# Review of Bycatch Prevention and Mitigation Measures for Sturgeons

Eric Rochard, Jörn Gessner, Beate Striebel-Greiter

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## To cite this version:

Eric Rochard, Jörn Gessner, Beate Striebel-Greiter. Review of Bycatch Prevention and Mitigation Measures for Sturgeons. European Commission. 2025, 60 p. hal-05213667

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European
Commission

# Review of Bycatch Prevention and Mitigation Measures for Sturgeons

## SUPPORT DOCUMENT FOR THE IMPLEMENTATION OF THE PAN-EUROPEAN ACTION PLAN FOR STURGEONS

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Environment
# Review of Bycatch Prevention and Mitigation Measures for Sturgeons

Compiled by: **Eric Rochard**

Edited by: **Joern Gessner, Beate Striebel-Greiter**

## CONTRIBUTORS

Produced with contributions from a working group on sturgeon bycatch in the frame of the EU Service Contract 09.0201/2022/885601/SER/D.3:

Anthony Acou, Alin Bădiliță, Niels Brevé, Sergiy Bushuiev, Steve Colclough, Alison Debney, Sybille De Mareschal, Keith Dunton, Emre Fakioglu, Dewayne Fox, Bern Gessner, Borislava Margaritova, Andy Moore, Simone Niedermüller, Eric Rochard, Matt Spencer, Beate Striebel-Greiter.

Luxembourg: Publications Office of the European Union,
2025 © European Union, 2025

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The reuse policy of European Commission documents is implemented by Commission Decision 2011/833/EU of 12 December 2011 on the reuse of Commission documents (OJ L 330, 14.12.2011, p. 39). Unless otherwise noted, the reuse of this document is authorised under a Creative Commons Attribution 4.0 International (CC BY 4.0) licence (https://creativecommons.org/licenses/by/4.0/). This means that reuse is allowed provided appropriate credit is given and any changes are indicated.

PDF ISBN 978-92-68-23867-7 / KH-01-25-010-EN-N / doi: 10.2779/7698226

This report was prepared under the contract No. 09.0201/2022/885601/SER/D.3, "Supporting Conservation and Protection Actions to Implement the Pan-European Sturgeon Action Plan" funded by the European Commission and implemented in 2023-2024 by a consortium comprising of WWF CEE as coordinator, IGB – Leibniz-Institute of Freshwater Ecology and Inland Fisheries, INRAE – French National Research Institute for Agriculture, Food and the Environment, Wildlife Estonia, University of Padua and two subcontractors: BOKU University of Natural Resources and Life Sciences and Dr. Ralf Reinartz.

Cover photos: © LFA-MV, © Hartmut Jungius / WWF
# Executive summary

ALT: The eight native sturgeons found in Europe are under massive threat of extinction. Anthropogenic pressures such as historic overexploitation and in some regions continued illegal fishing are primary reasons steep population declines. Damming, navigation, water abstraction, pollution and climate change also continue to impact the suitability of their habitats. Historically, the presence of sturgeon has been documented so far in at least 78 river systems throughout the European continent but today their presence is limited to approximately 15 river systems with almost all populations depending on active recovery measures.

Bycatch of sturgeon in a variety of marine, estuarine and freshwater fisheries poses a significant and so far often neglected threat to the recovery of critically endangered populations in Europe, as it removes rare individuals from already very small remaining populations. This impact is especially pronounced in late maturing ad long lived species such as sturgeons while the exact dimension of the impact is unknown due to the fact that, similar to other protected and endangered species, the real numbers of individual sturgeons accidentally caught in the diverse fisheries and their fate remains unknown. Despite existing obligations under

the Habitats Directive to establish a system to monitor the incidental capture and killing of the animal species listed in Annex IV, there are no official records on accidental captures available. Voluntary declarations by fishers that are collected in the different sturgeon recovery projects at best provide patchy data and are known to massively underestimate the extent of the impact.

In the frame of the EC Service Contract (09.0201/2022/885601/SER/D.3 "Supporting Conservation and Protection Actions to implement the Pan-European Action Plan for Sturgeons"), this report summarizes the available information on sturgeon bycatch in Europe supplemented by experience from North-America. Thereby, it contributes to the implementation of the PANEUAP aiming to "reduce accidental removal to levels allowing population recovery" (Result 1.2). It furthermore, outlines available approaches at hand for the prevention, the mitigation or the improved knowledge base on the impact of commercial and recreational fisheries. Among the options discussed are the reduction of fishing pressure through temporal or spatial closures, gear alterations, technical surveillance systems or awareness raising and involvement of fishers.

**Key conclusions include:**

No official bycatch reports for sturgeons are available in Europe (ICES identified 4 reports in 2022 across Europe) – both in rivers and seas. All information depends on voluntary reports and efforts of conservation projects. Thus the full extent and thereby the consequences of the bycatch issue remains unknown.
In addition, sturgeons are trapped in a vicious circle and the issue of bycatch is largely overlooked. Their populations are at very low levels, resulting in low absolute numbers of sturgeon detected in bycatch which nevertheless have a massive impact upon the populations affected. At the same time the low numbers lead to an underestimation of the dimension of the impact by the responsible authorities. This situation must be changed urgently, as the currently perceived low bycatch numbers reduce the chances of effective recovery for any of the population threatened by extinction and counteract investments made by conservation projects.

There is little effort spent on effective gear modifications in the fishery to prevent sturgeon bycatch until today – leaving temporal and spatial closures a one key instrument to avoid bycatch. Knowledge on habitats and distribution patterns of sturgeons along with better information on the impact of different fisheries upon sturgeons are thus a basic requirement for the planning of bycatch prevention measures.

From these conclusions the following key recommendations are derived:

* **Temporal and regional closures:**

>> Improve the knowledge base on sturgeon habitats, range and temporal distribution patterns (for example through species distribution models) to identify potential spatial and temporal overlaps with fisheries.

>> Sturgeon bycatch data from the fishery in question must be collected by national authorities in an obligatory reporting; additional surveillance systems may support this.

>> In shared river or sea regions, such data on sturgeon occurrence and bycatch must be exchanged transparently between countries.

>> Where necessary, establish temporal or spatial closures to protect important habitats where sturgeons aggregate.

* **Cooperation and involvement of key target groups:**

>> Raise awareness of fishers and fishing authorities to the threat level of the species and the impact of bycatch in different fisheries.

>> Actively involve fishers in conservation actions such as monitoring or bycatch reporting and train them in identifying and handling fish for safe release in case of bycatch.

>> Encourage collaboration between authorities, fishers, scientists, and conservation organizations to develop and apply methods to reduce sturgeon bycatch.

* **Improve and enforce regulations:**

>> Ensure that regulations (i.e. for bycatch reporting) are clear, concise for practical implementation and are known and respected in the fisheries.

>> Authorities must increase compliance with the existing regulations that prevent landing of sturgeons bycaught in any fishery under all conditions – every sturgeon must be returned to the waters as soon as possible.
>> To avoid overloading of fishers through a variety protection approaches for different endangered species a harmonization must be agreed and applied.

* **Research and Innovation:**

>> Research into the development of innovative fishing gear that catches target species while minimizing bycatch is urgently required.
# Table of Contents

1. Introduction ................................................................................................................6

2. Context ....................................................................................................................8

2.1 Sturgeon distribution and conservation status in Europe ........................................8

2.2 Bycatch definition ........................................................................................................8

2.3 Bycatch and sturgeon....................................................................................................9

2.4 Political framework........................................................................................................11

2.4.1 European Union Policies and Regulations ..........................................................11

2.4.2 Fisheries management organizations and Regional management organizations
(Sea Conventions) ........................................................................................................14

2.4.3 The Bern Convention ..................................................................................................16

2.5 General approaches to address the conservation related issues of bycatch .................16

2.5.1 Collection of bycatch data ..................................................................................16

2.5.2 Impact assessments of bycatch ........................................................................18

2.5.3 Preventive measures ..........................................................................................19

2.6 Lessons learned from the North American experiences on bycatch of sturgeon ............20

2.6.1 Background ............................................................................................................21

2.6.2 Interactions between sturgeon and fisheries ....................................................21

2.6.3 Dimension of bycatch and mortality rates ..........................................................22

2.6.4 Recommendations to limit bycatch or its effects ..................................................26

3. Situation in Europe ........................................................................................................30

3.1 Background ..................................................................................................................30

3.2 Available information (species, numbers of bycatch, links with fisheries).................30

3.2.1 Northeast Atlantic, North Sea and Baltic Sea ..................................................31

3.2.2 Mediterranean and Adriatic ..................................................................................33

3.2.3 Black Sea and Azov Sea ....................................................................................34

3.3 Measures put in place to limit bycatch ....................................................................38

3.3.1 Awareness campaigns..........................................................................................38

3.3.2 Reporting..................................................................................................................42

3.3.3 Alteration of fisheries techniques....................................................................42

3.3.4 Closures..................................................................................................................43

4. Recommendations ........................................................................................................44

4.1 Increase knowledge and awareness ........................................................................44

4.1.1 Assess fishery-independent data ........................................................................44

4.1.2 Involve fishers in conservation actions..................................................................45

4.1.3 Assess bycatch ........................................................................................................45

4.1.4 Ensure that on board activities are recorded ..........................................................46

4.2 Reduce bycatch probability ........................................................................................46
<table><tr><td>4.2.1 Reduce bycatch probability</td><td>47</td></tr><tr><td>4.2.2 Modify fishing gear</td><td>47</td></tr><tr><td>4.3 Increase survival of bycatch sturgeons</td><td>48</td></tr><tr><td>4.3.1 Effects of different fishing gear</td><td>48</td></tr><tr><td>4.3.2 Improved handling practices</td><td>48</td></tr><tr><td>4.3.3 Increase enforcement</td><td>49</td></tr><tr><td>5. Conclusions</td><td>49</td></tr><tr><td>6. Appendix</td><td>50</td></tr><tr><td>6.1 Bycatch related measures in sturgeon Action Plans</td><td>50</td></tr><tr><td>6.2 References</td><td>51</td></tr></table>
# 1. Introduction

Eight sturgeon species occur in Europe's rivers and seas, and all are featured in the IUCN Red List of Threatened Species. Seven of the eight species have been assigned a critically endangered status.

Sturgeons, although threatened by extinction, are key indicators for the ecological integrity of rivers, as habitat for completing the life-cycle may cover entire catchments (Schiemer, 2000). Within the EU, all sturgeon species are protected under the Habitats Directive (92/43/EEC) and their conservation is a legal obligation for the Member States of the EU. *Acipenser naccarii*, *A. oxyrinchus*<fnref n="1" /> and *A. sturio* are listed on Annexes II and IV and are considered species

of special concern to the EU, requiring Member States to "designate core areas of their habitat as SCIs and are to be included in the Natura 2000 network to be managed in accordance with the ecological needs of the species" and to "apply a strict protection regime across their entire natural range, within and outside Natura 2000 sites" (art 12 & 16). The other five species are listed in Annex V, obliging Member States to ensure that their exploitation and removal from the wild is compatible with maintaining them at a **favourable** conservation status. Yet, their return from a currently **unfavourable** status also requires urgent protection measures for their habitats.

> Reflecting the high risk of extinction for this species group, a Pan-European Action Plan for Sturgeons (PANEUAP)<fnref n="2" /> was adopted in November of 2018 as a recommendation<fnref n="3" /> from the Standing Committee to the Bern Convention to which all important European sturgeon range countries, as well as both the EU and its Member States, are Parties. In May 2019, the EU Nature Directive Expert Group (NADEG) also recommended the implementation of the Action Plan to EU Member States. The PANEUAP was designed to serve as a framework of almost 70 actions which aim to "restore all existing sturgeon populations to "least concern" (IUCN) or "favourable" conservation status (Habitats Directive) and re-establish self-sustaining sturgeon populations as well as their life-cycle habitat in their historic range to an extent that ensures species survival and representation of the subpopulations where possible."

The recommendation mandated the Secretariat of the Bern Convention to closely monitor the implementation of the Action Plan and to coordinate the implementation of regular reporting on the implementation of the Action Plan at national levels.

Since its adoption, the European Commission has closely followed the implementation of the PANEUAP and in 2022 issued a service contract (ENV/2022/OP/0019) to support its implementation.

<footnote n="1">¹ From a protection viewpoint in the European Union, the Baltic population of A. oxyrinchus must be treated like A. sturio because its separation from the latter species was only determined in 2002 (European Commission, 2014)</footnote>

<footnote n="2">² https://rm.coe.int/pan-european-action-plan-for-sturgeons/16808e84f3</footnote>

<footnote n="3">³ https://rm.coe.int/recommendation-199-2018-action-plan-sturgeon/1680a01895</footnote>
The scope of the contract covers the assessment of the implementation of the PANEUAP in 18 key sturgeon range countries, including 15 EU Member States (Romania, Bulgaria, Croatia, Slovenia, Hungary, Slovakia, Austria, Germany, Italy, Poland, Lithuania, Latvia, Estonia, France, and The Netherlands) as well as Serbia, Ukraine, and Georgia. Existing knowledge about sturgeon habitats and migration obstacles in 11 key river basins including Danube, Rioni, Po, Vistula, Oder, Nemunas, Gauja, Narva, Elbe, Rhine, and Gironde have been collected and displayed in maps.

Further, the contract encompasses (1) a study about sturgeon bycatch and possible measures to avoid or mitigate it, (2) guidelines for sturgeon population monitoring, (3) guidelines for habitat monitoring as well

as (4) guidelines for best practice ex situ breeding and release programs.

This document presents the “**Review of bycatch prevention and mitigation measures for sturgeons**” contributing explicitly to reaching the PANEUAP Objective 1 “Remaining wild sturgeon populations are protected from accidental and directed removal of individuals” more specifically to Result 1.2 of the PANEUAP to “reduce accidental removal to levels allowing population recovery”. The report compiles available information on bycatch across Europe, supplements it with experiences from North America and identifies possible management options to minimize bycatch in marine and freshwater fisheries.
## 2. Context

### 2.1 Sturgeon distribution and conservation status in Europe

Eight sturgeon species native to Europe, five are diadromous (i.e. they reproduce in freshwater and grow at sea): the European sturgeon *Acipenser sturio*, the Baltic sturgeon *A. oxyrinchus*, the Russian sturgeon *A. gueldenstädtii*, the stellate sturgeon *A. stellatus*, and the beluga sturgeon Huso huso. The other three species can complete their life-cycle in freshwater; the potamodromous sterlet, *A. ruthenus* is not able to survive at sea, while the Adriatic sturgeon *A. naccarii* is a freshwater euryhaline species which can survive in brackish water for short periods and the ship sturgeon *A. nudiventris* also has potamodromous populations while being able to survive at low salinities too. For more details about these species, see Holcik (1989).

