Research Ideas and Outcomes : Grant Proposal
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Grant Proposal
HaffStör: Unravelling Baltic sturgeon ecology in the Lower Oder River and Szczecin Lagoon to inform sustainable management
expand article infoCamille L. Musseau‡, Jessica Bathe-Peters‡, Jan Krzystolik‡, Jörn Geßner‡
‡ Leibniz Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany
Corresponding author: Camille L. Musseau (camille.musseau@igb-berlin.de)
Received: 06 May 2026 | Published: 07 Jul 2026
© 2026 Camille Musseau, Jessica Bathe-Peters, Jan Krzystolik, Jörn Geßner
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation: Musseau CL, Bathe-Peters J, Krzystolik J, Geßner J (2026) HaffStör: Unravelling Baltic sturgeon ecology in the Lower Oder River and Szczecin Lagoon to inform sustainable management. Research Ideas and Outcomes 12: e198587. https://doi.org/10.3897/rio.12.e198587
 Open Access

Abstract

The Baltic sturgeon Acipenser oxyrinchus, once widespread in rivers draining to the Baltic Sea, was extirpated by overfishing and habitat degradation and is now the focus of a basin-wide restoration programme. Since 2006, more than seven million hatchery-reared juveniles have been released in Baltic rivers, yet the movements, habitat use and survival of stocked fish remain poorly quantified. HaffStör aims to close these knowledge gaps and to provide an operational basis for adaptive, cross-border management of the recovering population in the Oder River–Szczecin Lagoon system (Germany/Poland).

The project combines movement ecology, conservation biology and social sciences in four interconnected work packages. First, we optimise rearing protocols, comparing juveniles produced under different degrees of environmental control (ambient vs. static recirculating aquaculture systems), coupled with behavioural experiments on habitat choice and anti-predator responses. Second, we release tagged juveniles in the Lower Oder and Szczecin Lagoon and track their movements using active and passive acoustic telemetry, complemented by habitat mapping and benthic sampling, to identify key migration routes, habitat utilisation and zones of overlap with human activities, mainly associated with fisheries and navigation. Third, we develop and test a standardised, cost-effective monitoring framework, based on passive gears, fishery-independent surveys and environmental DNA, aligned with Bern Convention guidelines and intended to be transferable to other Baltic catchments. Fourth, we establish cooperation with commercial fisheries through targeted outreach to initiate structured by-catch reporting, co-designed surveys and joint project activities.

By integrating ecological and fishery data, HaffStör will deliver robust estimates of juvenile survival and mortality drivers, refine release and monitoring strategies and generate spatially-explicit assessments of by-catch risk. Beyond new scientific insights into Baltic sturgeon ecology, the project seeks to strengthen stewardship amongst local communities and practitioners and to support evidence-based, transnational governance for this flagship migratory species.

Keywords

Acipenser oxyrinchus,Baltic sturgeon,Oder River,HaffStör,rearing conditions; by-catch mitigation,habitat use,acoustic telemetry,monitoring

HaffStör: Ökologische Untersuchung des Baltischen Störs (Acipenser oxyrinchus) in der Unteren Oder und im Stettiner Haff als Grundlage für ein nachhaltiges Management

Der Baltische Stör, Acipenser oxyrinchus, der einst in den Flusssystemen des Ostsee-Einzugsgebiets weit verbreitet war, wurde infolge von Überfischung und Habitatdegradation ausgerottet und steht heute im Fokus eines ostseeweiten Wiederansiedlungsprogramms. Seit 2006 wurden mehr als sieben Millionen in Aufzuchtanlagen aufgezogene Jungfische in Ostseezuflüsse ausgesetzt. Dennoch sind die Wanderbewegungen, die Habitatnutzung und das Überleben der besetzten Fische bislang nur unzureichend quantifiziert. Das Projekt HaffStör verfolgt das Ziel, bestehende Wissenslücken zu schließen und eine belastbare Grundlage für ein adaptives, grenzüberschreitendes Management der sich erholenden Population im Oder–Stettiner-Haff-System (Deutschland/Polen) zu schaffen.

