Prevalence of critically endangered European eel (Anguilla anguilla) in Hong Kong supermarkets

Milt androgen profile and evaluation of sperm morpho-functional characteristics of wild-caught and farmed European eels (Anguilla anguilla)

Evaluating milt samples before their preservation and/or reproductive use is critical to correctly develop assisted reproductive strategies for teleost species. This is especially true in case of "critically endangered" species, like the European eel (Anguilla anguilla), whose life cycle is not closed yet, leading to the necessity of capturing younglings from natural populations for both research and productive purposes. Despite androgens being involved in spermatogenesis and playing pivotal roles in the pre-migratory morphological and physiological changes, their quantification in different biological tissues is still to be refined in European eels. The aim of this study was to evaluate the feasibility of extraction and quantification of testosterone (T) and 11-ketotestosterone (11-KT) from male European eel milts. The secondary aim was to investigate potential differences in androgens' profiles and/or functional characteristics of spermatozoa between wild-caught and farmed specimens. Twenty-four male European eels obtained from the North Adriatic region (14 wild-caught and 10 farmed) underwent a maturation-inducing hormonal treatment for milt production; blood and milt samples were then collected for androgens quantification upon ELISA and RIA methodologies. Spermatozoa were also evaluated for viability and objective motility. Plasma showed average T and 11-KT levels of 2.32 and 6.88 ng/mL, respectively, while milt 0.24 (T) and 1.09 ng/mL (11-KT). Significantly higher spermatozoa concentrations and motility were observed in farmed eels' milts. This work contributes to deepening the knowledge on teleost physiology, being the first report quantifying T and 11-KT from European eels' seminal plasma and comparing the quality of milts of farmed vs wild specimens.

The hidden cost of illicit trade: Evaluating the physiological health of smuggled European glass eels (Anguilla anguilla)

European eel is considered a "critically endangered" species due to its population decline (c.a. 98 %) in all European waters, primarily because human activities. The eel life cycle is very complex as it includes long migrations, and although aquaculture can help in repopulation, at this time artificially raised eel larvae have little survival. Therefore, to reverse this situation, in 2007 the EU adopted the Eel Regulation, starting a series of plans to improve the conservation and the recovery of the eel population, which included a ban on importing and exporting eels in all EU countries. However, an illegal global market and food fraud developed, turning Europe into the source of the international illegal eel trade. This study reports the evaluation of the welfare consequences of the illegal transport of European glass eels using their epithelial mucus, one of the most promising tools for studying endangered fish species. We also aimed to determine the recovery time required in controlled conditions before their release to the Ebro River. The results showed that high metabolite and cortisol levels were observed in mucus. In addition, the defensive capacity against possible bacterial infections was also affected due to the transport conditions as bacterial co-culture with mucus analysis indicated. Regarding the recovery time, we analysed the same parameters as for the initial transport point resulting in a stabilisation of stress parameters and an increased defensive capacity from day 3 to the final release, but the best results were observed after 2 months under optimal conditions. These findings suggest that transport stress is critical for the survival of glass eels, and the stress and defensive capacities analysis suggests the need for a recovery period prior to release. This approach represents a valuable contribution both for species subject to illegal trade and for the conservation of endangered species.

Evaluating the readiness for river barrier removal: A scoping review under the EU nature restoration law

The European Union's Biodiversity Strategy 2030, reinforced by the new Nature Restoration Law, targets restoring a minimum of 25,000 km of 'free-flowing rivers' by 2030. Central to this endeavor is the imperative to restore natural longitudinal and lateral connectivity of rivers and floodplains. Focused on scrutinizing data, methods, and tools employed in published studies from 2000 to 2023, our literature review reveals both encouraging developments and significant challenges at pan-European and regional scales to prioritize barriers for removal. Positive advancements include notable efforts in (i) data collection for a diverse range of taxa, and (ii) barrier data acquisition over the past two decades. Additionally, (iii) robust prioritization algorithms have been established. However, there remain significant challenges in applying these frameworks consistently across diverse geographical regions. We identified knowledge gaps in the (iv) quality of the available data, emphasizing the need for more accurate information on barrier characteristics, (v) the lack of inclusion of social aspects, and (vi) the need for expanding the focus beyond commercially significant species. We conclude that the absence of unified efforts, along with disparities in data and the lack of clear objectives for the restoration of free-flowing rivers, pose a significant constraint. It is essential to further acknowledge the necessity to address the opportunity costs, culturally important freshwater species, and climate change impacts. Collaborative solutions based on clear objectives are required to apply the ambitious goals of restoring free-flowing rivers in the context of the Nature Restoration Law.

