Red List Assessments Research Articles

The current status of Henckelia peduncularis (Gesneriaceae): Taxonomy, typification, distribution and IUCN Red List assessment

The long lost Henckelia peduncularis (Gesneriaceae), was hitherto known from its type specimens collected from Burma, in 1926. Recently described Henckelia dasii from Arunachal Pradesh, India; revealed substantial similarities with the aforementioned Burmese element. Morphological analyses based on the type specimens of both the names revealed H. dasii is appropriate to be reduced as a heterotypic synonym of H. peduncularis. The present article also deals with the Red List assessment of H. peduncularis based on IUCN criteria and lectotype designation for the name Chirita peduncularis B.L. Burtt.

Rediscovery of rare steno-endemic Impatiens violoides Edgew. ex Hook.f. (Balsaminaceae) from Western Himalaya, after 179 years of type collection

Impatiens violoides Edgew. ex Hook.f. (Balsaminaceae) is a little known steno-endemic spurless balsam species that was known only from a single type collection by Edgeworth in 1844. It is rediscovered after a gap of 179 years from its type locality in Shimla district, Himachal Pradesh, Western Himalaya. Augmented and detailed morphological description based on observations of living material is given along with global distribution; information on habitat and associated species, floral morphology photographs and IUCN red list assessment are also provided for the first time.

Dealing with a Batrachochytrium salamandrivorans outbreak in Italy: Are conservationists prepared?

The recently updated IUCN Red List assessment indicates endemic amphibians in southern Europe are threatened by imminent arrival of the invasive pathogen Batrachochytrium salamandrivorans (Bsal). Several efforts have aimed to raise awareness of this threat, set up early warning networks, and explore management strategies. Should a Bsal outbreak be detected, rapid and effective actions are necessary to ensure containment and eradication. We surveyed a sample of salamander specialist researchers and conservationists in Italy to gauge the level of preparedness. Out of 35 respondents, the majority expressed incomplete awareness of the Bsal threat and of what management actions might be available, and were unsure or pessimistic about available resources and the necessary decision processes. We recommend continuing efforts on raising awareness of the Bsal threat, adding more practical measures such as clarifying available actions and stakeholders, running local stress tests and facilitating communications and procedures to be followed in an emergency.

Contributions of the IUCN Red List of Ecosystems to risk-based design and management of protected and conserved areas in Africa.

Protected and conserved areas (PCAs) are key ecosystem management tools for conserving biodiversity and sustaining ecosystem services and social cobenefits. As countries adopt a 30% target for protection of land and sea under the Global Biodiversity Framework of the United Nations Convention on Biological Diversity, a critical question emerging is, which 30%? A risk-based answer to this question is that the 30% that returns the greatest reductions in risks of species extinction and ecosystem collapse should be protected. The International Union for Conservation of Nature (IUCN) Red List protocols provide practical methods for assessing these risks. All species, including humans, depend on the integrity of ecosystems for their well-being and survival. Africa is strategically important for ecosystem management due to convergence of high ecosystem diversity, intense pressures, and high levels of human dependency on nature. We reviewed the outcomes (e.g., applications of ecosystem red-list assessments to protected-area design, conservation planning, and management) of a symposium at the inaugural African Protected Areas Congress convened to discuss roles of the IUCN Red List of Ecosystems in the design and management of PCAs. Recent progress was made in ecosystem assessment, with 920 ecosystem types assessed against the IUCN Red List criteria across 21 countries. Although these ecosystems spanned a diversity of environments across the continent, the greatest thematic gaps were for freshwater, marine, and subterranean realms, and large geographic gaps existed in North Africa and parts of West and East Africa. Assessment projects were implemented by a diverse community of government agencies, nongovernmental organizations, and researchers. The assessments have influenced policy and management by informing extensions to and management of formal protected area networks supporting decision-making for sustainable development, and informing ecosystem conservation and threat abatement within boundaries of PCAs and in surrounding landscapes and seascapes. We recommend further integration of risk assessments in environmental policy and enhanced investment in ecosystem red-list assessment to fill current gaps.