Das Projekt verbindet Bewegungsökologie, Naturschutzbiologie und Sozialwissenschaften in vier miteinander verknüpften Arbeitspaketen. Erstens werden Aufzuchtprotokolle optimiert, indem Jungfische verglichen werden, die unter unterschiedlich stark kontrollierten Umweltbedingungen (naturnahe Systeme versus statische Kreislaufanlagen) aufgezogen wurden. Ergänzend werden Verhaltensexperimente zur Habitatwahl sowie zu Antiprädatorreaktionen durchgeführt. Zweitens werden markierte Jungfische in der Unteren Oder und im Stettiner Haff ausgesetzt und ihre Bewegungen mithilfe aktiver und passiver akustischer Telemetrie verfolgt. Ergänzend erfolgen Habitatkartierungen und Benthosuntersuchungen, um zentrale Migrationsrouten, Muster der Habitatnutzung sowie Bereiche der Überlappung mit anthropogenen Nutzungen, insbesondere Fischerei und Schifffahrt, zu identifizieren. Drittens wird ein standardisiertes und kosteneffizientes Monitoringkonzept entwickelt und getestet, das auf passiven Fanggeräten, fischereiunabhängigen Erhebungen und Umwelt-DNA basiert. Es orientiert sich an den Leitlinien der Berner Konvention und ist auf eine Übertragbarkeit auf weitere Ostsee-Einzugsgebiete ausgelegt. Viertens wird die Zusammenarbeit mit der kommerziellen Fischerei durch gezielte Kommunikations- und Beteiligungsmaßnahmen aufgebaut, um ein strukturiertes Beifang-Meldewesen zu etablieren sowie gemeinsam entwickelte Befragungen und gemeinsame Projektaktivitäten zu initiieren.

Durch die Integration ökologischer und fischereibezogener Daten wird HaffStör belastbare Schätzungen zur Überlebensrate juveniler Störe und zu den Ursachen ihrer Mortalität liefern, Aussetzungs- und Monitoringstrategien weiterentwickeln und räumlich explizite Bewertungen des Beifangrisikos ermöglichen. Über neue wissenschaftliche Erkenntnisse zur Ökologie des Baltischen Störs hinaus zielt das Projekt darauf ab, Verantwortungsbewusstsein und Mitwirkung in lokalen Gemeinschaften und unter Praxisakteuren zu stärken sowie eine evidenzbasierte, grenzüberschreitende Governance dieser Leitart wandernder Fischpopulationen zu unterstützen.

HaffStör: Poznanie ekologii jesiotra bałtyckiego w dolnej Odrze i Zalewie Szczecińskim na rzecz zrównoważonego zarządzania

Jesiotr bałtycki, Acipenser oxyrinchus, niegdyś szeroko rozpowszechniony w rzekach uchodzących do Morza Bałtyckiego, został wytępiony wskutek przełowienia i degradacji siedlisk. Obecnie gatunek ten jest obiektem ogólnobałtyckiego programu restytucji. Od 2006 roku do rzek zlewiska Morza Bałtyckiego wypuszczono ponad siedem milionów młodocianych osobników wyhodowanych w warunkach kontrolowanych, jednak przemieszczanie się, wykorzystanie siedlisk oraz przeżywalność ryb pochodzących z zarybień nadal pozostają słabo poznane. Projekt HaffStör ma na celu uzupełnienie tych luk wiedzy oraz stworzenie operacyjnych podstaw dla adaptacyjnego, transgranicznego zarządzania odbudowującą się populacją w systemie Odry i Zalewu Szczecińskiego (Niemcy/Polska).

