km), Rameswaram (1.82 strandings/km), Chennai (0.32 strandings/km) and Bhubaneshwar (0.26 strandings/km) with a higher number of stranded animals reported. Emerging Hotspot Analysis located new and consecutive hotspots along the north-west coast, and sporadic hotspots along the south-east coast. We recommend establishing regional stranding response centres at the identified hotspots coordinated by a National Stranding Centre with adequately trained personnel and central funding support. Regular stranding response training programs for field veterinarians, and frontline personnel of State Forest Departments near stranding hotspots would provide an improved understanding of marine mammal health and threats in Indian waters. Further, the suggested National Stranding Centre needs to maintain a ‘National Stranding Database’ for long-term marine mammal conservation planning in India.
Article
The present study investigated the growth performance, intestinal morphology, body composition and organoleptic quality of large yellow croaker Larimichthys crocea fed a diet containing different proportions of Antarctic krill Euphausia superba meal (0, 15, 30, 45, 60 and 75%) as a substitute for fishmeal. After a 9-week feeding trial, results showed that the specific growth rate and feed efficiency ratio were not negatively affected by dietary krill meal levels. Increasing levels of dietary krill meal linearly and quadratically increased significantly FI (P < .05). Significant positive linear trends were found between the increasing levels of dietary krill meal and carotenoid concentrations, redness (a*), yellowness (b*) in skin (P < .05). And the color can be distinguished by the human eye when 15% fishmeal protein was replaced by krill meal protein due to the total color difference (ΔE) was >3. Texture and pH in muscle were not negatively affected, however, liquid holding capacity linearly decreased (P < .05). The increasing dietary krill meal resulted in a linear decrease in most of free amino acids and a linear increase in inosinic acid (P < .05). The concentrations of EPA was linearly increased with the increasing krill meal level, n-3/n-6 ratio ranged from 0.68–0.91 within the human dietary requirements. Total amino acid profile kept unchanged among all the treatments. Although the increase of dietary krill meal significantly linearly increased the content of fluorine in muscle (P < .05), the highest content was within the safe edible limit for human. The expression levels of mTOR, 4E-BP1, eIF4E, S6K1, S6 genes related to TOR signaling pathway and phosphorylation of mTOR were not significantly changed among all treatment. These results suggested that Antarctic krill meal could be a viable alternative dietary protein source for large yellow croaker. And 6.59%–32.93% of dietary krill meal can result in a better skin color and fatty acid nutritional value in muscle without negative effects on growth performance of large yellow croaker.
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The west Antarctic Peninsula (WAP) region has undergone significant changes in temperature and seasonal ice dynamics since the mid-twentieth century, with strong impacts on the regional ecosystem, ocean chemistry and hydrographic properties. Changes to these long-term trends of warming and sea ice decline have been observed in the 21st century, but their consequences for ocean physics, chemistry and the ecology of the high-productivity shelf ecosystem are yet to be fully established. The WAP shelf is important for regional krill stocks and higher trophic levels, whilst the degree of variability and change in the physical environment and documented biological and biogeochemical responses make this a model system for how climate and sea ice changes might restructure high-latitude ecosystems. Although this region is arguably the best-measured and best-understood shelf region around Antarctica, significant gaps remain in spatial and temporal data capable of resolving the atmosphere-ice-ocean-ecosystem feedbacks that control the dynamics and evolution of this complex polar system. Here we summarise the current state of knowledge regarding the key mechanisms and interactions regulating the physical, biogeochemical and biological processes at work, the ways in which the shelf environment is changing, and the ecosystem response to the changes underway. We outline the overarching cross-disciplinary priorities for future research, as well as the most important discipline-specific objectives. Underpinning these priorities and objectives is the need to better define the causes, magnitude and timescales of variability and change at all levels of the system. A combination of traditional and innovative approaches will be critical to addressing these priorities and developing a co-ordinated observing system for the WAP shelf, which is required to detect and elucidate change into the future.
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Investigating the influence of coastal development on marine environments is a priority to maintain healthy seas. Cetaceans are top predators, keystone and umbrella species and thus are good candidate models to evaluate the extent of anthropogenic impacts on coastal habitats. We employed a generalized linear model with spatial eigenvector mapping (SEV-GLM) to understand the influence of environmental and anthropogenic activities on migrant (humpback whale Megaptera novaeangliae) and non-migrant (Bryde’s whale Balaenoptera brydei and common bottlenose dolphin Tursiops truncatus) cetacean habitat use off Cabo Frio, Rio de Janeiro, Brazil. We hypothesized that both environmental and anthropogenic activities influence their habitat use. Data were collected during 118 boat trips between December 2010 and June 2014. The best SEV-GLM predicted humpback whales would increase linearly with distance to coast, with minimum sea surface temperature (SST) around 19.4−19.8°C and maximum SST around 25.5−26°C, with low variations in chlorophyll a (chl a) concentrations. The model also predicted that humpback whales would occur up to 10 km from diving areas, increasing linearly with distance to fishing grounds. The best non-migrant cetacean SEV-GLM predicted that they would occur more frequently around depths from 30−60 m, increasing with low SST and high chl a concentration. For the anthropogenic component, the model predicted that non-migrant cetaceans would occur up to 10 km from fishing grounds. Our study modeled the influence of anthropogenic activities on cetaceans, and indicates specific priority areas for cetacean conservation, contributing at a local and national scale.
