Large Whales Research Articles

Short‐term recovery of humpback whales after percutaneous satellite tagging

ABSTRACTLong‐term re‐sightings of individuals used in satellite telemetry research are important for determining the effects of tagging on large whales. We evaluated the initial behavioral response, healing process, and short‐term reproductive behavior and success of 7 percutaneous‐tagged humpback whales (4 M, 3 F) monitored for 4–10 years in the feeding ground of the Magellan Strait, Chile. We took post‐tagging photographs incidentally every year during re‐sighting expeditions. We did not observe an initial reaction to tagging or sudden change in behavior or direction of movement. Two of the females had 3 and 2 calves before tagging, and one of them had 2 calves every 3 years after tagging. Post‐tagging annual site fidelity remained nearly 100%. We did not observe initial tag protrusion in any individual. Four whales (57%) showed no signs of initial tissue damage shortly after tagging; we observed tissue shedding in 2 individuals, and traces of blood on 1 whale. Complete wound healing apparently occurred in all individuals within the first 2 years after tagging, and 5 of them showed no scars 3–6 years later. Four individuals showed small to medium (<5 cm) tumor‐like lumps for several years after tagging, but some were undistinguishable from other natural lumps (e.g., barnacles) observed near the tag injury. Overall, tagging did not seem to affect reproductive success or the behavior of individuals during and immediately after tagging. The development of new technologies always can pose a risk to animal welfare, thus studies such as this one are important for carefully evaluating the effects of tagging on whales. © 2017 The Wildlife Society.

Frequency of Injuries from Line Entanglements, Killer Whales, and Ship Strikes on Bering-Chukchi-Beaufort Seas Bowhead Whales

We analyzed scarring data for Bering-Chukchi-Beaufort (BCB) Seas bowhead whales (Balaena mysticetus) harvested by Alaska Native hunters to quantify the frequency of line entanglement, ship strikes, and killer whale-inflicted injuries. We had 904 records in our database for whales landed between 1990 and 2012, and after data quality screening, we found 521 records containing information on scarring. Logistic regression was used to evaluate different combinations of explanatory variables (i.e., body length, sex, year, year-group) to develop a prediction model for each scar type. We also list bowhead whales that were harvested, found dead, or observed alive entangled in commercial line/fishing gear. Our findings suggest that about 12% of harvested bowheads show entanglement scars. Their frequency is highly correlated with body length and sex: about 50% of very large bowheads (> 17 m) show such scars, while whales under 9 m rarely do, and males show a significantly higher rate than females. Scars associated with ship strikes are infrequent and occur on ~2% of all harvested whales; body length, sex, and year were not significant factors. Scarring from attempted killer whale predation was evident on ~8% of landed whales. As with entanglement injuries, the frequency of killer whale scars was much higher (> 40%) on whales more than 16 m in length and statistically more frequent in the second half of the study (2002 – 12). Increased killer whale injuries in the recent decade are consistent with studies conducted on bowheads of the Eastern Canada-West Greenland population. The findings presented here reflect the most thorough analysis of injury rates from entanglement, ships, and killer whales for the BCB bowheads conducted to date. They indicate that (1) entanglement rates primarily from pot fishing gear (crab or cod or both) are relatively high for very large and presumably older bowheads, (2) collisions with ships are infrequent at present, and (3) scarring from killer whales is frequent on very large adult whales (> 17 m). Considering that bowhead habitat is changing rapidly (e.g., sea ice reduction), industrial ship traffic in the Arctic is increasing, and commercial fishing operations are expanding to the north, we strongly recommend that monitoring of scarring and injuries on harvested bowheads continue into the future as a means of documenting change.

A right whale pootree: classification trees of faecal hormones identify reproductive states in North Atlantic right whales (Eubalaena glacialis).

