Biology subjects

Dulvy, N. K.

Publications and source records attributed to Dulvy, N. K..

At least 19 recordsLinked to original sources

bioRxiv2026

The allometry of spiracles and gill slits: a window into the respiratory capacity of rays

Metabolic rate governs the pace of life through the allocation and expenditure of energy, yet metabolic rate data are unavailable for most species. External morphological traits, such as gill slits, have been used to infer respiratory physiology and metabolism in sharks, yet, whether that pattern is generalizable across rays is unknown. In rays (Batoidea), spiracle length seems adaptive to oxygen uptake capacity, environmental oxygen availability, and activity level. Thus, we evaluate the allometry of external respiratory morphology (spiracles and gill slits) in rays using 550 museum specimens representing 88 species. We test whether spiracle length and gill slit height grow isometrically with body size (total length or disc width) within and across species. Overall, we find spiracles and gill slits are morphologically diverse, varying widely in shape within and between families. Spiracle length and gill slit height scale isometrically and are a consistent proportion of body size, despite such high morphological variability. While that proportion is consistent through ontogeny, each species proportion differs (e.g. gill slit height ranges from 0.93% of total length in Spotted Legskate to 2.93% in Pacific Electric Ray). Of the three swimming styles, pectoral oscillating species (Mobulid and Eagle Rays) may have steeper scaling of spiracle length with gill slit height - consistent with greater respiratory capacity in species with more active lifestyles. Our findings are consistent with literature hypothesizing external respiratory morphology (spiracles and gill slits) is tightly related to metabolic rate and activity level, and demonstrate the value of natural history collections in ecological research. Importantly, the isometry of both respiratory traits means that a single measure of any individual, irrespective of size, will be representative of the species thus providing a basis for expanding our understanding of metabolic morphology, enabling future work on life history, extinction risk, and ecological function.

ecology↗

bioRxiv2026

From wings to tails: the aspect ratio of propulsive surfaces as a general proxy for vertebrate dispersal potential

Dispersal shapes many fundamental processes, however, comprehensive measures of dispersal are unavailable for most taxa, limiting our ability to evaluate ecological theory at broad scales. Existing tracking data are often taxonomically and geographically biased, highlighting the need for alternative trait-based approaches to infer dispersal potential. Here, we test whether the aspect ratio of propulsive surfaces provides a general morphological basis for inferring dispersal potential. We show that caudal fin shape is a morphological indicator of dispersal potential in sharks, as it predicts swimming speed and geographic range size. Across 452 (82%) shark species, we find no latitudinal gradient in dispersal potential, contrasting with patterns observed in birds. Instead, dispersal potential is structured by ecological specialization, with no direct effect of environmental temperature on caudal fin shape. We find high dispersal potential is associated with pelagic habitats and metabolically relevant traits, including body size and oxygen uptake capacity. Because morphology can be measured from museum specimens and illustrations, this approach offers opportunities to compare dispersal potential across air and water dwelling vertebrates.

ecology↗

bioRxiv2026

Sharks, Rays, & MPAs: Evaluating protected area coverage in national waters across species ranges

Global conservation agreements emphasize protected area coverage targets, such as the Kunming-Montreal Global Biodiversity Frameworks 30x30 target, yet their effectiveness in safeguarding biodiversity remains uncertain. We measure the intersection between marine protected area (MPAs) coverage and the distribution of sharks and rays. Using global range maps and MPA boundaries within national Exclusive Economic Zones, we calculate the percent of species ranges within MPAs, focusing on no-take areas. We reveal significant shortfalls in species-level protection. Within national waters, no Critically Endangered species has more than 5% of its range in no-take MPAs, and 79% of threatened species have less than 1%. We also find the WDPA contains major gaps in take-status reporting, only one third of countries (34%) report take-status of any MPAs to the WDPA, further limiting estimates of meaningful protection. These results highlight the implementation gap between global coverage targets and biodiversity outcomes, reinforcing the need for species-focused protection.

