Dolphin and porpoise detections by the F-POD are not independent: Implications for sympatric species monitoring.

The F-POD is designed for passive acoustic monitoring of odontocetes. The offline classifiers can identify and separate porpoise-like sounds from dolphin-like sounds. We show that these two classifiers are not working independently. Run together, virtually no detections of both species were reported within the same minute, whereas 10% of the detection positive minutes were reported positive for both species when the two classifiers were run sequentially. This has important implications for interpretation of data in areas containing both species groups, and we call for reporting all analysis details in such studies and for further description and analysis of the classifiers.

Management and research efforts are failing dolphins, porpoises, and other toothed whales.

Despite being subject to intensive research and public interest many populations of dolphins, porpoises, and other toothed whales (small cetaceans) continue to decline, and several species are on the verge of extinction. We examine small cetacean status, human activities driving extinction risk, and whether research efforts are addressing priority threats. We estimate that 22% of small cetaceans are threatened with extinction, with little signs of improvement in nearly thirty years. Fisheries and coastal habitat degradation are the main predictors of extinction risk. Contrary to popular belief, we show that the causal impact of small-scale fisheries on extinction risk is greater than from large-scale fisheries. Fisheries management strength had little influence on extinction risk, suggesting that the implementation of existing measures have been largely ineffective. Alarmingly, we find research efforts for priority threats to be vastly underrepresented and so a major shift in research focus is required. Small cetaceans are among the lower hanging fruits of marine conservation; continued failure to halt their decline bodes poorly for tackling marine biodiversity loss and avoiding an Anthropocene mass extinction.

First report of kyphoscoliosis in the narrow-ridged finless porpoises (Neophocaena asiaeorientalis): Findings from congenital and degenerative cases comparison using post-mortem computed tomography.

INTRODUCTION: Spinal deformities, including kyphoscoliosis, have been consistently documented in cetaceans. However, the majority of reported cases of kyphoscoliosis in cetaceans pertain to bottlenose dolphins, with limited information on its occurrence in narrow-ridged finless porpoise (NFP) (Neophocaena asiaeorientalis). MATERIALS AND METHODS: In November 2021, two deceased NFPs were discovered stranded on the shores of the Republic of Korea. As part of the pioneer stranded cetacean imaging programme in the Republic of Korea, both carcasses underwent post-mortem computed tomography (PMCT), revealing congenital and degenerative traumatic kyphoscoliosis, respectively. RESULTS: Although kyphoscoliosis may not have directly caused the demise of these individuals, it is hypothesized that the reduced spinal range of motion and mobility associated with kyphoscoliosis may have contributed to their deaths. CONCLUSION: This case report presents the first documented cases of kyphoscoliosis in two NFPs stranded in Korean waters, utilizing PMCT as an efficient methodology for assessing skeletal abnormalities in cetaceans.

First determination of elevated levels of plastic additives in finless porpoises from the South China Sea.

Plastic additives, such as organophosphate esters (OPEs) and phthalate esters (PAEs), are raising public concerns due to their widespread presence and potential health risks. Nonetheless, the occurrences and potential health risks of these additives in marine mammals remain limited. Here, we first investigated the accumulation patterns and potential risks of OPEs and metabolites of PAEs (mPAEs) in Indo-Pacific finless porpoises inhabiting the northern South China Sea (NSCS) during 2007-2020. The average hepatic concentrations of ∑15OPEs and ∑16mPAEs in the NSCS finless porpoises were 53.9 ± 40.7 and 98.6 ± 54.8 ng/g ww, respectively. The accumulation of mPAEs and OPEs in the finless porpoises is associated with the chemical structures of the compounds. ∑5halogenated-OPEs were the most dominant category (62.6%) of ∑15OPEs, followed by ∑6aryl-OPEs (25.9%) and ∑6nonhalogenated alkyl-OPEs (11.5%). The accumulation of mPAEs displayed a declining trend with increasing alkyl side chain length (C0-C10). Although the hepatic burden of mPAEs in finless porpoises was sex-independent, some OPEs, including TDCIPP, TBOEP, TCIPP, TCrP, TPHP, and TDBPP, exhibited significantly higher concentrations in adult males than in adult females. TDBPP, as a new-generation OPE, exhibited a gradual increase during the study period, suggesting that TDBPP should be prioritized for monitoring in the coastal regions of South China. The estimated hazard quotient indicated that almost all mPAEs and OPEs pose no hazard to finless porpoises, with only DEHP presenting potential health risks to both adult and juvenile finless porpoises.

