Sperm Whale Research Articles

Automatic click detector for sperm and beaked whale distribution monitoring

Passive acoustic monitoring (PAM) is an effective method for monitoring marine fauna. Automatic detection, identification, and quantification of echolocation clicks by toothed whales is commonly computationally inefficient. We present an autoregression and correlation-based algorithm for detection and classification of odontocete clicks. The detection process consists of three steps: (1) detection and extraction of impulsive signals from PAM recordings, (2) cross-correlation of the extracted sounds with template signals, and (3) binary classification of detected clicks. The extraction of impulsive signals from background noise is based on automatic detection of outliers in an autoregression model of noise. The model settings can be adjusted to detect signals of certain length. The cross-correlation analysis involves the use of template signals of high signal-to-noise ratio, which aremanually identified and extracted from PAM data. Using the cross-correlationcoefficient as a criterion allows distinguishing echolocation clicks by sperm or beaked whales from other impulsive sounds. Finally, binary classification utilizes thresholds determined through the receiver operating characteristic analysis of an independent subset of manually labeled, extracted signals. The approach was tested for detection of sperm and beaked whales in PAM datasets recorded on the Northwest Shelf of Australia and demonstrated low false positive rates of 3%–5%.

Or, The Whale by Jos Sances: Ark of the Anthropocene

Abstract: This essay offers the first critical consideration of Jos Sances's 14- by 51-foot scratchboard mural, Or, The Whale (2019–20), a work of panoramic cultural-historical reference and eco-political urgency inspired by Moby-Dick . I set the mural in the context of the series of Moby-Dick illustrations that Sances executed in 2016–2018, showing how they record his formative engagement with Rockwell Kent and document his search for a visual language capable of matching the imagistic density and encyclopedic range of Melville's novel. If Rockwell Kent mediates Sances's portrait-scale encounters with Moby-Dick , C. L. R. James's Mariners, Renegades, & Castaways provides the keynote for Sances's biopolitical sequel to Melville's epic in mural form, a pictorial history of American capitalism inscribed on the body of a life-size sperm whale. Or, The Whale is a summa of Anthropocene visual art, its sweeping narrative of virtuosic hand-drawn scenes presenting densely layered constellations of images that perform the work of cultural memory, unearthing the damage done to exploited peoples and natural resources.

Establishing baselines for predicting change in ambient sound metrics, marine mammal, and vessel occurrence within a US offshore wind energy area

Abstract Evaluating potential impacts on marine animals or increased sound levels resulting from offshore wind energy construction requires the establishment of baseline data records from which to draw inference. This study provides 2 years of baseline data on cetacean species’ presence, vessel activity, and ambient sound levels in the southern New England wind energy area. With eight species/families present in the area for at least 9 months of the year, this area represents an important habitat for cetaceans. Most species showed seasonality, with peak daily presence in winter (harbour porpoise, North Atlantic right, fin, and humpback whales), summer (sperm whales), spring (sei whales), or spring and fall/autumn (minke whales). Delphinids were continuously present and blue whales present only in January. The endangered North Atlantic right whales were present year round with high presence in October through April. Daily vessel presence showed an increase from summer through fall/autumn. On average, ambient sound levels were lowest in summer and increased late 2021 through 2022 with most temporal variability occurring across lower frequencies. The area showed a complex soundscape with several species sharing time–frequency space as well as overlap of vessel noise with the communication range of all baleen whale species.

The observation records from whale and dolphin watching inshore of Hualien, eastern Taiwan.