Technical Report
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The Southern Ocean Research Partnership (IWC-SORP) was established in 2009 with the aim of developing a multi-lateral, non-lethal scientific research programme that would improve the coordinated and cooperative delivery of science to the IWC. There are now 13 member countries in the Partnership: Argentina, Australia, Belgium, Brazil, Chile, France, Germany, Italy, Luxembourg, New Zealand, Norway, South Africa, and the United States. This paper reports on the continued progress of IWC-SORP and its six ongoing research themes1 since the Scientific Committee meeting in 2018. This progress includes the production of at least 18 peer-reviewed scientific papers in 2018/19, bringing the total number of peer-reviewed publications related to IWC-SORP produced since the start of the initiative to ca. 144. Moreover, 133 IWC-SORP related papers have been submitted to the Scientific Committee, 8 of them this year. Fieldtrips to the western Antarctic Peninsula, Marion Island, the Southern Ocean (between 60°S – 67°S and 138°E – 152°E), the Ross Sea and the Great Barrier Reef, Australia have taken place in the past year. Thousands of images for photo-identification have been collected, satellite tags have been deployed on killer whales, Antarctic minke whales and humpback whales. As well as video suction cup tags on Antarctic minke and humpback whales. Biopsy samples have been collected from killer whales, humpback and Antarctic minke whales; and hundreds of hours of cetacean acoustic recordings have been made and analysed. KEYWORDS: SOUTHERN OCEAN RESEARCH PARTNERSHIP, IWC-SORP, ANTARCTICA, ABUNDANCE ESTIMATE, ACOUSTICS, BIOPSY SAMPLING, PHOTO-IDENTIFICATION, SATELLITE TAGGING, MOVEMENT, CONNECTIVITY, RESEARCH VOYAGE
Article
Fishery demand for Antarctic krill is increasing, and projected to continue increasing into the future. Krill has the potential to contribute approximately 10% to all future marine landings, adding significantly to global food security. However, the fishery is effectively data-limited so is currently managed using precautionary assessments that relate to large spatial and temporal scales that preclude the need for fine-scale ecological data. To respond to recent changes in fishery operation and to mitigate possible ecological impacts, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) plans to revise its management strategy so that it takes into account ecosystem operation at smaller spatial and temporal scales, such as those relevant to krill-dependent predators. Here, we consider how catches in coastal areas potentially present challenges for these predators, where cumulative catches over the fishing season can sometimes be greater than local consumption by predators, and sometimes greater than the standing stock of krill within an area because of krill transport and replenishment by ocean currents. Protecting feeding areas used by land-based predators such as penguins and seals, whilst also offering a high level of protection for pelagic predators such as some species of fish and recovering populations of cetaceans, will require innovative solutions. We highlight critical ecological research needed to reduce management uncertainty. This is important as we demonstrate that krill consumption by predators in near-shore coastal habitats relies absolutely upon krill movement and oceanographic transport. We also highlight the need to improve understanding about krill behaviour, especially in relation to observed seasonal changes in krill biomass. Finally, we highlight that without up-to-date data about changes in krill, krill-dependent predator populations and their oceanographic environment, management will remain challenging in the context of increasing fishing pressure, recovering populations of marine mammals and a changing climate.
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Understanding how closely related, sympatric species distribute themselves relative to their environment is critical to understanding ecosystem structure and function and predicting effects of environmental variation. The Antarctic Peninsula supports high densities of krill and krill consumers; however, the region is warming rapidly, with unknown consequences. Humpback whales Megaptera novaeangliae and Antarctic minke whales Balaenoptera bonaerensis are the largest krill consumers here, yet key data gaps remain about their distribution, behavior, and interactions and how these will be impacted by changing conditions. Using satellite telemetry and novel spatial point-process modeling techniques, we quantified habitat use of each species relative to dynamic environmental variables and determined overlap in core habitat areas during summer months when sea ice is at a minimum. We found that humpback whales ranged broadly over continental shelf waters, utilizing nearshore bays, while minke whales restricted their movements to sheltered bays and areas where ice is present. This presents a scenario where minke whale core habitat overlaps substantially with the broader home ranges of humpback whales. While there is no indication that prey is limiting in this ecosystem, increased overlap between these species may arise as climate-driven changes that affect the extent, timing, and duration of seasonal sea ice decrease the amount of preferred foraging habitat for minke whales while concurrently increasing it for humpback whales. Our results provide the first quantitative assessment of behaviorally based habitat use and sympatry between these 2 krill consumers and offers insight into the potential effects of a rapidly changing environment on the structure and function of a polar ecosystem.