Going back for the future: Incorporating Pleistocene fossil records of saiga antelope into habitat suitability models

AbstractAimMany species have suffered anthropogenic range contraction and no longer occupy all available suitable environmental conditions. This is particularly problematic for the construction of habitat suitability models (HSMs), which assume that a species' contemporary range reflects its full species–environment relationship. HSMs therefore risk underestimating suitable environment areas, and misinforming conservation decisions. Incorporating historic (centuries‐old) records partly reduces this bias, but even these records are also subject to human disturbance. We incorporated fossil records of the critically endangered saiga antelope (Saiga tatarica, L., 1776), alongside historic and current records, into current and future habitat suitability models. Saiga has experienced drastic range contraction and may have a truncated species–environment relationship. The results allowed us to test whether its current habitat provides optimal environmental conditions, or whether saiga should be considered a refugee species.LocationNorthern Hemisphere.TaxonSaiga tatarica (Bovidae, Artiodactyla).MethodsWe collated historic and fossil saiga occurrence records from published literature, museum archives and global databases. Modern occurrence records were obtained from the International Union for Conservation of Nature Red List assessment. Four bioclimatic variables were downloaded from Worldclim.org. HSMs were generated through Maxent, using the maxnet package in R. Three HSMs were developed: present only, present historic and present fossil. Each of these models was projected onto current and two future (2070) climate change scenarios.ResultsSaiga fossil records increased the predicted suitable environment area by 783% and 1416% for current and future climate projections respectively. Our results suggest the saiga is not a refugee species but occupies only a portion of its potential environmental niche. The saiga's contemporary range is predicted environmentally suitable throughout all models and projections, and therefore in situ conservation management is recommended.Main ConclusionsThis study highlights the importance of incorporating fossil records into HSMs to better understand species–environment relationships and develop more robust conservation strategies for appropriate endangered species.

Extinction risk predictions for the world's flowering plants to support their conservation.

More than 70% of all vascular plants lack conservation status assessments. We aimed to address this shortfall in knowledge of species extinction risk by using the World Checklist of Vascular Plants to generate the first comprehensive set of predictions for a large clade: angiosperms (flowering plants, c. 330 000 species). We used Bayesian Additive Regression Trees (BART) to predict the extinction risk of all angiosperms using predictors relating to range size, human footprint, climate, and evolutionary history and applied a novel approach to estimate uncertainty of individual species-level predictions. From our model predictions, we estimate 45.1% of angiosperm species are potentially threatened with a lower bound of 44.5% and upper bound of 45.7%. Our species-level predictions, with associated uncertainty estimates, do not replace full global, or regional Red List assessments, but can be used to prioritise predicted threatened species for full Red List assessment and fast-track predicted non-threatened species for Least Concern assessments. Our predictions and uncertainty estimates can also guide fieldwork, inform systematic conservation planning and support global plant conservation efforts and targets.

Advances in life-history knowledge for 35 seahorse species from community science.

Marine community science presents an important route to gather valuable scientific information while also influencing local management and policy, thus contributing to marine conservation efforts. Because seahorses are cryptic but charismatic species, they are good candidates for engaging diverse people to help overcome the many gaps in biological knowledge. We have synthesized information contributed to the community science project iSeahorse from October 2013 to April 2022 for 35 of 46 known seahorse species. We then compared the obtained results with information in existing IUCN Red List assessments, executed from 2014 to 2017, to explore the potential of iSeahorse in expanding seahorse knowledge. Our results show updated geographic ranges for 7 seahorse species, new habitats described for 24 species, observations outside the previously recorded depth range for 14 species, and new information on sex ratio for 15 species and on pregnancy seasonality for 11 species. As one example of the power of iSeahorse, contributed observations on Coleman's pygmy seahorse (Hippocampus colemani) indicated that its geographic range is thousands of square kilometers larger, its habitat more diverse, and its depth range shallower than previously known. It is clear that iSeahorse is expanding knowledge on seahorses to a level that will help improve IUCN Red List assessments. The power of community science for marine conservation in general needs to be fully explored.

Distribution and conservation status of Scutellaria rupestris subsp. cephalonica (Rech.f.) Greuter & Burdet

Abstract Scutellaria rupestris subsp. cephalonica (Rech.f.) Greuter & Burdet (Lamiaceae) is a perennial herb endemic to Mounts Ainos and Roudi on the island of Cephalonia. Until now, information about the taxon’s distribution has been sketchy: two fairly localized populations on Mt. Ainos have been reported, one of them extinct, and two on Mt. Roudi, without specifics. Because we thought that the taxon is much more common, we designed a survey along contours encircling the two peaks totaling 80 km. We recorded 112 locations of the taxon. We found that S. rupestris subsp. cephalonica prefers sunny clearings within fir forest as well as crevices among limestone rock on somewhat flat terrain. On Mt. Roudi, the taxon grows above 800 m, and is rather uncommon. On Mt. Ainos, the taxon is quite common above 1100 m; below that altitude it has not been confirmed. The findings were more abundant on the NE slope of Mt. Ainos which is wetter and possibly cooler than the SW slope due to being shaded and more forested, less eroded, and with a deep organic layer. The main threat to the survival of the taxon is illegal grazing. The proposed Red List assessment according to IUCN is EN B1ab(iii)+2ab(iii).