All eight sturgeon species are subjected to a very high risk of extinction. With the exception of *A. ruthenus*, which is listed as Endangered, the other seven sturgeon species are listed as Critically Endangered species on the IUCN Red List of Threatened Species (IUCN, 2022, Congiu et al., 2023). Their

historical presence has been documented so far in at least 78 river systems throughout the European continent but today their presence is limited to approximately 15 river systems with almost all populations depending on recovery measures. The populations were overfished in the past for their meat and caviar. Today, they are legally protected in almost all European waters. Anthropogenic pressures resulting from hydro-power production, navigation, water abstraction, pollution and climate change have and continue to modify the rivers and impact the suitability and accessibility of sturgeon habitats both in rivers and seas. Furthermore, the remaining populations are subjected to continued pressure from bycatch in legal fisheries targeting a variety of species while even illegal fishing remains an issue in some regions. This impact is especially challenging, since their life-cycle with late maturation and long reproduction cycles in conjunction with extreme longevity renders sturgeon extremely vulnerable to fisheries impacts both in rivers and at sea.

### 2.2 Bycatch definition

Numerous definitions exist for bycatch. Carpentieri et al. (2021) define it as "a term widely used to refer to the part of catch unintentionally captured during a fishing operation in addition to target species, and consisting of discards and incidental catches of vulnerable species". Catch methods are deployed to target a particular species but end up catching other species as well. It has

been assessed for 2002 that for every kilogram of target species caught globally, 0.7 kg of bycatch occurs (Univ. Michigan, 2019). Since fishing gear, such as nets, hook lines, and traps lacks selectivity, incidental bycatch occurs globally in almost every type of fishery, rendering the issue to a significant concern in commercial fisheries since it has detrimental effects on marine
ecosystems and fish populations (Bellido et al., 2011). Bycatch contributes to overfishing of non-target species, disruption of food chains, harms vulnerable and endangered species, and thus adversely affects biodiversity in general. Incidental bycatch may involve marine mammals, sea turtles, seabirds, and other marine fauna as well (Moore et al., 2009; Zollett, 2009; HELCOM ACTION, 2021; Birdlife International, 2022). The consequences of bycatch are diverse and depend on its fate: mortality if retained, mortality from interaction with the gear or handling (if the fish is released by the gear underwater, resulting in unobserved mortality, or are predated upon while in the gear), impacted survival when released as well as unimpacted (Crowder & Murawski, 1998; Fisheries and Oceans Canada, 2016).

In this document, the terms “bycatch” and “incidental bycatch” which are used in numerous documents (e.g. International Council for the Exploration of the Sea (ICES), 2022a), are applied as synonyms. The differentiation to directed poaching in this context is the lack of intent to catch the species and the fact that it is not utilized commercially. To prevent poaching in the EU protected species are exempted from the obligation to be landed but have to be released immediately after coming on board (Article 15 of Regulation (EU) No 1380/2013). In cases when the unintentionally caught sturgeon is retained by the fishery they must be considered illegal and poached.

## 2.3 Bycatch and sturgeon

With legal fisheries for sturgeons being prohibited throughout Europe (with the exception to managed sport fishing in three countries in the Upper Danube)<fnref n="4" />, bycatch remains one of the main factors, along with habitat degradation and IUU fishery, that significantly affect and hinder population recovery.

Sturgeon represent unusual combinations of morphology, behavior and life history characteristics that make them highly vulnerable to impacts from groundfish fisheries. As they reach maturity late and reproduce over decades, their reproductive potential is sensitive to fishing mortality

(Boreman, 1997; Jaric et al., 2010) since their populations depend upon the long-term survival of individuals (> 35 years) to repeatedly contribute to reproduction.

The three remaining freshwater species (i.e. *A. ruthenus*, *A. naccarii*; *A. nudiventris*) are at risk of bycatch in river systems from both commercial (e.g. shad fisheries in the Danube) and recreational fisheries which affect the diadromous species only during their reproductive periods when they migrate into the rivers, as well as during the early life cycle phases when they still forage in freshwater.

<footnote n="4">⁴ Austria, Slovakia and Croatia (as of 2023)</footnote>
<figure><img src="image_6.png" /><figcaption>**Figure 1:** Schematic life-cycle and main threats predominantly impacting the various stages (From Friedrich et al., 2018).</figcaption></figure>

Marine bycatch concerns diadromous sturgeon only. Their preference for shallow marine habitats utilized as feeding grounds, as well as their aggregations during migration (e.g. Ninua, 1976; Lyovin, 1981; Sbikin & Levin, 1985; Rochard et al., 1997; Zarkua, 1998; Gessner et al., 1999; Bat et al., 2005; Guchmanidze et al., 2009; Maximov et al., 2014; Charbonnel et al., 2023) place sturgeon at risk for bycatch in different coastal fisheries (e.g. gillnet fisheries for sole, monkfish, pikeperch, sea trout; trammel net fisheries for meagre, turbot, cod; benthic trawl fisheries for flatfish, groundfish, and shrimp; inshore purse seine for anchovy and sardines). The intensive fisheries in the European Seas and the associated high fishing pressure result in a multitude of capture opportunities during the

long marine phase of sturgeons, resulting in high likelihood of mortality associated with fishery interactions. Since the fish are caught in a variety of fishing gears, commercial and recreational fisheries impose a pronounced effect and accordingly, have a high responsibility for the survival of the individuals encountered.

In the frame of sturgeon conservation action plans and recovery strategies, restriction of fishing activities is one of the few levers available for conservation managers to make a real contribution to recover decimated populations in a short term while other, habitat related impacts are much more difficult to address. Such measures include the temporal or spatial prohibition of any fisheries activities and the limitation of gear (closed fisheries). All of these
measures require increased efforts for en-
forcement such as control for illegal fishing,
verification of gear used, as well as market
surveys in combination with effective pros-
ecution. The reduction of encounters of pro-

tected species with fishing gear limits mor-
tality, ensures the effective recovery of the
population in question, contributes substan-
tially to their conservation and serves as an
indicator of sustainable fisheries manage-
ment.

2.4 Political framework

As reflected in worldwide policies and
agreements, reducing bycatch to "insignifi-
cant levels" is a widely shared objective
whether to avoid wasting resources or to
protect endangered species. As an example
the Kunming-Montreal Global Biodiversity
Framework (GBF) target 5 states "Ensure
that the use, harvesting and trade of wild
species is sustainable, safe and legal, pre-

venting overexploitation, minimizing im-
pacts on non-target species and ecosystem-
ems" and makes a specific reference to the
"unintentional impacts on other species,
through bycatch". Several more specific le-
gal frameworks in particular in the context
of European Union policy have been devel-
oped and facilitate the implementation of
the measures required to reach the above
mentioned target.

**2.4.1** *European Union Policies and Regulations*

**2.4.1.1 The Habitats Directive (Directive 92/43/EEC)**

The Habitats Directive covers all eight spe-
cies of sturgeon in Europe and prohibits the
deliberate killing, as well as the disturbance
or destruction of the species and their hab-
itats listed therein. For species listed in An-
nex IV of this Directive, namely of A. sturio,
A. oxyrinchus<fnref n="5" /> and A. naccarii, bycatch
must be officially monitored. "Member
States shall establish a system to monitor
the incidental capture and killing of the an-
imal species listed in Annex IV" (Article 12).
Furthermore, fishers are obliged to register
the catch of Annex IV species in their log-
books. As such, the fishery administrations
would have the means to collect the info-
mation required. From interviews carried
out under this EU Service Contract, it be-
came evident that none of the EU member
countries has set a functional reporting sys-

tem. In cases where bycatch monitoring ex-
ists, these systems are based entirely on
voluntary declarations and registrations.
In conjunction with the EU Birds Directive
(Directive2009/147/EC), the Habitats Di-
rective established the Natura 2000 net-
work to protect natural sites identified for
their rare importance for endangered spe-
cies. Sturgeons are listed as targets for sev-
eral of these sites. However, fishing activi-
ties are not necessarily restricted by the
management plans of these sites (e.g. site
FR5400469 Pertuis charentais).

<footnote n="5">⁵ The Baltic population of A. oxyrinchus must be treated like A. sturio because its separation from the latter species was only determined in 2002 (European Commission, 2014)</footnote>
For the sturgeon species listed under Annex V of the Habitats Directive any taking from the wild is generally prohibited as long as the species is not in a favorable conservation status. In the latest available assessments (reporting period 2013-2018) of conservation status under Article 17 of the

Habitats Directive, EU Member States report all sturgeon species to be in an unfavourable conservation status<fnref n="6" /> and therefore, fishing for them must not be permitted.

### 2.4.1.2 Common Fisheries Policy (Regulation (EU) No 1380/2013)

The Common Fisheries Policy (CFP) is the primary framework for managing fisheries in the EU. It sets out principles and rules for the conservation of fish stocks, including measures to reduce bycatch. The CFP emphasizes the use of low impact fishing gear and encourages the development and implementation of selective fishing practices. One of the objectives of the CFP is to ensure that the negative impacts of fishing activities on the marine ecosystem are minimized. This includes, amongst other actions that adverse impacts are eliminated and unwanted catch of protected species is reduced.

The EU introduced the Landing Obligation as part of the new CFP (Article 15 of Regulation (EU) No 1380/2013⁷). It is fully in force since 2019, with the objective to eliminate discards by encouraging fishers to fish more selectively and to avoid unwanted catches. It requires fishers to land all catches of different regulated commercial species, but it only applies to species with a catch limit or a minimum conservation size and is hence not applicable for protected sturgeons. In any case, species listed in the Habitats Directive Annex II are considered as “prohibited” and must be released (Borges & Penas Lado, 2019), while monitoring of bycatch of Annex IV species is required.

As part of the CFP, the Fisheries Technical Measure Regulation (EU Regulation 2019/1241 on the conservation of fisheries resources and the protection of marine ecosystems through technical measures) lays down a whole set of technical measures concerning the specifications for design and use of gear, minimum mesh sizes for nets, requirements of selective gears to reduce unwanted catches, closed areas and seasons, measures to minimize the impact of fishing or the minimum size of catches (“minimum conservation reference size”). These measures shall “ensure that incidental catches of sensitive marine species, (...) that are a result of fishing, are minimized and where possible eliminated so that they do not represent a threat to the conservation status of these species”<fnref n="8" />. In this context, ‘sensitive species’ means a species whose conservation status, including its habitat, distribution, population size or population condition is adversely affected by pressures arising from human activities, including fishing activities. Sensitive species, in particular, include species listed in Annexes II and IV to Directive 92/43/EEC, species covered by Directive 2009/147/EC and species whose protection is necessary to achieve good environmental status under Directive 2008/56/EC.

<footnote n="6">⁶ https://nature-art17.eionet.europa.eu/article17/</footnote>

<footnote n="7">⁷ (Article 15 of Regulation (EU) No 1380/2013 "All catches of species which are subject to catch limits and, in the Mediterranean, also catches of species which are subject to minimum sizes as defined in Annex III to Regulation (EC) No 1967/2006, caught during fishing activities (...) shall be brought and retained on board the fishing vessels, recorded, landed and counted against the quotas where applicable, except when used as live bait..." (...) "The landing obligation referred to in paragraph 1 shall not apply to: (a) species in respect of which fishing is prohibited and which are identified as such in a Union legal act adopted in the area of the CFP; (b) species for which scientific evidence demonstrates high survival rates, taking into account the characteristics of the gear, of the fishing practices and of the ecosystem; (c) catches falling under de minimis exemptions."</footnote>

<footnote n="8">⁸ http://data.europa.eu/eli/reg/2019/1241/oj</footnote>
Annex XIII of this Regulation is dedicated to monitoring measures and reduction of incidental catches of sensitive species.

Annex I of the Fisheries Technical Measure Regulation lists prohibited species, and includes only two sturgeon species, the Adriatic sturgeon *A. naccarii* and the European sturgeon *A. sturio*. Annex III of this regulation is dedicated to monitoring measures and the reduction of accidental catch of sensitive species, requesting Member States to collect scientific data on bycatch of sensitive species and includes that "Member States shall submit joint recommendations for additional mitigation measures for the reduction of incidental catches of the concerned

species". However, specific provisions for fish species are not included in this Annex.

The revised EU Fisheries Control Regulation (Regulation (EU) 2023/2842⁹) for establishing a Community control system for ensuring compliance with the rules of the common fisheries policy came into force in 2024 and includes improvements for the reporting of vulnerable species bycatch including Remote Electronic Monitoring (REM) with on board cameras for large scale vessels (>18m) of high-risk fisheries and provisions for vessel tracking and electronic logbooks for all vessels including small vessels until 2030.

### EU ACTION PLAN: PROTECTING AND RESTORING MARINE ECOSYSTEMS FOR SUSTAINABLE AND RESILIENT FISHERIES (COM (2023) 102 FINAL)

The EU Action Plan is part of the Commission's efforts to achieve a more consistent implementation of the EU's environmental policy and the common fisheries policy with its three sustainability pillars - environmental, economic and social. In its Communication¹⁰ to the European Parliament, the Council, the European Economic and social Committee and the Committee of the Regions, the European Commission calls on Member States to adopt national measures or submit joint recommendations to the Commission to minimize bycatch (or reduce it to the level that enables the full recovery of the populations) of several species, including sturgeons (by the end of 2024).

#### 2.4.1.3 Marine Strategy Framework Directive (2008/56/EC) (MSFD)

The MSFD is the first EU legislative instrument related to marine biodiversity. Through the Commission Decision (EU) 2017/848 the MSFD seeks to establish "Good Environmental Status" for which a series of descriptors have been defined. An assessment of the levels of mortality due to incidental bycatch, comprising all catches of species not targeted in fisheries operations (=incidentally/accidentally caught), including those not taken on board, regardless of later treatment, is required to fulfil the objectives of the Marine Strategy Framework Directive (2008/56/EC) (MSFD).

Specifically, Criterion 1 (Mortality rate from bycatch) of Descriptor 1 (Biological diversity is maintained) should include species that are regionally at risk from bycatch. Underlying data by fleet segments are needed to enable the identification of those sectors contributing most to bycatch of each of the species considered. Assessing D1C1 for a species will involve aggregating bycatch estimates from different sectors to give a total bycatch mortality level per species or population. One must note that the inclusion and selection of species is at the discretion of the Member States (only Bulgaria and

<footnote n="9">⁹ https://eur-lex.europa.eu/eli/reg/2023/2842 | ¹⁰ https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:52023DC0102</footnote>
Germany have included some sturgeon species under D1) and threshold values for acceptable bycatch mortality rates have not been introduced.

