Code of good practices on fish welfare and fish welfare indicators : implementing the strategic guidelines for EU aquaculture.
Date: 2025-10-20
Institutions: Arechavala López, Pablo Arechavala, Bassett, David, European Climate, Infrastructure and Environment Executive Agency, Pacchiarini, Tiziana
Subjects: European fisheries fund, animal welfare, aquaculture, environmental standard, fish, fisheries policy, fishing industry, maritime economy, regulatory policy, report

Implementing the Strategic Guidelines for EU Aquaculture 

Code of good practices on fish    
welfare and fish welfare indicators 

European Maritime, Aquaculture and Fisheries Fund (EMFAF) 

Written by Pablo Manuel Xandri Royo, Tiziana Pacchiarini, Mayra Llorente Manzanares (NTT Data), David Bassett (EATIP) and 
Pablo Arechavala López (IMEDEA-CSIC) on behalf of the EU Aquaculture Assistance Mechanism 
October 2025 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
EUROPEAN COMMISSION 

European Climate, Infrastructure and Environment Executive Agency 
Unit Sustainable Blue Economy  

Contact:  CINEA EMFAF CONTRACTS 

E-mail:   CINEA-EMFAF-CONTRACTS@ec.europa.eu  

European Commission 
B-1049 Brussels 
BELGIUM 

 
 
EUROPEAN COMMISSION 

Implementing the Strategic Guidelines for EU aquaculture 

Code of good practices on fish 

welfare and fish welfare indicators 

CINEA/EMFAF/2023/3.5.1/SI2.915833 – EU Aquaculture Assistance Mechanism 

Call CINEA/2023/OP/0016 

Produced by the EU Aquaculture Assistance Mechanism  

which is part of a Service Contract jointly managed by DG MARE and the European Climate, 

Infrastructure and Environment Executive Agency (CINEA). 

European Climate, Infrastructure and Environment Executive Agency 

 
 
This report should be cited as:  

Arechavala López, P., Bassett, D., Llorente Manzanares, M., Pacchiarini, T., Xandri Royo, P.M., Code of 
good practices on fish welfare and fish welfare indicators, Publications Office of the European Union, 2025, 
doi:10.2926/4420264 

The information and views set out in this study are those of the author(s) and do not necessarily reflect the 
official opinion of CINEA or of the Commission. Neither CINEA nor the Commission can guarantee the ac-
curacy of the data included in this study. Neither CINEA, the Commission or any person acting on their be-
half may be held responsible for the use that may be made of the information contained therein. 

Manuscript completed in October 2025. 

This document should not be considered as representative of the European Commission’s official position.  

Luxembourg: Publications Office of the European Union, 2025 

© European Climate, Infrastructure and Environment Executive Agency, 2025 

The Commission’s reuse policy 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, ELI: http://data.eu-
ropa.eu/eli/dec/2011/833/oj). 

Unless otherwise noted, the reuse of this document is authorised under the 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 HZ-01-25-147-EN-N 

ISBN 978-92-9405-333-6 

doi:10.2926/4420264

 
 
 
 
 
Contents 

List of acronyms ........................................................................................... 5 

List of figures................................................................................................ 7 

List of tables ................................................................................................. 7 

1. 

Introduction .......................................................................................... 8 

2.  Overview of the document ................................................................... 9 

3.  Key topics addressed ......................................................................... 11 

4. 

Fish welfare good practices ............................................................... 14 

4.1. 

Introduction and overview ................................................................. 14 

4.2.  Factsheet on general good practices on fish welfare.......................... 16 

5. 

Fish welfare indicators ....................................................................... 40 

5.1. 

Introduction and overview ................................................................. 40 

5.2.  Type of indicators ............................................................................. 46 

5.3.  Selection of general fish welfare indicators ........................................ 48 

5.4.  Factsheets on general fish welfare indicators .................................... 51 
5.4.1.  Feeding .......................................................................................................51 
5.4.2.  Handling ......................................................................................................53 
5.4.3.  Water quality ...............................................................................................57 
5.4.4.  Stocking density ..........................................................................................61 
5.4.5.  Mortality removal.........................................................................................64 
5.4.6.  Transport .....................................................................................................68 
5.4.7.  Stunning and slaughter ...............................................................................71 
5.4.8.  Environmental enrichment ..........................................................................75 

6.  References .......................................................................................... 80 

7.  Annexes .............................................................................................. 93 

3 

 
7.1.  Annex 1 – Methodology .................................................................... 93 

7.2.  Annex 2 – References to relevant EU-funded projects ....................... 95 

4 

 
List of acronyms  

Term 

AAC 

AAM 

Description  

Aquaculture Advisory Council 

Aquaculture Assistance Mechanism 

APROMAR 

Spanish Aquaculture Business Association 

ASC 

BIM 

BoA 

CINEA 

CIWF 

Aquaculture Stewardship Council 

Ireland’s Seafood Development Agency  

Board of Ambassadors of AAM 

European Climate, Infrastructure and Environment Executive Agency 

Compassion In World Farming 

DG MARE 

Directorate-General for Maritime Affairs and Fisheries (European Commission) 

DG SANTE 

Directorate-General for Health and Food Safety (European Commission) 

EC 

EE 

EEA 

EFSA 

EMFAF 

EU 

European Commission 

Environmental enrichment 

European Economic Area  

European Food Safety Authority 

EU Maritime, Fisheries and Aquaculture Fund 

European Union 

EURCAW-Aqua 

European Union Reference Centre for Animal Welfare of Aquatic Animals 

FAO  

FHF 

fWEI 

FWI 

FWIs 

GHP 

GSA 

HACCP 

HAPO  

IFA 

ITA 

ITAVI 

MAPA  

MedAID 

MS 

NGO 

OD 

OIE  

OWI 

Food and Agriculture Organisation of the United Nations  

Norwegian Seafood Research Fund 

Fish Welfare Evaluation Index 

Fish Welfare Initiative 

Functional Welfare Indicators 

Good Husbandry Practice 

Global Seafood Alliance 

Hazard Analysis Critical Control Points 

Hellenic Aquaculture Producers Association (Greece) 

Irish Farmers’ Association 

Aquaculture Welfare Standards Initiative 

French Poultry Technical Institute 

Ministerio de Agricultura, Pesca y Alimentación (Spain)  

Mediterranean Aquaculture Integrated Development 

Member State 

Non-governmental organisation 

Oxygen demand 

Office International des Epizooties (now WOAH)  

Operational Welfare Indicator 

PECH  

European Parliament's Committee on Fisheries  

5 

 
Term 

Description  

QBA 

RAS  

RSPCA 

SWIM 

UK 

UNE 

WOAH 

WQM 

Qualitative Behavioral Analysis 

Recirculating aquaculture system  

Royal Society for the Prevention of Cruelty to Animals  

Salmon Welfare Index Model 

United Kingdom 

Asociación Española de Normalización - Spanish Association for Standardisa-
tion 

World Organisation for Animal Health  

Welfare Quality Measure 

6 

 
 
 
 
List of figures  

Figures  

Figure 1. Classifications of fish welfare indicators: a) based on the nature of the indicator; b) based on 
the operability and invasiveness of the indicator for welfare assessments (adapted from Noble et al., 
2018; Stien et al., 2020). ........................................................................................................................ 48 

List of tables 

Table 1. Description of key topics addressed ......................................................................................... 11 
Table 2. List of general fish welfare indicators and topics for which they have been selected............... 49 

Tables 

7 

 
 
 
 
 
 
1. 

Introduction  

In May 2021, the European Commission (EC) adopted a Communication on 
strategic guidelines for a more sustainable and competitive EU aquacul-
ture for the period 2021 to 2030 (1) (“the Strategic Guidelines”). These guide-
lines set the vision for the European Union (EU) aquaculture sector to grow into 
an even more competitive and resilient sector and become a global reference 
for sustainability by 2030. They result from extensive consultation with EU 
Member State (MS) experts on aquaculture and the Aquaculture Advisory 
Council (AAC) as well as a public consultation. 

“The Strategic Guidelines” cover all the relevant issues for the sustainable de-
velopment of aquaculture in the EU and provide concrete recommendations and 
proposals for action to the Commission, MS and the AAC. Among other actions, 
they propose the Commission to develop guidance and good practices on vari-
ous aspects of aquaculture activities. In this regard, “the Strategic Guidelines”, 
in Annex I section 2.2.2, call for the Commission to: 

●  “Support the development by EU MS, the EU aquaculture industry, EU sci-
entific bodies and non-governmental organisations (NGOs) of a code of 
good practice on fish welfare based on scientific research and evidence, 
covering farming, transport and killing". 

●  “Support the development by EU MS and the EU aquaculture industry of 
common, validated, species-specific and auditable fish welfare indicators 
throughout the production chain, including transport and slaughtering”. 

In the context of the implementation of “the Strategic Guidelines”, the EU Aqua-
culture Assistance Mechanism (AAM) developed this “Code of good practices 
on fish welfare and fish welfare indicators” (the Code, hereinafter). The 
Code complements the document on “Good husbandry practices for aquacul-
ture (2) that was developed in the context of the implementation of the animal 
health and welfare actions in “the Strategic Guidelines”.  

(1) Communication from the Commission to the European Parliament, the Council, the European 
Economic and Social Committee and the Committee of the Regions on the strategic guide-
lines for a more sustainable and competitive EU aquaculture for the period 2021 to 2030 
(COM/2021/236 final) (Aquaculture guidelines (europa.eu)). 

(2) Good husbandry practices | EU Aquaculture Assistance Mechanism 

8 

 
 
 
 
 
2. 

Overview of the document 

The aim of the Code is to outline non-species specific best practices for fish 
welfare and indicators used in welfare assessment in the EU, applicable across 
different life stages and production methods. It focuses on clear welfare issues, 
excluding health concerns, such as diseases, vaccination, etc. 

The Code is primarily intended for aquaculture producers, written in clear lan-
guage, to serve as a practical and user-friendly document.   

The document has been developed in close collaboration with the European 
Union Reference Centre for Welfare of Aquatic Animals (EURCAW-Aqua), 
which will later publish work on species-specific fish welfare good practices and 
indicators.   

This Code will be updated in the future including additional good practices on 
fish welfare and indicators used in welfare assessment. The Commission will 
provide these updates via the EU AAM website (3). It is important to note that 
hyperlinks included in this document are valid at the time of its publication. Up-
dates of these hyperlinks might be necessary in the future, and they will also be 
provided via the EU AAM website. 

The content of this document is organised according to the following structure: 

●  List of topics covered by the good practices on fish welfare and fish welfare 

indicators (Chapter 3). 

●  One factsheet on general good practices on the selected topics ad-
dressed in this document, with a focus on fish welfare (Chapter 4). 

●  Factsheets on general fish welfare indicators for the topics addressed in 

this document (Chapter 5). 

●  List of references used in the document for the production of good practices 

and welfare indicators (Chapter 6). 

●  Description of the methodological approach used to produce this docu-

ment (Annex 1). 

●  References including relevant EU-funded projects contacted as part of the 

cluster meeting held on November 8th, 2024 (Annex 2). 

(3) EU AAM website accessible at: https://aquaculture.ec.europa.eu/    

9 

 
 
 
The good practices and indicators outlined in this document are recommenda-
tions derived from the sources cited in the factsheets (listed in Chapter 6). 
These good practices and indicators are intended to provide guidance based on 
the best available information at the time of writing. Therefore, they should not 
be considered mandatory. Users are encouraged to consult the original 
sources. 

10 

 
 
 
3. 

Key topics addressed 

The definitions of the topics covered in this document have been drawn from a 
number of key sources and then adapted to the context of the Code, with focus 
on clear fish welfare impacts. These sources include: i) document on “Good 
Husbandry Practices (GHP) for aquaculture” (4), ii) European organisations 
(Council of Europe, Eurogroup for Animals, etc.), iii) guidelines produced by EU 
and non-EU countries (Greece, Ireland, Spain, Norway, United Kingdom (UK), 
etc.) and international organisations (Food and Agriculture Organisation of the 
United Nations (FAO), World Organisation for Animal Health (WOAH), etc.), iv)  
certification schemes (Aquaculture Stewardship Council (ASC), Global Seafood 
Alliance (GSA), etc.), and v) NGOs (Compassion in World Farming (CIWF), 
Royal Society for the Prevention of Cruelty to Animals (RSPCA), etc.). 

Table 1. Description of key topics addressed 

Topic 

Description  

Feeding 

Handling 

Feeding refers to the provision of food and nutrients to 
aquatic animals. It includes feeding and feeding-re-
lated activities but not feed production per se. Feeding 
is a crucial operation in aquaculture as it has a direct 
bearing on aquatic animals’ welfare. Feeding should 
ensure both the availability of feeds for all fish in the 
farm at the right times and in appropriate quantities, 
and a match between the composition of the feeds 
and the nutritional requirements of the species for 
each growth stage. This promotes good development 
of aquatic animals and reduces undesirable social in-
teractions. 

Handling comprises a series of routine operations re-
lated to the maintenance of the facilities (cleaning, 
changing of components, etc.) and the fish (sampling, 
transfers, grading and sizing, removing dead fish, 
etc.). Many of these operations affect fish welfare, so 
personnel must be qualified, use appropriate equip-
ment that does not harm the fish and perform the op-
erations in the shortest time possible, avoiding poten-
tial suffering and stress during these activities. 

Water quality 

Poor physicochemical and microbiological water qual-
ity cause a stress response in aquaculture animals. 

(4) Good husbandry practices | EU Aquaculture Assistance Mechanism 

11 

 
 
 
Topic 

Description  

When physicochemical parameters are inadequate for 
the species in production, fish cannot maintain home-
ostasis and experience chronic stress, which can im-
pair immune, growth and reproductive function. Micro-
biological water quality must also be considered to 
control opportunistic bacteria. This is essential to en-
sure aquaculture animals’ welfare. The potential for 
serious welfare problems related to water quality is 
greatest in intensive and hyper-intensive systems 
(such as recirculating aquaculture systems, RAS), 
where fish are reared at high densities in highly con-
trolled environments with narrow margins of error.  

Stocking density (also known as “per-unit stocking 
amount” or “stocking rate”) refers to the quantity of in-
dividuals per unit of water area. It is expressed as the 
number or weight of fish per unit area (square metres) 
or water volume (cubic metres). Unsuitable stocking 
densities (either too high or too low, depending on the 
species needs) can have a negative impact on welfare 
of aquaculture animals. Appropriate stocking density 
contributes to fish welfare and ensures good water 
quality. 

Mortality removal refers to the method for extracting 
dead aquatic animals from a facility, as well as the fre-
quency at which it is performed. 