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Animal-borne electronic instruments (tags) are valuable tools for collecting information on cetacean physiology, behaviour and ecology, and for enhancing conservation and management policies for cetacean populations. Tags allow researchers to track the movement patterns, habitat use and other aspects of the behaviour of animals that are otherwise difficult to observe. They can even be used to monitor the physiology of a tagged animal within its changing environment. Such tags are ideal for identifying and predicting responses to anthropogenic threats, thus facilitating the development of robust mitigation measures. With the increasing need for data best provided by tagging and the increasing availability of tags, such research is becoming more common. Tagging can, however, pose risks to the health and welfare of cetaceans and to personnel involved in tagging operations. Here we provide 'best practice' recommendations for cetacean tag design, deployment and follow-up assessment of tagged individuals, compiled by biologists and veterinarians with significant experience in cetacean tagging. This paper is intended to serve as a resource to assist tag users, veterinarians, ethics committees and regulatory agency staff in the implementation of high standards of practice, and to promote the training of specialists in this area. Standardised terminology for describing tag design and illustrations of tag types and attachment sites are provided, along with protocols for tag testing and deployment (both remote and through capture-release), including training of operators. The recommendations emphasise the importance of ensuring that tagging is ethically and scientifically justified for a particular project and that tagging only be used to address bona fide research or conservation questions that are best addressed with tagging, as supported by an exploration of alternative methods. Recommendations are provided for minimising effects on individual animals (e.g. through careful selection of the individual, tag design and implant sterilisation) and for improving knowledge of tagging effects on cetaceans through increased post-tagging monitoring.
Article
Most studies of cetacean habitat use do not consider the influence of anthropogenic activities. We investigated the influence of environmental and anthropogenic variables on habitat use by humpback Megaptera novaeangliae and Bryde’s whales Balaenoptera brydei off the coast of the Brazilian city of Rio de Janeiro. Although there are 2 marine protected areas (MPAs) in this area, few data are available on cetacean habitat use or on the overlap of different cetacean species within these MPAs. Our aim was to evaluate the effectiveness of the MPAs and propose a buffer zone to better protect the biodiversity of the study area. We conducted systematic surveys and developed spatial eigenvector generalized linear models to characterize habitat use by the species in the study area. Habitat use by humpback whales was influenced only by depth, whereas for Bryde’s whales there was the additional influence of anthropogenic variables. For Bryde’s whales, which use the area for feeding, sea surface temperature and the distance to anchorages had a major influence on habitat use. We also showed that neither of the MPAs in the study area adequately protects the hotspots of either whale species. Most of the humpback whale grid cells with high sighting predictions were located within 2 km of the MPAs, while areas of high sighting prediction of Bryde’s whales were located up to 5 km from the MPAs, closer to beaches. Our findings provide important insights for the delimitation of protected areas and zoning of the MPAs.
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Abstract Ecosystem dynamics at the northwest Antarctic Peninsula are driven by interactions between physical and biological processes. For example, baleen whale populations are recovering from commercial harvesting against the backdrop of rapid climate change, including reduced sea ice extent and changing ecosystem composition. Concurrently, the commercial harvesting of Antarctic krill is increasing, with the potential to increase the likelihood for competition with and between krill predators and the fishery. However, understanding the ecology, abundance, and spatial distribution of krill predators is often limited, outdated, or at spatial scales that do not match those desired for effective fisheries management. We update current knowledge of predator dependence on krill by integrating telemetry‐based data, at‐sea observational surveys, estimates of predator abundance, and physiological data to estimate the spatial distribution of krill consumption during the austral summer by three species of Pygoscelis penguin, 11 species of flying seabirds, one species of pinniped, and two species of baleen whale. Our models show that the majority of important areas for krill predator foraging are close to penguin breeding colonies in nearshore areas where humpback whales also regularly feed, and along the shelf‐break, though we caution that not all known krill predators are included in these analyses. We show that krill consumption is highly variable across the region, and often concentrated at fine spatial scales, emphasizing the need for the management of the local krill fishery at relevant temporal and spatial scales. We also note that krill consumption by recovering populations of krill predators provides further evidence in support of the krill surplus hypothesis, and highlight that despite less than comprehensive data, cetaceans are likely to consume a significant proportion of the krill consumed by natural predators but are not currently considered directly in the management of the krill fishery. If management of the krill fishery is to be precautionary and operate in a way that minimizes the risks to krill predator populations, it will be necessary in future analyses, to include up‐to‐date and precise abundance and consumption estimates for pack‐ice seals, finfish, squid, and other baleen whale species not currently considered.