Immunoassay of hormone metabolites extracted from faecal samples of free-ranging large whales can provide biologically relevant information on reproductive state and stress responses. North Atlantic right whales (Eubalaena glacialis Müller 1776) are an ideal model for testing the conservation value of faecal metabolites. Almost all North Atlantic right whales are individually identified, most of the population is sighted each year, and systematic survey effort extends back to 1986. North Atlantic right whales number <500 individuals and are subject to anthropogenic mortality, morbidity and other stressors, and scientific data to inform conservation planning are recognized as important. Here, we describe the use of classification trees as an alternative method of analysing multiple-hormone data sets, building on univariate models that have previously been used to describe hormone profiles of individual North Atlantic right whales of known reproductive state. Our tree correctly classified the age class, sex and reproductive state of 83% of 112 faecal samples from known individual whales. Pregnant females, lactating females and both mature and immature males were classified reliably using our model. Non-reproductive [i.e. 'resting' (not pregnant and not lactating) and immature] females proved the most unreliable to distinguish. There were three individual males that, given their age, would traditionally be considered immature but that our tree classed as mature males, possibly calling for a re-evaluation of their reproductive status. Our analysis reiterates the importance of considering the reproductive state of whales when assessing the relationship between cortisol concentrations and stress. Overall, these results confirm findings from previous univariate statistical analyses, but with a more robust multivariate approach that may prove useful for the multiple-analyte data sets that are increasingly used by conservation physiologists.

The oldest marine vertebrate fossil from the volcanic island of Iceland: a partial right whale skull from the high latitude Pliocene Tjörnes Formation

AbstractExtant baleen whales (Cetacea, Mysticeti) are a disparate and species‐rich group, but little is known about their fossil record in the northernmost Atlantic Ocean, a region that supports considerable extant cetacean diversity. Iceland's geographical setting, dividing North Atlantic and Arctic waters, renders it ideally situated to shed light on cetacean evolution in this region. However, as a volcanic island, Iceland exhibits very little marine sedimentary exposure, and fossil whales from Iceland older than the late Pleistocene are virtually unknown. Here, we present the first fossil whale found in situ from the Pliocene Tjörnes Formation (c. 4.5 Ma), Iceland's only substantial marine sedimentary outcrop. The specimen is diagnosed as a partial skull from a large right whale (Mysticeti, Balaenidae). This discovery highlights the Tjörnes Formation as a potentially productive fossil vertebrate locality. Additionally, this find indicates that right whales (Eubalaena) and bowhead whales (Balaena) were sympatric, with broadly overlapping latitudinal ranges in the Pliocene, in contrast to the modern latitudinal separation of their living counterparts.

Dolphin blubber/axial muscle shear: implications for rigid transdermal intramuscular tracking tag trauma in whales.

Whale tracking tags often penetrate semi-rigid blubber, with intramuscular sharp tips and toggling barbs under the subdermal sheath to reduce premature shedding. Tag sites can show persistent regional swellings or depressions. Fibroelastic blubber grips a tag, so if muscle shears relative to blubber during locomotion, the tag tip could cavitate the muscle within overall shearing distance. We modeled shearing of blubber relative to muscle, within the dorsal-ventral peduncular movement range of four common dolphin (Delphinus delphis) cadavers (mean length 186 cm). The net change in angle and hence tip distance moved was calculated with dorsal and ventral flexion, and compared between 1.5 mm diameter needles inserted into blubber only and through blubber into muscle. The greatest shearing value was 3.6 cm, and shearing was most pronounced in the areas ventral and caudal to the dorsal fin. Scaled dummy tags were also inserted and the animal cyclically flexed dorsally and ventrally for 18 h. Tag sites were dissected and cavities around the tag tips documented. If this shearing is comparable in large whales, depressions and regional swellings observed with intramuscular tracking tags are likely the result of tissue loss and repair, respectively. Placing tags para-sagittally anterior to the dorsal fin would cause the least trauma, but pain from such tags remains a concern.