Notably for *A. gueldenstaedtii*, *A. stellatus*, and *H. huso* based upon the age of maturity and the fishery in which the fish are landed, e.g. the size selectivity of the fishery (Jaric et al., 2015), the respective limits have been calculated based upon the IUCN criteria for Red Listing and vary between species. Similarly, the removal rates have been assessed for *A. sturio*, *A. oxyrinchus* and *A. fulvescens* in an attempt to outline the permissible mortality for the different species to avoid impacts on population sizes. (Jaric & Gessner, 2013; Atlantic Sturgeon Status Review Team, 2007; Bruch et al. 2017). Therefore such thresholds exist and could be applied in legislation.

## 2.4.2 Fisheries management organizations and Regional management organizations (Sea Conventions)

### 2.4.2.1 General Fisheries Commission for the Mediterranean – GFCM

The General Fisheries Commission for the Mediterranean is a regional fisheries management organization, established under the Constitution of the Food and Agriculture Organization of the United Nations (FAO)<fnref n="11" />. With 22 member countries and the EU<fnref n="12" />, its main objective is to ensure the conservation and the sustainable use of living marine resources as well as the sustainable development of aquaculture in the Mediterranean and in the Black Sea.

In 2021, the Working Group on the Black Sea (WGBS) noted the extremely critical situation of the sturgeon species in the region. The WGBS suggested the need for a pilot project to be conducted under the framework of the BlackSea4Fish project in collaboration with all relevant partners and in line with conservation needs at national, regional, and international levels, according to a set of general terms of reference. The proposal was endorsed by the 44th annual session of the GFCM (2021) which adopted Resolution GFCM/44/ 2021/5 on the mitigation of fisheries impacts for the conservation of sturgeons in the Black Sea (geographical subarea 29)<fnref n="13" />. This pilot project consists of three work packages (WPs). WP 1 aims at creating a network of scientific experts and raising awareness on the conservation status and critical issues related to

the marine portion of the sturgeon life cycle. The objective of WP 2 is to collate all information available on species biology, distribution and interactions with marine fisheries in consultation with national authorities and the network of scientific experts created in WP 1. Finally, WP 3 will cover an integrated analysis of all the information gathered under WP 1 and WP 2 towards identifying potential management and technical measures for the marine part of the sturgeon life cycle. To gather complementary information from fishers, local ecological knowledge has recently been explored on three main categories of information: seasonality, distribution, and illegal, unreported and unregulated (IUU) activities. The findings to be obtained through these semi-structured interviews with local fishers in four Black Sea countries (Bulgaria, Georgia, Romania, Turkey) are foreseen to support decision-making at the next session of the GFCM in 2024.

<footnote n="11">¹¹ https://www.fao.org/gfcm/about/en/</footnote>

<footnote n="12">¹² https://www.fao.org/gfcm/about/membership/en</footnote>

<footnote n="13">¹³ https://www.fao.org/faolex/results/details/en/c/LEX-FAOC217220/</footnote>
### 2.4.2.2 The Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR)

Since OSPAR does not primarily address issues related to fisheries, it does not have a specific position on the bycatch of endangered species. However, OSPAR's work indirectly contributes to the reduction of bycatch and the protection of endangered species. As an example, OSPAR promotes sustainable fishing practices and supports the implementation of measures to minimize the impact of fishing activities on marine ecosystems. These efforts include the development and implementation of regional fisheries management plans, the establishment of marine protected areas, and

the promotion of selective fishing gears and techniques. OSPAR organizes regular meetings to update and monitor the conservation status of endangered species (for A. sturio). In the last assessment<fnref n="14" /> OSPAR concludes that "Threats, mainly from habitat alteration and bycatch in the Greater North Sea, the Celtic Sea, the Bay of Biscay and the Iberian Coast as well as an increased abundance of alien sturgeon species still pose a significant threat to this species."

### 2.4.2.3 The Baltic Marine Environment Protection Commission (HELCOM)

"Constituting the foundation of HELCOM, the Convention on the Protection of the Marine Environment of the Baltic Sea Area - also known as the Helsinki Convention - was signed in 1974 by all Baltic Sea coastal countries. The Helsinki Convention seeks to protect the Baltic Sea from all sources of pollution from land, air, and sea, as well as to preserve biological diversity and to promote the sustainable use of marine resources."<fnref n="15" />

HELCOM's actions related to sustainable fisheries management and conservation of marine habitats in the Baltic Sea can contribute to minimizing bycatch. HELCOM works in coordination with other organizations (e.g. ICES) and initiatives to address broader environmental and fisheries management issues, and by doing so, it can help mitigate the impact of bycatch in the Baltic

Sea. However, specific policies and regulations related to bycatch may fall under the purview of national governments and international agreements outside of HELCOM's direct mandate. However, the HELCOM Baltic Sea Action Plan (2021), provides a good overview of the situation related to bycatch in the Baltic Sea. It identifies high-risk areas and proposes measures to reduce bycatch. It deals mainly with marine mammals (porpoises and seals) and seabirds. Unfortunately, protected fish, including sturgeons, are mentioned only superficially in this report while being addressed specifically in the Baltic Sea Sturgeon Action Plan (2019). Ongoing initiatives are underway to widen the focus of HELCOM, including, but not limited to, incorporating migratory species and specifically addressing sturgeon both with regard to bycatch and migration facilitation (HELCOM FISH 11/23).

<footnote n="14">¹⁴ https://oap.ospar.org/en/ospar-assessments/committee-assessments/biodiversity-committee/status-assessments/European-or-common-sturgeon/#threats-impacts</footnote>

<footnote n="15">¹⁵ https://helcom.fi/about-us/</footnote>
#### 2.4.2.4 The Convention on the Protection of the Black Sea Against Pollution (Bucharest Convention)

This Convention, mainly focusing on the protection of the Black Sea against pollution, was signed by all states bordering the Black Sea on 21 April 1992. Among others, it is mentioned that all Parties must protect

biodiversity and the marine living resources. Several sturgeon species are listed in Annex II and Annex IV of this Convention. However, there is no specific action addressing sturgeon bycatch.

### 2.4.3 The Bern Convention

Forty nine countries and the European Union have signed up to the Convention and committed to promoting national conservation policies, considering the impact of planning and development on the natural environment, promoting education and information on conservation, and coordinating research. Three sturgeon species are listed in Annex II of the Bern Convention (strictly protected fauna species): the Adriatic sturgeon *A. naccarii*, the European sturgeon *A. sturio*, and the beluga *Huso huso* (in the Mediterranean), as well as three others are

listed in its Annex III (protected species): *A. ruthenus*, *A. stellatus*, and the beluga *Huso huso* for the rest of its' distribution area. Notably, *A. gueldenstaedtii*, *A. nudiventris* and *A. oxyrinchus* are still missing on the Annexes. The Standing Committee has adopted Recommendation No. 199 (2018) on the Pan-European Action Plan for the conservation of the sturgeon providing a framework for countries to implement sturgeon recovery actions. Objective 1 of the PANEUAP refers to the reduction of bycatch.

## 2.5 General approaches to address the conservation related issues of bycatch

A prerequisite for the planning and implementation of actions would be the collection and provision of data that identify the dimension of bycatch related issues. Specifically, the number of encounters and the impact of different fishing techniques must be documented to enable regulators to set priorities in combatting the detrimental effects.

### 2.5.1 Collection of bycatch data

*"Collection of data on the incidental capture of vulnerable species ... is key in understanding the nature and extent of this problem. It is a necessary step towards developing and implementing adequate management measures for reducing interaction"*
(The Food and Agriculture Organization of the United Nations (FAO), 2019).

The International Council for the Exploration of the Sea (ICES) Working Group on Bycatch of Protected Species (WGBYC) focuses on assessing and addressing the issue of bycatch in fisheries across the ICES area. The WGBYC evaluates all bycatch data/information from multiple sources primarily to
be utilized for advisory purposes. It examines the impact of bycatch on different species, evaluates mitigation measures, and provides advice on reducing bycatch and minimizing its impact on marine ecosystems.

In the ICES road map for bycatch advice on protected, endangered, and threatened species (ICES, 2022a) two sturgeon species are listed of bycatch relevance. The Atlantic sturgeon *A. oxyrinchus* in the Baltic Sea ecoregion, and the European sturgeon *A. sturio* in the Bay of Biscay, Iberian Coast, Celtic Seas and in the Greater North Sea ecoregions.

As for other fish species that are listed as either Protected, Endangered and/or Threatened Species (PETS) the sampling is "described in the observer manual, but is labelled as "not mandatory", which leaves the possibility for the observer to not record this bycatch." (ICES 2012). This approach must be changed, especially when taking into account the perspective of the Working Group on Science to Support Conservation,

Restoration and Management of Diadromous Species (WGDIAD) on data deficient species, which is striving to obtain information of all aspects of these species.

Both, the ICES Report of the Joint WGBYC-WGCATCH Workshop on sampling of bycatch and PET species (WKPETSAMP) (ICES, 2019) and the FAO (2019) list and assess the strength and limitations of the different methods used to monitor the accidental capture of vulnerable species).

Potential data sources can be: fishery independent surveys from research vessels (e.g. Doray et al., 2014) targeting a specific group of species (e.g. groundfish, small pelagic fish, etc...) in a certain area, and fishery dependent surveys with observers on commercial boats<fnref n="16" /> (e.g. Bushuiev et al., 2020, 2021) or on shore (e.g. EU Data Collection Framework) upon landing, or by logbook analysis (Table 1). Possible sturgeon bycatch can be recorded within the framework of these surveys with varying levels of detail.

<table><caption>**Table 1:** Strength and weakness of bycatch data sources (adapted from FAO 2019 and ICES 2019).</caption><thead><tr><th></th><th>Data sources</th><th>Strength</th><th>Weaknesses</th></tr></thead><tbody><tr><td rowspan="4">Fishery dependent data</td><td></td><td>High representation of normal fishing</td><td></td></tr><tr><td>Independent observations by trained observers</td><td>The most reliable and useful means of collecting data</td><td>Difficult for smaller (space limitation) or unsafe vessels, impracticable for non-commercial fisheries.<br>Difficult to ensure true randomness<br>Large scale<br>Expensive</td></tr><tr><td>Interviews</td><td>A first step to get information and to prioritize broader studies</td><td>Need trust and credibility<br>Can be biased, voluntarily or not</td></tr><tr><td>Self-reporting</td><td>Low cost (based on logbooks)<br>When on board observers are refused</td><td>High degree of cooperation required<br>Too many forms to fill out<br>Risk of bias<br>Possible incorrect species identification</td></tr></tbody></table>

<footnote n="16">¹⁶ https://marinescience.blog.gov.uk/2022/11/21/fish-observers-the-life-and-sole-of-collaborative-fisheries-science/</footnote>
<table><tr><td></td><td></td><td></td><td>Not possible for small vessels (length &lt; 8m) that do not have to fill in logbooks</td></tr><tr><td></td><td>Remote electronic monitoring (video surveillance)</td><td>Cost-efficient and reliable Also useful for small scale vessels</td><td>Fishers' reluctance to use electronic recording devices Potential interference with personality rights and data protection</td></tr><tr><td></td><td>Market surveys</td><td>Cost efficient Detection of traffic, poaching of PET species Global overview</td><td>Limited to commercial fisheries Biased depending on market routes No direct link with gear and locations</td></tr><tr><td rowspan="2">Fishery independent data</td><td>Species sampling and tracking Bycatch studies</td><td>Remote sensing data to understand spatial ecology Tracking needed to identify environmental niches of target species</td><td>Misrepresentation of the interaction of vulnerable species with fisheries Sampling design biased toward a group of species Expensive Small spatiotemporal scale</td></tr><tr><td>Stranding data</td><td>Useful when little information available Enable biological sampling Low cost</td><td>No direct link with bycatch at sea Need strict protocol to identify the cause of death</td></tr></table>

When bycatch occurs frequently and poses a serious threat to endangered species, specific studies should be carried out to verify the data (e.g. Bahn et al., 2012) or to test gear and practice modifications (e.g. Morizur et al., 2008; He & Jones, 2013; Levesque et al., 2016). Unfortunately, no practical criteria and responsibilities are identified in the current legal framework to

do so. Depending on the results of such studies, authorities are enabled to implement measures to limit the number of deaths<fnref n="17" />.

There are many methods of recording sturgeon bycatch data, some of which have been put into practice as part of projects and plans, but none of which constitute “official recording”.

### 2.5.2 Impact assessments of bycatch

The conservation status of sturgeon is resulting from the cumulative impacts of numerous threats. Estimating the contribution of bycatch on conservation status is complex, but highly necessary to design well informed, adequate, and targeted measures to be implemented. Since populations with low abundances results in low absolute bycatch numbers, the impact of bycatch can

nevertheless be significant, despite the low absolute numbers. The effort that is required to obtain a sufficiently detailed picture is high and cannot be solely delegated to observer programs (such as EU-Northwest Atlantic Fisheries Organization observers<fnref n="18" />) who are considered to have plenty of tasks to fulfil on board already.

<footnote n="17">¹⁷ e.g. https://www.conseil-etat.fr/en/news/accidental-capture-of-small-cetaceans-the-government-must-act-within-six-months-to-ensure-the-survival-of-dolphins-and-porpoises-in-the-Bay-of-Biscay</footnote>

<footnote n="18">¹⁸ https://eur-lex.europa.eu/EN/legal-content/summary/transposition-of-northwest-atlantic-fisheries-organization-conservation-and-enforcement-measures-into-eu-law.html</footnote>
Once sturgeon populations recover as a result of conservation efforts, also the bycatch numbers are likely to increase and therefore the visibility of the impact will increase. Model calculations have shown that the recovery of populations of long lived, late maturing sturgeons such as A. sturio and A. oxyrinchus requires a minimal fisheries related mortality that must not exceed 5% annually (Jaric & Gessner, 2013). This constitutes a target that is already difficult to reach when bycatch rates of 20-60% of the fish released with only 20% observed mortality are encountered (Gessner et al., 2011, Stakenas et al., 2019).

Depending on the species, the gear used, the duration that the fish is captured in the gear, the mechanical impact of the catch method and the care taken during landing and handling, the impact of accidental catches can range from moderate stress to death. Whether or not an individual is released in good condition also depends on the behavior of the fisher. If they do not release a legally protected species immediately, the chances for survival drop significantly.