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A dedicated aerial cetacean survey was conducted concurrently to a standardised net trawl survey for krill in order to investigate distribution patterns of large whales and different krill species and to investigate relationships of these. Distance sampling data were used to produce density surface models for humpback (Megaptera novaeangliae) and fin whales (Balaenoptera physalus) around the West Antarctic Peninsula (WAP). Abundance for both species was estimated over two strata in the Bransfield Strait and Drake Passage. Distinct distribution patterns suggest horizontal niche partitioning of the two whale species around the WAP, with fin whales aggregating at the shelf edge of the South Shetland Islands in the Drake Passage and humpback whales in the Bransfield Strait. Krill biomass estimated from the concurrent krill survey was used along with CTD data from the same expedition, bathymetric parameters and satellite data on chlorophyll-a and ice concentration to model krill distribution. Comparisons of the predicted distributions of both whale species with the predicted distributions of Euphausia superba, Euphausia crystallorophias and Thysanoessa macrura suggest a complex relationship rather than a straightforward correlation between krill and whales. However, results indicate that fin whales were feeding in an area dominated by T. macrura, while humpback whales were found in areas of higher E. superba biomass. Our results provide abundance estimates for humpback whales and, for the first time, fin whales in the WAP and contribute important information on feeding ecology and habitat use of these two species in the Southern Ocean.
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It is a golden age for animal movement studies and so an opportune time to assess priorities for future work. We assembled 40 experts to identify key questions in this field, focussing on marine megafauna, which include a broad range of birds, mammals, reptiles, and fish. Research on these taxa has both underpinned many of the recent technical developments and led to fundamental discoveries in the field. We show that the questions have broad applicability to other taxa, including terrestrial animals, flying insects, and swimming invertebrates, and, as such, this exercise provides a useful roadmap for targeted deployments and data syntheses that should advance the field of movement ecology.
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State-space models provide a powerful way to scale up inference of movement behaviours from individuals to populations when the inference is made across multiple individuals. Here, I show how a joint estimation approach that assumes individuals share identical movement parameters can lead to improved inference of behavioural states associated with different movement processes. I use simulated movement paths with known behavioural states to compare estimation error between nonhierarchical and joint estimation formulations of an otherwise identical state-space model. Behavioural state estimation error was strongly affected by the degree of similarity between movement patterns characterising the behavioural states, with less error when movements were strongly dissimilar between states. The joint estimation model improved behavioural state estimation relative to the nonhierarchical model for simulated data with heavy-tailed Argos location errors. When applied to Argos telemetry datasets from 10 Weddell seals, the nonhierarchical model estimated highly uncertain behavioural state switching probabilities for most individuals whereas the joint estimation model yielded substantially less uncertainty. The joint estimation model better resolved the behavioural state sequences across all seals. Hierarchical or joint estimation models should be the preferred choice for estimating behavioural states from animal movement data, especially when location data are error-prone.
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Following an assessment of Antarctic krill (Euphausia superba) in the Scotia Sea, CCAMLR established a precautionary catch limit of 4 million tonnes and further adopted 15 small-scale management units (SSMUs). The intent was to subdivide the precautionary catch limit for krill among the SSMUs so as to preclude the inadvertent concentration of catches in a small portion of the surveyed area. Five options for allocating the catch limit among the SSMUs in the Scotia Sea are presented in this paper. The first four are static allocations where the allotment of catch to an SSMU is proportional to: (i) the historical catch within the SSMU; (ii) estimated predator demand in the SSMU; (iii) estimated standing stock of krill in the SSMU; and (iv) standing stock less predator demand in the SSMU. The fifth option is a dynamic allocation based on land-based predator monitoring conducted just prior to, or early in, the fishing season. For the purposes of illustration and comparison between the options, parameter estimates are made using available data, although it is recognised that considerable refinement of these estimates is possible. Qualitative conclusions are that: under the first two options a substantial portion (>65%) of the catch limit would be allocated to three or less of the SSMUs adjacent to large concentrations of land-breeding predators; under options (iii) and (iv) a similar portion of the catch limit would be directed to pelagic SSMUs beyond the foraging range of these predators but into areas where krill fishing has not regularly occurred; and under option (v), an example of an adjustable catch limit dependent on the results of ecosystem monitoring, the fishery would be restricted in some of its traditional fishing grounds during years of low krill availability. Under all five options there would be little effect on the existing fishery. However, as catches increase, a trade-off may be drawn between options that displace the fishery from its current operating area, but reduce the potential for contravening the terms of the Convention, and options that do not displace the fishery, but are likely to contravene the terms of the CCAMLR Convention.
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A population of humpback whales (Megaptera novaeangliae) spends the austral summer feeding on Antarctic krill (Euphausia superba) along the Western Antarctic Peninsula (WAP). These whales acquire their annual energetic needs during an episodic feeding season in high latitude waters that must sustain long-distance migration and fasting on low-latitude breeding grounds. Antarctic krill are broadly distributed along the continental shelf and nearshore waters during the spring and early summer, and move closer to land during late summer and fall, where they overwinter under the protective and nutritional cover of sea ice. We apply a novel space-time utilization distribution method to test the hypothesis that humpback whale distribution reflects that of krill: spread broadly during summer with increasing proximity to shore and associated embayments during fall. Humpback whales instrumented with satellite-linked positional telemetry tags (n = 5), show decreased home range size, amount of area used, and increased proximity to shore over the foraging season. This study applies a new method to model the movements of humpback whales in the WAP region throughout the feeding season, and presents a baseline for future observations of the seasonal changes in the movement patterns and foraging behavior of humpback whales (one of several krill-predators affected by climate-driven changes) in the WAP marine ecosystem. As the WAP continues to warm, it is prudent to understand the ecological relationships between sea-ice dependent krill and krill predators, as well as the interactions among recovering populations of krill predators that may be forced into competition for a shared food resource.