Report on 14 Large Whales That Died due to Ship Strikes off the Coast of Sri Lanka, 2010–2014

The greatest threat to cetaceans in Sri Lankan waters was considered to be the direct take of small- and medium-sized cetaceans using harpoons and/or as bycatch until recently. However, ship strikes have probably been occurring for years but have not been recognized for what they were. For the current study, only animals with visible and prominent injuries related to collisions were evaluated. Data gathered between 2010 and 2014 included the species, morphometry, location, and date; tissue samples were collected for genetic analysis. When possible, a complete necropsy was conducted; otherwise, partial necropsies were conducted. The study confirmed 14 reports of ship strikes between whales and vessels out of all the strandings reported from 2010 to 2014. Most strikes (n=09, 64%) involved blue whales (Balaenoptera musculus), although three other species were also documented, one Cuvier’s beaked whale, two great sperm whales, and one Bryde’s whale, as well as one unidentified baleen whale. Collision hotspots such as the southern waters of Sri Lanka are areas that warrant special attention in the form of vessel routing measures or speed limits, research on cetacean ecology, distribution, daily and seasonal movements, public service announcements, increased law enforcement presence, and other measures.

The development of an intermediate-duration tag to characterize the diving behavior of large whales.

The development of high‐resolution archival tag technologies has revolutionized our understanding of diving behavior in marine taxa such as sharks, turtles, and seals during their wide‐ranging movements. However, similar applications for large whales have lagged behind due to the difficulty of keeping tags on the animals for extended periods of time. Here, we present a novel configuration of a transdermally attached biologging device called the Advanced Dive Behavior (ADB) tag. The ADB tag contains sensors that record hydrostatic pressure, three‐axis accelerometers, magnetometers, water temperature, and light level, all sampled at 1 Hz. The ADB tag also collects Fastloc GPS locations and can send dive summary data through Service Argos, while staying attached to a whale for typical periods of 3–7 weeks before releasing for recovery and subsequent data download. ADB tags were deployed on sperm whales (Physeter macrocephalus; N = 46), blue whales (Balaenoptera musculus; N = 8), and fin whales (B. physalus; N = 5) from 2007 to 2015, resulting in attachment durations from 0 to 49.6 days, and recording 31 to 2,539 GPS locations and 27 to 2,918 dives per deployment. Archived dive profiles matched well with published dive shapes of each species from short‐term records. For blue and fin whales, feeding lunges were detected using peaks in accelerometer data and matched corresponding vertical excursions in the depth record. In sperm whales, rapid orientation changes in the accelerometer data, often during the bottom phase of dives, were likely related to prey pursuit, representing a relative measure of foraging effort. Sperm whales were documented repeatedly diving to, and likely foraging along, the seafloor. Data from the temperature sensor described the vertical structure of the water column in all three species, extending from the surface to depths >1,600 m. In addition to providing information needed to construct multiweek time budgets, the ADB tag is well suited to studying the effects of anthropogenic sound on whales by allowing for pre‐ and post‐exposure monitoring of the whale's dive behavior. This tag begins to bridge the gap between existing long‐duration but low‐data throughput tags, and short‐duration, high‐resolution data loggers.

Entanglement is a costly life-history stage in large whales.

Individuals store energy to balance deficits in natural cycles; however, unnatural events can also lead to unbalanced energy budgets. Entanglement in fishing gear is one example of an unnatural but relatively common circumstance that imposes energetic demands of a similar order of magnitude and duration of life‐history events such as migration and pregnancy in large whales. We present two complementary bioenergetic approaches to estimate the energy associated with entanglement in North Atlantic right whales, and compare these estimates to the natural energetic life history of individual whales. Differences in measured blubber thicknesses and estimated blubber volumes between normal and entangled, emaciated whales indicate between 7.4 × 1010 J and 1.2 × 1011 J of energy are consumed during the course to death of a lethal entanglement. Increased thrust power requirements to overcome drag forces suggest that when entangled, whales require 3.95 × 109 to 4.08 × 1010 J more energy to swim. Individuals who died from their entanglements performed significantly more work (energy expenditure × time) than those that survived; entanglement duration is therefore critical in determining whales’ survival. Significant sublethal energetic impacts also occur, especially in reproductive females. Drag from fishing gear contributes up to 8% of the 4‐year female reproductive energy budget, delaying time of energetic equilibrium (to restore energy lost by a particular entanglement) for reproduction by months to years. In certain populations, chronic entanglement in fishing gear can be viewed as a costly unnatural life‐history stage, rather than a rare or short‐term incident.