Projekt łączy ekologię ruchu, biologię ochrony przyrody oraz nauki społeczne w ramach czterech wzajemnie powiązanych pakietów roboczych. Po pierwsze, optymalizowane są protokoły chowu poprzez porównanie osobników młodocianych produkowanych przy różnym stopniu kontroli warunków środowiskowych (warunki naturalne versus recyrkulacyjne systemy akwakultury RAS), w połączeniu z eksperymentami behawioralnymi dotyczącymi wyboru siedliska oraz reakcji unikania drapieżnika. Po drugie, oznakowane osobniki młodociane są wypuszczane do Dolnej Odry i Zalewu Szczecińskiego, a ich przemieszczanie się jest monitorowane przy użyciu aktywnej i pasywnej telemetrii akustycznej, uzupełnionej mapowaniem siedlisk oraz badaniami bentosu, w celu identyfikacji kluczowych tras migracji, sposobów wykorzystania siedlisk oraz stref nakładania się z działalnością człowieka, przede wszystkim z rybołówstwem i żeglugą. Po trzecie, opracowywany i testowany jest ustandaryzowany, ekonomicznie efektywny system monitoringu oparty na pasywnych narzędziach połowowych, badaniach niezależnych od rybołówstwa oraz analizie środowiskowego DNA, zgodny z wytycznymi Konwencji Berneńskiej i przeznaczony do zastosowania także w innych zlewniach rzek bałtyckich. Po czwarte, rozwijana jest współpraca z rybołówstwem komercyjnym poprzez ukierunkowane działania informacyjne, mające na celu zainicjowanie ustrukturyzowanego raportowania przyłowu, badań ankietowych oraz wspólnych działań projektowych.

Integracja danych ekologicznych i rybackich pozwoli projektowi HaffStör na dostarczenie wiarygodnych szacunków przeżywalności osobników młodocianych oraz poznanie czynników warunkujących ich śmiertelność, udoskonalenie strategii zarybiania i monitoringu oraz opracowanie przestrzennie jednoznacznych ocen ryzyka przyłowu. Oprócz dostarczenia nowych danych naukowych dotyczących ekologii jesiotra bałtyckiego, projekt ma również na celu wzmocnienie poczucia odpowiedzialności wśród społeczności lokalnych i wybranych grup zawodowych oraz wsparcie opartego na dowodach, międzynarodowego zarządzania tym sztandarowym gatunkiem wędrownym.

Authors' note

This grant proposal is funded from 1 May 2024 until 31 July 2027 by the Federal Agency for Nature Conservation (Bundesamt für Naturschutz) under the Funding code 3522150500.

Contextualisation

The Baltic sturgeon

Acipenser oxyrinchus is an anadromous, migratory fish species that evolved on the North American continent and is commonly referred to as the Atlantic sturgeon. However, a study published in 2002 in preparation of the restoration measures in the Baltic Sea catchment revealed that the region was inhabited by A. oxyrinchus (Ludwig et al. 2002). Up to this point, the only sturgeon considered native to the European Atlantic, the North Sea and the Baltic Sea was A. sturio. Over the last two decades, the understanding of the historic colonisation of north-western Europe improved as a result of the analysis of archaeological remains and recent catches. The oldest sturgeon remains in the North and Baltic Seas are dated to 7,000- and 7,400-years BP, respectively (Makowiecki 2008, Nikulina and Schmölcke 2016a, Nikulina and Schmölcke 2016b, Thieren et al. 2016). Historically, A. oxyrinchus occurred in many rivers draining into the Baltic Sea. Its presence is evidenced by-catch reports, archaeological remains and zooarchaeological analyses. The species became extirpated from the Baltic region during the last century due to human pressures, such as fisheries and habitat alterations. Since 2003, attempts to re-introduce the species are carried out with genetically similar fish of Canadian origin (Gessner et al. 2011). The term Baltic sturgeon is internationally established when referring to the A. oxyrinchus population in the Baltic Sea region (Gessner et al. 2019). Individuals hatched in these river systems, migrated to brackish and then marine waters, where they spent up to two decades before the onset of sexual maturity and their return to their natal rivers to spawn (Fig. 1). Reproduction takes place over gravel banks in the river, while early juvenile development occurred in sections with high production of macroinvertebrates before moving out to sea at an age of 2-3 years and length of 40-60 cm. Maximum age of the fish is estimated to reach 120 years and a length of up to 4.5 m (Gessner et al. 2019).

Figure 1.  