The eastern waters of Taiwan have been lacking baseline and research data for several years. This study was initiated by Kuroshio Ocean Education Foundation (KOEF) in collaboration with the Turumoan whale-watching company since 1998, collecting long-term ecological data for cetaceans in the inshore of Hualien, eastern Taiwan. This dataset includes 10,675 records of cetacean sightings from June 1998 to December 2021. Collection of cetacean sighting records was paused for one year in 2001 due to budgetary reasons. All of the sighting records were collected by whale-watching boat guides that were trained by KOEF. Following a standardised protocol, guides used a handheld GPS device and cetacean sighting record sheets to document information about the cetacean species identification, location, time, number of individuals, the presence of mother-calf pairs and mixed-species groups and other states of each sighting during a whale-watching tour. The collection of citizen-science data during this period has significantly advanced Taiwan's cetacean baseline data in the study area. Additionally, we make data available to the public in the form of citizen-science, making a substantial contribution to the advancement of ocean scientific research. We have published the dataset on Global Biodiversity Information Facility, allowing users around the world to download the dataset. This is currently the largest dataset of cetacean sighting records in Taiwan (last updated on 2023-09-05). We have also recorded several species on the International Union for Conservation of Nature (IUCN) Red List categorised as "Data Deficient" during our survey inshore of Hualien, eastern Taiwan, including Ginkgo-toothed beaked whales (Mesoplodonginkgodens Nishiwaki & Kamiya, 1958), Omura's whales (Balaenopteraomurai Wada, Oishi & Yamada, 2003) and killer whales (Orcinusorca (Linnaeus, 1758)). There are also sperm whales (Physetermacrocephalus Linnaeus, 1758), categorised as "Vulnerable" in the IUCN Red List and false killer whales (Pseudorcacrassidens (Owen, 1846)), categorised as "Near Threatened". This study is also the first and only long-term study that has documented cetaceans in the study area.

Combining passive acoustic data from a towed hydrophone array with visual line transect data to estimate abundance and availability bias of sperm whales (Physeter macrocephalus).

Visual line transect (VLT) surveys are central to the monitoring and study of marine mammals. However, for cryptic species such as deep diving cetaceans VLT surveys alone suffer from problems of low sample sizes and availability bias where animals below the surface are not available to be detected. The advent of passive acoustic monitoring (PAM) technology offers important opportunities to observe deep diving cetaceans but statistical challenges remain particularly when trying to integrate VLT and PAM data. Herein, we present a general framework to combine these data streams to estimate abundance when both surveys are conducted simultaneously. Secondarily, our approach can also be used to derive an estimate of availability bias. We outline three methods that vary in complexity and data requirements which are (1) a simple distance sampling (DS) method that treats the two datasets independently (DS-DS Method), (2) a fully integrated approach that applies a capture-mark recapture (CMR) analysis to the PAM data (CMR-DS Method) and (3) a hybrid approach that requires only a subset of the PAM CMR data (Hybrid Method). To evaluate their performance, we use simulations based on known diving and vocalizing behavior of sperm whales (Physeter macrocephalus). As a case study, we applied the Hybrid Method to data from a shipboard survey of sperm whales and compared estimates to a VLT only analysis. Simulation results demonstrated that the CMR-DS Method and Hybrid Method reduced bias by >90% for both abundance and availability bias in comparison to the simpler DS -DS Method. Overall, the CMR-DS Method was the least biased and most precise. For the case study, our application of the Hybrid Method to the sperm whale dataset produced estimates of abundance and availability bias that were comparable to estimates from the VLT only analysis but with considerably higher precision. Integrating multiple sources of data is an important goal with clear benefits. As a step towards that goal we have developed a novel framework. Results from this study are promising although challenges still remain. Future work may focus on applying this method to other deep-diving species and comparing the proposed method to other statistical approaches that aim to combine information from multiple data sources.