Transport is the activity by which fish are moved from 
one location to another, varying considerably in dis-
tance. It may occur once during their life cycle or sev-
eral times between or within facilities and includes 
transport to slaughterhouse. This activity greatly influ-
ences fish welfare and can be divided into five 
phases: pre-transport, loading, transport, unloading 
and post-transport. 

Slaughter is the final phase of the aquaculture fish life 
cycle. Prior to slaughter, two procedures are carried 
out: fasting and crowding/confinement. These pro-
cesses can take a long period depending on the spe-
cies. The moment of slaughter is usually when a farm 
animal’s welfare is affected the most. This is a pro-
cess of different duration, that should be undertaken 
as quickly and efficiently as is possible. And it  is im-
portant to avoid unnecessary pain, distress or suffer-
ing throughout the entire process. Generally, stunning 
methods should be applied before slaughter to ensure 
the fish is unconscious and pain-free during slaughter. 

12 

Stocking density 

Mortality removal 

Transport 

Slaughter 

 
Topic 

Description  

Environmental en-
richment 

Environmental enrichment (EE) refers to the modifica-
tions of the captive environment to enhance the level 
of psychological, physical and social stimulation pro-
vided to the aquatic animals by helping to cope better 
with stressful situations and improving cognitive abili-
ties, as well as, to enhance the rearing environment 
and encourage the expression of normal species-spe-
cific behaviours. EE is a way of improving the living 
conditions of farmed fish, promoting positive mental 
and physical well-being. The broad types of enrich-
ments include social (e.g., contact with other fish for 
schooling), physical (e.g., addition of objects, sub-
strates, or shelters), sensory (e.g., appropriate tank 
colour or lighting), and dietary (e.g., feeding strategy, 
palatability, varied or novel feed types). Any change or 
modification by EE needs to be adapted to the biology 
of each species, monitored to ensure that it positively 
enhances welfare and does not cause any fish welfare 
or production issues (hygiene and biosecurity). 

13 

 
 
 
4. 

Fish welfare good practices 

In this chapter, general good practices, not species-specific, focused on fish 
welfare related to the topics presented in Chapter 3 are provided. 

4.1. 

Introduction and overview 

For the last 20 years, the scientific understanding and the research undertaken 
on fish welfare have significantly increased and evolved, resulting in the devel-
opment of improved fish welfare practices. This evolution has also involved the 
consolidation of differing protocols for the assessment of fish welfare, such as 
fish welfare indicators. 

Historically, very little was known about fish behaviour, and it was widely be-
lieved that fish did not feel pain. Fish welfare has not been researched to the 
same extent as that of mammals and birds. 

Over many years, aquaculture in the EU, the UK and Norway has made signifi-
cant progress in the development of good fish welfare practices. This progress 
has been driven by the collaboration between the aquaculture industry, the sci-
entific and research community, NGOs and public authorities, who have worked 
to create guidelines and recommendations that seek to improve the health and 
welfare of fish in production. 

Much of this work has been partly driven by the increased scientific understand-
ing of and the research into fish welfare aspects. With increased knowledge 
concerning the issues around fish welfare, the need for indicators to demon-
strate fish welfare has gained importance, alongside greater consideration of 
the ethics in the matter. 

Initiatives include the implementation of codes of good practice that address key 
issues such as the protection of fish from pain, anxiety and distress. Some of 
these codes include: “Code of good practices on fish welfare among aquacul-
ture producers” issued by AAC (among others), “Aquatic code” developed by 
WOAH, “Polish code of good practice for carp harvest, transport and slaughter” 

14 

 
(5), “Austrian farmed fish handbook” (6), “Italian handbook on fish welfare in farm-
ing fish” (7), “Mediterranean Fish Welfare: Guide to Good Practices and Assess-
ment Indicators” developed by the Hellenic Aquaculture Producers Association 
(HAPO), “The farmed salmonid health handbook” developed by experts from 
both private and governmental organisations representing the Irish aquaculture 
industry, “Guide of good practice for farming freshwater fish species for aqua-
culture” developed by Fisheries Research and Development Station Nucet (Ro-
mania) and “Guide on fish welfare in Spanish aquaculture”, prepared by the 
Spanish Aquaculture Business Association (APROMAR), among others (see 
references in Chapter 6). 

In addition, specific projects have been developed based on scientific research 
and practical experience, adapted to variations between species and production 
systems. These studies are fundamental to adapt aquaculture practices to the 
specific characteristics of each species, thus promoting a more tailored and ef-
fective approach to fish management. 

The EC has established “the Strategic Guidelines” to promote a more sustaina-
ble and competitive aquaculture, covering the period 2021-2030. These guide-
lines emphasise the importance of animal welfare, recognising that proper man-
agement of fish not only improves their quality of life, but can also positively in-
fluence the productivity and sustainability of the sector. In this context, codes of 
good practice have been developed by some Member States, international or-
ganisations, NGOs, national aquaculture associations, or scientists, addressing 
aspects such as stress management, water quality and feeding, with the aim of 
minimising fish suffering. 

In addition, EURCAW-Aqua was created on January 17th, 2024 in accordance 
with Regulation (EU) 2017/625 of the European Parliament and of the Council 
(notified under document C(2024) 209). Also, in 2024, the European Partner-
ship for Animal Health and Welfare (EUPAHW) was launched, a co-funded Eu-
ropean Partnership that includes research activities on health and welfare of 
aquatic animals.  

Support from MS and the EU has also been crucial, providing subsidies and 
grants for the adoption of greater welfare practices. This reflects a growing com-

(5) http://www.pankarprybacy.pl/KDP_2023.pdf  
(6)  http://www.tierschutzkonform.at/wp-content/uploads/2023/09/Checkliste-Nutzfische-Auflage-
1-1.pdf; https://www.tierschutzkonform.at/wp-content/uploads/2023/09/Handbuch-Nutz-
fische-Auflage-1-4.pdf   

(7) https://www.izsvenezie.it/manuale-benessere-specie-ittiche/  

15 

 
 
 
mitment to sustainability and responsibility in aquaculture, aligning with the rec-
ommendations of bodies such as the Council of Europe, European Food Safety 
Authority (EFSA) scientific opinions and WOAH. 

The current situation in European aquaculture shows a proactive approach to 
fish welfare, with a framework of good practices that is being consolidated and 
adapted to the needs of the sector. 

While the review of EU legislation on fish welfare is beyond the scope of this 
document, it is worth mentioning that European Regulations on the protection of 
vertebrate animals on farm, during transport and during slaughter have been in-
troduced (8).  

4.2. 

Factsheet on general good practices on fish welfare 

General Good Practices on fish welfare 

Feeding 

General indications 

1.  Feeding practices should be adapted to the biology of the species, life 
cycle stage, physiological state, production method, and environmen-
tal conditions. These practices must ensure that feed is provided in 
sufficient quantity and rate, over a large enough area and spread at 
regular intervals to maximise feed intake and minimise fish crowding 
and damage. Sudden changes in feeding practices should be avoided 
(IFA Aquaculture, 2017), (AAC, 2024), (Council of Europe, 2005), 
(Arechavala-López, Cabrera-Álvarez, Maia, & Saraiva, 2022) (Kristi-
ansen, Madaro, Stien, Bracke, & Noble, 2020). 

(8) In particular, the following legislation applies to aquaculture, among other activities: Council 
Directive 98/58/EC of 20 July 1998 concerning the protection of animals kept for farming 
purposes; Commission Delegated Regulation (EU) 2020/691 of 30 January 2020 
supplementing Regulation (EU) 2016/429 of the European Parliament and of Council in 
regards rules for aquaculture establishments and transporters of aquatic animals; Council 
Regulation (EC) No 1/2005 of 22 December 2004 on the protection of animals during 
transport and related operations and amending Directives 64/432/EEC and 93/119/EC and 
Regulation (EC) No 1255/97. On 7 December 2023, the Commission adopted a proposal for 
a Regulation of the Council and European Parliament on the protection of animals during 
transport to replace Council Regulation (EC) No 1/2005. Council Regulation (EC) No 
1099/2009 of 24 September 2009 on the protection of animals at the time of killing (Text with 
EEA relevance)Text with EEA relevance. 

16 

 
 
 
General Good Practices on fish welfare 

Feeding practices should also minimise feed competition and allow 
subordinate individuals access to feed, particularly in species with es-
tablished hierarchies or aggressive tendencies. 

2.  Consideration should be given to moving to automatic feeders which 
are recommended to better distribute and disperse the food (EFSA, 
2008b), (EFSA, 2008c), (EFSA, 2008d), (EFSA, 2008a). 

3.  Feeding strategies that result in poor body condition, including inade-
quate or excess nutrition, fin damage, hunger, frustration and aggres-
sion must be avoided (AAC, 2024), (Council of Europe, 2005). 

4.  Feeding should be monitored, especially for larvae and juveniles 

(Council of Europe, 2005). 

Handling 

General indications 

1.  Personnel must be properly equipped and qualified to minimise physi-
cal damage and stress. The operator should include relevant proce-
dures that identify critical points in the handling procedure, propose 
corrective measures and indicate when to discontinue handling in or-
der to maintain adequate fish welfare. These should include contin-
gency planning for unforeseen events that may have an impact on 
handling. The personnel involved, their roles, the approximate number 
of fish handled, health and welfare issues observed, as well as mortal-
ity rate and cause should be evaluated (FAO, 2011), (EFFAB, 2023), 
(AAC, 2024), (EU Platform on Animal Welfare Own Initiative Group on 
Fish, 2020).  

2.  Any handling should be limited to the minimum necessary in relation 
to the nature of the production. In addition, operations should be car-
ried out quickly and carefully to prevent damage to the fish (EFSA, 
2008a), (EFSA, 2008b), (EFSA, 2008c), (EFSA, 2008d), (RSPCA, 
2020), (CIWF, 2023), (AAC, 2024), (Council of Europe, 2005).  
3.  Handling should be done keeping the fish in the water with sufficient 
oxygen (O2) content, as well as taking into account other parameters 
that are explained in the topic “water quality” (EFSA, 2008a), (EFSA, 
2008b), (EFSA, 2008c), (EFSA, 2008d).  

4.  If fish have to be removed from water for handling, they should be 

kept moistened at all times. Fish should not be allowed to asphyxiate 
under any circumstances (EU Platform on Animal Welfare Own Initia-
tive Group on Fish, 2020), (AAC, 2024), (Council of Europe, 2005). 

5.  Time out of water for alive fish must be kept to the minimum possible 
and never exceed 15 seconds (unless anaesthetised, for which the 
time must be set by a veterinarian), (RSPCA, 2020), (CIWF, 2023), 
(Council of Europe, 2005). 

17 

 
General Good Practices on fish welfare 

6.  Fish should be anaesthetised if it is considered by a veterinarian to re-
duce the pain and stress during handling (EU Platform on Animal Wel-
fare Own Initiative Group on Fish, 2020), (AAC, 2024), (Council of Eu-
rope, 2005). 

7.  Fish should be in good welfare status before handling (IFA Aquacul-
ture, 2017), (EU Platform on Animal Welfare Own Initiative Group on 
Fish, 2020), (AAC, 2024). 

8.  When possible, handling should be done when the fish have lower 
metabolic activity and their need for oxygen is lower. For example, 
when the water temperature decreases the metabolic rate of the spe-
cies, and therefore feeding and oxygen consumption rates are lower. 
(EFSA, 2008a), (EFSA, 2008b), (EFSA, 2008c), (EFSA, 2008d). 

9.  The sensitivity of the fish to handling is temperature-dependent, thus 
handling should be avoided when water or air temperatures reach the 
outer lower and upper optimal limits respectively, in relation to the 
growth and physiological state. Contingency measures should be 
taken to avoid exposure of fish at the outer limits of the temperatures 
ranges they can tolerate (EU Platform on Animal Welfare Own Initia-
tive Group on Fish, 2020), (AAC, 2024).  

10. Fish should be inspected during and after handling for signs of exter-
nal injury or excessive time to recommence feeding that may result 
from the procedures or equipment used. In case of injury or excessive 
mortality, the handling procedure should be evaluated to identify pit-
falls in order to avoid similar occurrences in the future (EU Platform on 
Animal Welfare Own Initiative Group on Fish, 2020), (AAC, 2024). 

11. Fish should never be thrown onto solid objects, onto each other or hit 

with solid objects including when exiting pipes and pumps. Fish should 
not fall from a height that could compromise welfare (EU Platform on 
Animal Welfare Own Initiative Group on Fish, 2020), (AAC, 2024). 

12. Live fish must never be held by the gill covers or tail only, nor should 
gaffs be used on them (EFSA, 2008a), (EFSA, 2008b), (EFSA, 
2008c), (EFSA, 2008d), (RSPCA, 2020), (CIWF, 2023), (Council of 
Europe, 2005).  

Where handling is necessary, sedation or  anaesthesia should be 
used for procedures likely to induce substantial pain or strong aver-
sion, such as vaccination or biopsy sampling.  

13. Larvae require very gentle handling and should not be siphoned or re-
moved from the water. Instead, passive slow pumping and transfer in 
plastic bags should be used (RSPCA, 2020). 

Grading 

1.  Grading is necessary to make uniform the sizes of the batch, avoiding 
cannibalism in certain species and increased stress-related conditions 

18 

 
General Good Practices on fish welfare 

(susceptibility to disease, feed competition, pathogen accumulation, 
etc.) (9). 

2.  Grading should be carried out by qualified personnel to minimise 

stress and avoid damage stocks (EU Platform on Animal Welfare Own 
Initiative Group on Fish, 2020), (APROMAR, 2022), (BIM, 2022a), 
(AAC, 2024). 

3.  Grading operations should be carefully planned and kept to a mini-

mum (EU Platform on Animal Welfare Own Initiative Group on Fish, 
2020), (BIM, 2022a), (AAC, 2024). 

4.  Size grading should be carried out when required for avoiding unnec-
essary suffering and, if possible, in-water. If this is not possible, such 
as with large-sized fish, methods with specific procedures should be 
used to ensure or at least have a minimal impact on the welfare of the 
animals (Eurogroup for Animals, 2022).  

5.  The use of passive grading systems wherever possible is encouraged 

(IFA Aquaculture, 2017), (RSPCA, 2024). 

6.  It is necessary to ensure that the tools and machinery employed in the 

grading operations are in good condition (APROMAR, 2022). 

Water quality 

General indications 

1.  Sufficient water supply and good water quality is essential for fish wel-
fare in each life and production stage. (Eurogroup for Animals, 2022), 
(AAC, 2024), (EU Platform on Animal Welfare Own Initiative Group on 
Fish, 2020), (Council of Europe, 2005). 

2.  Species-specific tolerance limits should be ensured to maintain fish 

homeostasis (Eurogroup for Animals, 2022), (EU Platform on Animal 
Welfare Own Initiative Group on Fish, 2020). 