Life cycle of Acipenser oxyrinchus and age structured human-induced pressures, adapted from WWF.

As A. oxyrinchus was only later recognised as the historical sturgeon of the Baltic Sea, its protection has largely relied on legal instruments originally framed around A. sturio. Under the Bern Convention (Annex II) and the Convention on Migratory Species (CMS), this protection included strict conservation measures, habitat protection, removal of migration barriers and international cooperation, requirements that also apply for A. oxyrinchus as the taxonomic and biogeographic understanding has evolved. Within the EU, the Habitats Directive provides the main species-specific legal basis, while the Water Framework Directive (WFD) and the Marine Strategy Framework Directive (MSFD) provide complementary legal obligations to restore and maintain favourable ecological conditions across freshwater and marine habitats.

At the regional level, the HELCOM Baltic Sea Action Plan and the associated HELCOM Red List classify the Baltic sturgeon as Regionally Extinct (RE) and explicitly call for the restoration of its populations through re-introduction and associated support measures, such as designated Marine Protected Areas, river restoration, improved connectivity and long-term monitoring (Gessner et al. 2019). This regional framework is complemented by EU policy instruments, including the Common Fisheries Policy (CFP), the EU regulation on the use of alien and locally absent species in aquaculture, the EU Biodiversity Strategy and the Action Plan for nature, people and the economy, which together reinforce by-catch reduction, action against illegal, unreported and unregulated fishing and the conservation of threatened species like sturgeons. Several EU macro-regional strategies also support sturgeon conservation and facilitate cross-border coordination and funding.

Since 1996, sturgeon re-introduction and stock-enhancement in northern Germany have been developed through a series of projects. In 2003, wild mature individuals were obtained from the commercial fishery in the Saint John River (New Brunswick, Canada) fishery, transferred to the Huntsman Marine Science Centre for adaptation for adaptation to controlled rearing conditions and, subsequently, transported to Germany to establish the nucleus of a functional broodstock intended to support the long-term re-establishment of a self-sustaining population in the Oder River (Gessner et al. 2011). These efforts have since expanded under the HELCOM framework. Releases have taken place in Germany (since 2006), Poland (since 2008), Lithuania (since 2010), Latvia (since 2012), Estonia (since 2013) and, more recently, in Sweden (since 2024). In total, more than 7 million individuals of various sizes have been released in 10 rivers in the Baltic Sea Basin.

Current status of the recovery plan implementation in the Oder

On the German Baltic Sea coast, the Oder River is the only catchment historically known to have supported sturgeon habitat. Originating in Czechia, the river extends over 854 km and drains a catchment of 118,861 km², about 90% of which lies within Poland and encompasses the country’s central lowlands. Over more than 150 km of its lower course, the Oder forms the border between Germany and Poland before flowing into the Szczecin Lagoon, a shallow brackish-water forebay of about 687 km². From there, three outlets (the Peenestrom, Świna and Dziwna rivers) connect the lagoon to the Baltic Sea. The Lagoon and the Świna constitute an important maritime traffic corridor between the port of Szczecin and the open Baltic Sea (Pomeranian Bay), while also supporting intensive small-scale commercial fisheries. Together with the surrounding territory, which is also the focus of a rewilding initiative, this river–lagoon–coastal system represents a key zone of interaction between recovering Baltic sturgeon and human activities, including potential anthropogenic disturbances that may affect movement, habitat use and survival. Despite the presence of hydraulic infrastructure within the Basin, both the Oder and its main tributary, the Warta, still offer nearly 450 km of unobstructed migration routes. Historical records confirmed the presence of the species in this system (Grabda 1968, Grabda and Waluga 1968, Przybyl 1976), while more recent habitat assessments indicate that less than 40% of former sturgeon spawning habitats remain present and functional Gessner and Bartel 2000, Arndt et al. 2006 .