Biological characteristics of pregnancy in captive Yangtze finless porpoises revealed by urinary metabolomics†.

The Yangtze finless porpoises (Neophocaena asiaeorientalis a.) are an endemic and critically endangered species in China. Intensive captive breeding is essential for understanding the biology of critically endangered species, especially their pregnancy characteristics, knowledge of which is crucial for effective breeding management. Urine metabolomics can reveal metabolic differences, arising from physiological changes across pregnancy stages. Therefore, we used the urinary metabolomic technology, to explore urinary metabolite changes in pregnant Yangtze finless porpoises. A total of 2281 metabolites were identified in all samples, which including organic acids and derivatives (24.45%), organoheterocyclic compounds (20.23%), benzenoids (18.05%), organic oxygen compounds (7.73%), and phenylpropanoids and polyketides (6.48%). There were 164, 387, and 522 metabolites demonstrating differential abundance during early pregnancy, mid pregnancy, and late pregnancy, respectively, from the levels observed in nonpregnancy. The levels of pregnenolone, 17α-hydroxyprogesterone, and tetrahydrocortisone were significantly higher during all pregnancy stages, indicating their important roles in fetal development. The differential metabolites between nonpregnancy and pregnancy were mainly associated with amino acid and carbohydrate metabolism. Moreover, metabolic activity varied across pregnancy stages; steroid hormone biosynthesis was predominant in early pregnancy, and amino acid biosynthesis and carbohydrate metabolism were predominant in mid pregnancy and late pregnancy, respectively. Our results provide new insights into metabolic characteristics in the Yangtze finless porpoises' urine during pregnancy, and indicate that the differential levels of urine metabolites can determine pregnancy in Yangtze finless porpoises, providing valuable information for the husbandry and management of pregnant Yangtze finless porpoises in captivity.

Ship noise causes tagged harbour porpoises to change direction or dive deeper.

Shipping is the most pervasive source of marine noise pollution globally, yet its impact on sensitive fauna remains unclear. We tracked 10 harbour porpoises for 5-10 days to determine exposure and behavioural reactions to modelled broadband noise (10 Hz-20 kHz, VHF-weighted) from individual ships monitored by AIS. Porpoises spent a third of their time experiencing ship noise above ambient, to which they regularly reacted by moving away during daytime and diving deeper during night. However, even ships >2 km away (noise levels of 93 ± 14 dB re 1 µPa2) caused animals to react 5-9 % of the time (∼18.6 ships/day). Ships can thus influence the behaviour and habitat use of cetaceans over long distances, with worrying implications for fitness in coastal areas where anthropogenic noise from dense ship traffic repeatedly disrupt their natural behaviour.

Patterns of enrichment and acceleration in evolutionary rates of promoters suggest a role of regulatory regions in cetacean gigantism.

BACKGROUND: Cetaceans (whales, porpoises, and dolphins) are a lineage of aquatic mammals from which some species became giants. Only recently, gigantism has been investigated from the molecular point of view. Studies focused mainly on coding regions, and no data on the influence of regulatory regions on gigantism in this group was available. Accordingly, we investigated the molecular evolution of non-coding regulatory regions of genes already described in the literature for association with size in mammals, focusing mainly on the promoter regions. For this, we used Ciiider and phyloP tools. Ciiider identifies significantly enriched transcription factor binding sites, and phyloP estimates the molecular evolution rate of the promoter. RESULTS: We found evidence of enrichment of transcription binding factors related to large body size, with distinct patterns between giant and non-giant cetaceans in the IGFBP7 and NCAPG promoters, in which repressive agents are present in small cetaceans and those that stimulate transcription, in giant cetaceans. In addition, we found evidence of acceleration in the IGF2, IGFBP2, IGFBP7, and ZFAT promoters. CONCLUSION: Our results indicate that regulatory regions may also influence cetaceans' body size, providing candidate genes for future research to understand the molecular basis of the largest living animals.