3.  The correct management of the different physicochemical parameters 
involved in the production system, helps to reduce the state of stress 
farmed fish could experience (García-Ortega & Calvario-Martínez, 
2003). 

4.  It is recommended to regularly monitor water quality parameters, such 
as: temperature, dissolved oxygen, pH, salinity, carbon dioxide (CO2)  

(9) Information gathered at the Cluster meeting with experts of EU-funded project and members 

of the AAM Board (8th November 2024).  

19 

 
 
 
General Good Practices on fish welfare 

and ammonia. Regular monitoring ensures parameters meet the spe-
cies-specific requirements, align with the life stage, and account for 
variations between systems and feeding practices. Some water quality 
management aspects are system-specific, for example ammonia 
(NH3) is not normally critical in cage systems, whereas in RAS facili-
ties more frequent monitoring of more parameters is recommended 
(RSPCA, 2024), (Scottish Salmon Producers Organisation, 2015), 
(Pavlidis, et al., 2023), (AAC, 2024), (EU Platform on Animal Welfare 
Own Initiative Group on Fish, 2020), (Eurogroup for Animals, 2022), 
(Council of Europe, 2005). 

5.  RAS rely on multiple systems to maintain water quality and more in-
tensive monitoring of a wider range of parameters is recommended 
compared to other systems (Eurogroup for Animals, 2022). 

6.  Wherever possible, water parameters may be monitored in an auto-
mated manner. To this end, sensors for measuring water quality pa-
rameters should be integrated when possible, depending on the level 
of technical sophistication of the facility, into automated monitoring. 
However, sensors and measuring equipment needs to be maintained 
and calibrated at appropriate intervals and taking into account manu-
facturers’ guidelines. The measurements or sampling should be car-
ried out at appropriate points in each cycle in a risk-oriented manner. 
These automatic mechanisms should have alarm systems and backup 
generators necessary to handle possible power, water supply or 
equipment failure (AAC, 2024), (EU Platform on Animal Welfare Own 
Initiative Group on Fish, 2020). 

7.  When changes in water quality occur, in order to return to the optimal 
situation, it is important not to make abrupt changes as the homeosta-
sis of the fish to adapt to change is slow (AAC, 2024), (Council of Eu-
rope, 2005), (EU Platform on Animal Welfare Own Initiative Group on 
Fish, 2020). 

8.  In certain life stages of marine species reared in land-based facilities, 
as tanks or RAS, high salinities or seawater should be used with cau-
tion and monitored. The impact of salinity on the water chemistry and 
on the different water quality parameters (ammonia, CO2, pH, O2 and 
temperature) require good knowledge (Pavlidis, et al., 2023), (EU Plat-
form on Animal Welfare Own Initiative Group on Fish, 2020). 

9.  Relevant procedures should be put in place to ensure adequate water 
supply and quality are maintained at all times on farm, during transport 
and in holding tanks at the abattoir. The plan should cover unforeseen 
events that may have an impact on water quality (AAC, 2024), (EU 
Platform on Animal Welfare Own Initiative Group on Fish, 2020). 

Physicochemical parameters to be monitored (most relevant) 

20 

 
General Good Practices on fish welfare 

1.  Oxygen: In pond culture and net pens, the oxygen levels should be 

monitored closely in case of high density and warm water. In aquacul-
ture systems with high degrees of recirculation, the oxygen levels 
should be monitored continuously using a system that accurately re-
flects the oxygen available to the fish, also an alarm system should be 
in place (AAC, 2024), (EU Platform on Animal Welfare Own Initiative 
Group on Fish, 2020) (Kristiansen, Madaro, Stien, Bracke, & Noble, 
2020). 

2.  Ammonia: Total ammonia concentration should be closely monitored, 
particularly in systems with restricted water exchange such as high-
density fish tanks, as well as in aquaculture systems with high de-
grees of recirculation, and during and after transport (AAC, 2024), (EU 
Platform on Animal Welfare Own Initiative Group on Fish, 2020). 

3.  CO2: CO2 is produced by fish during respiration and dissolves in water 
to form carbonic acid thus lowering pH. The CO2 level may be affected 
by microbiological factors (e.g. bacterial metabolism) as well as by the 
temperature, salinity and alkalinity of the water. Accumulation of CO2 
to harmful levels shall be avoided, for example by using aeration sys-
tems or by chemical means, according to the farming system used 
(AAC, 2024), (EU Platform on Animal Welfare Own Initiative Group on 
Fish, 2020), (Council of Europe, 2005). 

4.  pH: As the toxicity or occurrence of several water quality parameters 
is dependent of pH, this should be monitored at appropriate intervals 
and in aquaculture systems with continuous high degrees of recircula-
tion (AAC, 2024), (EU Platform on Animal Welfare Own Initiative 
Group on Fish, 2020). 

5.  Temperature: It should be monitored continuously in aquaculture sys-
tems with high degrees of recirculation (AAC, 2024), (EU Platform on 
Animal Welfare Own Initiative Group on Fish, 2020) (Kristiansen, 
Madaro, Stien, Bracke, & Noble, 2020).  

Microbiological parameters 

1.  In closed systems it is recommended to have a microbiological com-

munity monitoring to maintain specific beneficial populations of micro-
organisms. One of the methods to control the microbial community in 
water is to increase the water refreshment rate at certain specific 
times (10), (Subasinghe, et al., 2023). 

(10) Information gathered at the Cluster meeting with experts of EU-funded project and members 

of the AAM Board (8th November 2024). 

21 

 
 
 
General Good Practices on fish welfare 

2.  Microbial maturation is recommended to protect marine larvae from 

harmful opportunistic bacteria. The process involves filtering the water 
through a membrane to remove more than 95% of the bacteria before 
it is transferred to larval incubators, and then temporarily retaining the 
water in a biofilter to enhance the growth of beneficial non-opportunis-
tic bacteria (Skjermo, Salvessen, Oie, Olsen, & Vadstein, 1997). 

3.  Whenever possible, control of pathogens is recommended, as they 
have a direct impact on fish welfare by causing stress, behavioural 
changes, diseases and in severe cases, mortality; the use of ozonis-
ers, ultraviolet in RAS, removal of uneaten feed, faeces or dead ani-
mals from the water is recommended (11).  

Stocking density 

General indications 

1.  Stocking density has complex interactions with a range of input factors 
and welfare outcomes. An unsuitably high stocking density can pose 
significant welfare risks, including water quality deterioration and 
higher rates of physical injuries, as well as changes in behavioural 
patterns such as reducing feed intake and increased aggression (Eu-
rogroup for Animals, 2022), (AAC, 2024). 

2.  Stocking density should be adjusted in line with the following criteria 

(Council of Europe, 2005): 

•  The biological needs of fish with regard to environmental condi-

tions in addition to health and welfare. 

•  The farming system used, in particular the ability to maintain water 

quality, and the feeding technology. 

•  Welfare indicators should be evaluated, and management prac-

tices and production controllable variables, including stocking den-
sities, should be adjusted according to the result. 

• 

In the absence of species-specific data, stocking densities should 
follow the precautionary principle, erring on the side of lower densi-
ties until evidence shows no welfare compromise 

3.  It is important to know whether the reared species are solitary, or likely 
to shoal in small or big groups at different life-stages, as well as if they 
usually co-habit with other fish species in the wild. On the other hand, 
most farmed species that do not shoal in the wild, or associate with 

(11) Information gathered at the Cluster meeting with experts of EU-funded project and members 

of the AAM Board (8th November 2024). 

22 

 
 
 
General Good Practices on fish welfare 

other species, are territorial and can engage in aggressive behaviours 
with conspecifics, which in both cases may be a big problem in the 
high stocking densities of captive environments (Arechavala-López, 
Cabrera-Álvarez, Maia, & Saraiva, 2022). 

4.  The species-specific maximum stocking densities that meet the fish 

needs should be also taken into account, including (Eurogroup for Ani-
mals, 2022): 

•  Control of aggressive behaviours. 

•  Minimisation of stress and injuries. 

•  Maintenance of adequate environmental conditions. 

•  Assurance of appropriate access to feed in the system. 

5.  Low stocking density in intensive systems may cause poor welfare in 
some species and life-stages where it permits some dominant individ-
uals to express territorial behaviour, resulting in aggression towards 
others (AAC, 2024).  

6.  For species located in extensive ponds, the stocking density should be 
adapted to the life cycle stage, the pond productivity and temperature 
conditions (EFSA, 2008a), (EFSA, 2008b), (EFSA, 2008c), (EFSA, 
2008d). 

Mortality removal 

1.  Any dead or near-death fish should be removed as soon as possible 

in a way that does not adversely affect the health and welfare of those 
remaining. Where possible, the cause of death should be recorded 
(EU Platform on Animal Welfare Own Initiative Group on Fish, 2020), 
(Council of Europe, 2005). 

2.  Farmed fish should not remain in the presence of dead fish for the fol-
lowing reasons: i) in fish production, the presence of mortalities can in-
crease the risk of diseases, especially if the main cause is an infec-
tious disease, which is particularly relevant to carnivorous fish, as can-
nibalism on weak fish or fish carcasses can impair the microbiological 
quality of the water and negatively impacting fish welfare, ii) mortalities 

23 

 
General Good Practices on fish welfare 

can also have negative effects on the water quality due to the bioac-
tive compounds that they give off during decomposition, further com-
promising the fish welfare (e.g. decrease of oxygen demand (OD)) (12). 

3.  A method for the removal and disposal of dead and near-dead fish ap-
propriate to the production system used should be available (Council 
of Europe, 2005). 

4.  Mortality removal varies according to the production system: in small-
medium tanks removal is easier (usually manually, so this can be 
done daily) than in bigger and deeper tanks; in ponds it is much more 
difficult; in cages it can be done in specific devices (air-lifts, pumps in 
the bottom) or manually (divers). Disposal of mortalities should adhere 
to relevant waste management regulations of MS concerned (IFA Aq-
uaculture, 2017). Mortality checks must be recorded as soon as possi-
ble after grading (RSPCA, 2020), (RSPCA, 2024). 

5.  In hatcheries, dead larvae should be removed daily (EFSA, 2008a), 

(EFSA, 2008b), (EFSA, 2008c), (EFSA, 2008d). 

Transport 

Pre-transport 

1.  Transport should be planned according to the authorisation of trans-
porters. Authorisation could include requirements that ensure that 
(AAC, 2022), (IFA Aquaculture, 2017), (Saraiva, Arechavala-López, 
Cabrera-Álvarez, & Waley, 2021), (WOAH, 2012), (APROMAR, 2022), 
(Ministero della Salute, 2017), (GSA, 2023), (GLOBALG.A.P., 2024), 
(ITA):  

•  Vehicles, fittings and equipment are designed, constructed, 

equipped and maintained to safeguard the welfare of the animals. 

•  Owners, managers, drivers, and relevant personnel in transport 

companies and aquaculture producers have the necessary training 
and competences.  

2.  Vehicles and equipment should be cleaned and disinfected between 
journeys (AAC, 2022), (Saraiva, Arechavala-López, Cabrera-Álvarez, 

(12) Information gathered at the Cluster meeting with experts of EU-funded project and members 

of the AAM Board (8th November 2024). 

24 

 
 
 
General Good Practices on fish welfare 

& Waley, 2021), (WOAH, 2012), (Council of Europe, 2005), (APRO-
MAR, 2022), (Ministero della Salute, 2017), (GSA, 2023), (ITA), 
(GLOBALG.A.P., 2024). 

3.  Vehicles should be equipped with devices or materials to dampen vi-
brations and limit their transfer to transport units. Additionally, they 
should have grills, caps and hinges as needed to make inspection, 
cleaning and disinfection of every area (Saraiva, Arechavala-López, 
Cabrera-Álvarez, & Waley, 2021). 

4.  Operators should ensure that equipment is checked, and that suffi-
cient staff, equipment, and contingency plans are in place including 
50% more oxygen than it is anticipated to be used on the journey 
(AAC, 2022), (Saraiva, Arechavala-López, Cabrera-Álvarez, & Waley, 
2021), (WOAH, 2012), (Council of Europe, 2005), (APROMAR, 2022), 
(Ministero della Salute, 2017), (GSA, 2023), (ITA). 

5.  The distance and expected duration of the journey are estimated and 
taken into account in the transporting planning within this phase. The 
latter should also be kept as short as possible (ITA). 

6.  Contact should be established between the different operators supply-
ing, transporting, and receiving the fish to ensure that suitable fish are 
loaded and that appropriate staff and equipment are ready for unload-
ing as quickly as possible (AAC, 2022), (Saraiva, Arechavala-López, 
Cabrera-Álvarez, & Waley, 2021), (WOAH, 2012), (Council of Europe, 
2005), (APROMAR, 2022), (Ministero della Salute, 2017), (GSA, 
2023), (ITA). 

7.  Fasting prior to transport serves to empty the digestive tract of the fish 
in order to prevent pollution of the transport water through excrement, 
in turn causing oxygen depletion. As fish physiology can be negatively 
affected after an excessively long fasting period, the duration of fast-
ing must always be adjusted to the fish species, life stage and temper-
ature, and kept as short as possible. In addition, fasting periods 
should be adjusted based on seasonal temperatures to optimise fish 
welfare (Martínez, A., et al., 2025), (Bermejo-Poza, R., et al., 2017), 
(AAC, 2022), (Wedekind, Harrer, Geiser, & Kraus, 2020), (Saraiva, 
Arechavala-López, Cabrera-Álvarez, & Waley, 2021), (WOAH, 2012), 
(Council of Europe, 2005), (Ministero della Salute, 2017), (EU Plat-
form on Animal Welfare Own Initiative Group on Fish, 2020),  (ITA).  

8.  In some cases, it is advisable to use a sedative under the guidance of 
a veterinarian, and to slowly reduce the water temperature prior to 
loading. It is even recommended for especially sensitive freshwater 
fish that sodium chloride is added to the water during the journey. The 
fish demonstrate more relaxed behaviour after the increase in salinity 
and are therefore less susceptible to injuries (AAC, 2022), (Saraiva, 
Arechavala-López, Cabrera-Álvarez, & Waley, 2021), (WOAH, 2012), 
(Council of Europe, 2005), (APROMAR, 2022), (Ministero della Salute, 

25 

 
General Good Practices on fish welfare 

2017), (GSA, 2023),  (ITA), (Wedekind, Harrer, Geiser, & Kraus, 
2020).  