Coupling state‐of‐the‐art modelling tools for better informed Red List assessments of marine fishes

Abstract In the face of biodiversity loss worldwide, it is paramount to quantify species' extinction risk to guide conservation efforts. The International Union for the Conservation of Nature (IUCN)'s Red List is considered the global standard for evaluating extinction risks. IUCN criteria also inform national extinction risk assessments. Bayesian models, including the state‐of‐the‐art JARA (‘Just Another Red List Assessment’) tool, deliver probabilistic statements about species falling into extinction risk categories, thereby enabling characterisation and communication of uncertainty in extinction risk assessments. We coupled the state‐of‐the‐art VAST (‘Vector Autoregressive Spatio‐Temporal’) modelling tool and JARA, for better informed Red List assessments of marine fishes. In this framework, VAST is fitted to scientific survey catch rate data to provide indices to JARA whose uncertainty is propagated to JARA outcomes suggesting extinction risk categories (under the population reduction criterion). In addition, VAST delivers a valuable habitat assessment to better understand what may be driving extinction risk in the study region. Here, we demonstrate the coupled VAST‐JARA modelling framework by applying it to five contrasting North Sea species, with or without a quantitative stock assessment and with different conservation statuses according to the latest global Red List assessments. The North Sea application coupled with previous assessments and studies suggest that, among the three elasmobranchs, starry ray is in most need of urgent research (and conservation actions where appropriate), followed by spurdog, while lesser‐spotted dogfish is increasing in biomass. Moreover, both the VAST‐JARA modelling framework and previous research indicate that, while European plaice is not of conservation concern, cod has likely met the IUCN criteria for being listed as Endangered recently. Synthesis and applications. The predictions of the VAST‐JARA modelling framework for North Sea species, including JARA output and VAST habitat assessment, constitute valuable supporting information to make interpretations based on Red List guidelines, which will help decision‐makers in their next North Sea Red List assessment. We foresee applications of the modelling framework to assist Red List assessments of numerous marine fishes worldwide. Our modelling framework has many potential advantageous uses, including informing resource management about climate change impacts on species' extinction risks.

Tracking IUCN extinction risk at sub-regional scale: lessons from comparing Italian Red List assessments for cartilaginous species within a decade (2013–2022)

This brief research report presents the 2022 updated IUCN Red List for the cartilaginous fish fauna (76 species) recorded in the Italian seas and compares it with the 2013 assessment. Overall, the number of Data Deficient (DD) species decreased in favor of both threatened and unthreatened categories. Out of five DD species in the 2013 assessment, three acquired the status of threatened species (Vulnerable or higher) and two an unthreatened (Least Concern or higher) status in the 2022 assessment. Additionally, the classification for one species changed from Least Concern in 2013 to DD in 2022. The comparison between assessments showed no significant change in the average extinction risk status of cartilaginous fish populations of the Italian seas. Even though 2013-DD species decreased in number, the latter still remains high in the updated Italian IUCN Red List assessment.

A standard approach for including climate change responses in IUCN Red List assessments.

The International Union for Conservation of Nature (IUCN) Red List is a central tool for extinction risk monitoring and influences global biodiversity policy and action. But, to be effective, it is crucial that it consistently accounts for each driver of extinction. Climate change is rapidly becoming a key extinction driver, but consideration of climate change information remains challenging for the IUCN. Several methods can be used to predict species' future decline, but they often fail to provide estimates of the symptoms of endangerment used by IUCN. We devised a standardized method to measure climate change impact in terms of change in habitat quality to inform criterion A3 on future population reduction. Using terrestrial nonvolant tetrapods as a case study, we measured this impact as the difference between the current and the future species climatic niche, defined based on current and future bioclimatic variables under alternative model algorithms, dispersal scenarios, emission scenarios, and climate models. Our models identified 171 species (13% out of those analyzed) for which their current red-list category could worsen under criterion A3 if they cannot disperse beyond their current range in the future. Categories for 14 species (1.5%) could worsen if maximum dispersal is possible. Although ours is a simulation exercise and not a formal red-list assessment, our results suggest that considering climate change impacts may reduce misclassification and strengthen consistency and comprehensiveness of IUCN Red List assessments.