Determining the sustainability of legal wildlife trade

Exploitation of wildlife represents one of the greatest threats to species survival according to the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. Whilst detrimental impacts of illegal trade are well recognised, legal trade is often equated to being sustainable despite the lack of evidence or data in the majority of cases. We review the sustainability of wildlife trade, the adequacy of tools, safeguards, and frameworks to understand and regulate trade, and identify gaps in data that undermine our ability to truly understand the sustainability of trade. We provide 183 examples showing unsustainable trade in a broad range of taxonomic groups. In most cases, neither illegal nor legal trade are supported by rigorous evidence of sustainability, with the lack of data on export levels and population monitoring data precluding true assessments of species or population-level impacts. We propose a more precautionary approach to wildlife trade and monitoring that requires those who profit from trade to provide proof of sustainability. We then identify four core areas that must be strengthened to achieve this goal: (1) rigorous data collection and analyses of populations; (2) linking trade quotas to IUCN and international accords; (3) improved databases and compliance of trade; and (4) enhanced understanding of trade bans, market forces, and species substitutions. Enacting these core areas in regulatory frameworks, including CITES, is essential to the continued survival of many threatened species. There are no winners from unsustainable collection and trade: without sustainable management not only will species or populations become extinct, but communities dependent upon these species will lose livelihoods.

Molecular identification of critically endangered European eels (Anguilla anguilla) in US retail outlets

The European eel (Anguilla anguilla) has declined by over 90% since the early 1980s and has been listed as critically endangered. Yet, despite strict export bans from the European Union, the European eel is still sold illegally in many countries. Efforts to monitor the trade of European eels have been primarily concentrated in Asian markets where concerningly high rates of European eel have been reported. Comparably fewer studies have assessed the identities of eel samples from the United States (US), despite the obvious implications for eel conservation. To address this knowledge gap, we purchased 137 eel products (134 freshwater eels and three saltwater eels) from grocers, sushi bars, and restaurants in nine states across the US from 2019 to 2021. Seven samples (5.2%) labeled as freshwater eels (or "unagi") were identified as European eels using a combination of mitochondrial (cytochrome b) and nuclear (18S rRNA) restriction digestion assays, a fast and inexpensive molecular tool for seafood identification that can identify hybrids between European eels (A. anguilla) and American eels (A. rostrata). No hybrids between European and American eels were found and all seven samples identified with restriction digestion as European eels were confirmed by sequencing of cytochrome b and 18S rRNA. Frequency of European eels in US markets did not significantly correlate with state or retail type. Although illegal eel exports are likely reaching US consumers, the frequency of European eel samples in this study of the US market is much lower than found in other non-European countries.

Meta-analyses of molecular seafood studies identify the global distribution of legal and illegal trade in CITES-regulated European eels

Authentication of seafood products by means of molecular techniques has relevance for food sustainability and security, as well as international trade regulation, linked to transparency in food manufacturing. We focus on the molecular detection of the depleted European eel Anguilla anguilla, a species for which strict international trade regulations are in place since 2010, in studies conducted outside Europe. We found thirteen studies from nine countries (Canada, China, Japan, Malaysia, Peru, Singapore, South Korea, Taiwan, and USA) for which, on average, 59 ± 28% of the 330 sequenced eel samples comprised European eel. Only China, Japan, South Korea, and USA reported the import of European eel in the years prior to sampling. The authentication of eel products demonstrates a global, in part illegal, trade in European eel, covered up by incomplete or fraudulent labelling. This calls into question the compliance with existing national and international trade regulations and its implications for food safety and sustainability.