DIASPARA - Diadromous Database

Executive summary The current poor status of several diadromous fish species, most notably the Atlantic salmon and the European eel, highlights the urgent need for effective management and scientifically robust assessment procedures. Achieving this requires high‑quality, coherent and accessible data, as conservation and management decisions can only be as reliable as the information on which they rely. Yet, despite the ecological and socio‑economic importance of these species, the data required to monitor their populations and pressures remain highly fragmented, scattered across institutions, stored in heterogeneous formats, and often maintained in locally developed systems. Such dispersion poses major limitations for transparency, reproducibility, long‑term maintenance, and ultimately for the provision of sound scientific advice. Atlantic salmon and European eel share life cycles that span both continental and marine ecosystems, inside and outside Europe. Although populations behave as relatively independent units in freshwater, they are biologically mixed during their marine phases, which requires coordination at regional and international scales for data collection, assessment, and management. Moreover, these species face multiple anthropogenic impacts, including fisheries, habitat degradation, and fragmentation caused by dams and hydropower plants, further emphasizing the need for robust and harmonized data systems. In this context, the International Council for the Exploration of the Sea (ICES) plays a central role in providing independent, high‑quality scientific advice for fisheries management, coordinating international expert groups that evaluate stock status and develop methodologies to support evidence‑based decision making. However, current ICES working groups (WGEEL, WGNAS and WGBAST) rely on locally maintained, heterogeneous databases and spreadsheets, an approach that hampers operability, transparency and long‑term sustainability, and is incompatible with the future Transparent Assessment Framework (TAF) aspirations (an ICES methodology and platform developed by to ensure that scientific assessments of fishery resources are fully transparent, reproducible, and auditable). To address these challenges, DIASPARA has developed the DIASPARA Fish Stock Database (StockDB), a new standardized and centralized database designed to support the assessment of diadromous fish species. StockDB consolidates biological data, fisheries information, habitat descriptors, and impact metrics (including dam‑related pressures), integrating datasets from legacy ICES databases. To do so, our work was carried out in different steps. The first was to review the databases and working procedures of three ICES expert groups related to diadromous species were analyzed: WGNAS, WGBAST and WGTRUTTA. These analyses, carried out after contacting and holding meetings with the experts involved in these groups, resulted in three dedicated reports: WGNAS, WGBAST. An analysis of the WGEEL database was not required, as the leaders of this work package have been directly involved in its development and maintenance, and therefore already have an in‑depth understanding of its structure and functioning. The second phase consisted of finding a database structure suiting the needs of all expert groups. ICES could only maintain one common structure for all diadromous working group, so we needed to merge all datasets into one database. The main structure of the database was presented and discussed, including potential improvements, during an online DIASPARA meeting : database structure. This structure enables the efficient storage, harmonisation and retrieval of the data needed to run international stock assessment models used by the working groups responsible for producing advice or scientific reports on diadromous species. Its design builds on, and remains consistent with, the architectures previously developed for the WGEEL and WGNAS databases. The objective here was to remain as close to possible to the current working format of the different working groups, so as to be able to continue operating with the minimal changes on scripts and tools. The third phase consisted in coding the whole database structure. It included referential tables (a set of standardized and controlled vocabularies) that would be compatible with vocabularies currently used in ICES. This part was done in constant contact with ICES data center to ensure the compatibility with ICES standards. Step by step we also tested that we could import all data into the stock database and ensuring that the resulting structure was fully operational and usable across all working groups, thereby complementing the earlier work of designing the database structure by validating it with real datasets and practical workflows. It's only when trying to practically import the data that missing elements were found, and that the final database structure was validated. At the end of this process, the diadromous fish database stores raw data (biometry, time series of abundance), preprocessed data used by models (e.g. landings at various scales, biomass ...), model parameters and outputs. For ease of use, the report is structured with four main parts. The first describes some principle about the database and it's structure. The second creates all the vocabularies (standard set of code alongside with their description used as reference for stage, species). Think of them as "dictionaries" of possible words and that the database would only be able to use those words as standard and not invent new ones. The third refers to the Stock and holds values aggregated at the scale of the assessment unit, or stock unit. The fourth is the Series and Trait and allows to have time series of data, group and individual life history trait data. This was previously coded in a separate report which has been merged into this main DIADROMOUS DATABASE report at the end of the project for ease of reading. Additionally, to accommodate both structures, a habitat database was created using a hierarchical structure of the habitat of the migratory fishes see habitat report. The script to create this report can be found in diaspara github code of the report, the SQL codes are found in the following link SQL code. All the code (R, SQL), reports (Quarto), and presentations (Quarto) were produced in DIASPARA migDB github repository All presentation, reports produced by WP3 are accessible online at the diaspara website for WP3