### 2.5.3 Preventive measures

Most efforts to reduce the impact of bycatch are developed with respect to marine mammals (e.g. FAO 2020), turtles and sea birds (e.g. Moore et al., 2009; Evans et al., 2021). Only recently efforts were extended to PETS fish, principally sharks and rays (Wosnick et al., 2022).

Preventing and thus avoiding bycatch is the most effective way to minimize its impact. There are various strategies to limit interactions between fisheries activities and PETS to reduce the encounter probability:

* Raising awareness among fishers and the public about the importance of fish conservation and the impact of bycatch has a key role in facilitating the understanding of the effects of bycatch. Promote responsible fishing practices and offer education and training programs to help fishers adopt bycatch reduction measures and increase compliance (e.g. Rajakaruna et al., 2020).

* Ensuring that legal requirements are clear, unambiguous, and concise over the entire set of regulations by different administrative bodies is an essential prerequisite for effective communication.

* Increasing the enforcement and resulting legal consequences if legal obligations are not met is a prerequisite for compliance; without enforcement, rules are not effective.

* Application of selective fishing techniques that specifically target the desired species while minimizing bycatch is applied in the monkfish fishing industry in the US to protect Atlantic sturgeon (*A. oxyrinchus*) (Dunton et al., 2015). Investments in research and the development of innovative fishing gear that specifically targets the desired catch while minimizing bycatch is urgently required (see Matsuoka, 2008 for a review).

* The development and applications of bycatch reduction devices (BRDs) that allow non-target species to escape from fishing gear (e.g. Willems et al., 2016) is a common method to limit bycatch. They exist for turtles in particular and are applied to
trawl fishing in Denmark, reducing cod (*Gadus morhua*) bycatch in saithe and flatfish fisheries (e.g. Madsen et al., 2006, see also Glass et al., 2012 for review).

» Acoustic deterrents that emit sound are utilized to repel dolphins and harbor porpoises from deep gillnets (e.g. Morizur et al., 2008, 2009; Chladek et al., 2020; Özdemir et al., 2023). For the same objective, visual deterrents are used to limit bycatch of sea turtles (e.g. Wang et al., 2010; Virgili et al., 2018).

» Magnetic fields were utilized to selectively reduce bycatch of species in static gear (Formicki et al., 2004).

» Visual cues and echo reflective materials are applied in gillnets to prevent the catch of small cetaceans (Kratzer, 2021; Kratzer et al., 2021; Özdemir et al., 2023).

» As the overlap between fishing zones and the habitats of PETS creates potential interactions, implementing fishing restrictions in areas and during periods when protected or endangered species are known to be present can help to reduce these interactions and limit bycatch (e.g. Evans et al., 2021; O'Keefe et al., 2023). This can involve seasonal closures or spatial management measures that prohibit fishing in critical habitats or during aggregation times (spawning).

» Implementing observer programs where trained personnel monitor fishing activities to collect data on bycatch rates and species composition allows to accurately assess the impact of fishing practices on non-target species (e.g. ICES 2023).

» By encouraging collaboration between government agencies, fishers, scientists, and conservation organizations, regulations can be drawn up and applied to reduce sturgeon bycatch. Establishing fishing quotas, gear restrictions, and monitoring programs can help protect sturgeon populations effectively (see Jenkins et al., 2022 for review).

## 2.6 Lessons learned from the North American experiences on bycatch of sturgeon

Most of the papers published on sturgeon bycatch concern North American sturgeon species, mainly the Atlantic sturgeon *A. oxyrinchus* and the shortnose sturgeon *A. brevirostrum* due to their protection status. Only a few publications address the green sturgeon *A. medirostris* and, very marginally, two freshwater species, the lake sturgeon *A. fulvescens* and the pallid sturgeon *Scaphirynchus albus*.

The United States have implemented drastic steps for population recovery, such as a 40 year fishing ban on Atlantic sturgeon, which includes scientific catches, or the listing of shortnose and Atlantic sturgeons under the Endangered Species Act (ESA), which in favor of the species listed, gives

protection management a priority over other resource uses. Due to the existence of numerous populations, some of which, although threatened, still are relatively abundant and which reveal substantial overlap of their (marine) habitats with commercial fisheries, the potential for bycatch is pronounced. Scientific evidence has helped to establish management targets that are implemented strictly. To give an example, reducing bycatch of shortnose sturgeon in commercial fisheries is a critical component of recovering populations throughout the Atlantic coast (Bahn, 2010) and for *A. oxyrinchus*, a bycatch mortality rate of 6% would put the recovering populations at risk
(Atlantic Sturgeon Status Review Team, 2007, ASMFC 2017).

As they are closely related to European sturgeons in terms of morphology, ecology, habitats used, behavior and life cycle, it is useful to analyze this corpus of articles to determine lessons to be learned, and to propose comparable management tools to

reduce bycatch or to at least mitigate the effects of bycatch on European species. Specifically, the identification of the relevant fisheries that cause the highest level of bycatch and sturgeon mortality as well as the tools proposed and used to limit them is of major interest.

## 2.6.1 Background

From a Scopus request and additional research, we have retrieved 37 journal articles, 20 reports, 4 theses and 3 conference papers in the timeframe between 1979 and 2022. The information has been derived

from fishery dependent database analysis (e.g. Stein et al., 2004 a, b; Eyler, 2006), a fishery-independent sampling program (Laney et al., 2007) and specific studies (e.g. Dunton et al., 2015).

## 2.6.2 Interactions between sturgeon and fisheries

Numerous North American fisheries result in sturgeon bycatch (Table 2). Most of these fisheries are applied similar in Europe. The analysis reveals a clear link between fisheries for certain target species and sturgeon habitats. A majority of the sturgeon captured along the continental shelf were juveniles aggregating in specific locations around the mouths of estuarine areas and along narrow dispersal corridors in shallow water.

<table><caption>**Table 2:** North American fisheries most frequently mentioned in sturgeon bycatch papers.</caption><thead><tr><th>Target species</th><th>Gear<sup>19</sup></th><th>References</th></tr></thead><tbody><tr><td rowspan="2">Monkfish</td><td>Gillnet</td><td>Armstrong et al., 2011; Dunton et al., 2015</td></tr><tr><td>Otter trawl</td><td>Armstrong et al., 2011; Dunton et al., 2015</td></tr><tr><td rowspan="2">Goosefish</td><td>Set gillnet</td><td>Stein et al., 2004a</td></tr><tr><td>Fixed gillnet</td><td>Dunton et al., 2015</td></tr><tr><td rowspan="2">Flounders</td><td>Bottom trawl</td><td>Dunton et al. 2015</td></tr><tr><td>Gillnet</td><td>Armstrong &amp; White 2000; Armstrong &amp; Hightower 2002; Hoos et al., 2019</td></tr><tr><td>Halibut</td><td>Bottom trawl</td><td>Richerson et al., 2022</td></tr><tr><td>Bluefish</td><td>Drift gillnet</td><td>Stein et al., 2004</td></tr><tr><td>Spiny dogfish</td><td>Set gillnet</td><td>Stein et al., 2004</td></tr><tr><td rowspan="3">American shad</td><td>Drift gillnet</td><td>Stein et al., 2004</td></tr><tr><td>Set gillnet</td><td>Collins et al., 1996; Collins et al., 2000; Bahn, 2010; Bahn et al., 2012</td></tr><tr><td>Gillnet</td><td>Dadswell, 1979; Hoos et al., 2019</td></tr><tr><td>Salmon</td><td>Gillnet</td><td>Meth, 1973 in Dadswell, 1979; Fisheries &amp; Oceans, 2016</td></tr><tr><td rowspan="4">Striped bass</td><td>Set gillnet</td><td>Eyler, 2006</td></tr><tr><td>Drift gillnet</td><td>Eyler, 2006</td></tr><tr><td>Gillnet</td><td>Meth, 1973 in Dadswell, 1979</td></tr><tr><td>Set gillnet</td><td>Hager et al., 2021</td></tr></tbody></table>

<footnote n="19">¹⁹ To harmonize the name of gears, we used those retained by He et al. (2023).</footnote>
<table><tr><td rowspan="2">Shovelnose sturgeon</td><td>Trotlines</td><td>Bettoli et al., 2008, 2009</td></tr><tr><td>Gillnet</td><td></td></tr><tr><td>Shrimp</td><td>Trawl</td><td>Collins et al., 1996</td></tr></table>

### 2.6.3 Dimension of bycatch and mortality rates

From the review of numerous papers, it is obvious that sturgeon bycatch and mortality rates are highly underreported. As an example, in one area a single fisher has reported more than 100 incidents of bycatch while others in the same fishery have declared no bycatch. As a result of local sturgeon abundance and fishing practices applied, the estimated number of accidentally caught fish varies greatly between regions and seasons (e.g. Stein et al., 2004; Bahn, 2010).

Bycatch rate can refer to different definitions:

* How many individuals end up as bycatch in which gear? (Table 3)

* What proportion of sturgeons are landed in relation to the landing of target species?

* Out of a known number of sturgeon (tagged or assessed) what percentage were caught, and by which gear? (Table 4)

* What proportion of a target species is caught in a certain gear type (Table 5)

<table><caption>**Table 3:** Absolute numbers of bycaught sturgeon in different fisheries by surveys in American coastal waters.</caption><thead><tr><th>Context (Data source?)</th><th>Species</th><th>Number</th><th>Comments</th><th>Ref.</th></tr></thead><tbody><tr><td rowspan="2">NEFSC Observer Dataset (mean 2001-2006)</td><td rowspan="2">A. oxyrinchus</td><td>5143/yr.</td><td>Set gillnet fisheries; 2752-7904</td><td rowspan="2">Sheperd et al., 2007</td></tr><tr><td>3829/yr.</td><td>Otter trawl</td></tr><tr><td>Northeast Fisheries Observer Program (NEFOP) data along long island (1989-2013)</td><td></td><td>413</td><td></td><td>Dunton et al., 2015</td></tr><tr><td>Albermale Sound (1990-2001)</td><td></td><td>618</td><td>Gill net</td><td>Armstrong & Hightower, 2002</td></tr><tr><td>New York Ocean trawl Survey (2006-2013)</td><td></td><td>825</td><td></td><td>Dunton et al., 2015</td></tr><tr><td>NMFS sea sampling program (2000-2004)</td><td></td><td>433</td><td>Gill net</td><td>ASSRT<sup>20</sup> 2007</td></tr><tr><td rowspan="2">Altamaha River commercial shad fishery (2007-2009)</td><td rowspan="2">A. breviros-trum</td><td>200/yr.</td><td></td><td>Dadswell, 1979</td></tr><tr><td>622</td><td></td><td>Bahn, 2010</td></tr><tr><td>Delaware River shad gillnet fishery (1817-1913)</td><td></td><td>1949</td><td></td><td>Brundage & Meadows 1982</td></tr><tr><td>Mississippi River Shovelnose commercial fishery (2005-2007)</td><td>S. albus</td><td>169</td><td>1.8% of sturgeon harvest</td><td>Bettoli et al., 2009</td></tr><tr><td rowspan="2">Westcoast Groundfish Observer Program (WCGOP) (2007-2019)</td><td rowspan="2">A. medirostris</td><td>128</td><td></td><td>Richerson et al., 2022</td></tr><tr><td>665</td><td>2015</td><td></td></tr></tbody></table>

<footnote n="20">20 Atlantic Sturgeon Status Review Team (ASSRT)</footnote>
<table><tr><td></td><td></td><td>29</td><td>2011</td><td>Doukakis et al., 2020</td></tr><tr><td>Commercial Groundfish trawl fishery observer program (1996-2013)</td><td></td><td>16.4 T</td><td>Uncertainty about the species</td><td>Fisheries & Oceans 2016</td></tr><tr><td>Halibut bottom trawl fishery (2015-2019)</td><td></td><td>1231</td><td>288-664 /yr.</td><td>Richerson et al., 2022</td></tr><tr><td>Commercial hook and line fisheries</td><td></td><td>±0</td><td></td><td>Fisheries & Oceans Canada, 2016</td></tr><tr><td>At-Sea Hake Observer Program (A-SHOP) (2006-2022)</td><td></td><td>0</td><td></td><td>Richerson et al., 2022</td></tr></table>

From the review of numerous papers, it is obvious that sturgeon bycatch and mortality rates are highly underreported. As an example, in one area a single fisher has reported more than 100 incidents of bycatch while others in the same fishery have declared no bycatch. As a result of local sturgeon abundance and fishing practices applied, the estimated number of accidentally caught fish varies greatly between regions and seasons (e.g. Stein et al., 2004; Bahn, 2010).

<table><caption>**Table 4:** Percentages of bycatch by gear based upon a known number in a population.</caption><thead><tr><th>Context</th><th>Species</th><th>Gear</th><th>Bycatch rate</th><th>Ref.</th></tr></thead><tbody><tr><td rowspan="3">Bycaught from 974 tagged and released ind. (along Long Island, NY)</td><td rowspan="3">A. oxyrinchus</td><td>Trawl</td><td>1%</td><td rowspan="3">Dunton et al., 2015</td></tr><tr><td>Gillnet</td><td>&lt;1%</td></tr><tr><td>Hook and line</td><td>&lt;1%</td></tr><tr><td>Bycaught from 5000 tagged ind. Atlantic coast Sturgeon tagging data base (1992-2003)</td><td></td><td>Gillnet</td><td>360/5000</td><td>Eyler 2006, ASSRT, 2007</td></tr><tr><td>Altamaha River GA, commercial shad fishery (2007-2009)</td><td>A. brevirostrum</td><td>Gillnet</td><td>37-60% of the spawning run</td><td>Bahn, 2010</td></tr></tbody></table>

Despite local variations in fishing effort and in the spatial distribution of such effort, it is clear that sturgeon can be caught in similar proportions by gillnets or bottom trawls (Table 5).