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We quantified species richness and abundance of seabirds and marine mammals in order to identify marine areas that are persistently attractive to top predators. Shipboard surveys across a 150 000 km2 grid off the Antarctic Peninsula were conducted once or twice each year from 2003 to 2011 during which the distribution and abundance of top predators were mapped. We hypothesized that spatial organization of species richness and abundance hotspots reflect persistent habitat use and are regionalized according to distance from land and oceanographic boundaries. To test this, we used a new hotspot variance metric based on the percentage of time that the species richness or abundance estimate at any one location is greater than 1 standard deviation above the long term means for the entire survey grid. Species richness hotspots were based on all species sighted, while abundance hotspots were based on concentrations of 16 species: 13 seabirds (penguins, petrels and albatrosses), 1 pinniped and 2 baleen whales. Species abundance hotspots reflected 2 major groupings-those with oceanic and coastal origins. We identified 15 richness hotspots, 9 of which were in proximity to the southern Antarctic Circumpolar Current front; the 6 others were associated with major breeding colonies and the location of 2 submarine canyon systems. Our approach integrates temporal and spatial variances over 14 individual surveys and provides useful reference points for identifying ecologically important areas, refining food web models and developing spatial management of and conservation strategies for marine ecosystems.
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In animal ecology, a question of key interest for aquatic species is how changes in movement behavior are related in the horizontal and vertical dimensions when individuals forage. Alternative theoretical models and inconsistent empirical findings mean that this question remains unresolved. Here we tested expectations by incorporating the vertical dimension (dive information) when predicting switching between movement states (‘‘resident’’ or ‘‘directed’’) within a state-space model. We integrated telemetry-based tracking and diving data available for four seal species (southern elephant, Weddell, antarctic fur, and crabeater) in East Antarctica. Where possible, we included dive variables derived from the relationships between (1) dive duration and depth (as a measure of effort), and (2) dive duration and the postdive surface interval (as a physiological measure of cost). Our results varied within and across species, but there was a general tendency for the probability of switching into ‘‘resident’’ state to be positively associated with shorter dive durations (for a given depth) and longer postdive surface intervals (for a given dive duration). Our results add to a growing body of literature suggesting that simplistic interpretations of optimal foraging theory based only on horizontal movements do not directly translate into the vertical dimension in dynamic marine environments. Analyses that incorporate at least two dimensions can test more sophisticated models of foraging behavior.
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We use data collected on the CCAMLR-IWC Krill Synoptic Survey (2000) to investigate relationships between cetacean density, krill density and oceanographic conditions. We explore the use of generalized additive models (GAMs) to model these relationships, and show how these models can provide abundance estimates for sub-areas within the survey region, as well as for the survey region itself. Abundance estimates from a simple conventional line transect analysis are also presented. Introduction The International Whaling Commission (IWC) and the Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR) share an interest in the Southern Ocean ecosystem. This shared interest led to the first multinational collaborative field program between the two commissions' scientific committees in January and February 2000. Four research vessels participated in this collaboration: the Yuzhmorgeologiya (USA), the James Clark Ross (UK), the Kaiyo Maru (Japan) and the Atlantida (Russia).
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Most humpback whale Megaptera novaeangliae populations partition their time between prey-rich feeding and prey-deficient breeding/calving regions. How these whales feed and optimize the consumption of prey resources prior to long-distance migrations and fasting is largely unknown. We deployed multi-sensor tags on humpback whales around the western Antarctic Peninsula to describe their daily activity patterns late in the feeding season to test the hypothesis that feeding behavior varies over the diel cycle so as to maximize energy intake and limit energy expenditure. Dives were assigned to a behavioral state (feeding, resting, traveling, exploring) to determine hourly rates and to build an ethogram of activity patterns. Our results show a distinct diel pattern of whales feeding exclusively at night. Feeding depth was deeper around sunrise/sunset and shallower (similar to 50 m) at night, consistent with diel vertical prey movement. Shallow feeding dives typically contained a single feeding lunge, a strategy known to increase feeding efficiency and maximize intake rates by maintaining proximity to the surface and reducing the energetic costs of deep diving. The lack of feeding during daytime may indicate prey being too deep for efficient foraging. Our results add information where currently there is a paucity of data describing how baleen whales optimize feeding behavior, specifically in relation to prey distribution and movement, to fuel their extraordinary energetic requirements necessary for growth, migration, and reproduction. Understanding behavioral patterns and predator/prey dynamics in rapidly changing marine environments, like the Antarctic Peninsula, is critical for understanding how these changes will affect ecosystem structure and function.
