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.

A deepening understanding of animal culture suggests lessons for conservation.

A key goal of conservation is to protect biodiversity by supporting the long-term persistence of viable, natural populations of wild species. Conservation practice has long been guided by genetic, ecological and demographic indicators of risk. Emerging evidence of animal culture across diverse taxa and its role as a driver of evolutionary diversification, population structure and demographic processes may be essential for augmenting these conventional conservation approaches and decision-making. Animal culture was the focus of a ground-breaking resolution under the Convention on the Conservation of Migratory Species of Wild Animals (CMS), an international treaty operating under the UN Environment Programme. Here, we synthesize existing evidence to demonstrate how social learning and animal culture interact with processes important to conservation management. Specifically, we explore how social learning might influence population viability and be an important resource in response to anthropogenic change, and provide examples of how it can result in phenotypically distinct units with different, socially learnt behavioural strategies. While identifying culture and social learning can be challenging, indirect identification and parsimonious inferences may be informative. Finally, we identify relevant methodologies and provide a framework for viewing behavioural data through a cultural lens which might provide new insights for conservation management.

Population ecology and the management of whale watching operations on a data-deficient dolphin population.

Whale watching is a popular commercial activity, producing socio-ecological benefits but also potential long-term effects on the targeted cetacean population. This industry is currently developing in data-deficient contexts in a largely unregulated fashion. Management schemes should adopt precaution and be informed by the relevant literature, but would be more effective if the assessment of the target population vulnerability, biological impacts, and management implications was drawn from site-specific data.This paper focuses on a reef-associated, data-deficient population of spinner dolphins in the Egyptian Red Sea. In Satayah Reef, new information on population size and dynamic parameters were documented using visual observation and photo-identification-based capture-recapture methods (Cormack-Jolly-Seber time-since-marking model).Dolphins occurred on 98% of the survey days. Average school size was 66 individuals (±42.1 SE), with most groups including calves. The population was equally divided into recurrent and transient individuals. An "emigration + mortality" model best described residence at the site. Five recurrent males (5% of the Satayah population) provided connectivity between this and the geographically close population of Samadai Reef.Average annual survival probability was 0.83 (±0.06 SE) in the year following first capture and 0.99 (±0.06 SE) for recurrent individuals. Mean yearly population sizes ranged 143-207 individuals.The study had the power to detect a 30% decline in the population, but not the rate of change in abundance estimated from the data (r = 0.018 ± 0.04), which would have required a 3- to 5-times longer study. Synthesis and application: These findings advance the assessment of the Satayah population's intrinsic vulnerability and have three major management applications: (a) the delineation of management units; (b) the identification of key indicators for future impact monitoring and assessment; and (c) realistic estimates of the statistical power for trend detection. Based on our results, we recommend supporting future research, devising site-specific time-area closure plans, and integrating them in a regional scheme. Approaches employed in this case study can inform the management of whale watching industries targeting other data-deficient populations.

Translating Marine Animal Tracking Data into Conservation Policy and Management.

There have been efforts around the globe to track individuals of many marine species and assess their movements and distribution, with the putative goal of supporting their conservation and management. Determining whether, and how, tracking data have been successfully applied to address real-world conservation issues is, however, difficult. Here, we compile a broad range of case studies from diverse marine taxa to show how tracking data have helped inform conservation policy and management, including reductions in fisheries bycatch and vessel strikes, and the design and administration of marine protected areas and important habitats. Using these examples, we highlight pathways through which the past and future investment in collecting animal tracking data might be better used to achieve tangible conservation benefits.

Behavioural responses of spinner dolphins to human interactions.

There is increasing evidence that whale and dolphin watching activities have detrimental effects on targeted cetacean populations. In Egypt, spinner dolphins regularly occur in the resting areas of Samadai, Satayah and Qubbat'Isa reefs. In-water human interactions with dolphins are regulated with a time-area closure system at Samadai, unregulated at Satayah and non-existent at Qubbat'Isa. This provided an ideal experimental setting to advance our understanding of the effects of tourism on a species highly sensitive to disturbances. Our study confirmed that the intensity and duration of interactions, and therefore, dolphin exposure to tourism, differed among the study sites. Compared with the Qubbat'Isa control site, behavioural reactions to boats and swimmers at the two tourism sites suggested that dolphin rest was disrupted, especially around the middle of the day and especially at Satayah, where dolphin tourism is unregulated. Our results indicate also that the dolphin protection measures at Samadai reduce the level of disturbance. We recommend that similar measures be implemented at other dolphin tourism locations, and that no new operations be initiated until the long-term impacts on dolphin populations are better understood. Our experience emphasizes the need to adopt precautionary approaches in research and management of whale and dolphin watching.

