American Eel: A Symposium. Session Four

Session Four considers lessons from European eel research and conservation

American Eel: A Symposium. Session Four

Session Four considers lessons from European eel research and conservation

First direct evidence of adult European eels migrating to their breeding place in the Sargasso Sea

The European eel (Anguilla anguilla) is critically endangered (according to the most recent IUCN assessment) and has suffered a 95% decline in recruitment since the 1980s, attributed in part to factors occurring during the marine phases of its life-cycle. As an adult, the European eel undertakes the longest spawning migration of all anguillid eels, a distance of 5000 to 10,000 km across the Atlantic Ocean to the Sargasso Sea. However, despite the passage of almost 100 years since Johannes Schmidt proposed the Sargasso Sea as the breeding place of European eels on the basis of larval surveys, no eggs or spawning adults have ever been sampled there to confirm this. Fundamental questions therefore remain about the oceanic migration of adult eels, including navigation mechanisms, the routes taken, timings of arrival, swimming speed and spawning locations. We attached satellite tags to 26 eels from rivers in the Azores archipelago and tracked them for periods between 40 and 366 days at speeds between 3 and 12 km day(-1), and provide the first direct evidence of adult European eels reaching their presumed breeding place in the Sargasso Sea

Workshop on accounting for fishers and other stakeholders’ perceptions of the dynamics of fish stocks in ICES advice (WKAFPA)

The objective of the Workshop on accounting for fishers and other stakeholders’ perceptions of the dynamics of fish stocks in ICES advice (WKAFPA) was to identify where and how stake- holder information could be incorporated in the ICES fisheries advice process. It adopted an operational definition of the concept of perception, where perceptions result from observations, interpreted in light of experience, that can be supported by data, information and knowledge to generate evidence about them. Stakeholder information can be either structured (e.g. routinely collected information in a standardized format) or unstructured (e.g. experiential information) and either of those can inform decisions made during the production of ICES advice. Most notably, the group identified there was a need to engage with stakeholders earlier in the process, i.e. before benchmarks meetings take place and before preliminary assessment results are used as the basis to predict total allowable catches for upcoming advice (Figure 4.2). It was therefore recommended to include in the ICES process the organisation of pre-bench- mark/roadmap workshops where science and data needs of upcoming benchmarks can be iden- tified, followed by making arrangements how scientists and stakeholders can collaborate to ac- cess, prepare for use (where relevant) and document the structured and unstructured infor- mation well ahead of the benchmark meetings. It was also recommended to organise ‘sense-checking’ sessions with stakeholders when prelim- inary assessments are available but not yet used as the basis for advisory production. This would allow stakeholders and assessment scientists to verify available knowledge and data against stock perceptions and provide additional considerations relevant for the production of TAC ad- vice. Next to these two additional activities, it is recommended that communication on differ- ences in stakeholder perception or data derived perceptions are communicated within the ICES assessment reports as well as in the ICES advice in a transparent manner. Not only should dif- ferences or similarities be documented and communicated, in those cases where there are differ- ences in perception between ICES stock assessments and stakeholders, a working group, external to the assessment working groups, should evaluate these differences and describe whether these differences can be logically explained or require further investigation. This outcome of this pro- cess may potentially lead to new data collection or additional analyses suitable for input to benchmarks. Essential in this entire process is making sure the same language is spoken between scientists and stakeholders, that there are clear and transparent processes in place on how to deal with stakeholder information and communicate clearly how this information is used in the prepara- tion of ICES advice.info:eu-repo/semantics/publishedVersio

REPORT OF THE JOINT EIFAAC/ICES/GFCM WORKING GROUP ON EELS (WGEEL)

