Sperm Whales Physeter Macrocephalus Research Articles

Analysis of the Spatial Distribution of Satellite-Tagged Sperm Whales (Physeter macrocephalus) in Close Proximity to Seismic Surveys in the Gulf of Mexico

Analysis of the Spatial Distribution of Satellite-Tagged Sperm Whales (Physeter macrocephalus) in Close Proximity to Seismic Surveys in the Gulf of Mexico

Magnetic resonance imaging and computed tomography as tools for the investigation of sperm whale (Physeter macrocephalus) teeth and eye

BackgroundScanning techniques such as magnetic resonance imaging (MRI) and computed tomography (CT) are useful tools in veterinary and human medicine. Here we demonstrate the usefulness of these techniques in the study of the anatomy of wild marine mammals as part of a necropsy. MRI and CT scans of sperm whale teeth (n = 4) were performed. The methods were compared and further compared to current standard methods for evaluation of tooth layering. For MRI a zero echo time sequence was used, as previously done for imaging of intact human teeth. For CT two different clinical scanners were used.ResultsThe three scanners did not provide sufficient information to allow age estimation, but both MRI and CT provided anatomical information about the tooth cortex and medulla without the need for sectioning the teeth. MRI scanning was also employed for visualizing the vascularization of an intact eye from one of the stranded sperm whale.ConclusionsClearly, MRI was useful for investigation of the retinal vasculation, but optimum results would require well-preserved tissue. It was not possible to estimate age based on CT scans of tooth growth lines. Further research is needed to clarify the usability of MRI and CT as tools for marine mammal research when samples need to remain intact or when a spatial (three dimensional) arrangement of features needs to be determined.

Resilience of the endangered sperm whale Physeter macrocephalus to foraging disturbance in the Gulf of Mexico, USA: a bioenergetic approach

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 589:241-261 (2018) - DOI: https://doi.org/10.3354/meps12457 Resilience of the endangered sperm whale Physeter macrocephalus to foraging disturbance in the Gulf of Mexico, USA: a bioenergetic approach Nicholas A. Farmer1,*, Dawn P. Noren2, Erin M. Fougères1, Abigail Machernis3, Kyle Baker4 1NOAA/National Marine Fisheries Service, Southeast Regional Office, 263 13th Ave S., St. Petersburg, Florida 33701, USA 2Conservation Biology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, NOAA, 2725 Montlake Boulevard East, Seattle, Washington 98112, USA 3JPS, Inc., under contract to NOAA/National Marine Fisheries Service, Southeast Regional Office, 263 13th Ave S, St. Petersburg, Florida 33701, USA 4Bureau of Ocean Energy Management’s Office of Renewable Energy Programs, Mail Stop VAM-OREP, 45600 Woodland Road, Sterling, Virginia 20166, USA *Corresponding author: nick.farmer@noaa.gov ABSTRACT: The endangered sperm whale Physeter macrocephalus spends the majority of its time foraging, relying upon echolocation to locate and consume several 100 kg of prey per day. In the northern Gulf of Mexico, sperm whales are exposed to a variety of anthropogenic stressors, including ship strikes, fisheries interactions, habitat loss and degradation due to oil and gas development, and chemical and noise pollution. In particular, they are exposed to high levels of anthropogenic noises related to geological and geophysical surveys for hydrocarbon deposits. The sounds produced by these surveys could reduce sensory volume, increase search effort required to locate resources, and interfere with auditory signal processing critical to foraging success. We developed a stochastic life-stage structured bioenergetic model to evaluate the consequences of reduced foraging efficiency on carbohydrate, lipid, and protein reserves in the blubber, muscle, and viscera. The model indicates that individual resilience to foraging disruptions is primarily a function of size (i.e. reserve capacity) and daily energetic demands. Mothers are the most vulnerable life stage due to the high energy demands associated with pregnancy and lactation. Continuous disruption has a greater impact than intermittent disruption; even minor foraging disruptions may lead to terminal starvation if the whales have no opportunity to replenish reduced reserves. Infrequent, minor disruptions in foraging are unlikely to be fatal, but may result in reduced body reserves that may be associated with reduced reproductive success. Our model provides a bioenergetic framework for evaluating the level, frequency, and consequences of foraging disruptions associated with anthropogenic stressors. KEY WORDS: Conservation · Disturbance · Foraging ecology · Risk assessment · Odontocete Full text in pdf format PreviousNextCite this article as: Farmer NA, Noren DP, Fougères EM, Machernis A, Baker K (2018) Resilience of the endangered sperm whale Physeter macrocephalus to foraging disturbance in the Gulf of Mexico, USA: a bioenergetic approach. Mar Ecol Prog Ser 589:241-261. https://doi.org/10.3354/meps12457 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 589. Online publication date: February 23, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.