Releases of Baltic sturgeon into the Oder River began in 2006 and continue to the present day, with 4.7 million juveniles being released so far. However, despite nearly twenty years of large-scale stocking, by-catch reports from coastal Baltic fisheries remain extremely scarce. This pattern may reflect either low reporting rates or high mortality of released individuals and identifying the causes of this mortality is essential for developing targeted conservation measures. Major uncertainties also remain: it is still unknown whether individuals released between 2006 and 2010, which are now reaching reproductive age, are returning to the Oder to spawn; whether the identified spawning sites are fully functional; whether reproduction will be successful; which habitats juveniles use during downstream migration in the river and lagoon and to what extent this habitat use is shaped by anthropogenic disturbances such as shipping traffic, fisheries activity and habitat alteration; and to what extent by-catch and other sources of mortality may constrain the establishment of a functional population. Addressing these knowledge gaps is the central objective of the HaffStör project presented here.

Project objectives, approaches and structure

The HaffStör project aims to support the sustainable recovery of Baltic sturgeon in the Oder River–Szczecin Lagoon system by identifying critical life stages, habitats and pressures, improving post-release survival and strengthening stakeholder participation in conservation action. To achieve this, it combines movement ecology, conservation biology and social sciences in a framework linking fish production and rearing conditions, post-release behaviour, habitat use, long-term monitoring and interactions with fisheries and other anthropogenic pressures. In doing so, the project generates ecological knowledge, while providing an operational basis for adaptive management in a transboundary river–lagoon–coastal system.

The project is organised into four interconnected work packages (Fig. 2). WP1 focuses on the production, rearing and release of captive-born juveniles under contrasting conditions to improve fish quality and evaluate how rearing history influences post-release performance. WP2 identifies spatial and temporal conflict zones between juvenile sturgeon and anthropogenic activities by analysing movement behaviour, habitat use and survival. WP3 develops and tests a standardised framework for long-term population monitoring adapted to the hydrological and operational conditions of the system. WP4 works with commercial fisheries to improve by-catch reporting, document fisheries-related pressures and strengthen stakeholder involvement in sturgeon recovery. A central coordination unit oversees project planning, administration, communication and integration across work packages, ensuring coherent implementation, methodological consistency and strong outreach and public awareness.

Figure 2.  

Organisation of the HaffStör project, interactions between the work packages, communication and outreach.

Work package 1: Fish rearing and release

Objectives

WP1 aims to optimise rearing and release conditions for captive-born juvenile Baltic sturgeon in order to enhance juvenile fitness and behavioural plasticity, thereby improving post-release performance and supporting population establishment (Fig. 3).

Figure 3.  

Conceptual workflow of WP1: rearing, behavioural testing, tagging and release of juvenile Baltic sturgeon.

Approaches

WP1 compares rearing performance across three facilities representing contrasting environmental conditions, with the aim of identifying practices that improve fish quality prior to release. The assessment includes growth, behavioural plasticity, morphological traits, body condition, survival and health status. Given that these facilities produce between 30,000 and 60,000 juveniles annually and form the foundation of the Baltic restoration programme, continuous evaluation and improvement of rearing conditions are essential.

Juveniles are reared in three complementary facilities representing different rearing conditions:

  1. a container system supplied with Oder River water to ensure adaptation to environmental fluctuations in the river, exposition to local pathogens and promote imprinting (Friedrichsthal, Brandenburg, Germany);
  2. a recirculating aquaculture system (RAS) operating at stable, elevated temperatures (19°C) to promote growth and robust body condition (Born Darss, Mecklenburg Vorpommern, Germany) and
  3. a semi-closed recirculation system with limited fluctuation of water quality parameters, representing an intermediate condition between the first two systems (Angermünde, Brandenburg, Germany). Rearing under river-water conditions is hypothesised to improve the fitness of stocked fish (Carrera-García et al. 2016).

In addition, WP1 includes behavioural experiments designed to enrich rearing environments and improve the adaptive capacity of juveniles produced in RAS systems. These include tests of young-of-the-year (YOY) preferences for tank colour and their effects on growth and body condition, as well as experiments assessing the role of substrate structure (sand, gravel, larger stones) in larval dispersal and microhabitat use.