Assessing cetacean surveys throughout the Mediterranean Sea: a gap analysis in environmental space.

Heterogeneous data collection in the marine environment has led to large gaps in our knowledge of marine species distributions. To fill these gaps, models calibrated on existing data may be used to predict species distributions in unsampled areas, given that available data are sufficiently representative. Our objective was to evaluate the feasibility of mapping cetacean densities across the entire Mediterranean Sea using models calibrated on available survey data and various environmental covariates. We aggregated 302,481 km of line transect survey effort conducted in the Mediterranean Sea within the past 20 years by many organisations. Survey coverage was highly heterogeneous geographically and seasonally: large data gaps were present in the eastern and southern Mediterranean and in non-summer months. We mapped the extent of interpolation versus extrapolation and the proportion of data nearby in environmental space when models calibrated on existing survey data were used for prediction across the entire Mediterranean Sea. Using model predictions to map cetacean densities in the eastern and southern Mediterranean, characterised by warmer, less productive waters, and more intense eddy activity, would lead to potentially unreliable extrapolations. We stress the need for systematic surveys of cetaceans in these environmentally unique Mediterranean waters, particularly in non-summer months.

Sympathy for the devil: a conservation strategy for devil and manta rays.

BACKGROUND: International trade for luxury products, medicines, and tonics poses a threat to both terrestrial and marine wildlife. The demand for and consumption of gill plates (known as Peng Yu Sai, "Fish Gill of Mobulid Ray") from devil and manta rays (subfamily Mobulinae, collectively referred to as mobulids) poses a significant threat to these marine fishes because of their extremely low productivity. The demand for these gill plates has driven an international trade supplied by largely unmonitored and unregulated catches from target and incidental fisheries around the world. Scientific research, conservation campaigns, and legal protections for devil rays have lagged behind those for manta rays despite similar threats across all mobulids. METHODS: To investigate the difference in attention given to devil rays and manta rays, we examined trends in the scientific literature and updated species distribution maps for all mobulids. Using available information on target and incidental fisheries, and gathering information on fishing and trade regulations (at international, national, and territorial levels), we examined how threats and protective measures overlap with species distribution. We then used a species conservation planning approach to develop the Global Devil and Manta Ray Conservation Strategy, specifying a vision, goals, objectives, and actions to advance the knowledge and protection of both devil and manta rays. RESULTS AND DISCUSSION: Our literature review revealed that there had been nearly 2.5-times more "manta"-titled publications, than "mobula" or "devil ray"-titled publications over the past 4.5 years (January 2012-June 2016). The majority of these recent publications were reports on occurrence of mobulid species. These publications contributed to updated Area of Occupancy and Extent of Occurrence maps which showed expanded distributions for most mobulid species and overlap between the two genera. While several international protections have recently expanded to include all mobulids, there remains a greater number of national, state, and territory-level protections for manta rays compared to devil rays. We hypothesize that there are fewer scientific publications and regulatory protections for devil rays due primarily to perceptions of charisma that favour manta rays. We suggest that the well-established species conservation framework used here offers an objective solution to close this gap. To advance the goals of the conservation strategy we highlight opportunities for parity in protection and suggest solutions to help reduce target and bycatch fisheries.

The Devil We Don't Know: Investigating Habitat and Abundance of Endangered Giant Devil Rays in the North-Western Mediterranean Sea.

The giant devil ray Mobula mobular, the only Mediterranean mobulid, is subject to mortality caused by directed and accidental captures in fisheries throughout the region. Whilst the combination of human impacts, limited range and a low reproductive potential is not inconsistent with its endangered listing, there are insufficient data to enable a quantitative assessment of trends. Without this, it is difficult to assess and prioritise threats and develop effective conservation actions. Using results from aerial surveys conducted between 2009 and 2014 over the Ligurian, Corsican, Sardinian, northern and central Tyrrhenian seas (626,228 km2), this study provides the first quantitative information on giant devil ray abundance and habitat choice in the western Mediterranean. Devil rays were observed in all seasons except winter, with their estimated abundance in the study area peaking in summer. The overall uncorrected mean density in the study area during summer was estimated at 0.0257 individuals km-2 (range: 0.017-0.044), resulting in a total abundance estimate of 6,092 (12.7%CV) individuals at the surface; once corrected for availability bias, this estimate indicates a summer presence of >12,700 devil rays in the study area. Rays were mostly observed alone even if occasionally, larger aggregations up to a maximum of 18 individuals were observed. Although observed throughout the study area, spatial modelling identified their preferred habitat to be over a broad strip connecting the Tuscan Archipelago to Eastern Sardinia, over a wide range of water depths ranging from 10 to 2000m. The observed seasonal changes in giant devil ray distribution in this study, combined with similar evidence from other areas in the Mediterranean, support the hypothesis that the species undertakes latitudinal migrations across the region, taking advantage of highly productive waters in the north during summer, and warmer southern waters during winter.