Implications of porpoise echolocation and dive behaviour on passive acoustic monitoring.

Harbour porpoises are visually inconspicuous but highly soniferous echolocating marine predators that are regularly studied using passive acoustic monitoring (PAM). PAM can provide quality data on animal abundance, human impact, habitat use, and behaviour. The probability of detecting porpoise clicks within a given area (P̂) is a key metric when interpreting PAM data. Estimates of P̂ can be used to determine the number of clicks per porpoise encounter that may have been missed on a PAM device, which, in turn, allows for the calculation of abundance and ideally non-biased comparison of acoustic data between habitats and time periods. However, P̂ is influenced by several factors, including the behaviour of the vocalising animal. Here, the common implicit assumption that changes in animal behaviour have a negligible effect on P̂ between different monitoring stations or across time is tested. Using a simulation-based approach informed by acoustic biologging data from 22 tagged harbour porpoises, it is demonstrated that porpoise behavioural states can have significant (up to 3× difference) effects on P̂. Consequently, the behavioural state of the animals must be considered in analysis of animal abundance to avoid substantial over- or underestimation of the true abundance, habitat use, or effects of human disturbance.

Wild harbour porpoises startle and flee at low received levels from acoustic harassment device.

Acoustic Harassment Devices (AHD) are widely used to deter marine mammals from aquaculture depredation, and from pile driving operations that may otherwise cause hearing damage. However, little is known about the behavioural and physiological effects of these devices. Here, we investigate the physiological and behavioural responses of harbour porpoises (Phocoena phocoena) to a commercial AHD in Danish waters. Six porpoises were tagged with suction-cup-attached DTAGs recording sound, 3D-movement, and GPS (n = 3) or electrocardiogram (n = 2). They were then exposed to AHDs for 15 min, with initial received levels (RL) ranging from 98 to 132 dB re 1 µPa (rms-fast, 125 ms) and initial exposure ranges of 0.9-7 km. All animals reacted by displaying a mixture of acoustic startle responses, fleeing, altered echolocation behaviour, and by demonstrating unusual tachycardia while diving. Moreover, during the 15-min exposures, half of the animals received cumulative sound doses close to published thresholds for temporary auditory threshold shifts. We conclude that AHD exposure at many km can evoke both startle, flight and cardiac responses which may impact blood-gas management, breath-hold capability, energy balance, stress level and risk of by-catch. We posit that current AHDs are too powerful for mitigation use to prevent hearing damage of porpoises from offshore construction.

Quantification by droplet digital PCR and species identification by metabarcoding of environmental (e)DNA from Blainville's beaked whales, with assisted localization from an acoustic array.

Detection and identification of species, subspecies or stocks of whales, dolphins and porpoises at sea remain challenging, particularly for cryptic or elusive species like beaked whales (Family: Ziphiidae). Here we investigated the potential for using an acoustically assisted sampling design to collect environmental (e)DNA from beaked whales on the U.S. Navy's Atlantic Undersea Test and Evaluation Center (AUTEC) in The Bahamas. During 12 days of August 2019, we conducted 9 small-boat surveys and collected 56 samples of seawater (paired subsamples of 1L each, including controls) using both a spatial collection design in the absence of visual confirmation of whales, and a serial collection design in the proximity of whales at the surface. There were 7 sightings of whales, including 11 Blainville's beaked whales (Mesoplodon densirostris). All whales were located initially with the assistance of information from a bottom-mounted acoustic array available on the AUTEC range. Quantification by droplet digital (dd)PCR from the four spatial design collections showed no samples of eDNA above the threshold of detection and none of these 20 samples yielded amplicons for conventional or next-generation sequencing. Quantification of the 31 samples from four serial collections identified 11 likely positive detections. eDNA barcoding by conventional sequencing and eDNA metabarcoding by next-generation sequencing confirmed species identification for 9 samples from three of the four serial collections. We further resolved five intra-specific variants (i.e., haplotypes), two of which showed an exact match to previously published haplotypes and three that have not been reported previously to the international repository, GenBank. A minimum spanning network of the five eDNA haplotypes, with all other published haplotypes of Blainville's beaked whales, suggested the potential for further resolution of differences between oceanic populations.