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We examined the spatial association between baleen whales and their principal prey, Antarctic krill Euphausia superba near the South Shetland Islands (Antarctic Peninsula) using data collected by the US Antarctic Marine Living Resources (AMLR) program during January surveys from 2003 through 2007. Whale distributions were determined using ship-based visual surveys, while data on krill distribution, abundance, and demographic characteristics were derived from net hauls. Approximately 25 000 km of transects and 500 net hauls were sampled over 5 yr. We defined hotspots based on statistical criteria to describe persistent areas of occurrence of both whales and krill. Hotspots were identified, and whales and krill length-maturity classes exhibited distinct spatial segregation in their distribution patterns. We found that baleen whales aggregated to krill hotspots that differed in size structure. Humpback whales Megaptera novaeangliae were associated with small (<35 mm) juvenile krill in Bransfield Strait, whereas fin whales Balaenoptera physalus were associated with large (>45 mm) mature krill located offshore. Overlapping these size-dependent krill distributions, Antarctic minke whales B. bonaerensis were associated with intermediate sized krill (35-44 mm). The correlation among different whale species and krill swarms of differing size composition presents an intriguing pattern that deserves further study.
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The Western Antarctic Peninsula (WAP) is a biologically rich area supporting large standing stocks of krill and top predators (including whales, seals and seabirds). Physical forcing greatly affects productivity, recruitment, survival and distribution of krill in this area. In turn, such interactions are likely to affect the distribution of baleen whales. The Southern Ocean GLOBEC research program aims to explore the relationships and interactions between the environment, krill and predators around Marguerite Bay (WAP) in autumn 2001 and 2002. Bathymetric and environmental variables including acoustic backscattering as an indicator of prey abundance were used to model whale distribution patterns. We used an iterative approach employing (1) classification and regression tree (CART) models to identify oceanographic and ecological variables contributing to variability in humpback Megaptera novaeangliae and minke Balaenoptera acutorstrata whale distribution, and (2) generalized additive models (GAMs) to elucidate functional ecological relationships between these variables and whale distribution. The CART models indicated that the cetacean distribution was tightly coupled with zooplankton acoustic volume backscatter in the upper (25 to 100 m), and middle (100 to 300 m) portions of the water column. Whale distribution was also related to distance from the ice edge and bathymetric slope. The GAMs indicated a persistent, strong, positive relationship between increasing zooplankton volume and whale relative abundance. Furthermore, there was a lower limit for averaged acoustic volume backscatter of zooplankton below which the relationship between whales and prey was not significant. The GAMs also supported an annual relationship between whale distribution, distance from the ice edge and bathymetric slope, suggesting that these are important features for aggregating prey. Our results demonstrate that during the 2 yr study, whales were consistently and predictably associated with the distribution of zooplankton. Thus, humpback and minke whales may be able to locate physical features and oceanographic processes that enhance prey aggregation.
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Knowledge of relationships between prey availability and predator performance is the key to using predators as indicators of the state of marine systems and to assessing potential consequences of competition between natural predators and man for common resources. Fluctuations in the abundance of Antarctic krill are believed to have a substantial influence on the reproductive performance of krill-dependent top predator species in the Southern Ocean; few quantifications of such interactions exist. At South Georgia, for 2 years in which acoustic surveys revealed a major difference in krill abundance, we compared diet, provisioning of offspring and breeding success in 4 main predator species (2 penguins, 2 albatrosses, with supporting data from Antarctic fur seal) whose dependence on krill typically ranges from 20 to 90%. The 4-fold difference in krill biomass between 1986 (ca 30 g m(-2)) and 1994 (ca 7 g m(-2)) was accompanied by (1) an 88 to 90% reduction in the mass of krill in predator diets (and some increase in the fish component), (2) greater prey diversity for most species, (3) reduced diet overlap between species and (4) a switch from krill to amphipods in macaroni penguin but no major dietary change in other species. Rates of provisioning of offspring decreased by 90% in gentoo penguin and 40 to 50% in the other 3 species; this was due to reduced meal size in penguins (by 90% in gentoo and 50% in macaroni) and to doubling of foraging trip duration in albatrosses. Breeding success was reduced by 50% in grey-headed albatross (the species least dependent on krill), by 90% in black-browed albatross and gentoo penguin (only 3 to 4% of eggs producing fledged chicks) but by only 10% in macaroni penguin, presumably reflecting its ability to switch to small prey unprofitable for the other species. However, all species (except for black-browed albatross), particularly macaroni penguin, produced fledglings significantly lighter than usual, probably affecting their subsequent survival. Some effects on adult survival could also be inferred. Our results show a coherent, though complex, pattern of within and between species similarities and differences. These mainly reflect the degree of dependence on krill, the feasibility of taking alternative prey and constraints on trip duration and/or meal size imposed by foraging adaptations (especially relating to travel speeds and diving abilities, whereby flightless divers and pelagic foragers differ markedly). The generality of these principles are explored through comparison with other studies, particularly of Shetland seabirds.