Distribution and seasonal abundance of large cetaceans in the Durban whaling grounds off KwaZulu-Natal, South Africa, 1972–1975

Daily charts of the aerial search effort (432 206 nautical miles) of the Union Whaling Company and 1 099 sightings of 10 497 whales were available from 628 flights off Durban between 1972 and 1975. Densities of whales were analysed by month and water depth distribution over the four-year period. Low observed densities of blue Balaenoptera musculus, right Eubalaena australis, sei B. borealis and humpback Megaptera novaeangliae whales most likely resulted from earlier whaling pressure. Seasonality of blue, sei and humpback whales was bimodal, indicative of winter migrations to the north of the Durban whaling grounds, whereas the unimodal seasonality of fin whales B. physalus and minke whales B. bonaerensis or B. acutorostrata suggest the offshore region as the northern terminus of their migrations. Sperm whales Physeter macrocephalus migrate northwards offshore of the KwaZulu-Natal coast in autumn/early winter and southwards in late winter/spring, with larger males migrating later than the smaller males and females. Killer whale Orcinus orca presence was coincident with that of offshore minke whales and the southward migrations of other baleen whales, whereas densities of animals deemed as bottlenose whale Hyperoodon planifrons suggest strong early and late summer seasonal abundance in the offshore region. Such extensive surveys offshore of the KwaZulu-Natal coast are unlikely to be repeated; hence, data-extraction of whaling records provides a valuable source of seasonal and distributional information for marine management.

An Unparalleled Sexual Dimorphism of Sperm Whale Encephalization

The sperm whale Physeter macrocephalus (Linnaeus, 1758) is the largest toothed whales and possesses the highest absolute values for brain weight on the planet (together with the killer whale Orcinus orca). Former calculations of the encephalization quotient (EQ), which is used to compare brain size of different mammalian species, showed that the sperm whale brain is smaller than expected for its body mass. However, the data reported in the literature and formerly used to calculate the sperm whale EQ suffered from a potential bias due to the tendency to measure mostly larger males of this extreme sexually dimorphic species. Accordingly, we found that the brains of female sperm whales are close to the absolute weight range of the males, but, given the much lower body mass of females, their EQ results more than double of what reported before for the whole species, and is thus nearly into the primate range (female EQ = 1.28, male EQ = 0.56). This sexual dimorphism is unique among mammals. Female sperm whales live in large families in which social interactions and inter-individual communication are essential, while adult males live solitarily. Thus the particular sex-specific behavior of SWs may have led to a maternally-driven social evolution, and eventually contributed to achieve female EQ values (but not male EQs) among the highest ever calculated for mammals with respect to their large body mass.