ecology↗

bioRxiv2024

Ecological lifestyle and gill slit height across sharks

Morphology that is linked to metabolic rate - metabolic morphology - provides broad comparative insights into the physiological performance and ecological function of species. However, some metabolic morphological traits, such as gill surface area, require costly and lethal sampling. Measurements from anatomically-accurate drawings, such as those in field guides, offer the opportunity to understand physiological and ecological relationships without the need for physical, lethal sampling. Here, we assess the relationship between the metabolic physiology and ecology of nearly all extant sharks. Specifically, we examine the relationship between gill slit height and each of the three traits that comprise ecological lifestyle: activity, maximum size, and depth. We find that gill slit heights are positively related to activity (measured by the aspect ratio of the caudal fin) and maximum size but negatively related to depth. We also show that gill slit height is best explained by the suite of ecological lifestyle traits rather than any single trait. These results suggest that more active, larger, and shallower species have higher metabolic demands and that these greater metabolic demands can be estimated from external morphological and ecological traits. Our work demonstrates that meaningful ecophysiological relationships can be revealed through measurable metabolic morphological traits from anatomically-accurate drawings.

ecology↗

bioRxiv2024

Offspring size resolves a latitudinal population growth rate paradox in rays and skates

The maximum intrinsic population growth rate, rmax, is a key determinant of the limits for sustainable fishing and is increasingly used in risk assessments. Metabolic theory suggests that rmax scales with adult body size, temperature (and hence depth) such that smaller-bodied species and those in warmer, shallower waters have greater rmax and, therefore, will be less sensitive to overexploitation. However, warm shallow-water tropical rays have lower rmax than cold deep-water temperate skates contra to the metabolic expectation. To resolve this paradox, we build from recent advances that suggest that offspring size may be key to understanding rmax. Specifically, we examine how rmax is related to adult size, offspring size, temperature, and depth across 85 ray and skate species. Our results show that offspring size mediates relationships between rmax, adult body size, temperature, and depth. Indeed, tropical rays had, on average, larger offspring and lower rmax compared to the temperate skates, despite living in warmer, shallower waters. Thus, despite the expectation from theory that tropical species should have faster life histories compared to temperate species, our result explains why tropical rays are actually less resilient. It remains unclear as to why tropical rays have such large offspring but we speculate that this is due to greater predation risk in shallow tropical waters driving the additional maternal investment in offspring size via the evolution of viviparity and matrotrophy. Our work highlights the complex relationships among life histories and the environment and may help explain global biogeographic patterns of intrinsic sensitivity to overexploitation.

ecology↗

bioRxiv2022

Guitarfishes are plucked: undermanaged in global fisheries despite declining populations and high volume of unreported international trade

Some sharks and rays are subject to fisheries catch and international trade regulations. However, the Guitarfishes (family Rhinobatidae) are a highly threatened group with minimal regulations. Substantial underreporting of catch and broad commodity codes for traded products are masking the true volume of Guitarfishes included in international trade. Here, we collate international trade information for Guitarfishes that have not readily been documented in trade, possibly due to poor resolution of molecular genetic markers, to begin to document the extent of trade. We assess the shortfall in fisheries management (M-Risk) for all species of Guitarfish based on 99 assessments across 28 countries. Globally, Guitarfishes are inadequately managed, with an average M-Risk of 45% of an ideal score, resulting in 76% of species being threatened globally. The high and unregulated catch and trade volume, paired with the management shortfalls, require global integrated improvement in fisheries management, supported by regulating international trade to sustainable levels.

ecology↗

bioRxiv2022

Gills, growth, and activity across fishes

Life history theory argues that an organisms maximum size and its corresponding growth rate have evolved to maximize lifetime reproductive output. The Gill Oxygen Limitation Theory suggests that in aquatic organisms, maximum size is instead constrained by the surface area of the gills, the primary site of gas exchange with the environment. A central prediction of this theory is a tight relationship among maximum size, growth, and gill surface area. Yet since this idea was first tested in the early 1980s, data availability has increased and analytical methods have advanced considerably. Here, we revisit this relationship with new data and a novel phylogenetic Bayesian multilevel modeling framework that allows us to understand how individual variation in gill surface area confers relationships of maximum size, growth, and gills across species. Specifically, we bring gill surface area into an allometric context and examine whether the gill surface area for a given body size (intercept) and the rate at which gill surface changes with size (slope), for a given species, explains growth performance -- an index integrating the life history tradeoff between growth and maximum size -- across fish species. Additionally, we assess whether variation in von Bertalanffy growth coefficients across species can be explained by gill surface area. Finally, we explore whether additional factors - here, activity and evolutionary history -- explain variation in maximum size and growth across species. Overall, we find that although a positive relationship exists among maximum size, growth, and gill surface area across fishes, it is weak. Additionally, gill surface area does not explain much variation in growth coefficients across species, especially for those that reach the same maximum size. However, we find that the activity level of a fish explains more variation in maximum size and growth across species compared to gill surface area. Our results support the idea that in fishes, growth and maximum size are not simply related to gill surface area, and that other covariates--both tractable (e.g., activity, metabolic rate, temperature) and less tractable (e.g., predation risk, resource availability, and variation)--appear to explain more variation in life history traits across species.