Predicting lethal entanglements as a consequence of drag from fishing gear

Large whales are frequently entangled in fishing gear and sometimes swim while carrying gear for days to years. Entangled whales are subject to additional drag forces requiring increased thrust power and energy expenditure over time. To classify entanglement cases and aid potential disentanglement efforts, it is useful to know how long an entangled whale might survive, given the unique configurations of the gear they are towing. This study establishes an approach to predict drag forces on fishing gear that entangles whales, and applies this method to ten North Atlantic right whale cases to estimate the resulting increase in energy expenditure and the critical entanglement duration that could lead to death. Estimated gear drag ranged 11–275N. Most entanglements were resolved before critical entanglement durations (mean±SD 216±260days) were reached. These estimates can assist real-time development of disentanglement action plans and U.S. Federal Serious Injury assessments required for protected species.

Southern Ocean biological iron cycling in the pre-whaling and present ecosystems

This study aimed to create the first model of biological iron (Fe) cycling in the Southern Ocean food web. Two biomass mass-balanced Ecopath models were built to represent pre- and post-whaling ecosystem states (1900 and 2008). Functional group biomasses (tonnes wet weight km-2) were converted to biogenic Fe pools (kg Fe km-2) using published Fe content ranges. In both models, biogenic Fe pools and consumption in the pelagic Southern Ocean were highest for plankton and small nektonic groups. The production of plankton biomass, particularly unicellular groups, accounted for the highest annual Fe demand. Microzooplankton contributed most to biological Fe recycling, followed by carnivorous zooplankton and krill. Biological Fe recycling matched previous estimates, and, under most conditions, could entirely meet the Fe demand of bacterioplankton and phytoplankton. Iron recycling by large baleen whales was reduced 10-fold by whaling between 1900 and 2008. However, even under the 1900 scenario, the contribution of whales to biological Fe recycling was negligible compared with that of planktonic consumers. These models are a first step in examining oceanic-scale biological Fe cycling, highlighting gaps in our present knowledge and key questions for future research on the role of marine food webs in the cycling of trace elements in the sea.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.

Population characteristics of a large whale shark aggregation inferred from seawater environmental DNA.

Population genetics is essential for understanding and managing marine ecosystems, but sampling remains challenging. We demonstrate that high-throughput sequencing of seawater environmental DNA can provide useful estimates of genetic diversity in a whale shark (Rhincodon typus) aggregation. We recover similar mitochondrial haplotype frequencies in seawater compared to tissue samples, reliably placing the studied aggregation in a global genetic context and expanding the applications of environmental DNA to encompass population genetics of aquatic organisms.

Seasonal and Diel Vocalization Patterns of Antarctic Blue Whale (Balaenoptera musculus intermedia) in the Southern Indian Ocean: A Multi-Year and Multi-Site Study.

Passive acoustic monitoring is an efficient way to provide insights on the ecology of large whales. This approach allows for long-term and species-specific monitoring over large areas. In this study, we examined six years (2010 to 2015) of continuous acoustic recordings at up to seven different locations in the Central and Southern Indian Basin to assess the peak periods of presence, seasonality and migration movements of Antarctic blue whales (Balaenoptera musculus intermedia). An automated method is used to detect the Antarctic blue whale stereotyped call, known as Z-call. Detection results are analyzed in terms of distribution, seasonal presence and diel pattern of emission at each site. Z-calls are detected year-round at each site, except for one located in the equatorial Indian Ocean, and display highly seasonal distribution. This seasonality is stable across years for every site, but varies between sites. Z-calls are mainly detected during autumn and spring at the subantarctic locations, suggesting that these sites are on the Antarctic blue whale migration routes, and mostly during winter at the subtropical sites. In addition to these seasonal trends, there is a significant diel pattern in Z-call emission, with more Z-calls in daytime than in nighttime. This diel pattern may be related to the blue whale feeding ecology.