Anthropogenic activity, hydrological regime, and light level jointly influence temporal patterns in biosonar activity of the Yangtze finless porpoise at the junction of the Yangtze River and Poyang Lake, China.

Under increasing anthropogenic pressure, species with a previously contiguous distribution across their ranges have been reduced to small fragmented populations. The critically endangered Yangtze finless porpoise ( Neophocaena asiaeorientalis asiaeorientalis), once commonly observed in the Yangtze River-Poyang Lake junction, is now rarely seen in the river-lake corridor. In this study, static passive acoustic monitoring techniques were used to detect the biosonar activities of the Yangtze finless porpoise in this unique corridor. Generalized linear models were used to examine the correlation between these activities and anthropogenic impacts from the COVID-19 pandemic lockdown and boat navigation, as well as environmental variables, including hydrological conditions and light levels. Over approximately three consecutive years of monitoring (2020-2022), porpoise biosonar was detected during 93% of logged days, indicating the key role of the corridor for finless porpoise conservation. In addition, porpoise clicks were recorded in 3.80% of minutes, while feeding correlated buzzes were detected in 1.23% of minutes, suggesting the potential existence of localized, small-scale migration. Furthermore, both anthropogenic and environmental variables were significantly correlated with the diel, lunar, monthly, seasonal, and annual variations in porpoise biosonar activities. During the pandemic lockdown period, porpoise sonar detection showed a significant increase. Furthermore, a significant negative correlation was identified between the detection of porpoise click trains and buzzes and boat traffic intensity. In addition to water level and flux, daylight and moonlight exhibited significant correlations with porpoise biosonar activities, with markedly higher detections at night and quarter moon periods. Ensuring the spatiotemporal reduction of anthropogenic activities, implementing vessel speed restrictions (e.g., during porpoise migration and feeding), and maintaining local natural hydrological regimes are critical factors for sustaining porpoise population viability.

Cetaceans as bio-indicators revealed the increased risks of triclosan exposure and associated thyroid hormone disruption during the COVID-19 pandemic.

The global surge in disinfection practices from the COVID-19 response has raised concerns about the marine exposure to the hazardous ingredients in disinfectant products, including triclosan (TCS) and triclocarban (TCC). However, there are very limited studies on the response of marine TCS and TCC (TCs) loading to the COVID-19 pandemic. Here we used cetaceans as bio-indicators for a long-term retrospective analysis of TCs loading to the South China Sea (SCS) between 2004 and 2022. Hepatic TCs was 100% detected in all nine cetacean species (n = 120). Interestingly, TCS concentrations decreased in Indo-Pacific humpback dolphins (IPHD) before the pandemic from 2010 to 2017. However, after 2019, TCS concentrations in IPHD significantly increased several-fold. Similarly, post-pandemic TCS concentrations in Indo-Pacific finless porpoises (IPFP) and two fish species were significantly higher than pre-pandemic levels. There were significant relationships between thyroid hormones (THs) and TCs in IPHD and IPFP, suggesting that increased TCs may worsen the interference of THs homeostasis and nutritional conditions in cetaceans. These findings demonstrate the profound impact of the surging use of TCs-containing products from the COVID-19 response on marine ecosystems.

Variations in echolocation click characteristics of finless porpoise in response to day/night and absence/presence of vessel noise.