The Joint EIFAAC/ICES/GFCM Working group on eels (WGEEL) met in a split meeting from 4–8 September (online) and 25 September–02 October 2023 (hybrid meeting) in Helsinki, Finland, to provide the scientific basis for the ICES advice on fishing opportunities and conservation as-pects for the European eel and address requests from EIFAAC and GFCM. WGEEL assessed the state of the European eel and its fisheries, collated and analysed biometric data, reviewed the implementation of the WKFEA (Workshop on the future of eel advice) roadmap, examined available recruitment data from coastal and marine habitats, reported on any updates to the scientific basis of the advice, new and emerging threats or opportunities, in-cluding developments in the Mediterranean region. After high levels in the late 1970s, the recruitment declined dramatically in the 1980s and remains low. Compared to 1960–1979, the recruitment in the “North Sea” was 0.4% in 2023 (provisional) and 0.7 % in 2022 (final). In the “Elsewhere Europe” index series was 8.8 % in 2023 (provisional) and 11.3% in 2022 (final). For the yellow eel data series, recruitment for 2022 was 9% (final). Time-series from 1980 to 2023 show that glass eel recruitment remains at a very low level, with an historical minimum value in the North Sea. Silver eel time series have been analysed to identify patterns in abundance trends. These analyses are exploratory and have enabled us to test certain statistical methods and their limitations for analysing temporal series on silver eels. Although they give us an initial idea of trends in silver eel abundance, their results should be treated with caution. In fact, several problems have been identified and these points need to be improved in order to be able to interpret the results. The trend of reported commercial landings shows a long-term continuing decline, from a level of around 10,000 t in the 1960s, reported commercial landings have now dropped to 2028 (glass eel + yellow eel + silver eel) in 2022. The commercial glass eel fishery in 2022 was 60.1 t and 53.6 t in 2023. Reported landings from yellow and silver eel commercial fisheries (Y, S, YS) add up to 2914 t in 2021 and 2437 t in 2022. Spain was the only country allowing a recreational catch of glass eel, with landings estimated at 0.72 t in 2022 and 1.32 t in 2023. Reported recreational land-ings for yellow and silver eel combined were 240 t for 2021 (11 countries reporting) and 249 t for 2022. Progress with regards to the ‘road map’ developed within WKFEA was evaluated. The returns from the three questionnaires distributed by WKSMEEL to WGEEL members were summarised. In relation to the progress of the WKFEA roadmap, item 1; the inclusion of biological data is advanced with biometry data included in the annual data call. Item 2 relates to the reconstruction of the landings data and a workshop will take place in December 2023. Items 3 and 4 are also in progress, the Spatial database and Model for Eel (WKSMEEL) workshop was held in June 2023 with a follow up workshop planned for October 2023. A questionnaire for 3 topics (electrofish-ing, hydrographic network, and river obstructions & hydropower) was circulated to WGEEL members in August 2023. Of the 21 countries who responded, a large majority carry out electro-fishing, have available hydrographic networks and hold some information of obstructions to migration. However, it was recognised that considerable effort and resources will be required before the available data could be collated.publishedVersio

Development and Experimental Validation of a 20K Atlantic Cod (Gadus morhua) Oligonucleotide Microarray Based on a Collection of over 150,000 ESTs

The collapse of Atlantic cod (Gadus morhua) wild populations strongly impacted the Atlantic cod fishery and led to the development of cod aquaculture. In order to improve aquaculture and broodstock quality, we need to gain knowledge of genes and pathways involved in Atlantic cod responses to pathogens and other stressors. The Atlantic Cod Genomics and Broodstock Development Project has generated over 150,000 expressed sequence tags from 42 cDNA libraries representing various tissues, developmental stages, and stimuli. We used this resource to develop an Atlantic cod oligonucleotide microarray containing 20,000 unique probes. Selection of sequences from the full range of cDNA libraries enables application of the microarray for a broad spectrum of Atlantic cod functional genomics studies. We included sequences that were highly abundant in suppression subtractive hybridization (SSH) libraries, which were enriched for transcripts responsive to pathogens or other stressors. These sequences represent genes that potentially play an important role in stress and/or immune responses, making the microarray particularly useful for studies of Atlantic cod gene expression responses to immune stimuli and other stressors. To demonstrate its value, we used the microarray to analyze the Atlantic cod spleen response to stimulation with formalin-killed, atypical Aeromonas salmonicida, resulting in a gene expression profile that indicates a strong innate immune response. These results were further validated by quantitative PCR analysis and comparison to results from previous analysis of an SSH library. This study shows that the Atlantic cod 20K oligonucleotide microarray is a valuable new tool for Atlantic cod functional genomics research