Larvae and juveniles are released in different seasons at selected sites in the Lower Oder River, generally located close to the rearing facilities in order to minimise transport stress and facilitate acclimatisation. Prior to release into natural habitats, a large proportion of juveniles exceeding 200 mm total length are marked with external T-bar anchor tags for individual identification, thereby supporting long-term monitoring (WP3) and improving survival and reporting fidelity in fisheries-related observations (WP4). A subset of these tagged fish is additionally equipped with acoustic transmitters to enable detailed assessment of migration patterns and habitat use in WP2.

Work package 2: Habitat utilisation and spatial overlap with anthropogenic activities

Objectives

WP2 aims to identify spatial and temporal conflict zones between juvenile Baltic sturgeon and anthropogenic activities by quantifying post-release movement, habitat use and survival and by assessing how these patterns are shaped by rearing history, release strategy and environmental conditions (Fig. 4).

Figure 4.  

Conceptual workflow of WP2: telemetry-based habitat use and movement patterns, habitat assessment and integration of anthropogenic pressures.

Approaches

WP2 builds on fish produced in WP1. Juveniles from different release groups, including two age classes (1- and 2-year-old fish), are released in different seasons at selected locations along the Lower Oder River. Following release, active acoustic telemetry is used to document short-term movements, habitat choice and post-release dispersal during the first weeks in the wild, allowing comparison of early behaviour and vulnerability amongst release groups.

To extend detection beyond this initial phase, a network of stationary acoustic receivers is deployed along the Lower Oder River, throughout the Szczecin Lagoon and at the outlets towards the Baltic Sea. This receiver array provides a fixed spatial framework for detecting tagged individuals and identifying migration routes, feeding grounds, resting areas and zones of prolonged residency. Telemetry data are analysed in relation to size class, season, release location and pre-release treatment in order to assess their effects on movement strategies, habitat residency and survival probabilities.

In parallel, WP2 characterises habitat conditions in key sections of the Lower Oder River using side-scan sonar to map substrate types, depth structure and physical features. Concurrent benthic sampling is carried out to quantify the availability and composition of potential prey in areas used by sturgeon. By linking these habitat and prey data with telemetry-derived movement patterns across release groups, WP2 assesses intra-specific variation in movement strategies, identifies potential aggregation areas and evaluates how habitat quality, environmental conditions and release strategy jointly influence dispersal and survival.

The resulting ecological data are integrated with environmental information, spatial data on fishing effort and by-catch records from WP4 to identify areas and periods of overlap between juvenile sturgeon and anthropogenic activities. Based on these combined datasets, WP2 develops spatial heat maps as a prerequisite tool for adaptive management, alongside statistical and mechanistic models of habitat use and risk exposure. These products support WP3 in the design of gear-based monitoring campaigns and are further refined through joint field activities used to cross-validate juvenile sturgeon presence and local density and to harmonise indicators of occurrence and abundance across telemetry- and catch-based monitoring approaches. They also provide an operational basis for discussing and testing mitigation options with fisheries stakeholders in WP4.

Work package 3: Monitoring

Objectives

Building on the Guideline for Sturgeon Population Monitoring (Neuburg et al. 2024), WP3 develops and standardises a cost-effective monitoring system for Baltic sturgeon tailored to the hydrological conditions of the Lower Oder River, the Szczecin Lagoon and adjacent coastal waters. Using released individuals of known origin and release history provided by WP1, the work package evaluates the performance of this framework under field conditions. A principal goal is to identify the life-cycle stages, habitat types and indicators that are most informative for assessing population status and recruitment under conditions of low abundance and high environmental variability. WP3 also assesses the added value of complementary tools, such as eDNA detection and fishery-dependent information. The main output will be a standardised monitoring protocol with harmonised reporting structures and a FAIR-compliant data management framework, enabling consistent assessments across the Baltic Sea region through the Sturgeon Recovery network under HELCOM (Fig. 5).

Figure 5.  

Conceptual workflow of WP3: development of a standardised monitoring framework for Baltic sturgeon.