Investigating fishery and climate change effects on the conservation status of odontocetes in the Northern Ionian Sea (Central Mediterranean Sea)

A modelling approach applied to the study of ecosystems from a management and conservation point of view allows their complexity to be investigated and represents a tool for meeting sustainability goals, part of the 2030 Agenda for Sustainable Development. Tying into Sustainable Development Goals (SDGs) 13 and 14, the human activities of fisheries and climate change represent two pivotal drivers for the marine environment, acting on keystone predators, such as odontocetes. A calibrated time-dynamic model (Ecopath with Ecosim) was developed to investigate the effects on the odontocetes and their main prey in the Northern Ionian Sea (Central Mediterranean Sea), according to changes in trawl fishery and primary productivity. In particular, the food web of the Gulf of Taranto (GoT) is described by 51 functional groups (FGs), with four odontocetes (striped, common bottlenose, Risso's dolphin and sperm whale) represented as a single FG, and 5 fishing fleets. The calibration of the Ecosim model was carried out during the period 2009–2018 using a combination of automatic and manual fitting procedures. Changes in trawling fishing effort (increases, reductions and bans) and in primary production were tested in the period until to 2040 to detect the effect on the biomass of odontocetes and their main prey. The cumulative effects of the two drivers were assessed using an Interaction Effect Index. Fishery showed negligible effects on all odontocetes, with the exception of the common bottlenose dolphin which respond in a negative way to an increase in fishing effort. The reduction in top-predators due to fishing seems to lead to a reduction in predation pressure on meso‑consumers, and thus to an increase in predation pressure on basal prey. Similarly, the bottom-up effect due to increased primary production tends to be diluted towards the top of the trophic network, with slight effects on odontocetes. The trophic interaction pattern tends to mediate the effects tested in the model with a variety of different outcomes on prey. The application of the interaction effects index could contribute to disentangling the effects of fishing and climate on the food web, providing information to address the analysis required by the SDG 14 targets.

Seasonal variation in the use of food resources by sperm whales in a submarine canyon

Understanding the food and habitat requirements of apex predators relies on characterising the food web structure and carbon sources that support them. We examined the food web of sperm whales (parāoa, Physeter macrocephalus) foraging in the submarine canyon of Kaikōura (Aotearoa New Zealand) by measuring bulk stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) in sperm whale skin, potential prey and two candidate primary producers. To determine the underlying drivers of variability in bulk ratios, we measured δ13C and δ15N from individual amino acids (AAs) in a subset of whale samples. Mixing models and food web δ13C:δ15N correlations strongly suggest a food web sustained mostly by pelagic production, with a marginal contribution from coastal macroalgae. In contrast to the cephalopod-based diet recorded in most populations, the sperm whales' diet at Kaikōura appeared to be a mixture of squid and demersal fish, which may be related to the extremely high benthic productivity of the canyon. Combined with evidence from studies of habitat use, differences in the whales’ stable isotope values between summer and winter suggested seasonal variability in targeted prey, and ultimately different utilisation of organic carbon sources at the base of the food web. In summer, sperm whales appear to depend mostly on mesopelagic squid, with an increased contribution from demersal fish in winter, consistent with patterns in diving behaviour and spatial distribution. This seasonal shift in food resources suggests that submarine canyons offer a temporally dynamic range of foraging opportunities for this apex predator. Our results provide new insights into the structure of food webs supporting sperm whales, and advance our understanding of the seasonal dynamics in the use of food resources by apex predators in submarine canyons.

A sperm whale cautionary tale about estimating acoustic cue rates for deep divers.

Passive acoustic density estimation has been gaining traction in recent years. Cue counting uses detected acoustic cues to estimate animal abundance. A cue rate, the number of acoustic cues produced per animal per unit time, is required to convert cue density into animal density. Cue rate information can be obtained from animal borne acoustic tags. For deep divers, like beaked whales, data have been analyzed considering deep dive cycles as a natural sampling unit, based on either weighted averages or generalized estimating equations. Using a sperm whale DTAG (sound-and-orientation recording tag) example we compare different approaches of estimating cue rate from acoustic tags illustrating that both approaches used before might introduce biases and suggest that the natural unit of analysis should be the whole duration of the tag itself.

Sperm and northern bottlenose whale interactions with deep-water trawlers in the western North Atlantic.