Collateral damage to marine and terrestrial ecosystems from Yankee whaling in the 19th century.

Yankee whalers of the 19th century had major impacts on populations of large whales, but these leviathans were not the only taxa targeted. Here, we describe the “collateral damage,” the opportunistic or targeted taking of nongreat whale species by the American whaling industry. Using data from 5,064 records from 79 whaling logs occurring between 1840 and 1901, we show that Yankee whalers captured 5,255 animals across three large ocean basins from 32 different taxonomic categories, including a wide range of marine and terrestrial species. The taxa with the greatest number of individuals captured were walruses (Odobenus rosmarus), ducks (family Anatidae), and cod (Gadus sp.). By biomass, the most captured species were walruses, grampus (a poorly defined group within Odontoceti), and seals (family Otariidae). The whalers captured over 2.4 million kg of nongreat whale meat equaling approximately 34 kg of meat per ship per day at sea. The species and areas targeted shifted over time in response to overexploitation of whale populations, with likely intensive local impacts on terrestrial species associated with multiyear whaling camps. Our results show that the ecosystem impacts of whaling reverberated on both marine and coastal environments.

Baby's first words: Vocal behavior and ontogeny of Northern right whales in the southeast critical habitat

North Atlantic right whales are one of the most endangered of the great whales. A remnant population of ~500 inhabits the eastern seaboard of North America. A small fraction (2%) travels south to their critical calving habitat along the Florida and Georgia coast. By late November and through the winter, right whales give birth and nurse their calves in these shallow waters before departing in early spring to their northern habitats. In the southeast critical habitat mother-calf pairs remain generally isolated from other whales, presenting a unique platform to study vocal development and learning in large whales. Using small boats, GPS-instrumented, free-drifting autonomous acoustic buoys were deployed in close proximity to 44 photo-identified mother-calf pairs over 7 calving seasons. Surface video and synchronized underwater recordings documented their social and vocal behavior. With the exception of some low-energy gunshot sounds, mothers, and their calves, remained predominantly silent during the first ...

Stereotyped, repetitive gunshot call patterns produced by the North Pacific right whale, Eubalaena japonica

The Marine Mammal Laboratory has deployed long-term passive acoustic recorders along the 50 m and 70 m isobaths throughout the Bering Sea since 2007. Instruments recorded at either 4 kHz on a ~7-11% duty cycle, or 8 kHz on a 30-45% duty cycle. In addition, directional sonobuoys were deployed during field surveys to allow real-time monitoring for large whale presence. During the 2010 survey, a stereotyped, repetitive gunshot call pattern was acoustically detected on sonobuoys. This same call pattern was then detected on two different long-term moored recorders in two separate years. Since then, six different stereotyped, repetitive patterns have been documented, three of which have been analyzed. Preliminary results show that each pattern has a minimum of 30 iterations repeated over several hours. Furthermore, in several cases, these patterns are repeated throughout the season, in consecutive years, and in one instance, in non-consecutive years. While male North Atlantic right whales produce long gunshot bouts similar to the reproductive advertisement known in other species, right whales are not known to produce any type of repeated stereotyped pattern. This represents the first study to document stereotyped repetitive gunshot patterning in right whales. [Work funded by the Bureau of Ocean Energy Management.]