POPs in free-ranging pilot whales, sperm whales and fin whales from the Mediterranean Sea: Influence of biological and ecological factors

The pilot whale Globicephala melas, the sperm whale Physeter macrocephalus, and the fin whale Balaenoptera physalus are large cetaceans permanently inhabiting the Mediterranean Sea. These species are subjected to numerous anthropogenic threats such as exposure to high levels of contaminants. Therefore, selected persistent organic pollutants POPs (29 PCBs, 15 organochlorine compounds, 9 PBDEs and 17 PCDD/Fs) were analysed in blubber biopsies of 49 long-finned pilot whales, 61 sperm whales and 70 fin whales sampled in the North Western Mediterranean Sea (NWMS) from 2006 to 2013. Contamination profile and species feeding ecology were then combined through the use of stable isotopes. δ13C, δ15N values and POPs levels were assessed through IR-MS and GC–MS respectively. To assess the toxic potency of the dioxin-like compounds, the TEQ approach was applied. δ15N values were 12.2±1.3‰ for sperm whales, 10.5±0.7‰ for pilot whales and 7.7±0.8‰ in fin whales, positioning sperm whales at higher trophic levels. δ13C of the two odontocetes was similar and amounted to −17.3±0.4‰ for sperm whales and −17.8±0.3‰ for pilot whales; whilst fin whales were more depleted (−18.7±0.4‰). This indicates a partial overlap in toothed-whales feeding habitats, while confirms the differences in feeding behaviour of the mysticete. Pilot whales presented higher concentrations than sperm whales for ΣPCBs (38,666±25,731ngg−1lw and 22,849±15,566ngg−1lw respectively), ΣPBDEs (712±412ngg−1lw and 347±173ngg−1lw respectively) and ΣDDTs (46,081±37,506ngg−1 lw and 37,647±38,518ngg−1lw respectively). Fin whales presented the lowest values, in accordance with its trophic position (ΣPCBs: 5721±5180ngg−1 lw, ΣPBDEs: 177±208ngg−1 lw and ΣDDTs: 6643±5549ngg−1 lw). Each species was characterized by large inter-individual variations that are more related to sex than trophic level, with males presenting higher contaminant burden than females. The discriminant analysis (DA) confirmed how DDTs and highly chlorinated PCBs were influential in differentiating the three species. Pollutant concentrations of our species were significantly higher than both their Southern Hemisphere and North Atlantic counterparts, possibly due to the particular Mediterranean geomorphology, which influences pollutants distribution and recycle. Dioxin-like PCBs accounted for over 80% of the total TEQ. This study demonstrated (1) an important exposure to pollutants of Mediterranean cetaceans, often surpassing the estimated threshold toxicity value of 17,000ngg−1 lw for blubber in marine mammals; and (2) how the final pollutant burden in these animals is strongly influenced not only by the trophic position but also by numerous other factors such as sex, age, body size and geographical distribution.

Residency and abundance of sperm whales (Physeter macrocephalus) in the Bleik Canyon, Norway

Sperm whales (Physeter macrocephalus) are widely distributed in the Norwegian Sea and feeding aggregations occur. One of these aggregations is in the Bleik Canyon, close to shore in Norway, where the present study was performed. The study used a whale safari company as a platform from which to conduct a photo-identification study of male sperm whales. Data for this study was comprised of a total of 3856 images from 22 seasons (1987–2010) of whale-watching tours. In total, 411 individuals were identified. This study supports the results from previous photo-identification studies in the Bleik Canyon and confirms the presence of both transient and resident male sperm whales in the Bleik Canyon. These results suggest that the sperm whale group(s) found there are a loose feeding aggregation and not a closed population. Total residence time varied between one day and 14 years, although most individuals were only seen in one or two years. The number of sighted whales fluctuated between years, from eight to 77 individuals. No trend in the number of sighted whales was found. The estimated size of the feeding aggregation in the Bleik Canyon also fluctuated between years, from 11 to 116 individuals, with no trend evident.