9.  Fish should be considered unfit for transport if they show unusual be-
haviour, such as rapid ventilation, abnormal swimming, or signs of dis-
ease or physical damage (IFA Aquaculture, 2017), (Wedekind, Harrer, 
Geiser, & Kraus, 2020), (Saraiva, Arechavala-López, Cabrera-Álvarez, 
& Waley, 2021), (WOAH, 2012), (APROMAR, 2022), (Council of Eu-
rope, 2005), (GLOBALG.A.P., 2024), (AAC, 2022), (Ministero della 
Salute, 2017), (GSA, 2023),  (ITA). 

10.  Acclimatisation and temperature: abrupt changes in the environmen-
tal conditions must be avoided. Where there are large differences be-
tween the initial water parameters and the ones in the transport con-
tainer or stocking water, the water must be slowly exchanged to allow 
the fish continuous acclimatisation. Cool water temperatures should 
be maintained during transport, as this reduces the metabolic activity 
and oxygen use of fish. An additional beneficial effect is the high oxy-
gen solubility in cold water. Furthermore, during the journey, the water 
temperature should be kept as much stable as possible and not fluctu-
ate more than 1-2°C (Wedekind, Harrer, Geiser, & Kraus, 2020), (Min-
istero della Salute, 2017), (GSA, 2023), (ITA). 

Loading and unloading 

1.  For most finfish species, loading and unloading is the most stressful 

part of live transport. Crowding and handling should be kept to a mini-
mum, it should be gentle, and, the time out of water should be mini-
mised (AAC, 2022), (Saraiva, Arechavala-López, Cabrera-Álvarez, & 
Waley, 2021), (WOAH, 2012), (Pavlidis, M., Samaras, A., 2020), 
(APROMAR, 2022), (Ministero della Salute, 2017), (Wedekind, Harrer, 
Geiser, & Kraus, 2020): 

•  The use of specialised fish transportation pumps is preferred over 
the use of nets for moving fish. If the use of nets is unavoidable, 
they should be soft, small mesh size, uncoated or unknotted 
coated and/or knot-free to limit trauma to the surface layer. 

•  Equipment should be designed and maintained to avoid fish inju-

ries, especially avoiding sharp edges or protrusions. 

•  Crowding should be carried out in short-time steps without invoking 
a significant stress response, and the duration and intensity of 
crowding prior to harvesting should be minimised. 

•  Fish should be progressively acclimated to the receiving water 

prior to unloading. A sufficiently large number of skilled people is 
necessary to ensure that the loading process runs as smoothly as 
possible, ensuring welfare of transferred fish. 

26 

 
General Good Practices on fish welfare 

• 

In the case of unloading, near-dead or seriously injured fish should 
be removed and appropriately sacrificed and disposed. Addition-
ally, fish should be unloaded as soon as possible, given that simi-
lar to the loading phase, fish stress increases significantly during 
this phase. Control of the pumping speed and pressure, and of the 
height at which the fish fall into the final tank should be done and, if 
hand nets are used, ensure that fish spend as little time as possi-
ble exposed to the air. 

Transport 

1.  Transport should be accompanied by appropriate documentation, de-

tailing origin, content and destination, to allow tracing if required (GSA, 
2023). 

2.  Documentation should include (AAC, 2022), (Saraiva, Arechavala-Ló-
pez, Cabrera-Álvarez, & Waley, 2021), (APROMAR, 2022), (Ministero 
della Salute, 2017), (GSA, 2023), (ITA): 

•  Journey start and end time.  

•  The species, size, and number of animals loaded. 

•  The number of animals injured and the number of mortalities dur-
ing loading, the journey, unloading and after unloading, together 
with the cause of the injuries and mortalities. 

•  The journey route. 

•  Time and place of any release or intake of water.  

•  Consumption of supplementary oxygen.  

•  Key water quality parameters, especially temperature before load-
ing, after loading, at regular intervals during the journey, and the 
receiving water before unloading. 

•  Proof of cleaning and disinfection of tanks.  

3.  There should be a contingency plan to address emergencies and mini-
mise stress during unloading, transferring and loading fish (WOAH, 
2015). 

4.  Fish should have settled in their transport units and be calm before 
starting the journey (AAC, 2022), (European Commission, 2017), 
(APROMAR, 2022),  (ITA). 

5.  A mandatory training is recommended to enable people involved in 

such transport operations to recognise and alleviate physical and psy-
chological signs of stress (Eurogroup for Animals, 2022), (Eurogroup 
for Animals, 2024), (EU Platform on Animal Welfare Own Initiative 
Group on Fish, 2020), (ITA). 

27 

 
General Good Practices on fish welfare 

6.  The driving style should be gentle (AAC, 2022), (European Commis-

sion, 2017), (APROMAR, 2022), (ITA). 

7.  The transport of different fish species and sizes together should also 
be avoided, as it can lead to additional stress or injuries (Wedekind, 
Harrer, Geiser, & Kraus, 2020), (Ministero della Salute, 2017). 

8.  The stocking density of the fish in a vehicle or container should not ex-
ceed what is generally accepted for a given species and it must there-
fore be adjusted to ensure that water quality is maintained at an ade-
quate level throughout the transport period (WOAH, 2012), (ITA). 

9.  Normally, no feed should be given during the journey (AAC, 2022), 

(European Commission, 2017), (APROMAR, 2022), (ITA). 

10. Visual inspections should be kept to a minimum and determined ac-
cording to the species, life-stage, transport method, and journey 
length. Visual inspections can be important, but opening containers to 
inspect fish can be an unnecessary stressor, so other systems such 
as underwater cameras are recommended (AAC, 2022), (European 
Commission, 2017), (APROMAR, 2022), (ITA). 

11. Temperature and other water parameters should be continually moni-
tored during the journey (AAC, 2022), (European Commission, 2017), 
(APROMAR, 2022), (ITA). It is recommended to maintain water quality 
parameters according to the total biomass, size, weight and fish spe-
cies being transported: O2, CO2, pH, temperature and ammonia. The 
oxygen supply determines the amount of fish that can be transported 
and the duration of the journey. Oxygen demand depends on the fish 
species, age, weight, water temperature, stress effects, conditions and 
time of last feed. It is recommended to use pure oxygen instead of 
pressurised air during transport, to achieve a high oxygen level and 
reduce the risk of heating caused by the external temperature as well 
as the risk of high levels of nitrogen. Air can be used for water aera-
tion and elimination of gases, mainly carbon dioxide and ammonia 
(AAC, 2022), (Eurogroup for Animals, 2024), (IFA Aquaculture, 2017), 
(Wedekind, Harrer, Geiser, & Kraus, 2020), (Saraiva, Arechavala-
López, Cabrera-Álvarez, & Waley, 2021), (WOAH, 2012), (European 
Commission, 2017), (Council of Europe, 2005), (Pavlidis, M., Sama-
ras, A., 2020), (APROMAR, 2022), (Ministero della Salute, 2017), (EU 
Platform on Animal Welfare Own Initiative Group on Fish, 2020), 
(GSA, 2023), (GLOBALG.A.P., 2024), (ITA). 

12. In the case of very short journeys (within a farm), movements within 

sites, and transport in plastic bags (eggs, fry, larvae), routine monitor-
ing of water quality parameters is not typically required. Operator ex-
perience allows for planned measures that maintain important water 
quality parameters without routine monitoring (AAC, 2022), (European 
Commission, 2017), (APROMAR, 2022), (ITA), (IFA Aquaculture, 
2017). 

28 

 
General Good Practices on fish welfare 

13. Transport containers: completely sealed containers should be used, 

with the necessary water and essential oxygen, for the entire duration 
of the journey. Water and the remaining atmosphere must be enriched 
with pure oxygen to guarantee the survival of fish. An example of 
closed systems are transport bags and rigid plastic containers. In 
practice, 50 l plastic bags are used for transporting fry and juvenile 
fish. It is recommended to tie the corners to prevent the fish collecting 
in them and becoming trapped. For security, double-bagging is recom-
mended. In addition, it is recommended to fill the bags at a ratio of 1:3 
or 2:3 (water:gas atmosphere). The transport bags should lie flat to fa-
cilitate and improve gas exchange. Furthermore, transport bags 
should lie at right angles to the direction of travel to reduce stress to 
the fish due to vehicle movements. Also, a dark cover is recom-
mended to reduce stress caused by light exposure. When smaller 
transport bags are used, it is strongly recommended that they are 
packaged in polystyrene boxes to ensure good insulation (Wedekind, 
Harrer, Geiser, & Kraus, 2020).  

14. Transport in big tanks: transport containers receive the necessary oxy-
gen from an external source. They are square, have a water depth of 
around 1 m and a volume of around 1000 to 2000 l. The water level is 
recommended to be as high as possible so that the oxygen has more 
time to dissolve in the water column. It is advisable to use fine-pored 
rubber or plastic tubing and ceramic stones placed in the container 
floor, which produce particularly small oxygen bubbles to increase the 
surface area and ensure maximum solution of the gaseous oxygen. 
The temperature of the containers must be monitored during the jour-
ney. And the containers must not be airtight to allow the released 
gases to escape and prevent excess pressure forming (Wedekind, 
Harrer, Geiser, & Kraus, 2020). 

15. In case of increased mortality during the journey, it is advisable to in-

form the operator of the place of destination, the competent veterinary 
services and the transport company in order to implement an emer-
gency plan. Following the emergency plan from the European stand-
ard (Regulation (EU) 2016/429), the competent veterinary services will 
first evaluate the application of the procedures to be carried out, 
based on a visual check of the fish's welfare and mortality rate. Fi-
nally, according to current European regulation (Regulation (EC) 
1069/2009), upon arrival at the destination, dead fish will be removed 
(Ministero della Salute, 2017). The competent veterinary services will 
assess if it is necessary to include any further action in the emergency 
plan. 

Post-Transport 

1.  The person in charge of receiving the fish should closely observe 

them and keep appropriate records. Any fish showing abnormal clini-

29 

 
General Good Practices on fish welfare 

cal signs should be killed, isolated or examined by a veterinarian, iso-
lated or killed and problems with transport should be evaluated. Appe-
tite, behaviours, disease, and mortality should be monitored in relation 
to the transport for a week after unloading (AAC, 2022), (Saraiva, 
Arechavala-López, Cabrera-Álvarez, & Waley, 2021), (WOAH, 2012), 
(APROMAR, 2022), (Ministero della Salute, 2017), (GSA, 2023 (ITA). 

Stunning and slaughter 

General indications 

1.  Personnel handling fish for stunning and killing should be experienced 
and competent in the handling of fish and understand their behaviour 
patterns as well as the underlying principles necessary to carry out 
their tasks (WOAH, 2015), (Humane Slaughter Association, 2016), 
(UNE, 2016), (FAWC, 2014).  

2.  Some stunning and killing methods may pose a risk to the personnel; 
therefore, training should cover occupational health and safety impli-
cations for any methods used (WOAH, 2015), (Humane Slaughter As-
sociation, 2016), (FAWC, 2014), (UNE, 2016), (AAC, 2019), (AAC, 
2017). 

3.  The choice of the stunning and killing method needs to be carefully 

designed to ensure that fish are rendered immediately insensible and 
remain so for a sufficient period, allowing them to succumb to death 
either from the stun itself or through a subsequent killing method 
(EURCAW-Aqua, 2024). Therefore, species-specific and size infor-
mation should be taken into account when available (AAC, 2019), 
(WOAH, 2015), (AAC, 2017), (UNE, 2016), (Humane Slaughter Asso-
ciation, 2016). 

4.  All handling, stunning and killing equipment should be maintained and 
operated appropriately; it should be tested on a regular basis to en-
sure that performance is adequate. Failure to maintain equipment will 
reduce its efficacy (WOAH, 2015), (UNE, 2016), (Humane Slaughter 
Association, 2016).  

5.  Contingency plans should be made for situations where there is an 

equipment failure or other unexpected events which could result in fish 
being left out of water or in the stunning machine. Manual percussion 
and gill cutting may be a suitable back up in these instances (Humane 
Slaughter Association, 2016), (UNE, 2016). 

6.  The use of electrical or mechanical stunning and killing methods for 

farmed fish is recommended (WOAH, 2015), (Pavlidis, M., Samaras, 
A., 2020). 

7.  The use of electrical or mechanical stunning and killing is not always 
practical throughout all farming systems and farms’ size in the Euro-
pean Economic Area (EEA) (European Commission, 2017). Where 

30 

 
General Good Practices on fish welfare 

this is considered to be the case, suitable methods and equipment 
should be identified, adapted or researched, and implemented as a 
matter of priority. 

8.  To avoid unnecessary suffering and pain, electrical or mechanical 

stunning methods, following the latest best scientific practices for the 
relevant species, are used prior to slaughter. Unconsciousness of the 
fish must be ensured until the fish have been slaughtered (13) (conclu-
sions drawn from the online survey (from 22nd October to 6th Decem-
ber 2024) sent to the EU MS, Norway, UK, AAC's members, WestMed 
Aquaculture Mechanism and European Partnership on Animal Health 
and Welfare).  

Pre-slaughter handling 

1.  Time before killing, especially if fish are (partially) out of water, should 
be minimised and they should be positioned for stunning with the less 
handling possible (FAWC, 2014). 

2.  It is essential that, regardless of the slaughter method employed, fish 
are prepared, handled and delivered to the stunning point in an appro-
priate way by a gentle handling (Humane Slaughter Association, 
2016). 

3.  As recommended for fish in transport, where fish are deprived of food 
before slaughter, the duration of fasting must be always adjusted to 
the fish species, weight, life stage and temperature, and kept as short 
as possible, as the immune response is negatively affected already af-
ter a short fasting period (AAC, 2017), (Humane Slaughter Associa-
tion, 2016), (UNE, 2016), (AAC, 2022), (Wedekind, Harrer, Geiser, & 
Kraus, 2020), (Saraiva, Arechavala-López, Cabrera-Álvarez, & Waley, 
2021), (WOAH, 2012), (Council of Europe, 2005), (Ministero della Sa-
lute, 2017), (EU Platform on Animal Welfare Own Initiative Group on 
Fish, 2020), (ITA). 

Harvesting 

1.  The duration and intensity of crowding prior to harvesting should be 

minimised, as should exposure to air during transport. Fish should be 
crowded at the lowest density possible and time appropriate for the re-
quired handling procedure. The crowding impact should be reduced 

(13) There is a wide variety of slaughter methods in each EU MS, Norway and the UK, many of 
which are species-specific methods and some of which do not meet with OIE (WOAH) 
standards. Depending on whether the country has a specific regulation for the slaughter of 
fish, there will be methods prohibited in that country. 

31 

 
 
 
 
General Good Practices on fish welfare 

primarily by carrying it out in several steps. Critically high-density peri-
ods and the frequency of crowding events should be kept to a mini-
mum. Water quality, especially oxygen levels, should be monitored 
and kept within acceptable limits (Pavlidis, M., Samaras, A., 2020), 
(EU Platform on Animal Welfare Own Initiative Group on Fish, 2020), 
(AAC, 2024), (Council of Europe, 2005). 