Approaches

WP3 adapts the Bern Convention Guideline for Sturgeon Population Monitoring to the Oder River Basin by identifying informative life stages (YOY, juveniles, older juveniles/subadults) and the most suitable catch methods for representative data collection in freshwater river sections, the Szczecin Lagoon and the nearshore Baltic Sea. Initial testing and calibration rely on individuals released within WP1, allowing monitoring tools to be assessed against known age classes and release histories. For each habitat–life-stage combination, WP3 defines indicators (e.g. CPUE, size structure, fish condition, associated costs), sampling windows and the minimum effort required to detect trends.

Fieldwork focuses on test fisheries conducted twice a year in the Lower Oder River. Standardised multimesh gillnets with different mesh-size ranges and adjusted panel heights are used to target specific size classes under varying hydrological conditions. Drifting trammel nets with two mesh configurations are tested as alternative or supplementary gears to evaluate catch efficiency, selectivity and effects on fish condition.

In parallel, eDNA sampling targets periods of potential spawning migration and larval drift, with intensive spring and early-summer campaigns. Species-specific primers are used to determine whether:

  1. adult individuals are present during upstream migration for spawning and
  2. early life stages, originating from natural spawning events, occur in the system.

Positive detections will be followed up with capture-based approaches.

Catch data are integrated with acoustic detections from WP2, release information from WP1 and fishery-dependent by-catch reports from WP4 to refine site selection, improve detectability estimates and support the further development of WP3 outputs into a HELCOM monitoring standard.

Work package 4: Fisheries cooperation, by-catch reporting and stakeholder integration

Objectives

WP4 aims to establish durable cooperation with commercial fisheries in the Lower Oder River and the Szczecin Lagoon in order to generate reliable fishery-dependent data on the spatio-temporal distribution of fishing effort, the occurrence of sturgeon by-catch and potential mitigation options. It also seeks to build trust and raise awareness amongst fishers, particularly with regard to the prompt release of accidentally caught sturgeon, in order to support individual survival and, ultimately, population establishment. A central expected outcome of WP4 is a stable by-catch reporting system supported by a small network of fisher coordinators, ensuring continuity of information flow beyond the project period. These data complement the scientific monitoring conducted in WP2 and WP3 and support continuous exchange between the fisheries sector and research institutions to provide information for Baltic sturgeon recovery (Fig. 6).

Figure 6.  

Conceptual workflow of WP4: stakeholder engagement, by-catch reporting and knowledge transfer.

Approaches

To achieve these objectives, WP4 has established a cooperation framework with the regional fisheries sector to systematically collect sturgeon by-catch information and strengthen collaboration with fishers. The project implements a voluntary reporting system for by-catch events, supported by reporting tools, regular feedback on how the data are used and small incentives for fishers who actively contribute information. A network of coordinators acts as an intermediary between the project team and a broader group of fishers, helping to overcome trust barriers, maintain engagement and promote awareness of handling and release practices that improve the survival of accidentally caught individuals.

By-catch reports include core information such as location, fishing gear type and basic metrics of captured individuals. These data are analysed in spatial and temporal dimensions to identify areas and periods of elevated by-catch risk. In conjunction with the data acquired in WP2 and WP3, the information is used to assess the overlap between sturgeon distribution, migration routes and fishing gears.

In parallel, WP4 conducts structured surveys with fishers to gather complementary information on fishing practices, effort and the socio-economic context of fisheries. These data help interpret by-catch patterns, identify management options compatible with fisheries livelihoods and support the co-development of mitigation measures with the fishing sector.

Communication and public outreach

Communication and public outreach are implemented through a communication framework that reports overall progress and work package developments to stakeholders and the general public. The framework covers all activities targeting audiences beyond the professional fisheries sector, including local communities in the Oder catchment, NGOs, authorities and the general public to raise awareness of the Baltic sturgeon as a flagship species for biodiversity protection and to foster a sense of shared stewardship for the recovering population. To this end, the framework maintains a project website (www.haffstoer.de) with regular updates on the objectives, approaches and interim results of the four WPs. It provides trilingual information materials (in German, English and Polish) and organises public stocking events as high-visibility outreach moments. These events link concrete conservation actions to political commitment and involve representatives of federal and regional governments, as well as hands-on educational activities. These allow young people, in particular, to participate directly in the return of the sturgeon and to learn about river ecology, migratory fish and conservation challenges. Whenever feasible, such activities are accompanied by local media, such as newspapers, regional radio or TV stations, which further amplify their outreach.