ecology↗

bioRxiv2022

Fear and foraging in the ecosystem size spectrum generate diversity in fish life histories

Understanding how growth and reproduction will adapt to changing environmental conditions is a fundamental question in evolutionary ecology, but predicting the responses of specific taxa is challenging. Analyses of the physiological effects of climate change upon life history evolution rarely consider alternative hypothesized mechanisms, such as size-dependent foraging and the risk of predation, simultaneously shaping optimal growth patterns. To test for interactions between these mechanisms, we embedded a state-dependent energetic model in an ecosystem size-spectrum to ask whether prey availability (foraging) and risk of predation experienced by individual fish can explain observed diversity in life histories of fishes. We found that asymptotic growth emerged from size-based foraging and reproductive and mortality patterns in the context of ecosystem food web interactions. While more productive ecosystems led to larger body sizes, the effects of temperature on metabolic costs had only small effects on size. To validate our model, we ran it for abiotic scenarios corresponding to the ecological lifestyles of three tuna species, considering environments that included seasonal variation in temperature. We successfully predicted realistic patterns of growth, reproduction, and mortality of all three tuna species. We found that individuals grew larger when environmental conditions varied seasonally and spawning was restricted to part of the year (corresponding to their migration from temperate to tropical waters). Growing larger was advantageous because foraging and spawning opportunities were seasonally constrained. This mechanism could explain the evolution of gigantism in temperate tunas. Our approach addresses variation in food availability and individual risk as well as metabolic processes and offers a promising approach to understand fish life-history responses to changing ocean conditions.

ecology↗

bioRxiv2022

High overexploitation risk and management shortfall in highly traded requiem sharks

Most of the international trade in fins (and likely meat too) is derived from requiem sharks (family Carcharhinidae), yet trade in only two of the 56 species is currently regulated. Here, we quantify catch, trade, and the shortfall in national and regional fisheries management (M-Risk) for all 56 requiem shark species based on 831 assessments across 30 countries and four Regional Fisheries Management Organisations (RFMOs). Requiem sharks comprise over half (60%) of the annual reported global chondrichthyan catch with most species (86%) identified in the international fin trade. Requiem sharks are inadequately managed by fisheries, with an average M-Risk of half (50%) of an ideal score, consequently 70% of species are threatened globally. The high catch and trade volume and shortfall in management of these iconic species requires a global integrated improvement in fisheries management, supported by regulating international trade to sustainable levels.

ecology↗

bioRxiv2022

M-Risk: A framework for assessing global fisheries management efficacy of sharks, rays, and chimaeras

Fisheries management is essential to guarantee sustainable capture of target species and avoid undesirable declines of incidentally captured species. A key challenge is halting and reversing declines of shark and ray species, and specifically assessing the degree to which management is sufficient to avoid declines in relatively data-poor fisheries. While ecological risk analyses focus on intrinsic productivity and extrinsic susceptibility, one would ideally consider the influence of fisheries management. Currently, there is no single management evaluation that can be applied to a combination of fishery types at the scale of individual country or Regional Fisheries Management Organisations (RFMOs). Here, we outline a management risk (M-Risk) framework for sharks, rays, and chimaeras used to evaluate species risk to overfishing resulting from ineffective management. We illustrate our approach with application to one country (Ecuador) and RFMO (Inter-American Tropical Tuna Commission) and illustrate the variation in scores among species. We found that while both management units assessed had similar overall scores, the scores for individual attributes varied. Ecuador scored higher in reporting-related attributes, while the IATTC scored higher in attributes related to data collection and use. We evaluated whether management of individual species was sufficient for their relative sensitivity by combining the management risk score for each species with their intrinsic sensitivity to determine a final M-Risk score. This framework can be applied to determine which species face the greatest risk of overfishing and be used by fisheries managers to identify effective management policies by replicating regulations from countries with lower risk scores.

ecology↗

bioRxiv2022

Extinction risk, reconstructed catches, and management of chondrichthyan fishes in the Western Central Atlantic Ocean