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The annual formation and loss of some 15millionkm2 of sea ice around the Antarctic significantly affects global ocean circulation, particularly through the formation of dense bottom water.As one of the most profound seasonal changes on Earth, the formation and decay of sea ice plays a major role in climate processes. It is also likely to be impacted by climate change, potentially changing the productivity of theAntarctic region.The sea ice zone supports much wildlife, particularly large vertebrates such as seals, seabirds and whales, some exploited to near extinction. Cetacean species in the Southern Ocean will be directly impacted by changes in sea ice patterns as well as indirectly by changes in their principal prey,Antarctic krill, affected by modifications to their own environment through climate change. Understanding how climate change will affect species at all trophic levels in the Southern Ocean requires new approaches and integrated research programs. This review focuses on the current state of knowledge of the sea ice zone and examines the potential for climatic and ecological change in the region. In the context of changes already documented for seals and seabirds, it discusses potential effects on the most conspicuous vertebrate of the region, baleen whales.
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In the Southern Ocean, humpback whales Megaptera novaeangliae were depleted by commercial whaling operations during the 20th century, but many populations now appear to be recovering. Previous surveys of whale distribution along the western Antarctic Peninsula (WAP) suggested that humpbacks feed on krill swarms over the continental shelf during the summer, but little is known about their movements and densities during autumn, when krill begin to seek inshore refugia for overwintering. Here we present estimates of humpback whale densities in some inshore regions of the WAP during the late autumn. We surveyed 653.9 km of track line in the Gerlache Strait and adjacent bays during 26 April to 1 June 2009. We detected 371 groups of humpback whales in a distance sampling framework that allowed us to calculate estimates of whale density along track lines in open and enclosed habitats within our study area. Density estimates along track lines ranged from 0.02 to 1.75 whales km -2; the highest densities were found along track lines in the enclosed regions of Wilhelmina Bay, the Errera Channel, and Andvord Bay. These results provide preliminary insight into the density and distribution of WAP humpbacks and indicate that large numbers of whales remain in Antarctic feeding grounds late into autumn. This study also provides details on the difficulties in estimating density of whales in the inshore regions of the WAP using traditional line transect/distance sampling methods, and provides direction for future studies including the use of model-based approaches to estimating whale densities in this region.
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A fundamental goal in animal ecology is to quantify how environmental (and other) factors influence individual movement, as this is key to understanding responsiveness of populations to future change. However, quantitative interpretation of individual-based telemetry data is hampered by the complexity of, and error within, these multi-dimensional data. Here, we present an integrative hierarchical Bayesian state-space modelling approach where, for the first time, the mechanistic process model for the movement state of animals directly incorporates both environmental and other behavioural information, and observation and process model parameters are estimated within a single model. When applied to a migratory marine predator, the southern elephant seal (Mirounga leonina), we find the switch from directed to resident movement state was associated with colder water temperatures, relatively short dive bottom time and rapid descent rates. The approach presented here can have widespread utility for quantifying movement-behaviour (diving or other)-environment relationships across species and systems.
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Remotely sensed tracking data collected on animal movement is vastly un-derutilized due to a lack of statistical tools for appropriate analysis. Features of such data that make analysis particularly challenging include the presence of estimation errors that are non-Gaussian and vary in time, observations that occur irregularly in time, and com-plexity in the underlying behavioral processes. We develop a state–space framework that simultaneously deals with these features and demonstrate our method by analyzing three seal pathway data sets. We show how known information regarding error distributions can be used to improve inference of the underlying process(es) and demonstrate that our frame-work provides a powerful and flexible method for fitting different behavioral models to tracking data.
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Adelie penguins (Pygoscelis adeliae), carabeater seals (Lobodon carcinophagus), humpback (Megaptera novaeangliae), and minke whales (Balaenoptera bonaernsis) are found in the waters surrounding the Western Antarctic Peninsula. Each species relies primarily on Antarctic krill (Euphausia superba) and has physiological constraints and foraging behaviors that dictate their ecological niches. Understanding the degree of ecological overlap between sympatric krill predators is critical to understanding and predicting the impacts on climate-driven changes to the Antarctic marine ecosystem. To explore ecological relationships amongst sympatric krill predators, we developed ecological niche models using a maximum entropy modeling approach (Maxent) that allows the integration of data collected by a variety of means (e.g. satellite-based locations and visual observations). We created spatially explicit probability distributions for the four krill predators in fall 2001 and 2002 in conjunction with a suite of environmental variables. We find areas within Marguerite Bay with high krill predator occurrence rates or biological hot spots. We find the modeled ecological niches for Adelie penguins and crabeater seals may be affected by their physiological needs to haul-out on substrate. Thus, their distributions may be less dictated by proximity to prey and more so by physical features that over time provide adequate access to prey. Humpback and minke whales, being fully marine and having greater energetic demands, occupy ecological niches more directly proximate to prey. We also find evidence to suggest that the amount of overlap between modeled niches is relatively low, even for species with similar energetic requirements. In a rapidly changing and variable environment, our modeling work shows little indication that krill predators maintain similar ecological niches across years around Marguerite Bay. Given the amount of variability in the marine environment around the Antarctic Peninsula and how this affects the local abundance of prey, there may be consequences for krill predators with historically little niche overlap to increase the potential for interspecific competition for shared prey resources. (C) 2010 Elsevier Ltd. All rights reserved.