Conflicting rates of increase in the sperm whale population of the eastern Caribbean: positive observed rates do not reflect a healthy population

Observed rates of increase calculated from trends in the numbers of animals present in a population should generally agree with those estimated from life-history data. However, for a small population of individually identified sperm whales Physeter macrocephalus occupying the waters of the eastern Caribbean there is a discrepancy. Using a mark-recapture analysis that included heterogeneity in identification, the population, numbering about 156 adults (95% CI 126−195) in 1998, has been increasing at 3.4% yr −1 (95% CI: 1.0−5.7% yr −1 ). However, a 2-stage matrix population model including unweaned calves and adults (and excluding mature males), whose parameters were estimated directly from empirical data, gave a projected rate of increase of −2.7% yr −1 (95% CI: −5.4 to −0.4% yr −1 ). This estimate is primarily sensitive to calculated adult mortality. The discrepancy between the observed and projected rates of increase for this popula- tion may be explained by a high, probably anthropogenic, mortality of sperm whales in the east- ern Caribbean, coupled with immigration from surrounding regions, so the area becomes an attractive sink (ecological trap). The analysis emphasizes the fragility of sperm whale populations. More generally, our analysis of this population shows that a positive observed rate of increase is not necessarily a sign of a healthy population. This case study highlights the importance of analysing populations of endangered species using multiple methodologies and with a solid base of individual-level empirical data based on longitudinal monitoring.

Testing a passive deterrent on longlines to reduce sperm whale depredation in the Gulf of Alaska

Abstract In Alaska, sperm whale (Physeter macrocephalus) depredation on longline sets has increased since implementation of the Individual Fishing Quota programme in 1995. A collaborative effort (SEASWAP) between longliners, scientists, and managers has undertaken research to evaluate this depredation with a primary objective to develop and test a passive deterrent that would reduce depredation without reducing catch rate of sablefish (Anoplopoma fimbria). Commercial longliners, fishing for their own sablefish quotas during the regular season, deployed beaded gear (25 mm lucite beads attached to gangions) with control gear and set recorders to collect acoustic data. Beaded and control gear were randomly assigned by skate quad (672 hooks) with 5 quads in each longline set. Acoustic recorders were used to document sperm whale creak–pause events, representative of depredation of the longline gear. Although there were more sablefish per skate quad on the beaded gear and there was a decrease in depredation events on the beaded gear compared with the control, neither effect was significant (p = 0.205 and 0.364, respectively). The SEASWAP project is testing other deterrent strategies including gear modifications and the establishment of a sighting network to improve avoidance.

Distribution of Soviet catches of sperm whales Physeter macrocephalus in the North Pacific

From 1948 to 1979, the USSR conducted extensive illegal whaling worldwide. Data from the North Pacific (NP) were analyzed to correct falsified International Whaling Commission catch records and to investigate the distribution of sperm whales Physeter macrocephalus (NP catch = 157 680). Information was available on the distribution of 123 264 sperm whale catches. Among a number of areas defined by the Soviet whalers, the largest catches were in the 3 main regions: 31 395 in the Eastern Region (ER), 29 518 in the Central Region (CR), and 19 313 in the Western Region (WR); an additional 23 090 catches were made at the Kuril land stations. Other areas with substantial catches included the Aleutians (5945) and Commander Islands (1448), the Bering Sea (3170), Olyutorsky Bay (3094), and other parts of the pelagic NP (6049). Four main areas of concentration included: a large pelagic area (30−50° N) in the ER, including the Gulf of Alaska and western coast of North America; the northeastern and southwestern CR; and the southern Kurils. Some of the distribution was similar to 19th century catches, notably in the ‘Japan Ground’ (in the pelagic western Pacific) and the ‘Coast of Japan Ground’. Many females were caught in Olyutorsky Bay and around the Commander Islands. There was also a division in catch composition at Amchitka Pass (Aleutians), with family groups to the west and mature males to the east. The extensive illegal catches of females removed a significant portion of the reproductively mature population, which likely continues to impact recovery of NP sperm whales today.