Small odontocetes produce echolocation clicks to feed and navigate, making it an essential function for their survival. Recently, the effect of vessel noise on small odontocetes behavior has attracted attention owing to increase in vessel activities; however, the effects of the surrounding environmental factor, vessel noise, and day/night on echolocation click characteristics have not been well studied. Here, we examined the effects of vessel noise and day/night on variations in echolocation clicks and click trains parameters. Passive acoustic monitoring of on-axis echolocation clicks produced by free-ranging finless porpoises (Neophocaena asiaeorientalis sunameri) was performed at two sites in Japan, Seto Inland Sea and Mikawa Bay, in June-September 2021 and March-August 2022, using A-tag and SoundTrap 300HF. Generalized Linear Model was used to elucidate the effect of vessel noise, day/night, and surrounding environmental factors (water temperature, synthetic flow velocity, and noise level) on echolocation click and click train parameters. Echolocation click and click train parameters were strongly affected by day/night, whereas the absence/presence vessel noise did not exhibit statistically significant influence. Particularly, -3 dB bandwidth was wider, click duration was shorter, and inter-click intervals in a train were shorter at night, which may facilitate information processing at night, thereby compensating for the lack of visual information. The interaction between day/night and the absence/presence of vessel noise affected the source level of finless porpoises, with higher levels observed in the absence of vessel noise during the daytime compared to other conditions at the site with low vessel traffic. Overall, these results suggest that echolocation clicks by finless porpoise were likely to fluctuate to adapt with surrounding complex environmental conditions, especially day/night.

Regional variation of polybrominated diphenyl ethers in East Asian finless porpoises in the East China Sea.

Certain polybrominated diphenyl ethers (PBDEs) have been banned for years, however, they still possess the potential to harm marine cetaceans. In this study, 56 East Asian finless porpoises (EAFPs) collected from three locations of the East China Sea between 2009 and 2011, were analyzed to determine the presence of typical PBDE congeners. Among all the samples, BDE47 was the main congener, constituting ∼48.3 % of the ΣPBDEs. Significant variations (p < 0.01) in PBDE abundance were observed among different regions (Pingtan: 172.8 ng/g, Lvsi: 61.2 ng/g and Ningbo: 32.9 ng/g). In addition, there was a significant positive correlation between PBDE abundance and male body length. The general ΣPBDEs concentration of this population was lower compared to other populations and cetaceans. Although combined risk assessments indicated a low risk to porpoise health, long-term surveillance is essential as PBDEs are not completely banned.

Identification of key features relating to the coexistence mechanisms of trace elements and per- and polyfluoroalkyl substances (PFASs) in marine mammals.

Organic and inorganic substances coexist in the livers of marine mammals and may correlate with one another; however, their coexistence mechanisms and relevant key features remain largely unknown. In this study, temporal variations (2011-2021) in the concentrations of nine trace elements and 19 per- and polyfluoroalkyl substances (PFASs) in the livers of Indo-Pacific humpback dolphins (Sousa chinensis) and finless porpoises (Neophocaena phocaenoides) were investigated. Interannual Cd in dolphins increased significantly whereas Pb concentrations decreased over the past decade (p < 0.05). Interannual levels of seven and four PFASs in dolphins and porpoises decreased significantly with time (p < 0.05). By further extending the timescale to 1993-2021, the sensitivity of trace elements to annual change further increased, whereas the sensitivity of PFASs remained relatively stable. Cu levels, similar to the majority of PFASs, were negatively correlated with the body length of the studied cetaceans, which led to positive correlations of Cu with six long-chain perfluoroalkyl carboxylic acids, perfluorodecane sulfonic acid, and perfluoroethylcyclohexane sulfonic acid. The concentrations of trace elements in the cetacean liver were closely correlated with cetacean sex, species, and body length, whereas PFAS concentration was responsive to time-related features such as stranded season and year. By further employing a machine learning method, we demonstrated that body length and a time-related factor (year) played a crucial role in predicting the concentrations of certain trace elements and PFASs, respectively, particularly Cu and perfluoroheptanoic acid.

Viral Diversity and Epidemiology in Critically Endangered Yangtze Finless Porpoises (Neophocaena asiaeorientalis asiaeorientalis).