Commercial fisheries have increased in all the world's oceans with diverse unintended impacts on marine ecosystems. As a result of resource overlap, interactions between cetaceans and fisheries are a common occurrence and, in many cases, can give rise to significant conservation issues. Research on the distribution and types of such interactions is important for efficient management. In this study, we describe the behaviors of two whale species: sperm whales (Physeter macrocephalus) and northern bottlenose whales (Hyperoodon ampullatus), interacting with benthic trawlers fishing off the eastern Grand Banks of the western North Atlantic in 2007. Whale interactions were only observed when vessels were targeting Greenland halibut (Reinhardtius hippoglossoides) in deep-water fishing areas and were most common during net hauling. Sperm whales and northern bottlenose whales appeared to engage in feeding behavior close to the surface during hauling, especially during the latter stages, suggesting they targeted fish escapees rather than discards. Using photo-identification methods, seven individual sperm whales were identified with multiple resights of six individuals being recorded over an almost two month period. The maximum distance between two resights was 234 km, suggesting individual sperm whales were repeatedly targeting and even following fishing vessels over multiple days and between fishing areas. By contrast, there were no photographic resights of individual northern bottlenose whales within this study, or with substantial photo-identification catalogues from other adjacent high density areas, suggesting that individuals of this species may be less likely to follow vessels or move between areas. This study documents the earliest confirmed records of northern bottlenose whales in this remote region. These interactions and high encounter rates may indicate that adjacent populations are recovering from the previous century of commercial whaling. Our study provides new insights and details on whale-fisheries interactions, which can inform future research and help managers understand the real and perceived impacts of depredation behaviour on fisheries and whales.

Cetaceans of the Saya de Malha bank region, Indian Ocean: A candidate Important Marine Mammal Area

The banks of Saya de Malha and the surrounding Mascarene Plateau in the Indian Ocean are among the least studied shallow sea water regions in the world. The steep sloping bathymetry of this region is thought to drive high levels of primary productivity and support a diverse range of marine species. Until now, no surveys for cetaceans have been conducted in the waters surrounding Saya de Malha, and so the diversity of cetaceans is unknown. Opportunistic visual and acoustic surveys for cetaceans were conducted onboard a platform of opportunity, the MY Arctic Sunrise, which was involved in a wider project to document the marine life in the region. Survey effort was conducted over 7,700 km, with twelve species of cetacean encountered, including Bryde’s, sperm, beaked and killer whales, along with spinner, striped, pantropical spotted and bottlenose dolphins. A match of a sperm whale coda vocalisation to another, well-studied population off the coast of Mauritius suggests possible connectivity between these regions although further data would be required to confirm this. The banks of Saya de Malha appear to support a diverse range of cetacean species and further systematic surveys are required to increase our understanding of how different species utilise the banks. We provide whistle contours from visually confirmed acoustic detections to contribute towards building a region-specific whistle classifier. Given the diversity of species detected in the region, we suggest that the Saya de Malha bank area be designated, either as an Important Marine Mammal Area or as a marine protected area.

Species distribution modeling of deep‐diving cetaceans

AbstractSpecies distribution models (SDMs) have been developed and extensively validated for diverse cetaceans within the California Current Ecosystem off the West Coast of the United States. These studies have recognized the challenges associated with developing robust models for deep‐diving cetaceans—sperm whales and beaked whales—thus limiting the accuracy of predictions for management and ecological understanding. In this study, we explore whether additional biologically relevant predictor variables can improve models for deep‐divers. These variables are related to the oxygen minimum layer and phytoplankton and micronekton biomass and could influence prey availability for cetacean top predators. We found that the addition of these variables improved the performance of SDMs for sperm whales, as well as for some more common baleen whale and dolphin species, but that the accuracy of deep‐diver models was nevertheless poor. The sightings data sets for deep‐diving cetaceans have small sample sizes compared to other cetaceans, and sightings are distributed nearly randomly across the study area and model domain. These factors hinder the development of useful environmentally driven models of spatial distribution.