Spatio-temporal distribution of sperm whales (Physeter macrocephalus) off Kaikoura, New Zealand, in relation to bathymetric features

Using a shore-based station we monitored the position of sperm whales (Physeter macrocephalus) within the Kaikoura submarine canyon from 2010 to 2012. We tracked sperm whales using a theodolite station for a total of 290 days. We extracted the distance from the nearest coast, the depth and the bathymetric slope using ArcGIS 10.1. We estimated the seasonal spatial distribution of sperm whales using general additive models. The distribution varied significantly between seasons; individuals were found in deeper water and further offshore in the spring than in winter. This study improved our understanding of the variability of sperm whale distribution patterns off Kaikoura. We determined that the distribution was linked to the bathymetric features and we hypothesized that whales adapted their use of the submarine canyon in relation to food aggregation. We would encourage further studies to evaluate the sperm whale relationship with oceanographic variables off Kaikoura.

Improved abundance and trend estimates for sperm whales in the eastern North Pacific from Bayesian hierarchical modeling

Population abundance and trends are informative metrics for assessing population status and basing management decisions, but it can be challenging to estimate these metrics for species that are difficult to detect. We used a Bayesian hierarchical approach to improve estimates of abundance and trends for sperm whales Physeter macrocephalus in the California Current based on 6 surveys conducted from 1991 to 2008. The method consists either of a regression trend or Markov process model for true abundance in the study area and an observation model used to estimate detection probability (in our case, based on line-transect distance sampling methods). Our approach improves upon models that we have applied to other cetacean species by incorpo- rating direct estimates of sampling variance in the number of groups encountered (to reduce esti- mates of process variance) and by using an alternative to the commonly used Horvitz-Thompson- like estimator to better deal with covariate-dependent detection probability estimation when sample sizes are small. Our abundance estimates were much less variable through time than pre- viously published estimates; this has important implications for management under the US Marine Mammal Protection Act. We were unable to precisely estimate overall abundance trends for sperm whales in the study area, but we estimated a high probability that small-group abundance, likely representing adult male abundance, has increased.

Estimating sperm whale (Physeter macrocephalus) daily abundance from a shore-based survey within the Kaikoura submarine canyon, New Zealand

The Kaikoura submarine canyon (New Zealand) is one of the few places in the world where male sperm whales (Physeter macrocephalus) can be found year round close to the shore. The objective of this study was to estimate the daily abundance of sperm whale within the study area. Positions of sperm whales were measured from a shore-based station over a 2-year study (2010–2012) which included information from 4613 sperm whale sightings. Distance sampling and mark-resight models were used to estimate daily abundance. Results showed a mean of four (SEM = 0.13) individuals present in the study area at any given time. These results differ from, and are much lower than, those from previous studies. A decline in the daily number of individuals suggests that a cautious management approach is necessary. Our study illustrated the application of distance sampling and mark-resight methods from a shore-based station.

Depredating sperm whales in the Gulf of Alaska: local habitat use and long distance movements across putative population boundaries

Satellite tags were attached to 10 sperm whales Physeter macrocephalus (1 whale was tagged in 2 different years) to determine the movements of sperm whales involved in removal of sablefish from longline fishing gear in the Gulf of Alaska (GOA). Tags transmitted from 3 to 34 d (median = 22) in 2007 and 7 to 158 d (median = 45) in 2009. Seven whales stayed in the GOA; all were associating with fishing vessels along the slope. Two whales headed south in June shortly after being tagged; one reached the inner third of the Sea of Cortez; the other's last location was offshore Mexico at 14°N. A third whale stayed in the GOA until October and then headed south, reaching central Baja, Mexico, 158 d after tagging. The whales that travelled to lower latitudes fol- lowed no pattern in timing of departure, and at least 2 had different destinations. All whales passed through the California Current without stopping and did not travel to Hawaii; both are areas with known concentrations of sperm whales. Whales travelled faster when south of 56°N than when foraging in the GOA (median rate of median horizontal movement = 5.4 (range: 4.1 to 5.5) and 1.3 (range: 0.6 to 2.5) km h �1 , respectively). Tagged sperm whales primarily travelled over the slope, but one spent considerable time over the ocean basin. Information on the timing and movement patterns of sperm whales may provide a means for fishermen to avoid fishing at whale hot spots, potentially reducing interactions between whales and fishermen.