Baleen whale calling behavior and response to anthropogenic sound

Without a means of studying large whales in a controlled experimental environment, less is understood about their sound production mechanisms than is understood about those of smaller odontocetes. To describe call production behavior in fin whales, we used a recent technique that correlates fast-sampling accelerometer signals from tags with concurrently recorded acoustic signals to identify calls produced by the tagged animal. We tagged 18 fin whales as part of the Southern California Behavioral Response Study (SOCAL BRS), of which four were confirmed to be calling. We were then able to describe their kinematic and social behavior in relation to call production. Behaviors associated with elevated call rates included shallow maximum dive depths, little body movement, and negative pitch in body orientation, similar to some other calling baleen whale species. These are the first descriptions of body orientation and dive depths at which fin whales are most likely to call. We also describe calling responses (or lack thereof) from blue and fin whales exposed to simulated mid-frequency active sonar. The call behavior characterizations presented here will help with predicting calling behavior from surface behavior, informing interpretation of passive acoustic data, and further investigating effects of anthropogenic sound on baleen whales.

Noninvasive unmanned aerial vehicle provides estimates of the energetic cost of reproduction in humpback whales

AbstractAn animal's body condition will affect its survival and reproductive success, which influences population dynamics. Despite its importance, relatively little is known about the body condition of large whales and its relationship to reproduction. We assessed the body condition of humpback whales (Megaptera novaeangliae) at a breeding/resting ground from aerial photographs recorded using an unmanned aerial vehicle (UAV). Photogrammetry methods were used to measure the surface area of individual whales, which was used as an index for body condition. Repeated measurements of the same individuals were not possible; hence, this study represents a cross‐sectional sample of the population. Intraseasonal changes in the body condition of four reproductive classes (calves, immature, mature, and lactating) were investigated to infer the relative energetic cost that each class faces during the breeding season. To better understand the costs of reproduction, we investigated the relationship between female body condition (FBC) and the linear growth and body condition of their dependent calves (CBC). We documented a linear decline in the body condition of mature whales (0.027 m2/d; n = 20) and lactating females (0.032 m2/d; n = 31) throughout the breeding season, while there was no change in body condition of immature whales (n = 51) and calves (n = 32). The significant decline in mature and lactating female's body condition implies substantial energetic costs for these reproductive classes. In support of this, we found a positive linear relationship between FBC and CBC. This suggests that females in poorer body condition may not have sufficient energy stores to invest as much energy into their offspring as better conditioned females without jeopardizing their own body condition and survival probability. Measurement precision was investigated from repeated measurements of the same animals both from the same and different photographs, and by looking at residual errors in relation to the positioning of the whales in the photographs. The resulting errors were included in a sensitivity analysis to demonstrate that model parameters were robust to measurement errors. Our findings provide strong support for the use of UAVs as a noninvasive tool to measure the body condition of whales and other mammals.

Oxygen diffusion capacity scales as oxygen consumption

Metabolic scaling is one of the central enigmas of comparative biology. Oxygen consumption, as a proxy for aerobic metabolism, does not scale proportionally with body mass. Expressed as an exponential function, oxygen consumption scales as mass to the 2/3–8/10 power. This fundamental principle explains why the appropriate drug dose per kilogram of pet cat is higher than that of an average adult human, and why the cat's resting heart rate is over 140 beats min−1 when my own is closer to 70 beats min−1, and a large whale's is closer to 15 beats min−1. The scaling pattern holds in endotherms and ectotherms alike. Yet, in spite of the tremendous utility of metabolic scaling, the cause of this phenomenon remains elusive.James Gillooly and colleagues at the University of Florida, Gainesville, used another fundamental principle of comparative physiology to look into one possible driver of metabolic scaling: Fick's law of diffusion. Passive diffusion of oxygen into the body may be a rate-limiting step in aerobic metabolism and, as the first step in the process, seemed a likely candidate. According to Fick's law, the rate of passive diffusion across a membrane is proportional to the surface area of that membrane, and inversely proportional to the thickness of the membrane. Given this relationship, if you know how membrane surface area and thickness relate to mass, you can relate passive diffusion capacity to mass directly.Gillooly and his team compiled data on respiratory membrane surface area and thickness for a range of vertebrates, including animals from all major vertebrate classes, with representatives from all ecosystems and all forms of locomotion. This is particularly remarkable for the amphibians included in the study, as they obtain oxygen through their mouths and skin in addition to their lungs. Once the team had this information, they found that respiratory surface area scales with mass strongly, whereas membrane thickness changes little with body size.Using the scaling exponents calculated from the published data, and estimates of the physiological properties of respiratory membranes, the researchers applied Fick's diffusion equation to model how passive oxygen diffusion capacity varies with mass. Doing so revealed that the relationship between oxygen diffusion capacity and body size was statistically indistinguishable from the relationship between resting oxygen consumption and metabolic rate for both endotherms and ectotherms. In other words, the body's capacity for passive oxygen diffusion precisely matches its resting metabolic oxygen requirements. This supports the idea of symmorphosis, a hypothesis suggesting that no one bodily system is over-engineered relative to the others.The researchers noted that the match between resting oxygen consumption rate and diffusion capacity is inconsistent with the idea that respiratory systems evolved to optimize performance at maximum activity levels: it would appear instead that the respiratory surface is acting at capacity during resting activity and that the jump between resting and active metabolic rate could be made by modifying the oxygen partial pressure gradient over the respiratory surface, consistent with their model.It may be a jump to suggest that oxygen diffusion capacity is the rate-limiting step in oxygen consumption, but Gillooly and colleagues present intriguing evidence of a structure–function match: a step in the right direction on the path to explaining the existence of metabolic scaling. Of course, only time will tell whether the symmorphosis hypothesis will hold for other components of the metabolic pathway.