2.  During harvesting operations, efforts should be made to maintain the 
fish in water of sufficient oxygen content, either by removing the fish 
as quickly as possible or by introducing fresh, oxygen-rich water dur-
ing the confinement (EFSA, 2008a), (EFSA, 2008b), (EFSA, 2008c), 
(EFSA, 2008d). 

3.  The use of specific fish pumps is preferred. It should be ensured that 

the pumps’ or pipes’ height, pressure and speed, as well as the height 
from which fish fall when they emerge, are adjusted in this regard. 
Pumps should have an appropriate diameter, and this should be ad-
justable when used for different fish sizes. The design of the pipes and 
pumping system should be such that sharp bends, rough surfaces, 
and protrusions are avoided in order to minimise injuries (EU Platform 
on Animal Welfare Own Initiative Group on Fish, 2020), (AAC, 2024), 
(Council of Europe, 2005). 

4.  Nets and landing nets should be designed to avoid physical injury, and 
they should not be overloaded not to crush or injure the fish (EU Plat-
form on Animal Welfare Own Initiative Group on Fish, 2020), (BIM, 
2022a), (AAC, 2024). 

5.  Equipment including nets, pumping devices, pipes, brailing devices, 

vaccination equipment, grading devices, etc., should be appropriate to 
the species, size, weight and number of fish to be handled. They 
should also be maintained in good condition. Equipment should be 
cleaned and disinfected between each use to reduce the risk of dis-
ease transmission (EU Platform on Animal Welfare Own Initiative 
Group on Fish, 2020), (GLOBALG.A.P., 2024), (BIM, 2022a), (AAC, 
2024). 

Stunning 

1.  As a general principle, farmed fish should be stunned before killing, 

and the stunning method (14) should ensure immediate and irreversible 
loss of consciousness. When the stunning method is reversible or 

(14) Suppliers and public authorities should provide guidance on the testing and licensing of 
stunning machines respectively. This would ensure that they are safe to use, that they 
deliver the required parameters, whether electrical or percussive, and that they effectively 
stun fish in practice. 

32 

 
 
 
General Good Practices on fish welfare 

does not cause death, it should be followed by a killing method before 
consciousness is recovered (European Commission, 2018), (WOAH, 
2015), (AAC, 2017), (Humane Slaughter Association, 2016), (FAWC, 
2014), (Aquatic Life Institute, 2023), (UNE, 2016). 

2.  A backup stunning system is necessary. Any fish mis-stunned, or re-

gaining consciousness before death, should be re-stunned as soon as 
possible (WOAH, 2015). 

3.  While absence of consciousness may be difficult to recognise, signs of 

correct stunning include (WOAH, 2015), (UNE, 2016), (Humane 
Slaughter Association, 2016), (EFSA, 2004), (Kestin, Robb, & Van de 
Vis, 2002), (Lines & Spence, 2012), (Van de Vis, Kestin, & Robb, 
2003) and many others (see Table section 5.4.7): 

•  Loss of body and respiratory movement (loss in opercular activ-

ity). 

•  Loss of visual evoked response (VER). 

•  Loss of vestibulo-ocular reflex (VOR, eye rolling). 

3.1. As new methods for detecting consciousness in fish become availa-
ble, especially for fish that appear to be unconscious using the 
signs above, they should be evaluated and adopted for use in the 
field where possible and appropriate to assess the effectiveness of 
stunning equipment and processes. It will also be good practice to 
recheck methods and equipment used regularly. 

3.2. Stunning equipment should first be tested in the laboratory by an 
approved institution using established protocols, to ensure that it 
delivers the parameters necessary to achieve unconsciousness for 
a given species. Secondly, the equipment should be tested for ef-
fectiveness in the field, with data from the tests made public (EFSA, 
2013). As new methods become available to detect consciousness 
in fish that have been stunned, such equipment should be tested 
again to ensure that stunning is effective according to the most up-
to-date scientific understanding. 

4.  Stunning should not take place if killing is likely to be delayed so that 
the fish will recover fully or regain partial consciousness (WOAH, 
2015). 

Percussive stunning 

1.  When using percussive methods, fish should be presented at a rate 
that they are only on the table for a few seconds prior to being 
stunned. When left on the table for too long, fish will move or flip and 
become more difficult to place in the stunner correctly (Humane 
Slaughter Association, 2016). 

33 

 
General Good Practices on fish welfare 

2.  Fish should not be kept out of water for longer than 15 seconds before 
stunning. Where procedures result in longer periods, the rate of deliv-
ery needs to be slowed down to an appropriate one for the stunning 
process (Humane Slaughter Association, 2016).  

3.  Percussive stunning must be performed with sufficient force to cause 

instantaneous unconsciousness and/or death (FAWC, 2014). 

4.  For percussive stunning and spiking, the suitable species, the required 
force and the correct target area should be specified. Mechanical per-
cussive stunning devices should be regularly tested for proper func-
tioning and efficiency (EFSA, 2004). 

5.  An effective stun is dependent on the blow being administered to the 

correct part of the skull (where the brain is closest to the surface of the 
head and where the skull is the thinnest) (Humane Slaughter Associa-
tion, 2016), (WOAH, 2015). 

Manual percussive stunning  

1.  The priest (15) still remains an option for slaughter when used appropri-
ately. However, it is not advisable for a commercial harvest and it is 
preferably used only as a back-up, for casualty fish or a very small 
number (Humane Slaughter Association, 2016). 

2.  Where manual stunning is employed, it is essential for both fish and 

operator’s welfare that the operators are given regular breaks and are 
allowed to work at a reasonable rate, otherwise accuracy and effec-
tiveness will be compromised as manual percussive stunning be-
comes less efficient with operator fatigue (Humane Slaughter Associa-
tion, 2016), (FAWC, 2014). 

Automated percussive stunning 

1.  The most commonly used automated stunning machines are powered 
by compressed air with an air pressure range from  6 to 8 bar. An opera-
tor can either manually move the fish towards the automatic stunner or 
through channels that guide the fish towards the stunner (Humane 
Slaughter Association, 2016). 

Electrical stunning 

1.  An electric stun must cause immediate unconsciousness and it must 
last long enough to ensure that the animal does not regain conscious-
ness before death supervenes  (Humane Slaughter Association, 
2016). 

(15) Name given to the tool used for manual percussive stunning. 

34 

 
 
 
General Good Practices on fish welfare 

2.  Fish could be electrically stunned before their removal from water so 
that they are unconscious, and easier to handle, to ease the process 
leading to percussive stunning (Humane Slaughter Association, 2016). 

3.  Several factors should be specified for electrical stunning to ensure 
immediate and sustained insensibility: the stunning current, voltage 
and exposure time, the species, size, fish condition, welfare status, 
the temperature, water conductivity and the number of fish in the stun 
tank (EFSA, 2004), (Humane Slaughter Association, 2016), (WOAH, 
2015). 

4.  Animals should be regularly monitored during the stunning machine 

operation, allowing problems to be identified and answered to quickly 
(Humane Slaughter Association, 2016). 

5.  It is essential to establish the parameters of the electrical current to 
ensure proper stunning at the site of stunning as the conductivity of 
fresh and brackish water varies (WOAH, 2015). 

6.  Fish should be confined beneath the surface of the water, and there 

should be a uniform distribution of the electrical current in the stunning 
tank or chamber (WOAH, 2015). 

7.  In semi-dry electrical stunning systems, fish should enter the device 
head first to ensure rapid and efficient stunning (WOAH, 2015).  

Killing 

1.  A thorough protocol is required to develop slaughter systems which 
ensure fish are killed effectively. This is necessary for any new sys-
tems being implemented and may also be needed to verify that exist-
ing commercial systems are functioning properly. The verification pro-
tocol must include steps to check that consciousness is not being re-
covered after stunning and should account for the potential difficulties 
in interpreting this due to physical immobilisation. The information re-
quired to carry out this process for each fish species, and the results 
from any testing of equipment should be collated for continual im-
provement and collaboration between MS (CIWF, 2018).  

2.  The speed at which death can be achieved and hence the choice of 
the killing method, is crucial in assessing whether the slaughter is hu-
mane (CIWF, 2018). In the case of killing of farmed fish for disease 
control purposes (not for human consumption), it is recommended for 
killing by an overdose of anaesthetic agent (WOAH, 2024) 

3.  According to the recommendations of these organisations: WOAH  

(2015), Humane Slaughter Association (2016), and FAWC (2014), and 
whenever it is technically feasible to use approved methods which 
achieve an effective and lasting stun,, the following methods of killing 
fish should NOT be used: chilling with ice in holding water; using car-
bon dioxide (CO2) in holding water; chilling with both ice and CO2 in 

35 

 
General Good Practices on fish welfare 

holding water; salt or ammonia baths; asphyxiation by removal from 
water; and exsanguination without stunning. Percussive and electrical 
stunning (followed by gill cut), shooting, and mechanical spiking and 
coring are acceptable slaughter methods for some species, with the 
potential to enable a humane death (WOAH, 2015), (CIWF, 2018).  

4.  The methods used for large fish, over 50 kg (such as tuna), are: spik-
ing or coring, which are based on physical damage to the brain by in-
serting a spike or core into the brain (WOAH, 2015), (AAC, 2017), as 
the brain is harder to target in smaller fish (CIWF, 2018); and shooting 
using a free bullet (WOAH, 2015), (AAC, 2017). 

Environmental enrichment 

General indications 

1.  Producers should adopt EE for several reasons:  

•  Physical structure has long been known to provide potential 

benefits for certain farmed fish species. A heterogeneous envi-
ronment can provide shelter from water currents, reduce ag-
gression from other fish and act as landmarks for establishing 
territories (Näslund & Johnsson, 2016), (Jones, Webster, & Sal-
vanes, 2021), (Zhang, Lin, Yunqi, Yuan, & et, 2023) as well as, 
inhibit cannibalism and aggressive behaviours, increase growth 
and survival and reduce stress (Arechavala-López, Cabrera-Ál-
varez, Maia, & Saraiva, 2022), (Zhang, Lin, Yunqi, Yuan, & et, 
2023). 

•  Structural enrichment benefits the welfare of the farmed  spe-
cies investigated so far (salmonids, cod, catfish, seabream, ti-
lapia, seabass, etc.), either by reducing fin injuries, lowering 
stress, or improving fish behaviour (Arechavala-López, 
Cabrera-Álvarez, Maia, & Saraiva, 2022), (Zhang, Lin, Yunqi, 
Yuan, & et, 2023), (and references therein). 

•  Adding complexity in the captive environment enhances cogni-
tive abilities (avoid repetitive behaviours or stereotypes) and 
improves brain plasticity (Arechavala-López, Cabrera-Álvarez, 
Maia, & Saraiva, 2022), (Kleiber, et al., 2023), (and references 
therein).  

2.  EE solutions should be adapted to the biology of the specific species 
as well as to control the intended effects are really achieved (Näslund 
& Johnsson, 2016), (Arechavala-López, Cabrera-Álvarez, Maia, & 
Saraiva, 2022), (Zhang, Lin, Yunqi, Yuan, et al., 2023). 

36 

 
General Good Practices on fish welfare 

3.  Any EE strategies applicable to fish farms must be previously tested 

and validated before being implemented at a commercial scale, taking 
into account both the fish and farming characteristics (Arechavala-
Lopez, Cabrera-Álvarez, Maia, & Saraiva, 2022).    

4.  Providing floor substrate (sand, pebbles, gravel, stones, etc.) can be 
seen as another type of physical EE to improve or guarantee fish wel-
fare, mostly for those species that regularly interact with the bottom or 
live closely associated to it during its whole life (e.g. benthic fish) 
(Arechavala-López, Cabrera-Álvarez, Maia, & Saraiva, 2022). 

5.  Life stages, with respect to its natural history and preferences, should 
be considered in order to select enrichment structures (Näslund & 
Johnsson, 2016). 

6.  For land-based flow-through, raceway systems and ponds, the back-
ground colour should be similar to the natural environment of the spe-
cies to reduce the risk of predation and stress (Jones, Webster, & Sal-
vanes, 2021). 

7.  Apart from RAS facilities, which are usually indoors, partial shading of 
facilities, depending on the species and the system and other factors 
(e.g. depth, water transparency), reduces stress and improves fish 
growth (Näslund & Johnsson, 2016). 

8.  Shelters are examples of structural enrichment that reduce stress, 
metabolic costs, improve growth rates, as well as fin and tail condi-
tions (Jones, Webster & Salvanes, 2021). Producers should include 
shelters in the production system taking into consideration they should 
be adapted to the behaviour of the breeding species (Jones, Webster 
& Salvanes, 2021). 

9.  Hygiene and biosecurity currently seem to be the main concerns re-

garding physical EE. Some structures or objects may accumulate food 
particles and faeces, making cleaning and disinfection difficult and 
compromising fish health and overall welfare. It can also happen that 
the structures leak out potentially hazardous chemicals to the environ-
ment (e.g. PVC phthalates), or that their design is inadequate and 
causes physical or psychological disturbances or damage to the fish 
(e.g. small holes, cracks, protrusions, noise), increasing the risk of in-
fection, stress or mortality. All these factors should be taken into ac-
count when planning EE. Contingency plans and corrective actions 
(e.g. increasing or modifying cleaning routines, monitoring fish behav-
iour upon deployment of EE, quickness to respond to negative effects) 

37 

 
General Good Practices on fish welfare 

must also be considered (Arechavala-López, Cabrera-Álvarez, Maia, 
& Saraiva, 2022), (Kleiber, et al., 2023). 

10. Fish farmers should also vary the location and/or the type of objects 
introduced into the tanks to avoid any habituation phenomenon (16) 
(Kleiber, et al., 2023). 

11. The use of self-feeders as a cognitive enrichment (17) showed that free 

access to them has more positive effects on fish welfare than re-
stricted access. Furthermore, free-access self-feeding enables fish to 
control their own feeding and to select both quantity and possibly nu-
tritious value as well as timing according to their appetite (Attia, et al., 
2012), (Kleiber, et al., 2023). 

Lighting 

1.  Light is a crucial regulator of fish biological processes, including di-
urnal and circannual rhythms (periodicity), developmental transi-
tions and behaviour. The quality of light, defined by its intensity 
and spectral composition, significantly influences biological re-
sponses via spectral-specific photoreceptors located in the eye, 
pineal gland, brain, and other tissues throughout the body (Ebbes-
son & Lal, 2024).  