The role of large marine vertebrates in the assessment of the quality of pelagic marine ecosystems.

The Marine Strategy Framework Directive (MSFD) establishing a framework for community action in the field of marine environmental policy has been developed and is being implemented, with the objective to deliver "Good Environmental Status" by 2020. A pragmatic way forward has been achieved through the development of 11 "qualitative descriptors". In an attempt to identify gaps in MSFD, regarding the data on large marine vertebrates, the SETAC--Italian Branch organised a workshop in Siena (IT). Particular attention was paid to the qualitative descriptors 8 (contaminants and pollution effects) and 10 (marine litter). The specific remit was to discuss the potential use of large marine vertebrates (from large pelagic fish, sea turtles, sea birds and cetaceans) in determining the environmental status of pelagic marine ecosystems. During the workshop it emerged that large pelagic fish may be especially useful for monitoring short- to medium-term changes in pelagic ecosystems, while cetaceans provided a more integrated view over the long-term. A theme that strongly emerged was the broad recognition that biomarkers offer real potential for the determination of good ecological status detecting the "undesirable biological effects" (indicator for descriptor 8).

Active sonar, beaked whales and European regional policy.

Various reviews, resolutions and guidance from international and regional fora have been produced in recent years that acknowledge the significance of marine noise and its potential impacts on cetaceans. Within Europe, ACCOBAMS and ASCOBANS have shown increasing attention to the issue. The literature highlights concerns surrounding the negative impacts of active sonar on beaked whales in particular, where concerns primarily relate to the use of mid-frequency active sonar (1-10kHz), as used particularly in military exercises. The authors review the efforts that European regional policies have undertaken to acknowledge and manage possible negative impacts of active sonar and how these might assist the transition from scientific research to policy implementation, including effective management and mitigation measures at a national level.

Discerning between recurrent gene flow and recent divergence under a finite-site mutation model applied to North Atlantic and Mediterranean Sea fin whale (Balaenoptera physalus) populations.

Genetic divergence among conspecific subpopulations can be due to either low recurrent gene flow or recent divergence and no gene flow. Here we present a modification of an earlier method developed by Nielsen and Wakeley (2001), which accommodates a finite-site mutation model, to assess which of the two models of divergence is most likely given the observed data. We apply the method to nucleotide sequence data collected from the variable part of the mitochondrial control region in fin whales (Balaenoptera physalus) from the Atlantic coast off Spain and the Mediterranean Sea. Our estimations strongly favor a model of recurrent gene flow over a model of recent divergence and zero gene flow. We estimated the migration rate at two females per generation. While the estimated rate is high by evolutionary standards, exchange rates of this order of magnitude is low from an ecological and conservation perspective and entirely consistent with the current paucity of fin whale sightings in the Strait of Gibraltar today. Intensive commercial shore-based whaling during the 1920s removed substantial numbers of fin whales in the Strait of Gibraltar and this local population has seemingly since failed to recover.

The rete mirabile cranica in the genus Mobula: A comparative study.

Devil rays (Mobulidae) have large brains that rest in a voluminous chondrocranium almost completely filled by a rete mirabile cranica (RMC). The RMC is a massive arterial network grossly divisible into a "caudal RMC" supplying blood to the brain, and an expanded, more complex "precerebral RMC" nested within the large cranial cavity rostral to the telencephalon. Both the caudal and precerebral retia originate from the posterior portion of the profundae cerebri arteries, which lie ventral to the brain and form the sides of a vascular triangle, the base of which is anterior and formed by the joining of the internal carotids; the vertex is posterior and median, corresponding to the anterior extreme of the spinalis impar artery. Vessels of the caudal RMC branch posteriorly from the profundae cerebri and course over and into the brain. Vessels branching more anteriorly course rostrally to form the precerebral RMC, which takes the shape of the cranial cavity and completely envelops the olfactory peduncles. Large retial arteries (1-mm diameter) branch and taper to about 50-150 µm, forming a system of small arteries or arterioles. Many give rise to a mesh of tertiary vessels (precapillary arterioles or capillaries, ca. 20-50 µm in diameter), which, along with arterioles, are embedded in the adventitia of these arteries, with which they communicate by numerous anastomoses. Although the function of the RMC remains enigmatic, its complexity and fine structure are suggestive, and hypotheses of its role are discussed.