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The fishery for Antarctic krill (Euphausia superba) is the largest by tonnage in the Southern Ocean. The catch remained relatively stable at around 120 000 tonnes for 17 years until 2009, but has recently increased to more than 200 000 tonnes. The Commission for the Conservation of Antarctic Marine Living Resources precautionary catch limits for this species total over 8.6 million tonnes so it remains one of the ocean’s largest known underexploited stocks. Recent developments in harvesting technology and in products being derived from krill indicate renewed interest in exploiting this resource. At the same time, there are changes in the Southern Ocean environment that are affecting both krill and the fishery. This paper summarizes the current state of this fishery and highlights the changes that are affecting it.
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Humpback whales were instrumented with satellite transmitters off the western Antarctic Peninsula in January of 2004–2006 to examine their movement patterns and habitat use. Whales were tracked from 4 to 80days (mean=36.5days). Distance and travel rate estimates for nine individuals ranged from 223 to 4,356km and from 17 to 75km/day, respectively. Considerable individual variation was observed in direction, speed and range of movements. The overall pattern was characterized by short- and long-distance movements between presumed foraging areas with relatively short residency times. Travel rates were lower at these sites, characterized by erratic movements, than during traveling between them. Area usage for six individuals based on the 95% fixed kernel home range with least squares cross-validation ranged from 2,771 to 172,356km2. The management boundary between the feeding grounds associated with Breeding Stocks G and A needs revision, as current available data suggest it should be located to the east of 50°W. This study is the first to present detailed information on the movements of humpback whales in the Southern Ocean.
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Acute effects of anthropogenic sounds on marine mammals, such as from military sonars, energy development, and offshore construction, have received considerable international attention from scientists, regulators, and industry. Moreover, there has been increasing recognition and concern about the potential chronic effects of human activities (e.g., shipping). It has been demonstrated that increases in human activity and background noise can alter habitats of marine animals and potentially mask communications for species that rely on sound to mate, feed, avoid predators, and navigate. Without exception, regulatory agencies required to assess and manage the effects of noise on marine mammals have addressed only the acute effects of noise on hearing and behavior. Furthermore, they have relied on a single exposure metric to assess acute effects: the absolute sound level received by the animal. There is compelling evidence that factors other than received sound level, including the activity state of animals exposed to different sounds, the nature and novelty of a sound, and spatial relations between sound source and receiving animals (i.e., the exposure context) strongly affect the probability of a behavioral response. A more comprehensive assessment method is needed that accounts for the fact that multiple contextual factors can affect how animals respond to both acute and chronic noise. We propose a three-part approach. The first includes measurement and evaluation of context-based behavioral responses of marine mammals exposed to various sounds. The second includes new assessment metrics that emphasize relative sound levels (i.e., ratio of signal to background noise and level above hearing threshold). The third considers the effects of chronic and acute noise exposure. All three aspects of sound exposure (context, relative sound level, and chronic noise) mediate behavioral response, and we suggest they be integrated into ecosystem-level management and the spatial planning of human offshore activities. Resumen: Los efectos agudos de los sonidos antropogénicos (como los provenientes de sonares militares, desarrollo energéticos y construcciones cercanas a la costa) sobre mamíferos marinos han recibido considerable atención internacional de parte de científicos, reguladores e industriales. Más aun, hay creciente reconocimiento y preocupación sobre los efectos crónicos potenciales de las actividades humanas (e.g., navegación). Se ha demostrado que los incrementos de la actividad humana y del ruido pueden alterar el hábitat de mamíferos marinos y potencialmente enmascarar la comunicación de especies que dependen de sonidos para buscar pareja, alimentarse, evitar depredadores y navegar. Sin excepción, las agencias reguladoras que han evaluado y manejado los efectos del ruido sobre mamíferos marinos solo han atendido los efectos agudos del ruido sobre la audición y la conducta. Más aun, se han basado en una sola medida de exposición para evaluar efectos agudos: el nivel de sonido absoluto recibido por el animal. Hay evidencia de peso de que otros factores, diferentes al nivel de sonido recibido, incluyendo el estado de los animales expuestos a sonidos diferentes, la naturaleza y novedad del sonido y las relaciones espaciales entre la fuente del sonido y los animales receptores, afectan fuertemente a la probabilidad de respuesta. Se requiere de una evaluación más integral que considere el hecho de que factores contextuales múltiples pueden afectar la manera en que los animales responden a rui