The Yangtze finless porpoise (YFP) (Neophocaena asiaeorientalis asiaeorientalis) is a critically endangered freshwater cetacean, with about 1,249 individuals thought to be left in the wild. However, viral entities and viral diseases of YFPs remain obscure. In this study, anal swabs for virome analysis were collected during the physical examination of YFPs in the Tian-E-Zhou Oxbow (TEO) ex situ reserve. A total of 19 eukaryotic viral species belonging to 9 families, including Papillomaviridae, Herpesviridae, Picornaviridae, Picobirnaviridae, Caliciviridae, Retroviridae, Parvoviridae, Virgaviridae, and Narnaviridae, and other unclassified viruses were identified based on metasequencing. Among these detected viruses, a novel herpesvirus (NaHV), two different kobuviruses (NaKV1-2), and six different papillomaviruses (NaPV1 to -6) were considered potential risks to YFPs and confirmed by PCR or reverse transcription-PCR (RT-PCR). Most YFPs sampled were found to harbor one or more kinds of detected viral genomes (52/58 [89.7%]). Surveillance results demonstrated that kobuvirus and herpesvirus displayed obvious age distribution and PVs showed significant gender difference in YFPs. According to species demarcation criteria in individual genera in Papillomaviridae, two novel species (referred to as Omikronpapillomavirus 2 and 3) and four novel isolates of PV were identified in YFPs. Further evolutionary analysis suggested that NaPVs would occupy the mucosal niche and that virus-host codivergence mixed with duplications and host-switching events drives the evolution of cetacean PVs. Divergence times of PVs in YFP and other cetacean reflect the incipient speciation of YFPs. In summary, our findings revealed the potential viral entities, their prevalence, and their evolutionary history in YFPs, which raises an important issue regarding effects of viral infection on the fitness of YFPs. IMPORTANCE The Yangtze finless porpoise (YFP) is the only cetacean species in freshwater following the functional extinction of the baiji (Lipotes vexillifer). Health management, disease treatment, and other special measures are important for maintaining the existing YFP populations, especially in in situ and ex situ reserves. The discovery of potential viral entities and their prevalence in YFPs raises an important issue regarding the effects of viral infection on the fitness of YFPs and may contribute to the conservation of YFPs. The evolutionary history of papillomaviruses in YFP and other cetaceans reflects the phylogeny of their hosts and supports the status of incipient species, opening a window to investigate the evolutionary adaptation of cetaceans to freshwater as well as their phylogeny to remedy the deficiency of fossil evidence.

Cetaceans as Bioindicators to Assess Alkylphenol Exposure and Hormone-Disrupting Effects in the South China Sea.

Alkylphenols (APs) represent one of the highest exposure levels among endocrine disrupting chemicals (EDCs) in the South China Sea (SCS) due to their extensive use as plastic additives. The concerns about EDCs, including APs, have been reiterated since the surge in plastic waste from the COVID-19 response, but far less is known about the response of AP loadings in the SCS to emerging public policies and activities, including the COVID-19 pandemic. Here, we used cetaceans as bioindicators for monitoring two major APs, 4-nonylphenol (4-NP) and 4-tert-octylphenol (4-t-OP), in nine stranded cetacean species (n = 110) in the SCS between 2004 and 2021. Prior to the COVID-19, APs loads showed decreasing temporal trends for finless porpoises and humpback dolphins, most likely due to China's restrictions on AP use or a shift in dominant prey species. Unexpectedly, AP loads continued to decline after the COVID-19 outbreak, probably due to a temporal-lag response of marine AP fluxes to the pandemic. The health risk assessments based on hormone biomarkers and toxicity thresholds suggest the potential adverse effects of APs on cetaceans, while recent declines in APs, though limited, may mitigate the detrimental impacts.

Temporal Trends and Suspect Screening of Halogenated Flame Retardants and Their Metabolites in Blubbers of Cetaceans Stranded in Hong Kong Waters during 2013-2020.

Halogenated flame retardants (HFRs) are a large class of chemical additives intended to meet flammability safety requirements, and at present, they are ubiquitous in the environment. Herein, we conducted the target analysis and suspect screening of legacy and novel HFRs and their metabolites in the blubber of finless porpoises (Neophocaena phocaenoides; n = 70) and Indo-Pacific humpback dolphins (Sousa chinensis; n = 35) stranded in Hong Kong, a coastal city in the South China Sea, between 2013 and 2020. The average concentrations of total target HFRs (ΣHFRs) were 6.48 × 103 ± 1.01 × 104 and 1.40 × 104 ± 1.51 × 104 ng/g lipid weight in porpoises and dolphins, respectively. Significant decreasing temporal trends were observed in the concentrations of tetra-/penta-/hexa-bromodiphenyl ethers (tetra-/penta-/hexa-BDEs) in adult porpoises stranded from 2013-2015 to 2016-2020 (p < 0.05), probably because of their phasing out in China. No significant difference was found for the concentrations of decabromodiphenyl ether and hexabromocyclododecane, possibly due to their exemption from the ban in China until 2025 and 2021, respectively. Eight brominated compounds were additionally identified via suspect screening. A positive correlation was found between the concentrations of tetra-BDE and methyl-methoxy-tetra-BDE (Me-MeO-tetra-BDE) (p < 0.05), indicating that the metabolism of tetra-BDE may be a potential source of Me-MeO-tetra-BDE in marine mammals.