Reducing the number of Data Deficient plant species

Although most plant species have yet to have their extinction risk evaluated for the IUCN Red List, current knowledge of plant diversity suggests that tens of thousands (8%–38% of species) are likely to remain assessed as Data Deficient (DD). This impacts evaluations of the overall proportion of threatened species, as well as on setting appropriate priorities for biodiversity conservation. One of the principle causes of Data Deficiency is taxonomic uncertainty: data permitting an IUCN Red List assessment is often lacking, because species that are poorly known are also taxonomically uncertain. Establishing the taxonomic status of DD species thus assists in determining whether confusion over this is causing their evaluation as DD. In this paper, three separate numerical methods – hierarchical clustering, ordination and phylogenetic ordination – were applied to three independent datasets of standardized traits for plant species from China in order to identify, for each DD species, morphologically similar Non-DD species. Semi-automated analysis of morphological disparity quickly identifies which species are in need of further taxonomic research, as shared traits can indicate either potential synonymy or, otherwise, successful adaptations of distinct species to similar ecological conditions. Extinction risk assessments of morphologically and phylogenetically distinct DD species could then be informed by data on habitat preferences, geographic range or population size from Non-DD species with the most similar traits. Ultimately, determination of the morphological distance between DD species and their most similar Non-DD species, and therefore of differences in the trait space occupied by DD and Non-DD species, could be the basis of future research for improved inference of conservation priorities, and help distinct DD species with similar ecological traits as other taxonomically accepted, threatened species to be identified as being threatened themselves.

Illuminating Firefly Diversity: Trends, Threats and Conservation Strategies.

Fireflies are a diverse group of bioluminescent beetles belonging to the family Lampyridae. Recent research on their diversity, evolution, behavior and conservation has greatly advanced our scientific understanding of these charismatic insects. In this review, we first summarize new discoveries about their taxonomic and ecological diversity, then focus on recent endeavors to identify and protect threatened fireflies around the world. We outline the main threats linked to recent population declines (habitat loss and degradation, light pollution, pesticide overuse, climate change and tourism) and describe relevant risk factors that predict which species will be particularly vulnerable to these threats. Although global coordination of firefly conservation efforts has begun only recently, considerable progress has already been made. We describe work by the IUCN SSC Firefly Specialist Group to identify species currently facing elevated extinction risks and to devise conservation strategies to protect them. To date, IUCN Red List assessments have been completed for 150 firefly taxa, about 20% of which face heightened extinction risks. The conservation status for many species has yet to be determined due to insufficient information, although targeted surveys and community science projects have contributed valuable new data. Finally, we highlight some examples of successful firefly habitat protection and restoration efforts, and we use the framework of the IUCN SSC Species Conservation Cycle to point out high-priority actions for future firefly conservation efforts.

More than 17,000 tree species are at risk from rapid global change

Trees are pivotal to global biodiversity and nature’s contributions to people, yet accelerating global changes threaten global tree diversity, making accurate species extinction risk assessments necessary. To identify species that require expert-based re-evaluation, we assess exposure to change in six anthropogenic threats over the last two decades for 32,090 tree species. We estimated that over half (54.2%) of the assessed species have been exposed to increasing threats. Only 8.7% of these species are considered threatened by the IUCN Red List, whereas they include more than half of the Data Deficient species (57.8%). These findings suggest a substantial underestimation of threats and associated extinction risk for tree species in current assessments. We also map hotspots of tree species exposed to rapidly changing threats around the world. Our data-driven approach can strengthen the efforts going into expert-based IUCN Red List assessments by facilitating prioritization among species for re-evaluation, allowing for more efficient conservation efforts.

Modelling the probability of meeting IUCN Red List criteria to support reassessments.