2.  Light characteristics and circadian biological rhythms can be artifi-
cially controlled and used to guarantee good welfare conditions. In 
fact, the species-specific behavioural and physiological responses 
to acute stressors depend heavily on the time of the day when the 
stress occurs (Sánchez-Vázquez, et al., 2019). In general, the 
overall performance, development and welfare of fish larvae are 
significantly affected by light characteristics, obtaining better re-
sults under the closest conditions to their natural environment 
(Sánchez-Vázquez, et al., 2019). Juvenile and adult fish also pre-
sent daily cycles of locomotor and food anticipatory activities, 
which are directly affected by lighting conditions (Ceinos, Chivite, 
López-Patiño, et al., 2019). Therefore, understanding the circadian 

(16) Habituation phenomenon is an automatic process in the brain decreasing the strength of a 

reflex upon multiple exposures to a stimulus (Lieberman, D.A., 2000) 

(17) Cognitive enrichment is a recent but promising concept to improve fish welfare by manipulat-
ing the predictability and controllability of their environment. It relies not only on  the ability of 
fish to predict positive and negative events but also on their ability to perform and succeed in 
operant conditioning (Kleiber, et al., 2023). 

38 

 
 
 
General Good Practices on fish welfare 

timing system of fish is essential for the optimisation of rearing pro-
tocols and the improvement of their well-being in farming environ-
ments (Arechavala-López, Cabrera-Álvarez, Maia, & Saraiva, 
2022). 

3.  Fish stress responses are strongly affected by the stressor expo-
sure time (e.g. day/night) according to their daily pattern of behav-
iour which will vary between species (diurnal/nocturnal) (Sánchez-
Vázquez, López-Olmeda, & Vera, 2019). 

4.  For early developmental stages, juveniles and breeders, it is gen-
erally recommended to provide short wavelength lights (blue 
and/or green colours) which, in combination with proper light perio-
dicity and intensity, induces positive effects on growth and perfor-
mance, enhances locomotor and feeding activity, and reduces 
stress and mortalities (Arechavala-López, Cabrera-Álvarez, Maia, 
& Saraiva, 2022). Therefore, avoiding long wavelength light (red 
colour) is recommended, as well as constant light or darkness, 
which negatively affect fish welfare in terms of embryo, larvae and 
juvenile development, spawning, malformations, eye damages and 
mortality (Sánchez-Vázquez, et al., 2019). 

5.  Given the importance of light, it is advisable to consider light wave-
lengths in the optimisation of fish rearing conditions (Zhu & Take-
mura, 2024). 

6.  By using the right wavelength (colour) and quantity (intensity), 

problems with growth and maturation can be avoided when rearing 
fish in RAS (Strauch, 2023). 

39 

 
5. 

Fish welfare indicators  

In this chapter, general indicators, not species-specific, focused on fish wel-
fare related to the topics presented in Chapter 3 are provided. 

5.1. 

Introduction and overview 

Aquaculture farming systems present specific welfare challenges for farmed 
fishes, and specific indicators can be used to assess welfare during critical 
points of rearing procedures, transport and slaughter. To ensure fish welfare in 
aquaculture, it is essential to have indicators that allow reliable and objective 
assessment of animal welfare during the different production phases (see sec-
tion 5.2). Assessment protocols based on welfare indicators will in turn allow the 
evaluation of the different procedures carried out in the company and the adop-
tion of the necessary measures to promote fish welfare and to ensure more eth-
ical and environmentally sustainable ethic aquaculture (Kristiansen et al., 2020). 
Many welfare assessment frameworks based on indicators have been recom-
mended for aquaculture (Browning, 2023). However, continuous and reliable 
welfare monitoring protocols in aquaculture are not widespread and common-
place yet (Barreto et al., 2022). 

The EFSA published welfare risk assessment reports for farmed Atlantic 
salmon (EFSA, 2008a), farmed European seabass and gilthead seabream 
(EFSA, 2008b), farmed common carp (EFSA, 2008c), and farmed trout (EFSA, 
2008d), where they identify and describe the main hazards depending on the 
fish life stage and the husbandry system they are reared in. Based on the se-
verity and duration of adverse effects and the frequency of hazards, a semi-
quantitative risk score is suggested in some reports (EFSA, 2008a), which can 
be used to rank the problems and designate areas of concern, as well as to pro-
vide guidance for research (Kristiansen et al., 2020).  

Other efforts have also been undertaken to develop protocols, methods and 
technological tools for the monitoring of fish welfare in aquaculture production 
systems. In 2012, a Fish Welfare Assurance System (FWAS) was published 
as the first proposal for monitoring and safeguarding fish welfare at a company 
level (van de Vis et al., 2012). This system was based on the analysis of haz-
ards that may impair fish welfare and on the identification of critical control 
points in the production process (Hazard Analysis Critical Control Points - 
HACCP). The initial steps for setting up FWAS for on-growing European sea-
bass, common carp, and European eel were presented. Operational welfare in-
dicators (OWIs) are needed at the FWAS to determine whether critical biotic, 
abiotic, managerial and environmental factors are controlled (van de Vis et al., 
2012).  

40 

 
The Salmon Welfare Index Model (SWIM) was later developed to assess the 
Atlantic salmon welfare based on indicators linked to physiological, behavioural 
and environmental needs (Stien et al., 2013). It aimed to combine the scores of 
different welfare indicators into a single welfare index, based on a weighting of 
the impact of each indicator on the fish welfare. SWIM was applied to assess 
welfare of salmon cages (Folkedal et al., 2016; Pettersen et al., 2014), and later 
adapted to European seabass in sea cages (Yildiz et al., 2021). A similar model 
is available for rainbow trout and pikeperch (Sander lucioperca) reared in recir-
culating systems (Müller-Belecke, 2020), and for lumpfish reared in hatcheries 
and marine farms (Gutierrez Rabadan et al., 2021). A manual on the welfare as-
sessment of lumpfish in sea cages based on external welfare indicators is also 
available (Boissonnot et al., 2022).  

A fish welfare evaluation index (fWEI) was proposed for rainbow trout in flow 
through systems based only on external morphological damage, due to the lim-
ited reliability and/or practicability of environmental, management and behav-
ioural parameters, according to the authors (Weirup et al., 2022). Welfare as-
sessment protocols based on external injuries as indicators are also available 
for Atlantic salmon reared in sea-cages (Nilsson et al., 2022; Noble et al., 
2012).  

The FISHWELL project, funded by The Norwegian Seafood Research Fund 
(FHF), launched four handbooks describing welfare assessment models 
based on welfare indicators for Atlantic salmon, rainbow trout, wrasse 
and lumpfish (Noble et al., 2020, 2019a, 2019b, 2018). The FISHWELL sys-
tems mostly provide a wide set of animal-based and context-specific environ-
mental indicators for different management systems.  

A more general model, and user-friendly application named MyFishCheck, was 
also developed to assess fish welfare on-site (Tschirren et al., 2021). The 
model incorporates parameters from the three animal welfare concepts (func-
tion-based, feeling-based, and nature-based approaches; see section 5.2 for 
more details) and includes welfare indicators covering internal and external fish 
appearance, fish group behaviour, water quality and farm management. My-
FishCheck can help fish farm personnel perform regular monitoring and control 
activities through an app, allowing a standardised evaluation and digital docu-
mentation of fish welfare. Both the model and the app are explicitly designed to 
be adaptable to new knowledge and any fish species and husbandry system.  

The Qualitative Behavioural Analysis (QBA) was also developed as a power-
ful on-farm method to assess fish welfare (Jarvis et al., 2021). QBA uses an ob-
server assessment of the overall behavioural profile of the animal (whole-animal 
indicators) to form a judgment about its welfare.  

The Mediterranean Aquaculture Integrated Development (MedAID) project, 
co-financed by the EU’s Horizon 2020 programme, delivered a report on fish 

41 

 
welfare and listed OWIs for gilthead seabream, based on Welfare Quality princi-
ples: good feeding, housing and health, and appropriate behaviour and man-
agement (Roque et al., 2020).  

A guide of good practices and welfare assessment for Mediterranean fish was 
published by the University of Crete in collaboration with, and financed by, the 
HAPO (Pavlidis and Samaras, 2020). The guide provides a detailed presenta-
tion of welfare indicators by production phase and husbandry practices for Euro-
pean seabass and gilthead seabream and serves as the National Welfare 
Guide for Mediterranean farmed species in Greek aquaculture. However, 
the need for the development of a welfare scoring system, based on welfare in-
dicators, was noted in this guide.  

A methodology for assessing fish welfare in Mediterranean marine fish farms 
was developed by the EU-funded Horizon 2020 project PerformFISH - Integrat-
ing Innovative Approaches for Competitive and Sustainable Performance 
across the Mediterranean Aquaculture Value Chain (18). The welfare assess-
ment tool (namely BBW-Tool) is based on a set of 24 OWIs, mostly focused on 
management, for seabream and seabass during the grow-out phase, from 
stocking to harvest.  

The AdriAquaNet project – Enhancing Innovation and Sustainability in Adriatic 
Aquaculture, funded by the Italy-Croatia Cross-Border Cooperation Programme 
(Interreg Italy-Croatia, European Regional Development Fund), published a list 
of 25 OWIs of seabass and seabream breeding in sea cages, as well as a man-
ual for use on field, based on those selected environment- and animal-based in-
dicators (Manfrin A., 2022). Subsequently, the Italian association of fish farm-
ers (API) and the Experimental Zooprohylactic Institute of the Venetias (IZSVe) 
published a “welfare manual for farmed fish species: operator´s guide”, funded 
by the Italian Ministry of Agriculture, Food Sovereignty and Forests (MASAF). 
The manual describes 25 OWIs and a welfare assessment system to be applied 
on diverse farmed fish species (i.e. rainbow trout, seabass, seabream, carp, eel 
and sturgeons) during breeding, transport and slaughtering (Spezzani et al. 
2025).    

The Spanish association of aquaculture producers (APROMAR) is develop-
ing a series of guides on fish welfare in Spanish aquaculture, in collaboration 
with research institutions and universities, aquaculture companies, NGOs and 
governmental bodies (19). The guides are financed by APROMAR, and co-fi-
nanced by the Ministry of Agriculture, Fisheries and Food of the Government of 

(18) Deliverable 3.6: https://performfish.eu/wp-content/uploads/2024/11/DL-3.6_Welfare_ISPRA-

V2_def.pdf  

(19) https://apromar.es/guia-bienestar/  

42 

 
 
 
Spain and the European Maritime and Fisheries Fund. Welfare concepts and 
generalities are published in the first volume (APROMAR, 2022), and a set of 
welfare indicators, critical points and good practices for all production phases 
for European seabass, gilthead seabream and rainbow trout are described in 
the following volumes (APROMAR, 2024a,b, 2025).  

Recently, a welfare assessment study for European seabass, gilthead sea-
bream and common carp has been delivered within the current EU-funded Hori-
zon Europe project Cure4Aqua - Curing EU aquaculture by co-creating health 
and welfare innovations (Pavlidis et al., 2024). Based on a risk assessment 
framework, the study present a set of specific indicators, validated by different 
stakeholders and a scoring index to measure the welfare assessment of farmed 
European seabass, gilthead seabream and common carp, proposing a welfare 
assessment scheme for on-growing phases.  

The French Poultry Technical Institute (ITAVI) developed a method for as-
sessing welfare in fish farming, based on the conceptual framework of the 
EBENE® method, and carried out within the framework of the CAS DAR “Aqua 
Bien-Etre” and FEAMP “B ABA” programmes. The first version of EBENE® in-
tended for trout farming was co-constructed by a consortium of scientists and 
fish farmers in order to arrive at a grid of animal welfare principles and criteria 
based on welfare indicators.  

The Ireland´s Seafood Development Agency (BIM) published some general 
guidance for common farming practices during handling to ensure fish welfare is 
maintained at a high standard (BIM, 2022b), as well as a brief overview of fish 
welfare and operational welfare indicators (BIM, n.d.). 

Farming, transport and slaughter survey guidelines for rainbow trout (Reiser et 
al., 2024a) and common carp (Reiser et al., 2024b) were developed as part of 
the National Animal Welfare Monitoring (NaTiMon) project, funded by the 
Framework of the National Livestock Strategy of the Federal Ministry of 
Food and Agriculture (BMEL), based on a decision of the German Bundes-
tag. These guidelines describe the protocols for surveying the welfare on farms, 
at any production phase, as well as the indicators to be collected on the opera-
tion, the individual animal level (external), and on the stunning and killing pro-
cesses.  

It is worth to mention the existence of welfare evaluation methods for pre-
slaughtering procedures, such as crowding for Atlantic salmon in sea cages 
(Stien et al., 2024). There are some studies on welfare assessments during 
stunning and slaughtering in aquaculture, based on visual indicators (reflexes) 
as potential loss of consciousness (Kestin et al., 2002; Morzel et al., 2003). This 
protocol has  already been applied to assess the efficiency of diverse stunning 
and slaughtering methods for the most common farmed fish species in Europe.  

43 

 
In line with previous reports, EFSA published semi-quantitative welfare risk 
assessment approaches for Atlantic salmon, rainbow trout, European sea-
bass, gilthead seabream, common carp,eels and turbot (EFSA, 2009a, 
2009b, 2009c, 2009d, 2009e, 2009f). EFSA risk assessment during stunning 
and slaughter is a systematic, scientifically based process to estimate the prob-
ability of exposure to a hazard, and the magnitude of the effects (conse-
quences) of that exposure. Three parameters were scored to assess the im-
portance of a hazard; the probability of exposure to it, and the intensity and du-
ration of the adverse effect that it causes. Operational indicators (to be used un-
der field conditions) of poor welfare for critical monitoring points are only sug-
gested for salmon (EFSA, 2009d), and it is highlighted that welfare indicators 
have not been satisfactorily assessed and validated at that time for the rest of 
species.  

The fair-fish database (20) is an open-access database designed to collect, sys-
tematise, and make available all welfare-related knowledge to be found on wild, 
captivity and during catching food fishes in order to help improve fish welfare 
and avoid harmful practices (Saraiva et al., 2019). This platform consolidates 
ethological knowledge into profiles of farmed aquatic species, namely Welfare-
Check profiles. These profiles are organised around welfare indicators, with 
each criterion receiving classifications regarding the likelihood and potential for 
individuals of a given species to experience good welfare in aquaculture sys-
tems, along with the associated certainty level (Maia et al., 2024). The aim is to 
cover all nowadays farmed fish species, as well as other aquatic species, deliv-
ering concrete solutions for aquatic animal farmers, pointing out knowledge 
gaps for researchers and providing awareness for the general public and other 
stakeholders (Maia et al., 2024; Saraiva et al., 2019).  