No evidence for recovery in the population of sperm whale bulls off Western Australia, 30 years post-whaling

The global sperm whale Physeter macrocephalus population has been protected from large-scale commercial whaling for >25 yr, yet there is no clear evidence of recovery in any heavily exploited stock. This may indicate that whaling has long-term demographic effects on this species or that other endogenous or exogenous processes are inhibiting population growth. This study investigates the status of mature sperm bulls off Albany, Western Australia, a population reduced through whaling by 74% between 1955 and 1978. We conducted an aerial survey designed as far as possible to provide an index of abundance comparable with that derived from the whale 'spotter' planes employed by the Albany whaling company from 1968 to 1978, using the number of sperm bulls seen on each morning flight as a comparative index between bulls seen historically and in 2009. The mean number of sperm bulls seen on transect in 2009 was 2.43 (95% percentile interval (0.96, 6.08)); this increased to 3.38 (95% percentile interval (1.30, 7.60)) when sightings off transect were included. Both 2009 point estimates were lower than the mean (±SE) number seen in any of the years between 1968 and 1978, which ranged from 6.30 (±1.18) in 1976 to 12.45 (±1.83) in 1968. The lack of recovery in the population of bull sperm whales off Albany, despite full protection, is of concern and adds weight to the growing body of evidence that sug- gests that sperm whales may not be recovering effectively from past exploitation.

Correcting Positional Errors in Shore-Based Theodolite Measurements of Animals at Sea

Determining the position of animals at sea can be particularly difficult and yet, accurate range and position of animals at sea are essential to answer a wide range of biological questions. Shore-based theodolite techniques have been used in a number of studies to examine marine mammal movement patterns and habitat use, offering reliable position measurements. In this study we explored the accuracy of theodolite measurements by comparing positional information of the same objects using two independent techniques: a shore-based theodolite station and an onboard GPS over a range of 25 km from the shore-based station. The technique was developed to study the habitat use of sperm whales (Physeter macrocephalus) off Kaikoura, New Zealand. We observed that the position accuracy fell rapidly with an increase in range from the shore-based station. Results showed that the horizontal angle was accurately determined, but this was not the case for the vertical angle. We calibrated the position of objects at sea with a regression-based correction to fit the difference in distance between simultaneously recorded theodolite fixes and GPS positions. This approach revealed the necessity to calibrate theodolite measurements with objects at sea of known position.

An acoustic valve within the nose of sperm whalesPhyseter macrocephalus

Sperm whales Physeter macrocephalus emit impulsive sound signals in short series of rhythmic clicks (codas) for communication, and in long series of single acoustic events (usual clicks) for echolocation. Both click types are generated pneumatically within the hypertrophied nasal complex, at the ‘monkey lips’ at the rostral end of the right nasal passage. Each individual click comprises repetitive pulses decaying in intensity. However, the decay rate is distinctly higher in usual clicks than in coda clicks. The mechanism of decay rate control in the clicks is still unclear, and it is unclear why the right nasal passage crosses the nasal acoustic pathway between two hypertrophied acoustic fat bodies (spermaceti organ, junk), so that it resembles a ‘bent acoustic horn’. We present a new concept to explain how the flat right nasal passage can serve as a variable acoustic valve, and how the amount and distribution of its air filling can be controlled by muscle action. This mechanism allows the whale to determine the pulse decay rate and thus switch between the two modes of click production. Coda clicks are generated by reverberations within the spermaceti organ (partial trapping of sound) and by the release of sound energy in fractions through the air-filled right nasal passage. In contrast, echolocation clicks as single events are released during the partial collapse of the right nasal passage between the spermaceti organ and the junk. This interpretation of the right nasal passage as an adaptive acoustic valve elucidates why the spermaceti organ and the junk are separated from each other by an air-filled space of variable volume crossing the sound path of the ‘bent acoustic horn’ in the posterior part of the nasal complex.