Chondrichthyan fishes are among the most threatened vertebrates on the planet because many species have slow life histories that are outpaced by intense fishing. The Western Central Atlantic Ocean, which includes the greater Caribbean, is a hotspot of chondrichthyan biodiversity and abundance, but is historically characterized by extensive shark and ray fisheries and a lack of sufficient data for effective management and conservation. To inform future research and management decisions, we analyzed patterns in chondrichthyan extinction risk, reconstructed catches, and regulations in this region. We summarized the extinction risk of 180 sharks, rays, and chimaeras using contemporary IUCN Red List assessments and found that over one-third (35.6%) were assessed as Vulnerable, Endangered, or Critically Endangered largely due to fishing. Reconstructed catches from 1950 to 2016 reached their peak in 1992, then declined by 40.2% through the end of the series. The United States, Venezuela, and Mexico were responsible for most catches and hosted large proportions of the regional distributions of threatened species; these countries therefore held the greatest responsibility for chondrichthyan management. The abundance and resolution of fisheries landings data were poor in much of the region, and national-level regulations varied widely across jurisdictions. Deepwater fisheries represent an emerging threat, although many deepwater chondrichthyans currently find refuge beyond the depths of most fisheries. Regional collaboration as well as effective and enforceable management informed by more complete fisheries data, particularly from small-scale fisheries, are required to protect and recover threatened species and ensure sustainable fisheries.

ecology↗

bioRxiv2022

Maternal investment evolves with larger body size and higher diversification rate in sharks and rays

Across vertebrates, live-bearing has evolved at least 150 times from ancestral egg-laying into a diverse array of forms and degrees of prepartum maternal investment.1,2 A key question is how this reproductive diversity arose and whether reproductive diversification underlies species diversification?3-11 To test these questions, we evaluate the most basal jawed vertebrates, sharks, rays, chimaeras of Class Chondrichthyans, which have one of the greatest ranges of reproductive and ecological diversity among vertebrates.2,12 We reconstructed the sequence of reproductive mode evolution across a time-calibrated molecular phylogeny of 610 chondrichthyans.13 We find egg-laying is ancestral, and live-bearing evolved at least seven times. Matrotrophy (i.e. maternal contributions beyond the yolk) evolved at least 15 times, with evidence of one reversal. In sharks, transitions to live-bearing and matrotrophy are more prevalent in larger-bodied species in the tropics. Further, the evolution of live-bearing is associated with a near-doubling of the diversification rate, but, there is only a small increase in diversification associated with the appearance of matrotrophy and increased rates of speciation are associated with the colonization of novel habitats, contrary to what has been demonstrated in teleosts.3,4 This highlights a potential key difference between chondrichthyans and other fishes, specifically a slower rate of reproductive isolation following speciation, suggesting different rate-limiting mechanisms for diversification between these clades.14 The chondrichthyan diversification and radiation, particularly throughout the shallow tropical shelf seas and oceanic pelagic habitats, appears to be associated with the evolution of live-bearing and the proliferation of a wide range of maternal investment in developing offspring.

evolutionary biology↗

bioRxiv2021

Post-2020 Kunming 30% target can easily protect all endemic sharks and rays in the Western Indian Ocean and more

Sharks and rays are possibly the most threatened Class of marine fishes and their declines can be halted if protected areas are optimised to benefit these species. We identify spatial priorities for all 63 endemic sharks and rays in the marine biodiversity hotspot, the Western Indian Ocean (WIO). Collectively, while the WIO nations currently surpass the 10% Aichi ocean protection target, this amounts to a dismal protection of only 1.57% of each species distribution range. We show that the entire ranges of all endemics can be achieved by protecting 11% of EEZs of WIO nations, well within reach of the new 30% of oceans by 2030 target. Regional management bodies exist, which if taken advantage of to implement shark and ray management, provide opportunities to implement more efficient management across the region. We recommend key management actions to implement and explicit incentivisation of international cooperation in the post-2020 biodiversity framework. Science for SocietyThe past decade has seen massive growth in the establishment of marine protected areas (MPAs), driven by the Aichi biodiversity target of protecting 10% of all ocean areas. This expansion of MPAs, however, has largely occurred in areas residual to extractive uses, often coinciding with less threatened areas of lower conservation value. This coming decade will see a further push to ensure 30% of the oceans are protected by 2030. It is important to understand how existing and future MPAs should be placed to benefit threatened biodiversity. Currently this is unclear for sharks and rays, comprising a species group that is the most evolutionarily distinct vertebrate radiation in the world and also one of the most threatened. We identify both regional and national conservation priorities for expanding marine protected areas to benefit all 63 endemic sharks and rays occurring in the Western Indian Ocean region. We find that the region has already exceeded the 10% ocean protection target, but this amounts to an average of only 1.57% protection of the distribution ranges of these species. We show that protecting the top 10% priority sites will conserve almost half of the geographic range of each species yet require only 1.16% of the total EEZ - a tiny fraction of the 30% by 2030 target. We also show that regional collaboration among all nations can result in more spatially efficient conservation priorities. We recommend that the post-2020 biodiversity framework needs to explicitly incentivise regional cooperation between nations to efficiently achieve urgent targets and maximise benefits to biodiversity.