Young humpback whale Megaptera novaeangliae feeding in Santa Catarina coastal waters, Southern Brazil, and a ship strike report

Humpback whales Megaptera novaeangliae are cosmopolitan and highly migratory animals that rarely feed in low latitude waters during their breeding seasons. The western South Atlantic humpback whale population breeds off the Brazilian coast, from Natal (4°S) to Cabo Frio (23°S) and migration to their feeding grounds is known to be undertaken through offshore waters. Here we report on an unusual stranding of a young humpback whale that was feeding in the coastal waters of Santa Catarina state (27°S), in October 2014. Evidence of a ship strike and that the animal had fed in no more than a few hours before death are also presented. Additionally, it is the first time that Peisos petrunkevitchi, a sergestid shrimp species, is described as prey for large whales. Although more information is required before we can further discuss whether the area could provide an important source of food for young humpback whales, the present ship strike highlights a possibly important threat in case this ecological feature is confirmed in the future.

Diversity and Distribution Patterns of Cetaceans in the Subtropical Southwestern Atlantic Outer Continental Shelf and Slope

Temporal and spatial patterns of cetacean diversity and distribution were investigated through eight ship-based surveys carried out during spring and autumn between 2009 and 2014 on the outer continental shelf (~150m) and slope (1500m) off southeastern and southern Brazil (~23°S to ~34°S). The survey area was divided into southeast and south areas according to their oceanographic characteristics. Twenty-one species were observed in 503 sightings. The overall number of species was similar between the two areas, though it was higher in the spring in the south area. Five species were dominant and diversity varied more seasonally than spatially. ANOVA and kernel analyses showed that overall cetacean densities were higher in spring compared to autumn. Physeter macrocephalus, the most frequent species, concentrated throughout the south area at depths over 1000m in both seasons. Despite the overlapped occurrence at a broader scale, small delphinids presented latitudinal and in-offshore gradients as well as seasonal variation in distribution patterns, which could indicate habitat partitioning between some species. Delphinus delphis was only recorded in the south and its density decreased in areas where the presence of Stenella frontalis increased, mainly beyond the 250m isobath. Densities of S. longirostris and S. attenuata increased in lower latitudes and beyond the shelf break. The large delphinids Tursiops truncatus and Globicephala melas formed mixed groups in many occasions and were observed along the study area around depths of 500m. Grampus griseus was twice as frequent in the south area and densities increased in waters deeper than 600m. As expected, densities of both small and large migratory whales were higher during spring, over the continental slope, in the southeast area. The results presented here provided strong evidence on the importance of the outer continental shelf and slope to a diverse community of cetaceans occurring in the subtropical Southwestern Atlantic.