Comparative extinction risk analysis-which predicts species extinction risk from correlation with traits or geographical characteristics-has gained research attention as a promising tool to support extinction risk assessment in the IUCN Red List of Threatened Species. However, its uptake has been very limited so far, possibly because existing models only predict a species' Red List category, without indicating which Red List criteria may be triggered. This prevents such approaches to be integrated into Red List assessments. We overcome this implementation gap by developing models that predict the probability of species meeting individual Red List criteria. Using data on the world's birds, we evaluated the predictive performance of our criterion-specific models and compared it with the typical criterion-blind modelling approach. We compiled data on biological traits (e.g. range size, clutch size) and external drivers (e.g. change in canopy cover) often associated with extinction risk. For each specific criterion, we modelled the relationship between extinction risk predictors and species' Red List category under that criterion using ordinal regression models. We found criterion-specific models were better at identifying threatened species compared to a criterion-blind model (higher sensitivity), but less good at identifying not threatened species (lower specificity). As expected, different covariates were important for predicting extinction risk under different criteria. Change in annual temperature was important for criteria related to population trends, while high forest dependency was important for criteria related to restricted area of occupancy or small population size. Our criteria-specific method can support Red List assessors by producing outputs that identify species likely to meet specific criteria, and which are the most important predictors. These species can then be prioritised for re-evaluation. We expect this new approach to increase the uptake of extinction risk models in Red List assessments, bridging a long-standing research-implementation gap.

Assessing the conservation status of mangroves in Rakhine, Myanmar

Abstract Ecosystem degradation is a key challenge that human society faces, as ecosystems provide services that are tied to human well‐being. Particularly, mangrove ecosystems provide important services to communities but are suffering heavy degradation, loss and potential collapse due to anthropogenic activities. The IUCN Red List of Ecosystems is a transparent and consistent framework for assessing ecosystems' risk of collapse and is increasingly used to inform legislation and ecosystem management globally. Satellite data have become increasingly common in environmental monitoring due to their extensive spatial and temporal coverage. Here, recent advances in analyses using satellite‐derived data were implemented to reassess the conservation status of the ‘Rakhine mangrove forest on mud’, an important intertidal ecosystem in Myanmar, extending a previous national Red List assessment that assessed the ecosystem as Critically Endangered. By incorporating additional data sources and analyses, the extended assessment produced more robust results and reduced the uncertainty in the previous assessment. Overall, the ecosystem was assessed as Critically Endangered (range: Vulnerable to Critically Endangered) as a result of historical mangrove extent loss. Recent losses and biotic disruptions were also observed, which would have led to the ecosystem being assessed as Vulnerable. While the final outcome of the Red List assessment remained at Critically Endangered due to the historical state of the mangroves pre‐dating the temporal coverage from satellite data, the uncertainty of the ecosystem's status was reduced, and the reassessment highlighted the recent areal changes and mangrove degradation that has occurred. The importance of conducting reassessments when new data become available is discussed, and a template for future mangrove Red List assessments that use satellite data as their primary source of information to improve the robustness of their results is presented.

A 21‐year recovery trend in green turtle nesting activity: 2002–2022

Abstract Long‐term monitoring and conservation are crucial for effective protection, since sea turtles migrate cyclically every 2–3 years and lay multiple nests during a breeding season. Therefore, this study aimed to investigate the long‐term trend of nesting activities of green turtles over a 21‐year period (2002–2022) on Samandağ beach. An early morning survey was conducted every year during both nesting and hatching seasons. The trend analyses in nesting activities were performed using Mann–Kendall and Sen's slope tests together with the augmented Dickey–Fuller stationarity test. The nest count and female abundance increased significantly, whereas clutch size, fecundity, and hatching success tended to decrease insignificantly. The percentage change between the most recent and oldest 3‐year mean nest count and mean female abundance, which is performed to comply with the Red List assessment method used by the International Union for Conservation of Nature Marine Turtle Specialist Group, was 769% and 764% respectively. Samandağ nesting population accounts for one‐third of the Mediterranean's total nest count and one‐fourth of its total female abundance. The decrease in clutch size and fecundity may be due to the recruitment of individuals with smaller body sizes or malnutrition as a result of population growth. There was an increase in the number of dead embryos and a decline in hatching success. This may be explained by density‐dependent population regulation as a result of an increase in the number of nests. It may be argued that adherence to a uniform strategy and the maintenance of continuous protection through collaboration with governmental and non‐governmental organizations with scientifically rigorous methodology are significant factors contributing to the high recovery. This study emphasizes the necessity of adopting a comprehensive conservation approach encompassing both foraging habitats and the significant role played by the population in Samandağ in the proliferation of Mediterranean green turtles.