Acoustic and visual observations of Sperm Whales, <em>Physeter macrocephalus</em>, off the Southeast Coast of Sri Lanka, April 2013

An opportunistic study was carried out from a 113’ motor-sailing vessel along the southeast coast of Sri Lanka from April 11 to 19, 2013. Passive acoustic monitoring allowed pods of sperm whales (Physeter macrocephalus) to be detected and tracked before being sighted. Key observations included sightings of whales along the 1000 m drop-off, repeated breaching of whales on two separate occasions within 50 m of a driftnet, and the presence of a single bull male with mating-related behaviour and jaw-clapping. These observations and other visual observations during the ship’s voyages indicate that sperm whales are located in Sri Lanka waters for feeding, breeding and calving.

Variation of sperm size and evolution of giant spermatozoa in Lonchopteridae (Diptera)

Among species of the spear-winged flies (Lonchopteridae) there is remarkable variation in sperm size, with some species producing giant spermatozoa. With a length of 7500 μm and a width of 1.3 μm the spermatozoon of Lonchoptera fallax ranks among the largest known to date. In the present study body size, testis size, sperm size, and spermatid number per bundle and per testis were examined across 11 Lonchoptera species. Results are discussed in terms of how these characters are related with each other and how their evolution affects the resource allocation amongst spermatozoa. Based on some discrete morphological characters and a molecular tree derived from DNA barcodes a phylogenetic hypothesis of the genus Lonchoptera is proposed. The occurrence of giant spermatozoa in Lonchopteridae is compared to convergent occurrences reported in other taxa.

Estimation of coconut maturity based on fuzzy neural network and sperm whale optimization

Coconut water is the clear liquid found inside coconuts, famous for rehydrating after exercise or while suffering from a minor sickness. The essential issue tackled in this paper is how to estimate the appropriate stage of maturity of coconut water, which is a time-consuming task in the beverage industry since, as the coconut age increases, the coconut water flavor varies. Accordingly, to handle this issue, an adaptive model based on Fuzzy Neural Network and Sperm Whale Optimization, dubbed FNN–SWO, is developed to assess coconut water maturity. The Sperm Whale Optimization (SWO) algorithm is a meta-heuristic optimization algorithm. It is embedded in this model along with neural networks and fuzzy techniques (FNN system), which can be employed as an essential building block in the beverage industry. The proposed FNN–SWO model is trained and tested utilizing fuzzy rules with an adaptive network. In contrast, the SWO algorithm is adopted to determine the optimal weights for the fuzzy rules. Three subsets of data divided according to three levels of coconut water maturity-tender, mature, and very mature, are used to validate the combined FNN–SWO model. Depending on these three subsets of data, a comparison of the proposed FNN–SWO model has been conducted against a set of the most common conventional techniques. These techniques include Support Vector Machine, Naïve Bayes, FNN, Artificial Neural Network, as well as their embedding with other meta-heuristic optimization algorithms. For various key performance indicators, such as recall, F1-score, specificity, and accuracy, the proposed FNN–SWO model provides the best prediction outcomes compared to the current time-consuming techniques. The dominance of the proposed FNN–SWO model is evident from the final findings compared to its time-consuming peers for estimating coconut water maturity on time. As a result, the proposed FNN–SWO model is an effective heuristic for locating optimal solutions to classification problems. It can thereby be reassuringly applicable to other similar prediction problems. Additionally, it would benefit the scientific community interested in evaluating coconut water.