<table><caption>**Table 5:** Relative contribution (%) of reported bycatch by the gear applied in different fisheries.</caption><thead><tr><th>Context</th><th>Gear</th><th>Species</th><th>By-catch rate</th><th>Ref.</th></tr></thead><tbody><tr><td rowspan="2">State water (1986-2000)</td><td>Set gillnet</td><td rowspan="2">A. oxyrinchus</td><td>84%</td><td rowspan="2">Stein et al. 2004a, b</td></tr><tr><td>Drift gillnet</td><td>1%</td></tr><tr><td>Atlantic Coast Sturgeon tagging data base (1992-2003)</td><td>Set gillnet</td><td></td><td>62%</td><td>Eyler et al., 2006</td></tr><tr><td rowspan="2">Northeast Fisheries Observer program (NEFOP) data for bycatch along</td><td>Set gillnet</td><td rowspan="2"></td><td>48%</td><td rowspan="2">Dunton et al., 2015</td></tr><tr><td>Otter bottom trawl</td><td>46%</td></tr></tbody></table>
<table><tbody><tr><td rowspan="3">Long Island, NY (1989-2013)</td><td>Drift gillnet</td><td rowspan="3"></td><td>6%</td><td rowspan="3"></td></tr><tr><td>Anchored floating gillnet</td><td>0%</td></tr><tr><td>Bottom long lines</td><td>0%</td></tr><tr><td>NMFS sea sampling program (2000-2004)</td><td>Set gillnet</td><td></td><td>91%</td><td>ASSRT, 2007</td></tr><tr><td rowspan="4">Altamaha River (GA)</td><td>Gillnet</td><td rowspan="4">A. breviros-trum</td><td>52%</td><td rowspan="4">Collins et al., 1996</td></tr><tr><td>Trawl</td><td>39%</td></tr><tr><td>Gillnet</td><td>83%</td></tr><tr><td>Trawl</td><td>8%</td></tr></tbody></table>

To verify the effect of the bycatch on the population in question, the immediate mortality rate among bycaught sturgeon is assessed as the proportion of dead individuals at capture in relation to the total catch of the species. This rate is highly variable, some gears however (e.g. set gillnet and fixed gillnet) generally induce more than 10% mortality, while others (e.g. baited hooks, lines, or trawl) result in less than 5% (Table 6).

Fishing conditions and conditions of the environment at catch can obviously have effects upon the mortality rate. It can be assumed that rocks collected in a trawl of ex-

tended duration surely increase the mortality rates of fishes in the trawl through mechanical damage. In gillnets, the soak time, apart from the mesh size and the water temperature, has a clear impact on the survival of sturgeon caught. Mesh sizes that are large enough to allow the fish to enter with the entire head result in opercular covers that are kept firmly closed, disabling the fish to breathe. Elevated temperature increases oxygen demand and as a result affect fish that are retained in the nets over time. Especially in gillnets utilized in inner coastal waters, mortalities increase drastically due to suffocation (Place, 2009; Stakenas & Pilinkoskij, 2019).

<table><caption>**Table 6:** Immediate mortality rate of sturgeon in different regions and in different gear types. In brackets are the number of fish considered.</caption><thead><tr><th>Context</th><th>Gear</th><th>Species</th><th>Mortality rate (proportion of dead sturgeon)</th><th>Ref.</th></tr></thead><tbody><tr><td rowspan="2">NEFSC Observer Dataset (2001-2006)</td><td>Set gillnet</td><td rowspan="4">A. oxyrin-chus</td><td>12,6%-13.8%</td><td rowspan="2">Sheperd et al., 2007</td></tr><tr><td>Otter trawl</td><td>&lt;1%</td></tr><tr><td>NMFS (2000-2004)</td><td>Set gillnet</td><td>30%</td><td>ASSRT 2007</td></tr><tr><td>NMFS east coast of USA (1989-2000)</td><td>Drift gillnet</td><td>10%</td><td>Stein et al., 2004a, b</td></tr><tr><td rowspan="2">Northeast Fisheries Observer program (NEFOP) data for bycatch along Long Island (NY) (1989-2013)</td><td>Set gillnet</td><td rowspan="4"></td><td>22%</td><td rowspan="2">Dunton et al., 2015</td></tr><tr><td>Otter trawl</td><td>0-0.2%</td></tr><tr><td rowspan="2">Gillnet</td><td>38%</td><td rowspan="2"></td></tr><tr><td>Otter bottom trawl</td><td>4%</td></tr><tr><td>Minas basin (NS), scientific sampling</td><td>Otter trawl</td><td></td><td>0%</td><td>Beardsall et al., 2013</td></tr></tbody></table>
<table><tbody><tr><td rowspan="2">ASMFC stock assessment</td><td>Trawl</td><td></td><td>0-5%</td><td>ASMFC 1998, Sheperd et al., 2007</td></tr><tr><td>Set gillnet</td><td></td><td>13.8%</td><td>Sheperd et al., 2007</td></tr><tr><td>Cooperative winter tagging (1988-2006)</td><td>Trawl</td><td></td><td>0% (146)</td><td>Laney et al., 2007</td></tr><tr><td>Brunswick River, Cape Fear River (NC)</td><td>Gillnet</td><td></td><td>24% (100)</td><td>Moser &amp; Ross, 1995</td></tr><tr><td>Virginia striped bass fishery (20005-2006)</td><td>Gillnet</td><td></td><td>5-8%</td><td>Place, 2009</td></tr><tr><td>James River</td><td>Set gillnet</td><td></td><td>4% (508)</td><td>Place, 2009</td></tr><tr><td>Cape Fear Independent survey (North Carolina) (2002-2007)</td><td>Set gillnet</td><td></td><td>25-37% (228)</td><td>Daniel, 2010</td></tr><tr><td>Pamlico Sound North Carolina Observer Program (2001-2004)</td><td>Gillnet</td><td></td><td>0-12%</td><td>ASSRT 2007; Daniel, 2010</td></tr><tr><td rowspan="2">Albemarle Sound (NC) scientific survey (IGNS)</td><td rowspan="2">Gillnet</td><td rowspan="2"></td><td>2% (107)</td><td>Armstrong &amp; Hightower, 2002</td></tr><tr><td>3% (1190) (1990-2009)</td><td>Daniel, 2010</td></tr><tr><td>Winyah Bay (SC), commercial shad fishery (1994-1995)</td><td>Set gillnet</td><td>A. brevirostrum</td><td>16%</td><td>Collins et al., 1996</td></tr><tr><td rowspan="2">St John River (NB) estuary</td><td>Gillnet</td><td></td><td>10%</td><td>Dadswell, 1979</td></tr><tr><td>Angling (catch and release)</td><td></td><td>0% (33)</td><td>Struthers et al. 2018</td></tr><tr><td>Altamaha River (GA) (2007-2009)</td><td>Set gillnet</td><td></td><td>&lt;8%</td><td>Bahn, 2010; Bahn et al., 2012</td></tr><tr><td>BiOP</td><td>Trawl</td><td>A. medirostris</td><td>5.2%</td><td>Richerson et al., 2022</td></tr><tr><td rowspan="5">Fraser River (BC)</td><td>Drift gillnet</td><td>A. transmontanus</td><td>0%</td><td>Nelson et al., 2013</td></tr><tr><td rowspan="2">Set gillnet</td><td></td><td>46.9%</td><td>Nelson et al., 2013</td></tr><tr><td></td><td>9-14 % (1663)</td><td>Robichaud et al., 2006</td></tr><tr><td>Hook and line</td><td></td><td>2.7%</td><td>Nelson et al., 2013</td></tr><tr><td>Angling (Catch and release)</td><td></td><td>0-0.01%</td><td>McLean et al., 2020; Robichaud et al., 2006</td></tr><tr><td rowspan="2">Mississippi River</td><td>Gillnet</td><td rowspan="2">S. albus</td><td>0%</td><td>Bettoli et al., 2009</td></tr><tr><td>Trotline</td><td>0%</td><td></td></tr></tbody></table>

Even if released alive, the fish are stressed (Struthers et al. 2018; McLean et al., 2020)

and sometimes even injured, putting them at risk of contracting infections. Handling
before being returned to the water adds on to the elevated stress levels (Beardsall et al., 2013), while the air temperature (below zero or above 25°C) increases the long-term mortality rate associated with this handling.

Only very few reports are available on the assessed post-released mortality of sturgeon. Collins et al. (1996) reported 20% of *A. brevirostrum* being injured during capture in the commercial gillnet shad fishery, leading to post release mortality. Post-release mortality in *A. medirostris* caught by trawl is estimated at 26% (Doukakis et al., 2020) while a report on *A. oxyrinchus* caught by otter trawl results in an estimated 6% post-release mortality (Beardsall et al.,

2013). Comparing the effects of the different gears, Robichaud et al (2006) found a higher mortality rate for *A. transmontanus* caught in set gillnet (46.9%, N=64) compared with those caught in drift gillnet (0%, N=32) or angled (2.6%, N=76). By studying the fate of individuals caught in catch and release recreational fisheries, McLean et al. (2020) for *A. transmontanus* in the Fraser River and Struthers et al. (2018) for *A. brevirostrum* in the Saint John River (New Brunswick, Canada) observed 0% immediate mortality. In addition, Moser and Ross (1995) pointed out that after capture, most of the adults they had sampled on the spawning migration returned downstream, interrupting their upstream breeding migration due to the stress experienced.

### 2.6.4 Recommendations to limit bycatch or its effects

To effectively reduce and eliminate the bycatch of sturgeon, bespoke solutions need to be developed. For this purpose it is necessary to undertake a thorough assessment of the number of sturgeon caught and the injury and mortality rates observed. In addition it is also essential to know the fishing conditions (location, gear details, target species, etc.) as well as the post release survival to determine delayed effects that bycatch induces (Talmage et al., 2022).

To achieve the objective of bycatch reduction regardless of the species under consideration, the first step is to assess the fishing

risk, i.e. to compare the spatiotemporal distribution of fishing effort with that of protected species (e.g. Evans et al., 2021). Potential bycatch appears where the presence of fish and the utilization of suitable gear overlap. However, for rare species this exercise is difficult to implement since:

i) generally, the knowledge of the distribution of the species is limited,

ii) this knowledge mainly originates from bycatch and as such is closely coupled to the fishing method and site selection applied,

iii) data about post release survival are extremely scarce.

To reduce bycatch, a number of tools have been proposed in North America to limit interactions between sturgeons and fisheries, while trying to maintain viable fisheries:

* **Regulations**

>> Establishing gear restrictions and monitoring programs can help to protect sturgeon populations effectively while the effectiveness increases if the restrictions are applied on a larger scale (transnational).
>> In the few cases an accidental take permit has been imagined, it enables a fishery to legally continue to operate as long as the maximum number of bycatch of PETS has not been reached (Hoos et al., 2019), with the maximum numbers being strictly associated to the size of the populations in question.

>> Spatial management measures that prohibit fishing in critical habitats can involve permanent (e.g. marine reserves), or temporary closures (e.g. time-area closures during aggregation periods) (ASSRT, 2007; Bahn et al., 2012; Dunton et al., 2010; Hoos et al., 2019; Melnychuk et al., 2017). This may apply to all fishing gears, or only to some (e.g. no trawling zones in Georgia and North Carolina).

* **Collaboration:**

>> Encourage collaboration between government agencies, fishers, scientists, and conservation organizations to develop and enforce regulations aimed at reducing sturgeon bycatch (Bahn et al. 2012).

* **Time and area avoidance:**

>> Knowledge of the habitats used by sturgeon (for example through species distribution models (e.g. Breece et al., 2017; Richerson et al., 2022)) allows to identify potential overlaps between sturgeon and fisheries and to recommend the implementation of fishing restrictions in areas and during periods when sturgeon are known to be present. An app was developed by University of Delaware to inform local fishers and resource managers on the habitat use of *A. oxyrinchus* helping them to avoid high risk areas (Figure 2).

<figure><img src="image_7.png" /><figcaption>**Figure 2:** Screen shot of the "Atlantic sturgeon warning system" © Delaware University. http://ro-bots.ceoe.udel.edu/shiny/sturgeon</figcaption></figure>
* **Selective fishing techniques:**

>> Encourage the use of selective fishing techniques that specifically target the desired species while minimizing bycatch. This can include using different gear types, such as hook-and-line or traps that are more selective in their capture.

>> Modify fishing gear to reduce the likelihood of sturgeon entanglement or capture. For example, using larger mesh sizes or modifying the design of gillnets can allow sturgeon to escape (e.g. low-profile gillnet: Fox et al., 2011; 2013; He & Jones, 2013; Trice, 2013; Levesque et al., 2016; Hager et al., 2021; Talmage et al., 2022). At least the mesh size is very fishery specific, as increased mesh size of the net may result in a higher risk and selective catch of large adult sturgeon specimens. When the target species are smaller than sturgeon, increasing mesh size would result in catching large specimens, such as sturgeon. As such specific solutions need to be adapted to the fishery in place. Modifications of gillnets have been successfully applied for instance in low profile gillnets with various tie-downs length and space (see Talmage et al., 2022 for a review). In some cases, decreasing sturgeon bycatch unfortunately induces an increase of bycatch of other endangered species such as harbour porpoise (Phocoena phocoena) or short-beaked common dolphin (*Delphinus delphis*) (e.g. Armstrong et al., 2011; Fox et al., 2011). Such effects need to be taken into consideration before the implementation of regulations.

<figure><img src="image_8.png" /><figcaption>**Figure 3:** "Experimental section gear specifications. It should be noted that the monofilament webbing in the experimental section did not hang in the water in a typical mode (i.e., vertical wall), it was more like a half moon or mushroom shape" (reprint from Levesque et al., 2016).</figcaption></figure>
* **Selective fishing devices:**

>> Develop and utilize bycatch reduction devices (BRDs) that allow non-target species to escape from fishing gear (see Glass et al., 2012 for a review). These devices can include escape panels, grids, or vents that enable sturgeon to swim out while retaining the target catch. They exist for turtles but the review has not found any examples dedicated to sturgeon escapement in North America.

>> Invest in research and development of innovative fishing gear that specifically targets the desired species while minimizing bycatch. This can involve exploring new technologies and materials (e.g. Bouyoucos et al., 2014) that reduce interactions with sturgeon and other non-target species.

>> Develop passive gear types that maintain the fish alive until net retrieval (traps) reducing the impact upon a variety of protected species (including cetaceans and birds) (Kratzer et al. 2020).

* **Education and awareness:**

>> Raise awareness among fishers and the public about the importance of sturgeon conservation and the impacts of bycatch.

>> Promote responsible fishing practices (e.g. limited soaked time, no overnight sets inshore: ASSRT, 2007; He & Jones 2013; Talmage et al., 2022) and provide education and training programs to help fishers adopt bycatch reduction measures. Financial support can be necessary to implement changes in gear type or to enhance reporting, especially when the transition to other species is not easy to facilitate.

>> In the event of accidental capture, careful handling (limited handling time, shade, keep individuals wet and cool, etc.) can limit post release mortality, and again it is vital to train fishers to handle the fish appropriately.