A review of conservation status of freshwater fish diversity in China.

China harbors a high species diversity of freshwater fishes not shared with any of its neighboring nations. Freshwater fish diversity in the country has been under severe threat from human activities over the past decades, thus conservation freshwater fishes and ecosystems is urgently needed. To accumulate baseline data for guiding protection actions, the third red list assessment of Chinese freshwater fishes was carried out. Among Chinese freshwater fishes assessed, there are 355 at-risk species (22.3% of the total), including 69 ranked as Critically Endangered, 97 as Endangered, and 189 as Vulnerable. Two species are classified as Extinct and one as Regionally Extinct. China's threat level seems to be lower than the known average level found in the IUCN's global assessment of freshwater fishes, but this is an artifact of a high rate of species classified as Data Deficient. Conservation of freshwater fishes is presently facing a grim situation in China. Imperilment of Chinese freshwater fishes is primarily attributed to habitat loss and degradation arising from human perturbations, particularly river damming. Despite the adoption of protected areas setting up, captive breeding and release, and a fishing moratorium, conservation efforts for freshwater fishes are compromised by disproportional attention in China's biodiversity conservation, baseline data deficiency, insufficiently designed protection networks, and inefficient or inadequate implementation of conservation strategies. To achieve the objectives of Chinese freshwater fish conservation, it is proposed to conduct a national-scale survey of fish diversity and reassess their at-risk status, develop systematic conservation planning of freshwater fish diversity and ecosystems, prioritize strategies for protected areas development, perform genetic-based captive breeding for releasing in concert with other protection actions, and implement flexible fishing moratorium strategies in different water bodies.

Annotated Checklist of Cartilaginous Fishes in Palawan Waters

An annotated checklist of 67 species of sharks, rays, and chimaeras (Chondrichthyes) confirmed to be present in Palawan waters was described based on (1) market visits in Puerto Princesa, Aborlan, Brookes Point, and Roxas between October 2021 and March 2022; (2) contributory citizen science soliciting photographs and video footage validated by the authors; and (3) review of various ichthyologic types of research in Palawan that include museum collection records, taxonomic papers, results of DNA analysis, institutional project reports, and related literature, particularly on the occurrence and distributional range of the species. An additional 24 species were placed on the unconfirmed list due to insufficient evidence collected and thus required further investigation. The Province of Palawan exercises environmental jurisdiction over its surrounding marine areas under Republic Act No. 7611, known as the Strategic Environmental Plan for Palawan, with the Palawan Council for Sustainable Development (PCSD), as its regulatory, enforcement, and policy-making authority. In response to the Wildlife Act (Republic Act 9147), the PCSD drafted Resolution 15-521(s. 2015), which updated the list of terrestrial and marine wildlife species in Palawan for protection and management and included only 15 shark and ray species. This paper provides an updated list of Palawan Chondrichthyes (with notes on the conservation status based on the IUCN Global Red List Assessment), suggests a prescriptive approach to enhancing conservation policies in the province, and addresses some critical issues of conservation and management of the Philippine sharks and related species, in particular, and the Philippine fisheries in general.

A review of the assessment techniques used for population monitoring at different life stages of sturgeons

Sturgeons are a unique group of species which were historically widespread across the northern hemisphere. According to the latest IUCN Red list assessment, more than 80% of the species globally are threatened with extinction, making it essential to identify the life stages at which they are suffering from impacts the most while at the same time to compare among river systems and populations based upon standardized assessment techniques. Sturgeon all have similar, but not identical, life-history strategies. Therefore, monitoring techniques developed for one sturgeon species would be applicable to most other species. Monitoring can be conducted at each life stage. However, while each life stage will provide different information about the population, not all will necessarily help to assess population trend or status. Life stages that are highly variable prove to be less quantifiable even after expending very high effort. Collectively, these assessments could be very informative on population status, limitations, and trends. However, monitoring at each stage is time consuming and expensive. Clearly defined objectives are therefore required when embarking on an assessment program. The objective of this study was to review the assessment techniques used for the different life stages including eggs, drifting larvae, age-0, juveniles, subadults and adults to provide a common basis for population assessments that can be standardized to some extent and thus facilitate comparisons between the results obtained. For this purpose, this review presented the most common assessment techniques for each life stage, assessed the pros and cons of assessing each life stage, and examined if the methodology was qualitative or quantitative to assist in establishing long-term monitoring initiatives.