Predictive model of sperm whale prey capture attempts from time-depth data

BackgroundHigh-resolution sound and movement recording tags offer unprecedented insights into the fine-scale foraging behaviour of cetaceans, especially echolocating odontocetes, enabling the estimation of a series of foraging metrics. However, these tags are expensive, making them inaccessible to most researchers. Time-Depth Recorders (TDRs), which have been widely used to study diving and foraging behaviour of marine mammals, offer a more affordable alternative. Unfortunately, data collected by TDRs are bi-dimensional (time and depth only), so quantifying foraging effort from those data is challenging.MethodsA predictive model of the foraging effort of sperm whales (Physeter macrocephalus) was developed to identify prey capture attempts (PCAs) from time-depth data. Data from high-resolution acoustic and movement recording tags deployed on 12 sperm whales were downsampled to 1 Hz to match the typical TDR sampling resolution and used to predict the number of buzzes (i.e., rapid series of echolocation clicks indicative of PCAs). Generalized linear mixed models were built for dive segments of different durations (30, 60, 180 and 300 s) using multiple dive metrics as potential predictors of PCAs.ResultsAverage depth, variance of depth and variance of vertical velocity were the best predictors of the number of buzzes. Sensitivity analysis showed that models with segments of 180 s had the best overall predictive performance, with a good area under the curve value (0.78 ± 0.05), high sensitivity (0.93 ± 0.06) and high specificity (0.64 ± 0.14). Models using 180 s segments had a small difference between observed and predicted number of buzzes per dive, with a median of 4 buzzes, representing a difference in predicted buzzes of 30%.ConclusionsThese results demonstrate that it is possible to obtain a fine-scale, accurate index of sperm whale PCAs from time-depth data alone. This work helps leveraging the potential of time-depth data for studying the foraging ecology of sperm whales and the possibility of applying this approach to a wide range of echolocating cetaceans. The development of accurate foraging indices from low-cost, easily accessible TDR data would contribute to democratize this type of research, promote long-term studies of various species in several locations, and enable analyses of historical datasets to investigate changes in cetacean foraging activity.

A note on the preparation of sperm whale (Physeter macrocephalus) teeth for age determination

We describe a modification to the most common method of preparing sperm whale teeth for age determination. The first mandibular or nearest straightest tooth was sectioned in half with a slow-rotating band saw, polished and, rather than subjecting the sectioned tooth to 10% formic acid for 30 hours, etched in 15% formic acid. The exposure time of each tooth to the acid varied depending on the size, and especially, the density of the tooth. Clear, well defined growth layer groups in sperm whale teeth suitable for age determination can be produced in substantially shorter periods of time. A method for the preparation of teeth from young sperm whales is also described. Thin sectioning and staining of teeth is used to prepare small teeth from young animals and avoids potential decalcification, which may possibly occur using acid etching methods.

A note on the release and tracking of a rehabilitated pygmy sperm whale (Kogia breviceps)

A stranded, rehabilitated 220cm female pygmy sperm whale was radiotracked from 31 May-4 June 1994 after its release in the Gulf Stream off Cape Canaveral, Florida. The whale moved directly off the continental shelf and headed northward within a corridor bounded by the shelf break and the eastern edge of the Gulf Stream. It moved offshore up to 32 n.miles from the shelf break during the late afternoons and nights and headed back toward the shelf break during the day. The average travelling speed was 3.0kts, and ranged from 0-6kts. Speeds were greatest offshore of the shelf break (4.7kts), where the speed of the Gulf Stream was the greatest, and both travelling speeds and Gulf Stream speeds decreased with distance offshore. The whale did not appear, however, to be drifting passively with the current. Diving duration varied significantly with light levels. The whale made long dives ( > 8min) at night and on overcast days when squid are known to be closer to the surface. During clear days, the whale’s dives were significantly shorter, typically less than five minutes (n = 841). Although these results come from only a single, rehabilitated animal, the four days of data provided the first information on pygmy sperm whale movements and diving behaviour at sea: how its behaviour was influenced by time of day, oceanographic features, and environmental conditions, and how the whale’s surfacing behaviour could allow survey estimates to be adjusted for diving whales missed along the trackline.