The conservation of endangered sturgeon requires a combination of measures, including habitat protection, sustainable fishing practices, and international cooperation. It is crucial to engage stakeholders and implement comprehensive management strategies to ensure the long-term survival of these remarkable fish. While sturgeon protection is highly required, synergies as well as counter effects for other species need to be considered in the development of measures. In an optimal case, a win-win situation is resulting from the active involvement of the fishers affected.
## 3. Situation in Europe

Currently, despite legal protection, sturgeon species have become very rare in the Baltic Sea, the North Sea, the Channel, the Eastern North Atlantic, the Mediterranean Sea, and in the Black Sea basins. In these areas, interviews conducted in the frame of this EU Service Contract highlighted that for fisheries administration they are considered too rare to be an issue of relevance (e.g. compared to more than 4000 dolphins caught annually by commercial fisheries in the Bay of Biscay, Peltier et al., 2019). At least, the species are considered too rare to invest into the development of specific technology to be imposed upon fisheries. Here, a clear link to the population sizes in question and the effects of bycatch imposed upon these populations would be urgently required. Since even limited bycatch mortality could result in population level impacts in endangered species and, resultingly, annihilate investments into major conservation efforts (such as habitats protection, restocking, etc.), a clear prioritization of protection over the commencement of business as usual in fisheries is urgently required.

The Pan-European Action Plan for Sturgeons identified bycatch as a serious problem to be solved for the conservation of these species and listed a series of actions to be implemented:

* "Action 1.2.1 Identification of by-catch and its impacts in marine- and freshwater.

* Action 1.2.2 Identification and implementation of management options (technical solutions, fishery restriction, closed areas, closed season) and gear modifications to reduce bycatch in marine and inland fisheries.

* Action 1.2.3 Monitoring of compliance with bycatch avoidance measures and adaptive management."

### 3.1 Background

The number of published scientific articles on sturgeon bycatch in Europe is very limited. A total of 11 papers in international journals, 1 PhD thesis, 6 reports, 5 conference papers and 1 book section were identified. Furthermore, unpublished information was also provided through contacts

from the network of consortium partners implementing this EU Service Contract. Most information on bycatch is collected by regional recovery projects and their networks that collect information on voluntarily reported catches.

### 3.2 Available information (species, numbers of bycatch, links with fisheries)

Despite the legal obligation to register and report bycatch of protected species by fisheries, there are not any official recording

systems of sturgeon bycatch in Europe. For example, the ICES report on bycatch (ICES
2022b) mentions only one bycatch incidence for sturgeon in 2021, being identified as *A. oxyrinchus*. Neither are logbooks systematically retrieved and analyzed nor are market surveys carried out systematically. As such, no official bycatch data are available for the entire European region.

However, within action plans and projects, bycatch assessments are implemented in conjunction with awareness raising actions to limit the effects and to record relevant information. Existing voluntary declarations

or accidental observations provide rare but valuable data on the characteristics of fish caught (species, size, state), the presence of tags and characteristics of the capture event (date, location, gear used, target species, water depth, substrate composition, fate of the fish) (Gessner et al., 1999). More recently pictures and video documents have been collected, mainly from the Lower Danube enforcement programs (WWF). The major drawback of these voluntary reports is the fact that the reporting rate is largely unknown.

### 3.2.1 Northeast Atlantic, North Sea and Baltic Sea

#### 3.2.1.1 Species concerned

*Acipenser sturio* is present in the Northeast Atlantic, the British Channel, and the North Sea (Rochard et al., 1997; Gessner et al., 1999; Lepage & Rochard, 2011), and stocking takes place in the Gironde and Elbe basins, while experimental releases take place in the Rhine Delta (Brevé et al., 2013, 2019).

*Acipenser oxyrinchus* is reintroduced in the Baltic Sea basins (Gessner et al., 2011, Kolman, 2011, Gessner et al. 2019 (Baltic Sea Sturgeon Action Plan), Purvina & Medne, 2018; Stakenas & Pilinkovskij, 2019); and is observed in the North Sea (Gessner et al., 2011; ICES, 2022b).

#### 3.2.1.2 Legal status and regulation measures

*A. sturio* and its habitats are strictly protected in Europe through several regulatory texts (cf. Rochard, 2011 for a synthesis), among them the Habitats Directive (Council Directive 92/43/EEC), Annex II and IV. National Action Plans have been implemented in Germany (Gessner et al., 2010; 2011) and in France (Ministère de l'écologie du développement durable et des transports, 2011; Adam (coord.), 2020) including the monitoring of sturgeon bycatch. Bycatch is also mentioned as an issue to be addressed

in the conservation strategy documents for the Netherlands (Visser et al., 2020) and the UK (McCormick et al., 2023). From a protection viewpoint in the European Union, the Baltic population of *A. oxyrinchus* must be treated like *A. sturio* because its separation from the latter species was only determined in 2002 (European Commission, 2014). An Action Plan is currently implemented for the rivers and marine area of the Baltic Sea (HELCOM Expert Group on Sturgeon remediation, 2019).
### 3.2.1.3 Bycatch

A database developed within the French National Action Plan "SturWild France" was started in the 1980s. It contains information about multiple thousands of bycatch events, mainly from the Atlantic Northeast, the English Channel, the North Sea, and their respective estuaries. In conjunction with the recorded bycatch from Germany (>260 catch events), and the Netherlands (>40 catches) this database enabled an analysis of *A. sturio* marine distribution and

habitats (Rochard et al., 1997; Lepage & Rochard, 2011; Charbonnel et al., 2023). The data originate from voluntary declarations by fishers, but the proportion of unknown/undeclared bycatches in these areas cannot be quantified and due to this, the outcome is clearly biased. However, they provide information about habitats used at sea and interactions between fisheries. Most bycatch data come from gillnet and trammel net fisheries. (Figure 3).

<figure><img src="image_9.png" /><figcaption>**Figure 4:** Share of different types of gear in bycatch declarations of *A. sturio* (left), number and status of fish declared by period (right) (© M.L. Acolas, Sturwild France DB, 1980-2022) (N=1148 events).</figcaption></figure>

The inter-annual variability in voluntary declarations (Figure 3) is linked both to the number of sturgeons at sea - the more there are, the more that are caught as exemplified by the French releases of 1.5 million young *A. sturio* between 2007 and 2014 - and to the behavior of fishers. Increasing numbers and increasing catches tend to result in reduced reporting rates, either due to the extra work or because the fishers consider the underlying problem solved. Behavioral aspects depend both on the fishers' awareness as to the conservation of this species, which requires regular information campaigns, and on their relationship with the fisheries authorities. For example in the Bay of Biscay cooperation with fishers has

become very challenging, due to falling quotas and the threat of fishery closures to reduce accidental catches of dolphins.

The condition of fish upon catch depends on the catch method as well as the awareness of fishers. According to the French Sturwild data base, 81% of fish were declared in good condition when they were released, 4% in poor condition, 7% dead, and for the remaining 8% no information is available. Declared mortality rates vary between baited hook lines (0%), gillnets (4%), trammel nets (8%) and trawls (22%). The information obtained originates from various regions and fisheries targeting different species.
After several information campaigns in the regional fisheries, among anglers and the general public, Arndt et al. (2000, 2002) collected and analyzed voluntary declarations of sturgeon bycatch of native as well as exotic species in Dutch, German, and Polish coastal waters prior to the onset of recovery measures. During this period, anglers were the main source of bycatch reports, mainly in rivers and estuaries (53%) followed by gillnets (37%) in coastal waters and estuaries. The results highlighted a decrease of bycatch of *A. sturio* and, at the same time, an increase of exotic species (i.e. *A. baerii*, *A. gueldenstaedtii*). This trend was reversed after 2007 when releases began with *A. oxyrinchus* in Baltic rivers and with *A. sturio* in the Elbe River. In a subsequent analysis, the recapture rate was dominated by gillnets, followed by stow nets, with anglers contributing only with a marginal 3% share in the reports of the species.

While *A. oxyrinchus* is regularly stocked in the Baltic, only harbor porpoise and sea birds are mentioned in the chapter on bycatch of HELCOM Sea Action Plan (2021). Throughout this area, with the exception of the single southern areas of the Baltic Sea and its tributaries, sturgeon poaching is considered negligible. For the German Baltic Sea coast and the Odra River mouth, the reporting rates vary between fisheries communities between an estimated 80% of the fishers to factually 0% due to internal pressure in their communities (Gessner pers. comm.). Bycatch varies significantly, rang-

ing from 5% to almost 70% of the fish released during the season (Gessner et al., 2011; Stakenas & Poviliunas, 2019; Stakenas et al., 2022).

Large numbers of tagged *A. oxyrinchus* have been stocked in Lithuania, and from bycatch reports in the Curonian Lagoon and the Baltic Sea, Stakenas et al. (2019) estimated a bycatch rate of 7.4% to which an unknown but most likely significant number of IUU catches must be added. Surprisingly, they reported a mortality rate of 83% in gillnet, which is much higher than what is found in literature, but only negligible mortality in fyke nets used in the lagoon (Stakenas et al., 2021). In the Odra River, the same type of studies have led to a negligible mortality rates from gillnets (1%) in reported captures, while the unreported mortalities would have probably been much higher (Gessner et al., 2011). It is frequently observed that mortalities for a variety of protected species are not reported. The main difference lies in the fishing season, which takes place mainly in summer in the Curonian Lagoon and in late autumn in the Odra River. In addition, soak time varies considerably with 12 hours in Odra River and up to 3 days in the lagoon.

When the numbers of fish released until 2022 are considered, which have reached more than 6 million fish from feeding fry to late juveniles in the Baltic range states, even the reported bycatches have a considerable impact. If these impacts are not significantly reduced, they inherit the risk of annihilating efforts made for recovery.

### 3.2.2 Mediterranean and Adriatic

Once abundant in the Mediterranean, the European sturgeon disappeared during the first half of the 20th century (Brosse et al., 2009; Bronzi et al., 2011; Chassaing et al.,

2016). However, experimental stocking occurred in 2023 in the lower Ebro River (Catalonia, Spain,) within the MigratoEbre Life Nature project.
The Adriatic sturgeon *A. naccarii* benefits from a restoration plan in Italy (Caramori et al., 2007; Arlati & Poliakova, 2009) with regular stocking of juveniles in the Po Basin (Bronzi et al., 2011). This euryhaline species may also use coastal waters. As such, the species potentially benefits from a closure of coastal fisheries within the 3-miles zone along the coast, which is to be expanded to 5 miles in the near future (P. Bronzi pers. comm.).

Information about bycatch from commercial fisheries is rare, while over the last 5 years the fishing association Federazione Italiana Pesca Sportiva e Attività Subacquee (FIPSAS) has received anecdotal reports of bycatches in the River Po. Increasing numbers of large, mature Adriatic sturgeon are

reported as bycatch in recreational fisheries for wels catfish (*Silurus glanis*) with rod and reel.

To the best of our knowledge, there are no bycatch records from the Adriatic Sea from recent years. This can be explained in part by the low abundance of sturgeon in marine waters, but also due to the lack of systematic data collection.

With the expected increase of the sturgeon population in the Po Basin, and consequently in the northwest Adriatic coastal region, there is an urgent need to develop a coordinated information collection system for the Padano Vento district and the Northwest Adriatic marine region.

### 3.2.3 Black Sea and Azov Sea

#### 3.2.3.1 Species concerned

Today, in the Black Sea basin, *A. sturio* is considered extinct and *A. nudiventris* is extinct in all rivers except the Rioni, where single individuals of unknown origin were found (Beridze et al., 2021). *A. gueldenstaedtii*, *A. stellatus* and *H. huso* are still encountered in the Black Sea and in the lower reaches of several rivers (Danube, Don, Kuban, Rioni). Several populations that have been considered functional by 2005 have

ceased to function in the meantime, revealing the increased impact of bycatch and poaching in the area. The only species that is considered relatively safe from acute extinction is the freshwater species, the sterlet (*A. ruthenus*). It is listed as threatened in the Danube Basin, but is also the subject of stockings in Austria, Slovakia, and Hungary, in an attempt to stabilize populations.

#### 3.2.3.2 Legal status and regulation measures

All Danube countries and all Black Sea range states have existing regulations for sturgeon fishing (Strat & Gheorghe, 2023), and all Black Sea range countries have effectively prohibited targeted fishing for sturgeons. In Bulgaria, the current sturgeon fishing ban is limited until the end of 2025 and a discussion about renewal is soon expected to start. Also the majority of Danube

range states prohibit sturgeon fishing, with the exception of Austria (for the Federal states of Lower Austria, Carinthia, and Styria), Slovakia and Croatia which still allow sport angling for sterlet, with closed seasons and minimum size limits applied<fnref n="21" />.

The obligation to report bycatch of sturgeon in marine and river waters has only been

<footnote n="21">²¹ DSTF (June 2020) assessment on fishing regulations in the Danube/Black Sea region. https://dstf.info/wp-content/uploads/2020/09/Annex-F-Information-on-existing-fishing-bans.pdf</footnote>
introduced recently (2021) in Romania and Bulgaria. These obligations are not yet put into practice, as the hesitation of fishers to report needs to be overcome. In Bulgaria, after bycatch declaration became mandatory only 2 specimens have been recorded in 2 years with one of them being misidentified as a sterlet instead of a stellate sturgeon (B. Margaritova, Pers. Com.).

In Turkey, all sturgeon species have been protected since 1997 (Zengin et al., 2010). The country adopted a National Action Plan for Sturgeons in 2014. In Ukraine sturgeons are listed in the national Red Data Book and a National Sturgeon Conservation Action Plan (2021-2029) has been formally adopted. However, WWF (2021b) has documented large discrepancies between regulations and implementation. In the Azov Sea basin, the commercial capture of sturgeons has also been banned since 2000. Before the war, Ukraine and Russia decided to maintain this ban until the species have

recovered commercially (Demyanenko & Diripasko, 2003).

Despite legal protection through national legislation or regional policies such as the Agreement on Port State Measures (FAO, 2016) to eliminate IUU fishing signed by four of the seven Black Sea range states, poaching continues both at sea and in the rivers during spawning migration (Ustaoglu & Okumus, 2004; Bloesch et al., 2005; WWF, 2021a). Poaching is documented by authority reports with seizures of illegal fishing gear, sturgeons caught (WWF, 2023) and their products entering the market illegally (WWF 2021a; Ludwig et al., 2023). Sturgeons caught with trawls and gillnets are still frequent on Black Sea and Sea of Azov markets (Shlyakhov, 2003) imposing a major problem on the respective sturgeon populations.

Several Ecologically or Biologically Significant marine Areas (EBSAs) are including habitats of sturgeon species, but do not entail any management measures.