A global agenda for advancing freshwater biodiversity research

Global freshwater biodiversity is declining dramatically, and meeting the challenges of this crisis requires bold goals and the mobilisation of substantial resources. While the reasons are varied, investments in both research and conservation of freshwater biodiversity lag far behind those in the terrestrial and marine realms. Inspired by a global consultation, we identify 15 pressing priority needs, grouped into five research areas, in an effort to support informed stewardship of freshwater biodiversity. The proposed agenda aims to advance freshwater biodiversity research globally as a critical step in improving coordinated actions towards its sustainable management and conservation

Workshop on accounting for fishers and other stakeholders’ perceptions of the dynamics of fish stocks in ICES advice (WKAFPA)

The objective of the Workshop on accounting for fishers and other stakeholders’ perceptions of the dynamics of fish stocks in ICES advice (WKAFPA) was to identify where and how stakeholder information could be incorporated in the ICES fisheries advice process. It adopted an operational definition of the concept of perception, where perceptions result from observations, interpreted in light of experience, that can be supported by data, information and knowledge to generate evidence about them. Stakeholder information can be either structured (e.g. routinely collected information in a standardized format) or unstructured (e.g. experiential information) and either of those can inform decisions made during the production of ICES advice. Most notably, the group identified there was a need to engage with stakeholders earlier in the process, i.e. before benchmarks meetings take place and before preliminary assessment results are used as the basis to predict total allowable catches for upcoming advice (Figure 4.2). It was therefore recommended to include in the ICES process the organisation of pre-benchmark/roadmap workshops where science and data needs of upcoming benchmarks can be identified, followed by making arrangements how scientists and stakeholders can collaborate to access, prepare for use (where relevant) and document the structured and unstructured information well ahead of the benchmark meetings. It was also recommended to organise ‘sense-checking’ sessions with stakeholders when preliminary assessments are available but not yet used as the basis for advisory production. This would allow stakeholders and assessment scientists to verify available knowledge and data against stock perceptions and provide additional considerations relevant for the production of TAC advice. Next to these two additional activities, it is recommended that communication on differences in stakeholder perception or data derived perceptions are communicated within the ICES assessment reports as well as in the ICES advice in a transparent manner. Not only should differences or similarities be documented and communicated, in those cases where there are differences in perception between ICES stock assessments and stakeholders, a working group, external to the assessment working groups, should evaluate these differences and describe whether these differences can be logically explained or require further investigation. This outcome of this process may potentially lead to new data collection or additional analyses suitable for input to benchmarks. Essential in this entire process is making sure the same language is spoken between scientists and stakeholders, that there are clear and transparent processes in place on how to deal with stakeholder information and communicate clearly how this information is used in the preparation of ICES advice.Peer reviewe

Diving into the vertical dimension of elasmobranch movement ecology

Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first global synthesis of vertical habitat use by elasmobranchs from data obtained by deployment of 989 biotelemetry tags on 38 elasmobranch species. Elasmobranchs displayed high intra- and interspecific variability in vertical movement patterns. Substantial vertical overlap was observed for many epipelagic elasmobranchs, indicating an increased likelihood to display spatial overlap, biologically interact, and share similar risk to anthropogenic threats that vary on a vertical gradient. We highlight the critical next steps toward incorporating vertical movement into global management and monitoring strategies for elasmobranchs, emphasizing the need to address geographic and taxonomic biases in deployments and to concurrently consider both horizontal and vertical movements

Diving into the vertical dimension of elasmobranch movement ecology

Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first global synthesis of vertical habitat use by elasmobranchs from data obtained by deployment of 989 biotelemetry tags on 38 elasmobranch species. Elasmobranchs displayed high intra- and interspecific variability in vertical movement patterns. Substantial vertical overlap was observed for many epipelagic elasmobranchs, indicating an increased likelihood to display spatial overlap, biologically interact, and share similar risk to anthropogenic threats that vary on a vertical gradient. We highlight the critical next steps toward incorporating vertical movement into global management and monitoring strategies for elasmobranchs, emphasizing the need to address geographic and taxonomic biases in deployments and to concurrently consider both horizontal and vertical movements