A note on strandings and age of sperm whales (Physeter macrocephalus) on the Brazilian coast

This note compiles recorded strandings of sperm whales on the Brazilian coast. A known total of 95 sperm whales (62 single and one mass stranding of 33 individuals) stranded along the Brazilian coast from 1967-2000. A higher incidence of single strandings was observed in northeastern Brazil ( ~ 05°-17°S). No strandings occurred in lower latitudes ( < 14°S) from June-September. The seasonal and spatial pattern observed by the reported strandings may indicate higher stranding rates in higher latitudes ( ~ 18-25°S) between June and August (winter) and in lower latitudes ( ~ 3-7°S) between January and April (summer and spring). Strandings of smaller sperm whales (3-4.5m) were observed during the austral summer and autumn, indicating seasonality in the birth season. Growth-layer counts of three specimens provide the first data on age of sperm whales for Brazil.

Mark-recapture analysis of sperm whale (Physeter macrocephalus) photo-id data from the Azores (1987-1995)

Population estimates for female or immature male sperm whales (Physeter macrocephalus) in a region within the Azores archipelago are given, based on photo-identification studies with mark-recapture analysis. The study area encompassed the Central Group of islands and the island of São Miguel. Data indicate that the recapture rate of animals likely to be females differs from other animals, and this heterogeneity is incorporated into the models. Closed population (Petersen) estimates, using data from within summers, suggest a population of between 300-800 female or immature sperm whales in summer in the study area. Estimates of the population that visits the study area in summer were made using a model selected from the Jolly-Seber family. The open population visiting the study area appeared to vary between about 400-700 between the years 1988-1990, increasing by a factor of three to about 1,600-2,200 between the years 1991-1994. The fraction of whales which are not suitably marked for identification is estimated to be about 12%, so these estimates should be increased by a factor of 1.14. These estimates are reliable if the study area covers the range of a wider population which moves into and out of the study area randomly. The increase in abundance in 1991 is probably due to change in the composition of the population visiting the area. It is not yet possible to clearly define the wider population that the Azores samples are from, nor are migration patterns to and from the area understood. Investigations on a larger spatial scale are needed for a better understanding.

Estimates of abundance south of 60°S for cetacean species sighted frequently on the 1978/79 to 1997/98 IWC/IDCR-SOWER sighting surveys

Estimates of abundance are calculated for six cetacean species in the Southern Ocean south of 60° in the austral summer, using the IWC database estimation package (DESS). The sightings data in DESS were collected during the 1978/79 to 1997/98 IWC/IDCR and SOWER circumpolar surveys. Abundance estimates are developed for the first (1978/79–1983/84), second (1985/86–1990/91) and currently incomplete third (1991/92–1997/98) circumpolar sets of surveys. The strata surveyed in these three sets cover about 65%, 81% and 68% respectively of the open ocean area south of 60°S. The surveys were designed for Antarctic minke whales and may not be optimal for all these species. Furthermore, the estimates presented below (CVs in brackets) should not necessarily be considered as estimates for the whole Southern Hemisphere. Some results are also presented for hourglass dolphins and sei whales, but estimates of abundance are not considered reliable for those two species. Effective search half-width and mean school size were estimated by pooling across strata and years. Pooling is effected separately for each circumpolar set of surveys. Additional pooling across closing and passing modes did not introduce substantial bias. The most frequently sighted species were minke, southern bottlenose, sperm, humpback and killer whales; the effective search half-widths for all five increase over time. The sensitivity of the abundance estimates to a number of factors is investigated, none of which appears to impact the results substantially, except that the incorporation of ‘like species’ would increase the estimate for blue whales from the third circumpolar set of surveys by 25% and for fin whales by 61%. In general, the assumption that 100% of schools on the trackline are sighted introduces variable negative bias to estimates for all species. Only two significant trends in abundance over time (for comparable areas) were detected, but both may be artefacts of changes in survey design.