Red-list status and extinction risk of the world's whales, dolphins, and porpoises.

To understand the scope and scale of the loss of biodiversity, tools are required that can be applied in a standardized manner to all species globally, spanning realms from land to the open ocean. We used data from the International Union for the Conservation of Nature Red List to provide a synthesis of the conservation status and extinction risk of cetaceans. One in 4 cetacean species (26% of 92 species) was threatened with extinction (i.e., critically endangered, endangered, or vulnerable) and 11% were near threatened. Ten percent of cetacean species were data deficient, and we predicted that 2-3 of these species may also be threatened. The proportion of threatened cetaceans has increased: 15% in 1991, 19% in 2008, and 26% in 2021. The assessed conservation status of 20% of species has worsened from 2008 to 2021, and only 3 moved into categories of lesser threat. Cetacean species with small geographic ranges were more likely to be listed as threatened than those with large ranges, and those that occur in freshwater (100% of species) and coastal (60% of species) habitats were under the greatest threat. Analysis of odontocete species distributions revealed a global hotspot of threatened small cetaceans in Southeast Asia, in an area encompassing the Coral Triangle and extending through nearshore waters of the Bay of Bengal, northern Australia, and Papua New Guinea and into the coastal waters of China. Improved management of fisheries to limit overfishing and reduce bycatch is urgently needed to avoid extinctions or further declines, especially in coastal areas of Asia, Africa, and South America.

Estado en la lista roja y riesgo de extinción de las ballenas, delfines y marsopas del mundo Resumen Para comprender el alcance y la escala de la pérdida de biodiversidad, se necesitan herramientas que puedan aplicarse de forma estandarizada a todas las especies a nivel mundial y que abarquen todos los ámbitos desde la tierra hasta el océano. Utilizamos datos de la Lista Roja de la Unión Internacional para la Conservación de la Naturaleza para proporcionar una síntesis del estado de conservación y el riesgo de extinción de los cetáceos. Una de cada 4 especies de cetáceos (26% de 92 especies) se encuentra amenazada (es decir, en peligro crítico, en peligro o vulnerable) y el 11% de las especies está clasificado como casi amenazada. El 10% de las especies de cetáceos carecía de datos, por lo que predijimos que 2-3 de estas especies también podrían estar amenazadas. La proporción de cetáceos amenazados ha aumentado: 15% en 1991, 19% en 2008 y 26% en 2021. El estado de conservación evaluado del 20% de las especies ha empeorado de 2008 a 2021, pues sólo 3 pasaron a categorías de menor amenaza. Las especies de cetáceos con áreas de distribución geográficas pequeñas tenían más probabilidades de ser catalogadas como amenazadas que aquellas con áreas de distribución extensas, y aquellas que ocurren en hábitats de agua dulce (100% de las especies) y costeros (60% de las especies) eran las que se encontraban bajo mayor amenaza. La superposición de los mapas de distribución de las especies reveló la existencia de puntos calientes de pequeños cetáceos amenazados en el sudeste asiático y en una zona que abarca el Triángulo de Coral y se extiende por las aguas cercanas a la costa de la Bahía de Bengala, el norte de Australia, Papúa Nueva Guinea y las aguas costeras de China. Urge mejorar la gestión de las pesquerías para limitar la sobrepesca y reducir la captura accesoria con el fin de evitar extinciones o mayores descensos, especialmente en las zonas costeras de Asia, África y Sudamérica.