#### 3.2.3.3 Bycatch

Data on sturgeon population monitoring and bycatch at sea are scarce. Historically, data on sturgeon abundance were assessed in Ukraine and in Russia (e.g. Demyanenko & Diripasko, 2003). Today no official statistics on the state of sturgeon populations and bycatch are available.

To assess the current situation, the General Fishery Commission for the Mediterranean (GFCM) adopted Resolution GFCM/44/2021/5 on the mitigation of fisheries impacts for the conservation of sturgeons in the Black Sea (geographical subarea 29)<fnref n="22" /> and launched a pilot project (see chapter 2.4.2.1).

Maximov et al. (2014) carried out surveys on the status of the sturgeon populations in Romanian marine waters by bottom trawl and gillnets. They documented that *A. stellatus* is the most common sturgeon at sea in spring and summer in coastal shallow waters. Compared to results from Bulgarian (Margaritova, 2022) and Ukrainian reports (Bushuiev et al., 2022) about bycatch, Maximov et al., (2014) reported a higher frequency of *H. huso* in their samples.

<footnote n="22">²² https://www.fao.org/faolex/results/details/en/c/LEX-FAOC217220/</footnote>
More recently, sturgeon bycatch in the Danube River and the Black Sea was explored for the first time after the introduction of the sturgeon fishing ban in 2011 (Margaritova, 2022). The LIFE for Danube Sturgeon project23 has carried out awareness campaigns to inform fishers about the situation of sturgeons. Additionally, WWF staff have organized theoretical and practical training courses on the Bulgarian side of the Danube, to inform fishers on how to identify sturgeon species, handle them safely and record useful data24 (Margaritova, 2022). To enable bycatch data recording, smartphones were distributed to fishers. This approach has been very fruitful, as trained fishers have contributed voluntarily and, over the period 2018-2022, have provided information (including photos and videos) on 136 accidentally caught sturgeon, both from the Danube River and the Black Sea (Figure 4). Four sturgeon species were reported as bycatch, of which *A. stellatus* was the most frequent (56%), followed by *A. gueldenstaedtii* (23%), *A. ruthenus* (15%) and *H. huso* (4%). 59% of *A. gueldenstaedtii* caught were originating from releases.

<figure><img src="image_10.png" /><figcaption>**Figure 5:** Registered sturgeons as bycatch in the Bulgarian sections of the Danube River and the Black Sea for the period 2018-2022 (according to data from fishers). © B. Margaritova, WWF-Bulgaria.</figcaption></figure>

Bycatch of sturgeons in the Danube River mainly takes place in gillnet fisheries targeting cyprinid species. Along the Bulgarian coast, young sturgeons are bycatch of small-scale fisheries targeting shad (*Alosa sp*.), bluefish (*Pomatomus saltatrix*), Atlantic bonito (*Sarda sarda*) and mugilidae. Trawlers fish further offshore and target red mullet (*Mullus barbatus ponticus*), horse mackerel (*Trachurus mediterraneus ponticus*) and blue fish. As mentioned in other areas, accidental bycatch occurred in shallow coastal zones for *A. stellatus* and *A. gueldenstaedtii* (5-16 m depth), sometimes very close to the coast, but deeper for *H. huso* (>20 m) (Margaritova, 2022).

Following the stocking of juveniles in the Danube in 2014-2015, an increasing number of bycatch was observed in the Pontic shad *Alosa pontica* fishery operating in the Ukrainian branch of the Danube, leading to a temporary closure of this fishery (WWF 2021b).

Along the Ukrainian coast, a study by WWF (2021b) reveals that only juveniles in the bycatch are released, as they have no commercial value, while larger fish are landed (poached). As part of a GFCM project, Ukrainian scientists placed observers on board trawlers of the sprat (*Sprattus sprattus*) fishery (Figure 5) in order to document accidental bycatch in 2018 and 2019 (Bushuiev & Balatskyi, 2020; Bushuiev et al., 2021) and 2021 (Bushuiev et al., 2022). This fishery operated in the northwestern Black Sea, ranging from 2 to 50 km from the shore. The catches occurred mainly in shallow waters and comprised *A. stellatus* (N=346), *A. gueldenstaedtii* (N=12) and *Huso huso* (N=10). Most individuals caught were young specimens of 2 years, which were released live at sea. This fishery appears highly selective, and sturgeon bycatch rate varied from 0.24 sturgeon/trawl tow (2018) to 4.91 sturgeon/trawl tow (2021). However, on a fishery scale, the

<footnote n="23">23 http://danube-sturgeons.org/danube-sturgeons/</footnote>

<footnote n="24">24 https://danube-sturgeons.org/wp-content/uploads/2021/03/Factsheet-3_Involving-Fishermen-in-Sturgeon-Monitoring-in-Bulgaria.pdf</footnote>
number of sturgeon accidental bycatch is high, with an average of 400 individuals caught per year, 90% of which are juvenile

stellate sturgeons, in a fishery yielding 1,500 t of sprat.

<figure><img src="image_11.png" /><figcaption>**Figure 6:** Sturgeon bycatch from the Ukrainian sprat fishery (from WWF 2021b).</figcaption></figure>

With the same approach, Bushuiev et al. (2021) recorded and analyzed the bycatch from an experimental beam trawl fishery targeting “rapana” (*Rapana venosa*), a large gastropod, along Ukrainian coasts. Selectivity of this fishing gear was not as high as expected, with numerous accidental bycatch of several fish species. However, in 2019 experiments, for 76 t of “rapana” captured in 341 trawl tows, only two small sturgeons were caught (1 A. *stellatus* and 1 A. *ruthenus* caught close to the Dniester estuary).

Bycatch of sturgeon occurred frequently along the Black Sea Coast of Turkey but, despite legal protection, the fish are not systematically released alive (Zengin et al., 2010). From these authors, a substantial part of the sturgeon accidentally caught are landed and sold illegally. Only small individuals (Figure 6), mainly A. *gueldenstaedtii*

and A. *stellatus* were released (Zengin et al., 2010).

Trawling is taking place along the entire Turkish Black Sea coast partly (Knudsen et al., 2010). Fifty-five percent of the documented bycatch of sturgeon species occurred in commercial bottom trawl nets in Samsun Bay. Gillnets (35%), purse seines (5.4%), dredge nets (2%) and line and hook (2.6%) also contributed to the bycatch (Zengin et al., 2010). According to these authors, set gillnets operated in coastal water induced higher mortality rates than floating gillnets. In another study conducted between 2008-2010 during the fishing seasons on the Turkish Black Sea coasts, it was reported that 11 *A. gueldenstaedtii* and seven *A. stellatus* individuals were captured in 72 commercial pelagic trawl operations (Özdemir & Erdem, 2011).
<figure><img src="image_12.png" /><figcaption>**Figure 7:** Distribution and fate of tagged sturgeon bycatch along the Turkish coast (pooled data; 2004-2008). Released (N=45), landed (N=93) (Zengin et al., 2010).</figcaption></figure>

More recently, Ozdemir et al. (2023) randomly sampled fishing vessels working in the southeastern part of the Turkish coast in 2011-2016. They observed a high frequency of sturgeon bycatch. In 60 trawl tows they recorded 21 *A. stellatus* and 33 *A. gueldenstaedtii* (i.e. 1.1 sturgeon per trawl tow) and in 40 turbot gillnet operations they recorded 4 *A. stellatus* and 8 *A. gueldenstaedtii*. All sturgeon were juveniles, but the authors do not provide information on survival rates.

As demonstrated through the compiled data above and the scattered picture provided, there is an urgent need for a coherent and systematic bycatch data assessment and structured database across Black Sea range states, to identify the risk areas where fisheries overlap with sturgeon distribution and start the development of bycatch avoidance measures.

## 3.3 Measures put in place to limit bycatch

### 3.3.1 Awareness campaigns

Informing fishers about what a sturgeon is, its status as an endangered species, the efforts carried out to restore populations, providing handling guidelines to release incidentally caught fish and to contribute to its conservation is considered to change the fishers behavior and increase compliance with existing regulations. In France, aware-

ness campaigns have been realized to inform fishers, auctions staff, and fisheries officers about the status of sturgeon and how to respond upon an encounter. From a comparison between pre- and post-information campaign a change in fishers' behavior can be interpreted as a result of the intervention (Lepage & Rochard, 2011). Arndt et al. (2000, 2002) also stressed the importance
of campaigns to raise awareness on bycatch while they noted a decreasing interest among fishers when bycatches become increasingly frequent.

Before the stocking of *A. oxyrinchus* in Lithuania in the northeastern Baltic Sea, an information campaign was carried out in the media (Stakenas et al., 2021), and after the releases a common leaflet was developed by HELCOM EC Nature in all the languages

of the countries surrounding the Baltic Sea, in order to increase awareness of the fisheries. First results have been extremely positive, especially in the Danish and Swedish fisheries, which continuously report catches of sturgeons through national contacts (Gessner et al., 2011). This outcome is further dependent upon the direct frequent and continuous contact with the fishing communities.

<figure><img src="image_13.png" /><figcaption>**Figure 8:** Flyer explaining the recovery plans for *A. sturio* and *A. oxyrinchus* in Germany (left), and cover of a leaflet to inform about the recovery project of sturgeon in the Black Sea. © FAO-GFCM, 2023.</figcaption></figure>

The materials developed as part of the French National Action Plan (Figure 8) have been translated into different languages in range countries to the Northeast Atlantic from Spain to Germany to obtain standardized information. It is also a way of linking up cooperation among National Action Plans.

In some cases, the information concerned sturgeon as well as other threatened species, such as the one carried out in The Netherlands in 2010 (Figure 9).
<figure><img src="image_14.png" /><figcaption>**Figure 9:** Flyers distributed in different languages of range countries (left), and sticker (right) targeting fishers and explaining what to do in case of bycatch.</figcaption></figure>

<figure><img src="image_15.png" /><figcaption>**Figure 10:** Dutch awareness poster including sturgeon with other protected species present in the North Sea and the Rhine delta (left); sticker, stuck on board, stating what to note and what to do in the event of accidental capture of sturgeon (right) (© ARK rewilding Nederland and Sportvisserij Nederland).</figcaption></figure>

Scientists and managers are interested to obtain information about bycatch of various data poor species to improve the knowledge

about their ecology, especially their distribution, and interactions with fisheries. Different forms have been developed for this purpose on paper (e.g. Figure 10 left) or on
websites and have provided valuable information. At minimum, information is needed about each fish caught (species, length, weight, tagged or not, healthy, injured, or dead, released alive or not) and the fishing event (date, location, depth, gear, mesh, target species, soak time, etc.). In the absence of official surveys, the involvement of fishers in monitoring will provide crucial data for assessing the state of sturgeon populations and characterizing bycatch (Figure 11).

By equipping fishers with smartphones, it is easy for them to take photos and videos and to transmit information about bycatch to the people responsible for recording (e.g. Margaritova, 2022). In cases when it is important not to confuse a protected species with an exotic species some support materials have been developed for this purpose (Figure 11 and Mihov 2020a). In a few

cases, training courses have been organized for fishers and for fisheries inspections. An important point addressed in these training sessions was about how to handle and release sturgeons safely (Figure 11 and Mihov 2020b). Information disseminated in the media and the presence of sturgeons in public aquariums (e.g. in all range countries) are useful in gaining the support of the authorities and the public. Visitors to aquariums displaying threatened species are generally keen to learn more about conservation issues (Yalowitz, 2004). In such cases fishers are targeted indirectly (by neighbors, children, etc.) while the impact on their attitude towards bycatch is not understood. In more complex contexts, programs such as "Life for Danube sturgeons" inform fishers about these species, their importance, and work closely with them to find appropriate solutions to resolve socio-economic issues associated to sturgeon conservation.

<figure><img src="image_16.png" /><figcaption>**Figure 11:** Example of form to get information about the bycatch, characteristics, and state of the fish, tagged or not, target species, gear used, locations, date of bycatch (left), and leaflet developed after a huge escapement of Siberian sturgeon to enable fishers to be able to identify them and to know what to do (right).</figcaption></figure>
<figure><img src="image_17.png" /><figcaption>**Figure 12:** Part of a leaflet produced during the LIFE project "Life for Danube sturgeons" (© WWF) (left) and guidelines to ensure a safe release (© WWF, Mihov 2020b) (right).</figcaption></figure>

<figure><img src="image_18.png" /></figure>

### 3.3.2 Reporting

To date no official recording system for sturgeon bycatch exists. The information currently available depends on recording voluntary declarations of bycatch by projects which obviously vary greatly in space and time. Therefore, the available knowledge of this phenomenon is biased. Information on bycatch, recorded as part of a project can also trigger official investigations.

This was the case in the Bay of Biscaay, where fisheries administration staff improperly authorized a commercial fisher to sell an *A. sturio* from an accidental bycatch (Guth & Laurent, 2004). This led to a reminder of the sturgeon's status and the steps to be taken throughout the fisheries administration.

### 3.3.3 Alteration of fisheries techniques

The only attempt to develop and adapt fishing techniques to decrease the bycatch of sturgeon was carried out to limit the risk of bycatch of *A. oxyrinchus* in the coastal waters of Odra River in the frame of a recovery project (Gessner & Arndt 2006; Gessner et

al., 2007). Modified set gillnets with "bottom escape windows" were designed (Figure 12) and tested in large earthen ponds with Siberian sturgeon, indicating the potential to substantially reduce sturgeon bycatch (Gessner & Arndt, 2006).
<figure><img src="image_19.png" /><figcaption>**Figure 13:** Schematic model of the gillnet modification with "bottom escape windows" to reduce sturgeon bycatch in perch and pikeperch fisheries by using spacers between the bottom line and the lead line (from Gessner & Arndt, 2006).</figcaption></figure>

Along the Turkish coast, there is a high probability of accidental bycatch of sturgeon (Özdemir et al., 2023). These authors suggest using trawl with grids and square mesh panels that can enable large fish to escape (Figure 13). A similar approach is applied in the shrimp fishery in the North Sea seasonally, which has led to a marked reduction of sturgeon bycatch declarations (N. Brevé, pers. comm.)