Cephalopods in the potential prey field of sperm whales (Physeter macrocephalus) (Cetacea: Physeteridae) in the northern Gulf of Mexico

Cephalopods of the northern Gulf of Mexico are widely distributed and provide an important food source for a variety of marine animals. Sperm whales are year-round residents in the northern Gulf of Mexico. Prey availability has been proposed as an explanation for this non-migratory whale population. To examine this explanation, a short pilot cruise was conducted during the summer of 2009 to test equipment and to obtain preliminary observations. Then the 3-month Sperm Whale Acoustic Prey Study (SWAPS) was conducted during the winter/spring of 2010 to sample the mid-water pelagic community for possible prey of sperm whales. It also compared sperm whale distribution and prey composition across habitats of the northern Gulf of Mexico. This paper focuses on the cephalopod diversity within the mid-water pelagic community and assesses potential prey of the endangered sperm whales.

Trace elements in tissues of sperm whales stranded along the Italian coast

Five sperm whales (Physeter macrocephalus) stranded along the Italian coast between 2007 and 2009 were analysed for concentrations of trace elements in the muscle, liver, kidney, lung, heart and skin. Essential elements (Zn, Cu, Fe, Cr, As, V and Se) show ranges of variability comparable with the limited data reported in the literature on this species and a homeostatic physiological control. Very low concentrations of nonessential elements (Hg, Cd and Pb) were detected in all tissues, suggesting a minor impact of these pollutants on the sperm whale populations of the Mediterranean Sea. This finding possibly reflects the pelagic lifestyle and deep-sea cephalopod diet of this group of giant cetaceans. In addition, this finding contrasts with the high levels of nonessential elements measured in many other species of cetaceans (e.g. Stenella coeruleoalba, Tursiops truncatus) stranded along Mediterranean coasts and which reflects significant coastal anthropogenic effects. The main result of this work is the compiled dataset which provides a preliminary target for conceptual understanding of the potential effects of open marine pollution on the Mediterranean sperm whale population.

The cetaceans of Aruba, southern Caribbean

Aruba is one of the most densely populated islands in the Caribbean. However, very little is known about its cetaceans. In 2010 and 2011, a total of 19721 km (1686 h) boat-based surveys over nearshore transects resulted in 117 positively-identified sightings comprising eight species. New records are also added for one of three previously-documented species. Five additional species were documented from strandings or reports by others. This brings the total number of cetacean species identified in Aruban waters to 16, of which nine are authenticated here for the first time. Atlantic spotted dolphin (Stenella frontalis(N = 59) and bottlenose dolphin (Tursiops truncatus) (N = 33) were the most frequently observed species, with sightings of both year-round, followed by spinner dolphin (S. longirostris) and false killer whale (Pseudorca crassidens). Additional species recorded are pantropical spotted dolphin (S. attenuata), striped dolphin (S. coeruleoalba), common dolphin (Delphinus capensis), rough-toothed dolphin (Steno bredanensis), short-finned pilot whale (Globicephala macrorhynchus), killer whale (Orcinus orca), Risso's dolphin (Grampus griseus), humpback whale (Megaptera novaeangliae), Bryde's/Eden's whale (Balaenoptera brydei/edeni), sperm whale (Physeter macrocephalus) and an unidentified beaked whale (Mesoplodonsp.). All cetaceans were sighted within 22 km of the coast in relatively shallow waters. Sighting rate was low (0.69 cetacean sightings per 100 km). Sightings of calves and neonates indicate that Aruba may be a nursing or breeding area for some species. The presence of several species of cetaceans in Aruba's coastal waters year-round indicates that status and threat assessments are needed to protect them.