Scientific impacts

The HaffStör project will substantially advance understanding of juvenile Baltic sturgeon ecology following release into the wild and provide a robust methodological foundation for long-term monitoring that can be transferred to other Baltic river systems and management contexts. It will generate reliable estimates of survival, detectability and key mortality drivers across riverine and inner coastal habitats; describe post-release movements, habitat use and behavioural strategies along the Oder River and in the Szczecin Lagoon; and develop cost-effective rearing and release protocols to improve post-release performance and future stocking efficiency. The project will also establish a transferable monitoring strategy combining standardised passive fishing gears, telemetry and complementary tools. Finally, by linking sturgeon movements with fishing effort and gear characteristics, HaffStör will deliver a spatiotemporal assessment of by-catch risk and gear impacts, identifying high-risk areas, periods and practices.

Societal impacts

The project fosters community engagement by working with local actors and building long-term collaborations with the fisheries sector in Poland and Germany. It promotes cooperation with fishers and integration of stakeholder knowledge by actively involving fishers in monitoring, by-catch reporting and the co-development of mitigation measures. It will enhance environmental awareness through targeted outreach, education and public communication on sturgeon conservation and river–lagoon ecosystems. In the longer term, this approach may encourage a shift within parts of the fishing community from illegal poaching towards active engagement in conservation and sustainable fisheries management. Finally, the project will support governance, regulation and cross-border management by providing evidence-based inputs to national administrations and regional frameworks, such as HELCOM.

Data availability policy and open science

In line with open science principles, the HaffStör project will provide regular updates on scientific progress through a dedicated topical collection in Research Ideas and Outcomes (RIO) published in English, German and Polish. Data generated across all work packages will be deposited in open-access repositories and accompanied by appropriate metadata and reusable formats to support transparency, reproducibility and re-use. However, to protect Baltic sturgeon and ensure the long-term viability of the restoration programme, access to sensitive information will be restricted whenever disclosure could elevate conservation risks, including by exposing fine-scale aggregation sites, potential spawning areas or other information that could facilitate illegal activities or increase pressure on the species. In such cases, data will be shared in aggregated or anonymised form, while maintaining the highest level of openness compatible with conservation needs.

Scientific collaboration

This project will be undertaken in close collaboration with the State Research Institute for Agriculture and Fisheries Mecklenburg-Vorpommern (LFA), the Stanisław Sakowicz Inland Fisheries Institute in Olsztyn, the West Pomeranian University of Technology, local fishers, the Polish Anglers Association (PZW Szczecin) and German and Polish environmental organiations. Scientific collaboration is also being developed with INRAE (Bordeaux, France).

Funding

The HaffStör project is funded by the Federal Agency for Nature Conservation (BfN) with resources from the Federal Ministry for Environment, Nature Conservation and Nuclear Safety (Germany) (BMUKN) for 36 months for a total budget of €1,834,871.

Funding program

3522150500

Grant title

HaffStör: Unravelling Baltic sturgeon ecology in the Lower Oder River and Szczecin Lagoon to inform sustainable management

Hosting institution

Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany

Ethics and security

The project will complies applicable animal welfare, data protection and conservation requirements. Fish handling and tagging are conducted under appropriate permits and in ways that minimise stress and injury. Personal data collected through stakeholder engagement is handled confidentially. Sensitive ecological information related to Baltic sturgeon occurrence, release sites and potential spawning areas is protected to avoid increasing risks to the species.

Author contributions

JG secured the project funding. This project description was developed collaboratively by all authors, who contributed to the refinement and presentation of the project, the development of the work package descriptions and the writing and revision of the manuscript.

Conflicts of interest

The authors have declared that no competing interests exist.

References

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