NGOs have also developed and published some reports with recommendations 
on good practices and potential welfare indicators for diverse fish species in aq-
uaculture. CiWF published a series of technical resources for the improvement 
of welfare at rearing and slaughter for the main farmed fish species in Europe 
(21). Welfare issues are identified in those reports, as well as recommendations 
on potential good practices and welfare outcomes for Atlantic salmon, rainbow 
trout, European seabass, gilthead seabream, pangasius and Nile tilapia. Simi-
larly, Fish Welfare Initiative (FWI) published internal and external research re-
ports on the improvement of fish welfare in aquaculture (22), covering general as-
pects such as issues, assessments, indicators and potential improvements, 
among others. FAI farms have developed a free, easy-to-use Welfare Assess-
ment App for farmers' day-to-day use at any production stage, based on welfare 

(20) https://fair-fish-database.net/  
(21) https://www.compassioninfoodbusiness.com/transforming-animal-welfare/fish/  
(22) https://www.fishwelfareinitiative.org/research  

44 

 
 
 
indicators (Pedrazzani et al., 2020). To date, it is only applicable to tilapia (23), 
though it might be potentially used on other farmed fish species. 

Furthermore, there are a variety of different certification programmes used for 
aquaculture. Among them, the RSPCA welfare standards for Atlantic salmon 
and rainbow trout are guidelines for the housing and husbandry of these spe-
cies, describing the requirements for a range of management and environmen-
tal conditions for assuring fish welfare in aquaculture (RSPCA, 2024, 2020). 
They list some “welfare assessment outcomes” and provide a template for 
farmed fish “welfare risk assessment” to be applied at on-farm, handling, 
transport, health management, water quality, feeding, and slaughter proce-
dures. Other widely used certifications, such as the GLOBAL G.A.P Aquacul-
ture standard and the ASC Farm Standards for sustainable aquaculture are 
rather focused on sustainability and limiting environmental impact from fish 
farming than on specific fish welfare standards. However, their checklists for 
fish welfare provide important requirements to ensure fish welfare and can be of 
great help to farmers (Stien et al., 2020). Organic aquaculture certifications 
(e.g. EU organic aquaculture) verifies that products are produced and pro-
cessed in compliance with regulations, where animal welfare aspects are con-
sidered. 

Conclusions:  

From the literature review, the urgent need for the development of standard-
ised monitoring measures, assessment protocols and tools to provide a 
scientifically sound basis for an assessment of the welfare status of fish 
produced in the EU can be highlighted. A robust routine welfare monitoring 
protocol should be instigated, using a selection of appropriate operational wel-
fare indicators (OWIs) tailored to the site. A good monitoring strategy can help 
to minimise negative welfare effects and optimise outcomes over the entire cy-
cle, leading to healthy fish and more profitable fish farming. 

A challenge exists in developing more objective and technology-driven 
measures to reduce subjectivity, as well as in creating uniform protocols for 
evaluating welfare across different farming systems to enhance comparability 
and reliability.  

Standardised welfare assessment protocols should be based primarily on gen-
eral operational indicators that allow a rapid and objective assessment of 
fish welfare in any scenario, followed by specific indicators that take into 

(23) https://www.mytilapia.farm/about  

45 

 
 
 
account not only the needs of the species and life stage, but also the pro-
duction system.  

Training and education are important aspects on fish welfare in aquaculture, 
providing thorough instruction for farmers and evaluators to ensure consistent 
and accurate welfare assessments. It is therefore a priority to provide general 
and species-specific OWIs, assessment protocols, and codes of good 
practices to help fish farmers improve the life quality of farmed fish, but also to 
allow the development of fish legislation (Pavlidis et al., 2023). It is also recom-
mended to nominate a welfare officer for each fish farm. The person in charge 
must safeguard that fish welfare needs and the implementation of fish welfare 
recommendations are taken care of. The welfare officer is responsible for pre-
paring all relevant documentation for the competent authorities (annual report 
on fish welfare related outputs, including mortalities, injured animals, and dis-
ease outbreaks). 

5.2. 

Type of indicators 

Welfare indicators should include different aspects related to the behavioural, 
physiological and psychological characteristics of the captive animals, covering 
the three welfare approaches (Fraser, 2009; Huntingford et al., 2006). A feel-
ings-based approach requires that for an animal to be in a state of good wel-
fare it should be free from negative experiences and have access to positive 
ones. This approach works under the assumption that fish are sentient animals, 
capable of feelings, emotions or equivalent affective or mental states. The feel-
ing-based views focus on measurable behavioural variables, such as prefer-
ences and, to a secondary extent, on physiological criteria (e.g. feeding, growth 
and reproductive performance). A function-based approach requires that for 
good welfare, an animal must be able to adapt effectively to its environment, en-
suring that all its biological functions are working effectively. Scientists that em-
phasise the function-based approach mostly use physiological indicators, such 
as molecular, biochemical, immunological, hormonal, health status and growth 
performance indicators, to monitor or evaluate fish welfare. Lastly, a nature-
based approach assumes that each species has an inherent biological nature 
and that the ability to express it (particularly to express a natural repertoire of 
behaviour) is essential for good welfare. The fish welfare status is strictly evalu-
ated in the nature-based approach through ethological criteria.  

Fish welfare indicators can be generally applicable to all species and production 
systems, whereas specific indicators take into account the species-needs, pro-
duction system, production phase or life stage. Therefore, it is essential to iden-
tify and select the most appropriate indicators. These must provide a valid re-
flection of welfare, be reliable (yielding consistent results regardless of who 
measures them or how they are measured), repeatable (producing consistent 

46 

 
results when measured multiple times or in different contexts), cost-effective, 
and suitable for use within the system or procedure to assess during husbandry 
practices (Stien et al., 2020). Welfare indicators must provide complementary 
information about the welfare state of the fish and can be categorised based on 
the animals (individual-based or group-based, such as behaviour or external 
appearance), on the aquatic environment fish are reared in (resource-based, 
such as water quality parameters), and on the rearing routines and protocols 
performed on-site (management-based, such as those for feeding, handling, 
transport, etc.) (AAC, 2024), (Figure 1a). Indicators observed on the animals 
(animal-based) are also called direct or output-based indicators. They meas-
ure the outcome or the consequences and evaluate how well their welfare 
needs are met. They can be based either on observations of a group of individ-
uals (e.g. survival percentage, swimming behaviour) or of individual fish (e.g. 
external appearances, injuries). Behaviour is the first and foremost indicator of 
the biological state of an animal, and behavioural observations are the best tool 
to understand not only the physiological state of the individual but also its men-
tal state, being therefore essential for the correct welfare evaluation (Saraiva et 
al., 2022). Indirect or input-based indicators typically refer to parameters con-
cerning the physical environment (e.g. water temperature, oxygen) and availa-
ble resources, as well as the operational system and rearing practices to which 
animals are subjected.  

Welfare indicators may also be grouped into Operational Welfare Indicators 
(OWIs) that the farmer should be able to assess and interpret on-farm (North et 
al., 2008), and laboratory welfare indicators, that require samples to be sent 
to a designated, specialised laboratory for further analysis and evaluation (No-
ble et al., 2018).  

They can also be classified according to their invasiveness, referring to the ac-
tion of physically invading the animal to sample or measure the indicator by the 
farmer. Understanding and monitoring these fish welfare indicators is essential 
to maintain a healthy, morally ethical and sustainable aquaculture industry. By 
regularly monitoring welfare indicators, fish farmers can quickly identify and ad-
dress any welfare issues. Therefore, in order to be useful for welfare assess-
ments, indicators can be categorised based on their operability and invasive-
ness (Barreto et al., 2022; Noble et al., 2018; Pavlidis et al., 2023; Toni et al., 
2019), (Figure1b):  

●  Operational Welfare Indicators (OWIs) are practical and easy to meas-
ure. These are based on observations that provide immediate feedback on 
the fish welfare status (e.g. behaviours, mortality, growth, stand-out infec-
tions or injures). They can be monitored on a daily basis, but it requires 
trained staff in order to avoid subjective assessment. The development of 
physical and behavioural indicators allows the state of fish well-being to be 
assessed simply by observing the fish through operational and non-invasive 
monitoring.  

47 

 
●  Welfare Quality Measures (WQMs) require more effort as they need vis-
ual inspections but can provide valuable insights into the underlying 
health and welfare of the fish. They can be measured during routine 
checks (e.g. injures, deformities, internal diseases). Although operational, 
they require some capture and invasiveness, as well as specialised staff.   

●  Functional Welfare Indicators (FWIs) provide information about the bio-
logical functioning of the fish (e.g. stress, physiological and molecular re-
sponse), and therefore, a deeper understanding of the welfare status. They 
are more invasive and require sampling, specialised knowledge and infra-
structure.  

Based on the existing literature, a series of OWIs that allow for objective, rapid, 
effective and minimum invasive assessment of fish welfare in any production 
system, species and life-stage, can be identified. For the purpose of this docu-
ment – that aims to be practical and user-friendly - the most practical on-farm 
OWIs have been selected for the different procedures or topics (see Table 
1 in Chapter 3 for the description of key topics addressed) based on the critical 
points identified above.   

Figure 1. Classifications of fish welfare indicators: a) based on the nature of the indica-
tor; b) based on the operability and invasiveness of the indicator for welfare assess-
ments (adapted from Noble et al., 2018; Stien et al., 2020). 

5.3. 

Selection of general fish welfare indicators 

The list of selected general fish welfare indicators in Table 2 can be easily 
used as a first attempt to evaluate fish welfare, applicable to any species and 

48 

 
 
farming system. Species-specific indicators are out of the scope of the current 
document.  

It must be noticed that the list of indicators has been reduced to promote its ef-
fectiveness, knowing that some indicators have been left out, and they focus 
primarily on animal behaviour, as well as other relevant and general parame-
ters.  

Management-based indicators were not selected but were included as good 
practices on fish welfare in Chapter 4.  

Integrated general on-farm indicators that can be easily used and compared are 
the first step to assess fish welfare conditions effectively and to improve the 
quality of husbandry practices not only from a productive point of view but also 
from a more holistic, ecological and ethical perspective (Toni et al., 2019). They 
provide valuable insights for anyone interested in how fish welfare is at specific 
farming conditions or procedures, from researchers and policymakers to con-
sumers, certifiers, and animal rights advocates.  

Table 2. List of general fish welfare indicators and topics for which they have been se-
lected 

# 

1 

Indicator 

Key topic and factsheet  

Food anticipatory be-
haviour 

Feeding (factsheet 5.4.1). 

2 

Feeding response 

3 

Condition factor or 
emaciation state 

4 

Body injures 

5 

Use of space 

Feeding (factsheet 5.4.1); Handling (fact-
sheet 5.4.2); Water quality (factsheet 
5.4.3); Mortality removal (factsheet 5.4.5); 
Transport (factsheet 5.4.6); Environmental 
enrichment (factsheet 5.4.8). 

Feeding (factsheet 5.4.1); Water quality 
(factsheet 5.4.3); Stocking density (fact-
sheet 5.4.4); Stunning and slaughter (fact-
sheet 5.4.7); Environmental enrichment 
(factsheet 5.4.8). 

Handling (factsheet 5.4.2); Stunning and 
slaughter (factsheet 5.4.7); Environmental 
enrichment (factsheet 5.4.8). 

Handling (factsheet 5.4.2); Water quality 
(factsheet 5.4.3); Mortality removal (fact-
sheet 5.4.5); Transport (factsheet 5.4.6); 
Environmental enrichment (factsheet 
5.4.8). 

49 

 
# 

Indicator 

Key topic and factsheet  

Handling (factsheet 5.4.2); Water quality 
(factsheet 5.4.3); Stocking density (fact-
sheet 5.4.4); Mortality removal (factsheet 
5.4.5); Transport (factsheet 5.4.6); Stun-
ning and slaughter (factsheet 5.4.7); Envi-
ronmental enrichment (factsheet 5.4.8). 

Handling (factsheet 5.4.2); Water quality 
(factsheet 5.4.3); Stocking density (fact-
sheet 5.4.4); Mortality removal (factsheet 
5.4.5); Stunning and slaughter (factsheet 
5.4.7). 

Water quality (factsheet 5.4.3); Stocking 
density (factsheet 5.4.4); Mortality removal 
(factsheet 5.4.5); Environmental enrich-
ment (factsheet 5.4.8). 

Feeding (factsheet 5.4.1); Stocking den-
sity (factsheet 5.4.4); Transport (factsheet 
5.4.6); 

6 

Dissolved oxygen 

7 

Respiration rate 

8 

Swimming activity 

Skin and/or fin condi-
tion 

9 

10 

11 

Surface activity 

Stunning and slaughter (factsheet 5.4.7). 

Vestibulo-Ocular Reflex 
(VOR) 

Stunning and slaughter (factsheet 5.4.7). 

50 

 
 
 
5.4. 

Factsheets on general fish welfare indicators 

5.4.1. 

Feeding 

General fish welfare indicators for feeding 

Indicator 

Metrics 

Food anticipatory behaviour 

Presence / Ab-
sence 

Operational recommenda-
tions 

In case of the presence of 
food anticipatory behaviour, 
farmers must keep routinary 
procedures, but check if the 
feeding strategy (distribution, 
quantity, periodicity, etc.) is 
adequate. In case of the ab-
sence of food anticipatory 
behaviour, farmers must 
check the feeding strategy 
and adjust it if necessary. In 
both cases, other indicators 
must be checked (e.g. feed-
ing response or emaciation).   

Comments and rationale 

Fish are agitated before feeding, 
showing movements or actions that 
precede the delivery of feed, indi-
cating that the animals are aware of 
routine procedures taking place im-
minently. Observing food anticipa-
tory behaviour indicate an emo-
tional qualitative component of 
wanting and liking the food sources. 
However, it can also increase when 
fish are deprived of food, indicating 
emotional states of hunger and an 
urge to eat. 

Feeding behaviour 

High / Medium / 
Low 

Observing high feeding re-
sponse may indicate high 
level of hunger, then the 

Feeding behaviour refers to forag-
ing behaviour and food intake dur-
ing feeding. Feeding response may 

51 

 
General fish welfare indicators for feeding 

feeding strategy must be 
checked and adjusted. Low 
or lack of feeding response 
may indicate stress due to 
environmental and hus-
bandry factors or health is-
sues. It is essential to check 
records from previous days, 
to confirm if the feeding re-
sponse observed is punctual 
or kept in time. If the latter, 
consult with the veterinarian 
and, in any case, check other 
indicators listed in this table.   