ecology↗

bioRxiv2021

Body mass, temperature, and depth shape the maximum intrinsic rate of population increase in sharks and rays

An important challenge in ecology is to understand variation in species maximum intrinsic rate of population increase, rmax, not least because rmax underpins our understanding of the limits of fishing, recovery potential, and ultimately extinction risk. Across many vertebrates, terrestrial and aquatic, body mass and environmental temperature across important correlates rmax across species. In sharks and rays, specifically, rmax is known be lower in larger species, but also in deep-sea ones. We use an information-theoretic approach that accounts for phylogenetic relatedness to evaluate the relative importance of body mass, temperature and depth on rmax. We show that both temperature and depth have separate effects on shark and ray rmax estimates, such that species living in deeper waters have lower rmax. Furthermore, temperature also correlates with changes in the mass scaling coefficient, suggesting that as body size increases, decreases in rmax are much steeper for species in warmer waters. These findings suggest that there (as-yet understood) depth-related processes that limit the maximum rate at which populations can grow in deep sea sharks and rays. While the deep ocean is associated with colder temperatures, other factors that are independent of temperature, such as food availability and physiological constraints, may influence the low rmax observed in deep sea sharks and rays. Our study lays the foundation for predicting the intrinsic limit of fishing, recovery potential, and extinction risk species based on easily accessible environmental information such as temperature and depth, particularly for data-poor species.

ecology↗

bioRxiv2021

Fishing for survival: importance of shark fisheries for the livelihoods of coastal communities in Western Ghana

Small-scale shark fisheries support the livelihoods of a large number of coastal communities in developing countries. Shark meat comprises a cheap source of protein and is traded locally in many parts in developing countries, while the skins, oil, and fins are exported to the international market. This study addresses a gap in literature regarding the importance of elasmobranchs to key shark-fishing communities and the degree to which trade in shark products (meat and fins) vary in time and among fishing communities in Ghana. We interviewed 85 fishers and traders involved in shark fisheries in Axim, Dixcove, and Shama communities using semi-structured questionnaires. Fishing was the primary source of income and accounted for 58.5% of the total household income of respondents. Other important economic activities were fish processing (16.0%), fish retailing (13.3%), and small businesses (2.5%). One-third and often two-thirds of respondents generated between 80-100% of their income from shark fisheries: Axim (65%), Dixcove (68%), and Shama (35%). Shark meat consumption was common among fishers and traders and represents a substantial source of protein in the diet of the study communities. Hammerhead sharks (Sphyrna spp) and Bull Shark (Carcharhinus leucas) have the most valuable fins and meat. Further, 75% and 95% of fishers and traders, respectively, see fishing and trading of shark meat as their last safety-net and, therefore, tend to be satisfied with their jobs. Non-fishing related livelihood streams including small businesses and transportation were the major fallback activities both fishers and traders preferred to rely on if there is a ban on the exploitation of sharks in Ghana. Overexploitation of these species will compromise food ecosystem functionality and security. Thus, any shark management strategy needs to urgently restraint mortality to sustainable levels, which, in the short-term, must take into consideration the preferred livelihood fallback options outlined by fishers and traders, and implement them to ensure the long-term benefits of the intervention.

zoology↗

bioRxiv2021

Local ecological knowledge, catch characteristics and evidence of elasmobranch depletions in Western Ghana