<figure><img src="image_20.png" /><figcaption>**Figure 14:** An example for prevent of accidental sturgeon catch in trawl nets (Grid system) (From Özdemir et al., 2023).</figcaption></figure>

### 3.3.4 Closures

As protected species listed in the EU Habi-tats Directive (92/43/EEC), sturgeons are mentioned as target species in several Natura 2000 areas. However, this does not imply that action is being taken to protect them specifically. For example, fishing prac-tices are not regulated to protect the spe-

cies. For instance, bottom trawling is gen-erally prohibited in estuaries, but can take place in most French and Spanish Natura 2000 areas. Most closures are dedicated to protect several fish species, and sturgeon are then indirectly protected (e.g. in marine reserves).
# 4. Recommendations

The Pan-European Action Plan ("Recommendation No. 199(2018) of the Standing Committee on the Pan-European Action Plan for the conservation of the sturgeon") emphasizes:

i) the urgency to eliminate the directed removal of individuals and

ii) to reduce accidental removal to levels allowing population recovery.
Regionally, it is essential that the various players coordinate closely in their efforts to assess the scale of the catches and their effects.

## 4.1 Increase knowledge and awareness

In areas where poaching regularly occurs, it is imperative to stop illegal harvest while at the same time addressing the bycatch issue (Bloesch et al., 2005).

Since the same fishing gear is used to target the same fish species in North America and Europe it is more than likely that the gear has the same impact on sturgeon. Using this approach, we can at least focus awareness and control on large mesh-soaked gill net fisheries, such as those used to target sharks, rays, and monkfish (high probability of capture and high risk of mortality), as well as the commercial shad fisheries in rivers. On the other hand, there is no need to devote too much energy towards pelagic trawlers (low probability of capture).

In the framework of the European CFP, joint recommendations should "develop lists of

sensitive species and habitats most at risk from fishing activities within the relevant region based on the best available scientific advice" (Article 21). Based on these lists, the Commission can adopt delegated acts (Article 19).

The legal framework to be effective needs to provide the prerequisite that whenever sturgeon bycatch frequently occurs, specific studies should be carried out to assess the data, to test gear, or practice modifications.

In areas where sturgeons have been rare for several decades (i.e. North Sea, Atlantic Ocean, Mediterranean Sea, Adriatic Sea), it is crucial to inform fishers and recreational anglers about these species and their legal status. From what has been done in the Atlantic Ocean and the North Sea, it is necessary to regularly repeat these awareness campaigns.

### 4.1.1 Assess fishery-independent data

To be able to support temporary or permanent closures initiatives, it is absolutely necessary to improve the knowledge about the habitats used in rivers, estuaries, and at sea with fishery independent data. This information can come from sampling campaigns carried out in estuaries or at sea, such as the surveys carried out every two months in the Gironde estuary
(Brosse et al., 2011; Lamour et al., 2024), from biotelemetry monitoring from networks of acoustic receivers (e.g. Breece et al., 2017; Melnychuk et al., 2017), or with satellite tags (Cooke et al., 2013).

### 4.1.2 Involve fishers in conservation actions

Involvement of fishers in conservation actions is crucial for success and provides mutual benefits. Fishers can contribute their expertise on fishing techniques and fish behavior to better prepare the campaigns and interpret the results. They take part in actions and can individually participate in monitoring or sampling. Responsiveness by fishers may be increased through appreciation and social recognition schemes, for example by officially thanking the fishers who have provided data on bycatch with letters, gifts, or public statements. In such cases where fishers are organized, this may be done through the professional organizations, and, in other cases, conservation organizations fill this gap.

The need to involve fishers in regions such as the Black Sea, where fishing communities have had substantial income from sturgeon fishing in recent history, is even more strident, as well as challenging, as the economic opportunity to sell landed sturgeons on the market outweighs the risk of being caught, or the fines applied.

When informed and convinced, fishers can contribute by providing information about

their bycatch. Various supports can be used to get data, from paper forms, to cell phones, and websites. Modern tools are useful, as we can obtain pictures, which allows us to be sure of the identification of the species. In a pilot project, WWF distributed smartphones to fishers in Bulgaria. Fishers responded positively and sent hundreds of pictures or videos of released bycatch to the organization (e.g. Figure 14).

<figure><img src="image_21.png" /><figcaption>**Figure 15:** A fisher releasing a Russian sturgeon caught as bycatch in the Danube River. © Stoyan Mihov, WWF-Bulgaria.</figcaption></figure>

### 4.1.3 Assess bycatch

In the absence of information from sturgeon bycatch by fisheries and on their populations, it is not possible to address the issue of sturgeon bycatch.

As mentioned in all the action plans (cf. Appendix 1), it is essential to obtain infor-

mation on bycatch. Depending on the country, whether this information is either compulsory or provided on a voluntary basis, it should be mandatory and officially recorded. Officially, recognized data bases recording bycatch and their characteristics are essential to support the implementation
of appropriate management measures. Na-
tional authorities must collect sturgeon by-
catch data from the fishery in an obligatory
reporting. This is the only means to obtain
official data on the status and the impact of
the fisheries upon the populations.

The fisheries observers are on the front line, but when they observe Protected, Endangered, and Threatened Species, data collection should be mandatory. Sturgeon bycatch is rare. Therefore, every opportunity to obtain detailed information is valuable and fishery observers need to be informed about how to handle sturgeon and what information is useful to collect.

There are available protocols to assess cap-
tures and mortality rates according to gear
types (e.g. Bettoli et al., 2009; Bahn et al.,

2012; Bushuiev et al., 2021). Using tagged
individuals, it is possible, in certain condi-
tions, to assess bycatch and mortality rates
(e.g. Doukakis et al., 2020).

Bycatch will always be underreported, but
the data obtained will make it possible to
focus awareness on specific ports or fisher-
ies and gradually gain a more precise idea
of the time, place, gear used, and the target
species that led to sturgeon bycatch.

By the overlay of existing databases on fishing effort and incidental bycatch, it is possible to get a first assessment of existing and potential hotspots for bycatch. This would be very useful to focus the effort in communication and can be used as a benchmark for assessing how the situation is evolving.

4.1.4 Ensure that on board activities are recorded

To verify the bycatch data provided by the
fishery, the monitoring systems imple-
mented to assess marine mammals bycatch
and fishers' behavior/response should be
used to broaden the range of species for
which monitoring is used.

The EU plans to introduce Remote Electronic
Monitoring (REM), for small fishing vessels
from January 2028. REM is an integrated ar-
ray of sensors and video cameras used to

monitor fishing activities on a vessel at sea. It provides the precise location of activities as well as information about catch composition, catch handling methods, and discard activity. It will certainly improve the quality and quantity of the information available. Make it more independent from voluntary feedback and as such will increase the knowledge on accidental bycatch of PETS while at the same time will increase compliance.

**4.2 Reduce bycatch probability**

As seen from the North American expertise, there are several ways to reduce the bycatch
probability. The first idea is to inform fishers about the locations of sturgeons (c.f. 4.1.). A
good example is the smartphone application developed by Delaware University (cf. Figure 2)
to avoid these areas. However, in contexts where poaching still exists, this could be coun-
terproductive.
### 4.2.1 Implement closures

When sufficient knowledge of the distribution of the species targeted by commercial fishing and sturgeon distribution is available, conflicts can be avoided by means of temporal and spatial closures. This is particularly efficient to limit bycatch when sturgeon aggregate or during their spawning migration. As an example, gillnet shad fisheries in North America and in Europe estuaries and rivers lead to numerous bycatch of migrating sturgeon. As sturgeon use preferentially coastal and shallow waters, particularly in summer, it could be helpful to set up temporary closures to limit bycatch. These closures can be permanent for all gears or only for some (e.g. trawl exclusion in coastal areas or in estuaries). States must ensure actual and effective protection of sturgeon in existing and new Marine Protected Areas (MPAs) by implementing and enforcing fisheries management measures (e.g., prohibiting or restricting certain fishing gears, mandatory bycatch mitigation measures) for all sites. Either closures are implemented, or drastic modifications to fishing gear need to be imposed.

If effective protection measures are to be put in place in these MPAs, the regulations and management of these zones must be reviewed. The marine protected areas are becoming more important in the frame of EU policy. As such, these might offer opportunities for the increased protection not only of the species but also of their habitats, which are massively affected by bottom touching gear that destroys multiple year's assemblages of invertebrate communities. In 2023, the European Community reaffirmed the need to protect the marine environment in order to guarantee the prosperity of the fishing industry and food safety. Despite this, the governments of several countries, notably France and Spain, under pressure from the fishing industry, have categorically refused to ban bottom trawling in Marine Protected Areas. At the same time, the United Kingdom has decided to ban trawling in 13 of its Marine Protected Areas. In the long term, this is certainly the most effective and least costly way of maintaining suitable habitats for PETs and limiting their bycatch.

### 4.2.2 Modify fishing gear

Unlike for marine mammals and turtles, no repellent techniques (sound, visual, magnetic) that can effectively keep sturgeon away from nets were identified so far. In some cases, where bycatch rates and mortality rates are high in a specific fishery, gear modifications may be considered to limit bycatch. There is no generally applicable solution, and it will be necessary to test different solutions depending on the target species, the gear used and the possible presence of other threatened species that may also be caught. Numerous gillnet configurations have been tested along the

North American Atlantic coast and examples have been presented in this report (Figure 3 and Figure 13). To convince fishers, there is a need to continue trials to limit bycatches while maintaining captures of target species. It is also suggested to equip trawl with grids and square mesh panels that can enable large fish to escape (cf. Figure 14). This has shown positive results for turtles, and it is recommended to test this technique for sturgeon. In the same way as for gillnets, as far as trawls are concerned, the devices have yet to be tested and refined to maximize the selectivity-.
## 4.3 Increase survival of bycatch sturgeons

Observations in the field allow to assess the immediate mortality rate of sturgeons, i.e. those that are dead when the net is lifted. Despite, however, the reputed hardiness of sturgeons, it is known that even when released alive, some of them will not survive for more than a few hours or days. This delayed mortality is more complicated to assess and requires specific studies. Understanding such delayed mortality effects better will be key for any bycatch prevention and gear modification measure.

### 4.3.1 Effects of different fishing gear

Survival depends first and foremost of the fishing gear used, with hooks and lines and fyke nets producing a very low mortality rate in sturgeon. Mortalities caused by trawls and gillnets vary depending on the fishery and the practice, but from the North American experiences, it appears that in general, trawls cause much lower immediate mortality rates than gillnets. Among gillnets, set nets and staked nets induce a much higher mortality rate than drift nets and trammel nets.

It can be generally stated that the longer the nets are soaked, the greater the risk of

mortality. At the extreme, this happens with ghost nets (Kappenman & Parker, 2007). Therefore, it is recommended to limit the soaked time for gillnet to less than 12h, especially when temperature is high (i.e. >18°C).

For trawlers, the duration of haul is also a factor that increases the risk of mortality. Although it would be counterproductive for fishers, limiting the duration of hauls to 1 hour would drastically limit the risks for accidentally caught sturgeons.

### 4.3.2 Improved handling practices

Bycatch avoidance is the best mechanism to reduce mortality. However, handling recommendations certainly limit the impact upon catch. In particular in regions where sturgeon bycatch is frequent (e.g. in the Black Sea, the Danube, etc.) it is useful to raise awareness and to train fishers to adopt appropriate handling behavior to release sturgeon as safe as possible back into the waters.

Once on board, sturgeon survival increases if the time spent out of the water is short. They should also be protected from shocks, and a hose or other source of water should be used to keep them moist and fresh during the interval they are exposed on deck through the sorting and data acquisition period before release, ideally in a recovery tank where possible, especially if the air temperature is high or very low.
#### 4.3.3 Increase enforcement

There are still sturgeons being landed, auction staff, fishmongers, and fisheries officers are not necessarily well informed about the legal status of these species and at the very least, it is crucial to raise their awareness.

Furthermore, enforcement in the case of misconduct must reflect the severity of the impact. In the case of struggling sturgeon populations, each individual counts and as such, each illegally removed animal is a public offence and requires strict penalties.

### 5. Conclusions

To date there is no serious approach from the Parties to the Bern Convention that adopted the Pan-European Action Plan for Sturgeons to reduce sturgeon bycatch. Official data recording of sturgeon bycatch is urgently needed to be able to focus awareness and control on fisheries whose fishing zones overlap sturgeon habitats. This may come from the same approach of observers on board or electronic devices used for marine mammals and sea birds.

By cross-referencing available data on fisheries (type of gear, spatial and temporal distribution) with data on incidental catches, it should be possible to produce an initial estimate of the number of incidental catches by major area. This could serve as a benchmark against which to measure trends.

From this point, depending on the results (scattered or concentrated sturgeon bycatch, one or several fisheries concerned, throughout the year or on a seasonal basis, etc.) different tools should be implemented to limit this bycatch. Available tools that could result in decreasing bycatch of sturgeon were reviewed in this report.

As with other threatened species, sturgeon will benefit of the implementation of Remote Electronic Monitoring on small scale fleets.

Guidelines for fishery observers should include some observations to be made in the event of sturgeon bycatch.

Closures could be very effective in limiting interactions between fisheries and sturgeon, and while there are already a few, there could be more with the creation of additional protective rules. To achieve this, however, it is essential to gain a better understanding of the habitats used by sturgeon, using data that is independent of fisheries.

> In any case, it is imperative that authorities take their responsibility for the survival of the species and the success of their recovery serious and prioritize their efforts to maintain biodiversity over economic considerations.
# 6. Appendix

## 6.1 Bycatch related measures in sturgeon Action Plans

**Danube Action plan (Bloesch et al., 2005)**

* Action 2.3 Assess the level of sturgeon bycatch in Black Sea coastal fisheries

* Action 3.4 Eliminating incidental capture

**French Action Plan (Adam, coord.2020)**

* Action 6 Monitoring of sightings and accidental bycatches at sea, in estuaries and rivers.

**German Action plan (Gessner et al., 2010)**

* Objective 1: Significant reduction in mortality due to fishing catches

**HELCOM Action plan (HELCOM Expert Group on Sturgeon Remediation, 2019)**

* Action 4 Significantly reduce bycatch mortality

**PANEUAP: the Pan-European Action Plan for Sturgeons was adopted by the Standing Committee to the Bern Convention in the form of Recommendation N° 199(2018)**

* Action 1.2.1 Identification of bycatch and its impacts in marine and Freshwater.

* Action 1.2.2 identification and implementation of management options (technical solutions, fishery restriction, closed areas, closed season) and gear modifications to reduce bycatch in marine and inland fisheries.

* Action 1.2.3 Monitoring of compliance with bycatch avoidance measures and adaptive management.

**Rhine Action Plan (Visser, 2020)**

* Accidental removal and mortality due to subsequent handling is reduced for professional fisheries and recreational fisheries (bycatch and handling on board)

**UK Sturgeon conservation strategy (McCormick et al., 2023)**

* Goal 3 Sturgeon bycatch reduction.
## 6.2 References

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