Local Ecological Knowledge has the potential to improve fishery management by providing new data on the fishing efforts, behavior, and abundance trends of fish and other aquatic animals. Here, we relied on local knowledge of fishers to investigate ecological factors that affect elasmobranch fishers" operations and the changes in stock status of sharks and rays from 1980 to 2020 in five coastal communities in Ghana. Data were gathered from fishers using participant observation, interviews, focus group discussions, and participatory rural appraisal techniques. The results revealed fisher"s understanding of six main ecological variables, which are mostly applied to enhance their fishing operations: season and weather conditions, lunar phase, bait type, presence of seabirds and fish movement, color of seawater, and sea current. These ecological features have been applied over the years to enhance fishing operations as well as maximize fisher catch. Fishers reported a profound decline in shark and ray catch from 1980 to 2020 and attributed the decline in size, number, and composition of their catch to overfishing and Illegal, Unreported and Unregulated (IUU) fishing operations. In general, most shark and ray species were abundant in 1980 but have been severely depleted as of 2020, with the exception of Blue Shark (Prionace glauca) and Devil rays (Mobula spp), which were reported to be common by the interviewed fishers. The first species depleted were the Thresher sharks (Alopiidae), Tiger Shark (Galeocerdo cuvier), Blackchin Guitarfish (Glaucostegus cemiculus), and Lemon Shark (Negaprion brevirostris), which were depleted early in the 2000s. The next depletions of Hammerhead sharks (Sphyrnidae), Bull Shark (Carcharhinus leucas), Sand Tiger Shark (Carcharias taurus), Stingrays (Fontitrygon spp), and Spineback Guitarfish (Rhinobatos irvinei) occurred in the 2010s. We found Local Ecological Knowledge of fishers to be surprisingly consistent with scholarly knowledge and call for their inclusion in research, decision-making and management interventions by biologists and policy makers.

zoology↗

bioRxiv2020

The metabolic pace of life histories across fishes

All life acquires energy through metabolic processes and that energy is subsequently allocated to life-sustaining functions such as survival, growth, and reproduction. Thus, it has long been assumed that metabolic rate is related to the life history of an organism. Indeed, metabolic rate is commonly believed to set the pace of life by determining where an organism is situated along a fast-slow life history continuum. However, empirical evidence of a relationship between metabolic rate and life histories is lacking, especially for ectothermic organisms. Here, we ask whether three life history traits - maximum body mass, generation length, and growth performance - explain variation in resting metabolic rate (RMR) across fishes. We found that growth performance, which accounts for the trade-off between growth rate and maximum body size, explained variation in RMR, yet maximum body mass and generation length did not. Our results suggest that measures of life history that encompass trade-offs between life history traits, rather than traits in isolation, explain variation in RMR across fishes. Ultimately, understanding the relationship between metabolic rate and life history is crucial to metabolic ecology and has the potential to improve prediction of the ecological risk of data-poor species.

ecology↗

bioRxiv2019

Predicting the conservation status of Europe’s Data Deficient sharks and rays

Shark and ray biodiversity is threatened primarily by overfishing and the globalisation of trade, and Europe has been one of the most documented heavily fished regions for a relatively long time. Yet, we have little idea of the conservation status of the hundreds of Data Deficient shark and ray species. It is important to derive some insight into the status of these species, both to understand global extinction rates and also to ensure that any threatened Data Deficient species are not overlooked in conservation planning. Here, we developed a biological and ecological trait model to predict the categorical conservation status of 26 Northeast Atlantic and 15 Mediterranean Sea Data Deficient sharks and rays. We first developed an explanatory model based on all species evaluated on the International Union for Conservation of Nature (IUCN) Red List of Threatened SpeciesTM, using maximum body size, median depth (as a proxy for fisheries exposure), and reproductive mode, and then predicted the status of all Data Deficient species. Almost half of Northeast Atlantic (46%, n=12 of 26), and two-thirds of Mediterranean (67%, n=10 of 15) Data Deficient species are predicted to be in one of the three IUCN threatened categories. Northeast Atlantic Data Deficient species are predicted to be 1.2 times more threatened than evaluated species (38%, n=36 of 94), whereas threat levels in the Mediterranean Sea are relative for each (66%, n=38 of 58). This case study is intended for extrapolation to the global shark and ray dataset upon completion of the global IUCN Red List assessment. Trait-based, categorical prediction of conservation status is a cost-effective approach towards incorporating Data Deficient species into (i) estimates of lineage-wide extinction rates, (ii) revised protected species lists, and (iii) Red List Indices, thus preventing poorly known species from reaching extinction unnoticed.

ecology↗