Fish with stunted growth or 
emaciated are most likely 
near-dead, and should be re-
moved from production when 
possible. Check the feeding 
strategy (distribution, quan-
tity, periodicity, etc.) and ad-
just it if necessary. It is im-
portant to follow recommen-
dations from the feed manu-
facturer regarding how much 
to feed the fish. Checking 
other indicators listed in this 

be an indicator of both positive and 
negative welfare. An appropriate 
feeding strategy adjusted to the bio-
logical needs of each species, life-
stage and water temperature can 
help control foraging behaviour and 
food intake, reducing undesired be-
havioural responses and social in-
teractions as well as food waste. 
Non consumption, or reduced in-
take, of the feed offered on the ba-
sis of feeding tables should serve 
as a warning sign to monitor other 
welfare indicators. 

Condition factor (K) is a well-estab-
lished indicator of the growth per-
formance or nutritional status of fish 
(emaciation state). Reduced condi-
tion factor can result from under-
feeding and/or prolonged feed with-
drawal, leading to emaciated fish. 
Since the condition factor varies 
with species, life stage and season, 
it is difficult to define exact values 
that are indicative of reduced wel-
fare. However a very low condition 

52 

Condition factor  

High / Medium / 
Low 

 
General fish welfare indicators for feeding 

Skin and/or fin condition 

Presence / Ab-
sence 

table may add valuable infor-
mation. Consult with the vet-
erinarian in case of potential 
health issues related to ema-
ciation.  

In case of observing physical 
injures in the skin or fins of 
some fish, farmers must ad-
just the feeding strategy (dis-
tribution, quantity, periodicity, 
etc.) and consult with the vet-
erinarian to prevent or palli-
ate potential health issues. 
Checking other indicators 
listed in this table may add 
valuable information. 

References 

(< 0.9) is usually indicative of ema-
ciation. 

In adequate feeding strategy may 
affect social interactions, inducing 
high competition and other agonis-
tic behaviours, thereby increasing 
dangerous or lethal injuries in the 
skin or fins of the fish. 

(APROMAR, 2022; Noble et al., 2020, 2018; Pavlidis and Samaras, 2020; Saraiva et al., 2022)  

5.4.2. 

Handling 

Indicator 

Metrics 

Operational recommenda-
tions 

Comments and rationale 

General fish welfare indicators for handling 

53 

 
General fish welfare indicators for handling 

Body injures 

Presence / Ab-
sence 

Feeding behaviour 

High / Medium / 
Low 

In case of observing physical 
injuries in the fish body, 
check operational protocols 
for handling (e.g. number of 
fish get at the same time in a 
hand-net, during brailing, or 
speed of pumping). Also 
check the condition of the 
equipment used, in case 
there are protrusions, holes 
or any need for repair. In 
case of high prevalence of 
injures, consult with the vet-
erinarian to prevent or palli-
ate potential health issues. 
Checking other indicators 
listed in this table may add 
valuable information. 

If feeding response is not ob-
served for a long time after 
handling, farmers must con-
sult with the veterinarian 
since stress after handling 
can lead to fish health is-
sues. In any case, other indi-
cators listed in this table 
must be checked. In case of 

Inadequate handling may result in 
physical injuries, particularly to the 
fins and skin, but also to eyes or 
gills and may contribute to skeletal 
or vertebral deformities. Inadequate 
handling implies poor maintenance 
of operating tools, such as nets, 
pumps, etc., but also their improper 
use. 
Fins and gills can get entangled, 
skin and eyes can be rubbed, caus-
ing, in all cases, external wounds 
and injures that are easily and 
quickly visible, including eye dam-
age or lesions. These wounds can 
also lead to the entry of infections 
and diseases, or even mortality.  

It is essential to check feeding re-
sponse after handling as it indicates 
fish recover appetite or interest for 
food in a short time, meaning that 
handling was carried out properly. 
Lack of feeding response immedi-
ately after handling can be a normal 
fish response due to stress. Fish 
may show medium or high feeding 
response in a short time after the 

54 

 
General fish welfare indicators for handling 

poor handling, training of 
personnel is required. 

Use of space 

All space used / 
Some parts 
avoided 

In case fish do not use most 
of the space in the rearing 
unit in a short time after han-
dling, farmers must consult 
with the veterinarian (stress 
after handling can lead to 
fish health issues). In any 
case, handling protocols 
must be checked and up-
dated. In case of poor han-
dling, training of personnel is 
required. Checking other in-
dicators listed in this table 
may add valuable infor-
mation. 

55 

stress if handling was carried out 
appropriately. However, inadequate 
handling may cause a lack or low 
feeding response maintained in 
time.    

Observing the fish distribution or 
use of space after handling is cru-
cial to understand how they recover 
from the stress induced by han-
dling. Monitoring the spatial use or 
distribution of fish within the rearing 
environment, during and after han-
dling, indicates the reaction of fish 
to the stress. After handling, 
stressed fish may concentrate in 
certain parts, only using some parts 
of the rearing unit. If fish are widely 
distributed and use most of the 
space of the rearing unit, including 
excessive surface activity. If fish 
are widely distributed and use most 
of the space of the rearing unit in 
short 
time it is a sign of good welfare 
conditions which means that han-
dling procedure was carried out 
properly. 

 
General fish welfare indicators for handling 

Dissolved oxygen 

High (above 
100% satura-
tion) / Medium 
(about 70% 
sat.) / Low (be-
low 70% sat.) 

Respiration rate 

Regular-normal 
rate / Increase 
and/or irregular 
rate 

Monitoring the dissolved oxy-
gen concentration in water is 
crucial during handling pro-
cedures. It must be meas-
ured during and after the 
handling, making sure the 
water contains the highest 
possible concentration. 
Farmers must secure a back-
up aeration or oxygenation 
system ready to be used in 
any rearing unit if necessary.    

Assessing this indicator in-
volves recording the number 
of respiratory movements of 
the opercular bone per unit 
of time. Farmers can make a 
comparative estimation of 
respiration rate during daily 
routine practices, with 
marked increases in it being 
used as an advance warning 
for more detailed monitoring 
of other finer indicators. Res-

Sufficient dissolved oxygen in the 
water is a crucial welfare need for 
fish. It is essential to keep the high-
est concentrations of dissolved oxy-
gen during and after handling given 
the stressful situation fish experi-
ence. Even more so if the fish are 
taken out of the water. During han-
dling, gills can be also affected, and 
their respiratory function reduced. 
The failure of an oxygen supple-
mentation system, following any 
type of handling, can lead to mortal-
ities due to a rapid reduction of 
available dissolved oxygen.  

 Oxygen demand increases when 
organisms are under stress, and 
this may be reflected in a rapid in-
crease in respiration rate. Respira-
tion rate can be used as a non-spe-
cialised, non-invasive stress indica-
tor when carrying out stress-induc-
ing husbandry practices. In particu-
lar, increase in respiration rate may 
result from stress, which should be 
recorded for retrospective assess-
ment of handling. A further difficulty 

56 

 
General fish welfare indicators for handling 

piration rate should be rec-
orded for the retrospective 
assessment of operations.  

lies in the fact that measuring respi-
ration rate requires the animal to be 
stationary or slow moving. 

References 

(APROMAR, 2022; Noble et al., 2020, 2018; Pavlidis and Samaras, 2020; Roque et al., 2020; Saraiva et al., 2022) 

5.4.3. 

Water quality  

General fish welfare indicators for water quality  

Indicator 

Metrics 

Dissolved oxygen 

High (above 
100% sat.) / 
Medium (about 
70% sat.) / Low 
(below 70% 
sat.) 

Operational recommenda-
tions 

Dissolved oxygen must be 
measured regularly during 
the whole rearing process, 
making sure the water con-
tains the highest concentra-
tion possible. Farmers must 
count with a back-up aera-
tion or oxygenation system 
ready to be used in any rear-
ing unit if necessary. Check-
ing other indicators listed in 
this table may add valuable 
information of water quality.  

Comments and rationale 

A minimum concentration of dis-
solved oxygen (above 70%) is cru-
cial for farmed fishes. Dissolved ox-
ygen is a parameter influencing 
welfare, metabolism, robustness 
and fish performance. Sufficient 
dissolved oxygen in the water is a 
crucial welfare need for fish. It is 
essential to keep the highest con-
centrations of dissolved oxygen 
during the whole rearing process. 
Any detrimental of water quality can 
cause stress to fish, affecting their 
respiratory function, and leading to 

57 

 
General fish welfare indicators for water quality  

Condition factor 

High / Medium / 
Low 

Use of space 

All space used 
(high) / Some 
parts avoided 
(low) 

an increase of oxygen consump-
tion. The failure of an oxygen sup-
plementation system can lead to 
mortalities due to a rapid reduction 
of available dissolved oxygen. 

Condition factor (K) is a well-estab-
lished indicator of the growth per-
formance. Reduced condition factor 
can result from poor water quality, 
leading to emaciated fish. As condi-
tion factor is variable and changes 
with species, life stage and season, 
it is difficult to define exact values 
indicative of reduced welfare, but 
very low condition (< 0.9) usually in-
dicates emaciation. 

Poor water quality may cause 
stress in fish due to inadequate 
temperature, low oxygen saturation, 
or other adverse environmental 
conditions, and therefore, alter fish 
behaviour. Stressed fish may clus-
ter in certain areas, using only 
some parts of the rearing unit.  

Water quality parameters 
and other indicators listed in 
this table must be checked. 
Consult with the veterinarian 
in case of observed recurrent 
emaciation. 

If low use of space is ob-
served for a long period, 
farmers must consult with the 
veterinarian since health is-
sues may be involved. In any 
case, water quality parame-
ters must be routinely moni-
tored by trained personnel. 
Checking other indicators 
listed in this table may add 
valuable information. 

58 

 
General fish welfare indicators for water quality  

Feeding behaviour 

High / Medium / 
Low 

It is essential to check feed-
ing response during the 
whole rearing process, ob-
serving if fish show appetite 
or interest for food in a short 
and long period. Feeding re-
gimes and strategies must 
be adjusted to feeding re-
sponse in order to avoid 
overfeeding. However, if 
feeding response is not ob-
served, fish may be stressed, 
and farmers must check 
other indicators listed in this 
table for a better welfare as-
sessment in a short term. If 
feeding response is not pre-
sent for a long period, farm-
ers must consult with the vet-
erinarian since health issues 
may be involved. In any 
case, water quality parame-
ters must be routinely moni-
tored by trained personnel.  

Lack of feeding response is a good 
indicator of fish under stress, and 
poor water quality may be the 
stressor. In this case, poor water 
quality may cause a lack or low 
feeding response maintained in 
time. On the other hand, overfeed-
ing can lead to reduced water qual-
ity due to excess uneaten food pel-
lets or the excretion of nutrient rich 
faeces. This can be especially im-
portant in closed- or semi-closed 
containment rearing systems.  

Swimming activity 

Normal / Al-
tered 

If normal group swimming 
behaviour is not observed for 
a prolonged period, farmers 

Observing group swimming behav-
iour is a sign of good welfare condi-
tions. Poor water quality may cause 

59 

 
General fish welfare indicators for water quality  

Respiration rate 

Regular-normal 
rate / High or 
increased rate 

must consult with the veteri-
narian since health issues 
may be involved. In any 
case, water quality parame-
ters must be routinely moni-
tored by trained personnel. 
Checking other indicators 
listed in this table may add 
valuable information. 

Farmers can make a com-
parative estimation of respi-
ration rate during daily rou-
tine practices. Marked in-
creases of the respiration 
rate can be used as an ad-
vance warning for more de-
tailed monitoring of other 
finer indicators. Respiration 
rate should be recorded for 
the retrospective assessment 
of operations. If the respira-
tion rate remains high long 
time, farmers must consult 
with the veterinarian since 
fish health issues may be in-

stress in fish, and therefore, alter 
group swimming behaviour. Fish 
can abnormally shoal, school or 
disperse, but alterations of their 
natural or regular behaviour may in-
dicate some detrimental in the wa-
ter quality. 

Assessing this indicator involves re-
cording the number of respiratory 
movements of the opercular bone 
per unit of time. Oxygen demand in-
creases when organisms are under 
stress. This may be reflected in a 
rapid increase in respiration rate. 
Respiration rate can be used as a 
non-specialised, non-invasive 
stress indicator. In particular, in-
crease in respiration rate may be a 
consequence of poor water quality, 
such as adverse temperature, salin-
ity or oxygen saturation, and there-
fore, a result from stressful environ-
mental conditions. A further diffi-
culty lies in the fact that measuring 
respiration rate requires the animal 
to be stationary or slow moving. 

60 

 
General fish welfare indicators for water quality  

volved. Checking other indi-
cators listed in this table may 
add valuable information. 

Therefore, it might be not applica-
ble in all farming systems (e.g. sea-
cages). 

References 

(APROMAR, 2022; Noble et al., 2020, 2018; Pavlidis and Samaras, 2020; Roque et al., 2020; Saraiva et al., 2022) 

5.4.4. 

Stocking density 

General fish welfare indicators for stocking density 

Indicator 

Metrics 

Dissolved oxygen 

High (above 
100% sat.) / 
Medium (about 
70% sat.) / Low 
(below 70% 
sat.) 

Operational recommenda-
tions 

Dissolved oxygen must be 
measured regularly during 
the whole rearing process, 
making sure the water con-
tains the highest concentra-
tion possible. Farmers must 
secure a back-up aeration or 
oxygenation system ready to 
be used in any rearing unit if 
necessary. Checking other 
indicators listed in this table 
may add valuable infor-
mation.  

Comments and rationale 

A minimum concentration of dis-
solved oxygen (above 70%) is cru-
cial for farmed fishes, especially at 
high stocking densities. Sufficient 
dissolved oxygen in the water is a 
crucial welfare need for fish. It is 
essential to keep the highest con-
centrations of dissolved oxygen 
during the whole rearing process. 
High fish stoking densities increase 
the oxygen consumption due to a 
high number of animals in the rear-
ing unit. The increase of fish den-
sity along the rearing process due 

61 

 
General fish welfare indicators for stocking density 

Condition factor 

High / Medium / 
Low 

Skin and/or fin condition 

Presence / Ab-
sence 

to fish growth can increase the oxy-
gen consumption rate, threatening 
the welfare conditions of fish. The 
failure of an oxygen supplementa-
tion system can lead to mortalities 
due to a rapid reduction of available 
dissolved oxygen. 

Condition factor (K) is a well-estab-
lished indicator of the growth per-
formance. Reduced condition factor 
can result from high stocking den-
sity due to high competition or low 
food availability, leading to emaci-
ated fish. As condition factor is vari-
able and changes with species, life 
stage and season it is difficult to de-
fine exact values that are indicative 
of reduced welfare, but very low 
condition (< 0.9) is usually indica-
tive of emaciation. 

Fish with stunted growth or 
emaciated are most likely 
near-dead, and should be re-
moved from production when 
possible. If low condition fac-
tor or emaciated fish is ob-
served, stocking density 
must be immediately re-
duced. Check the water qual-
ity parameters and other indi-
cators listed in this table. 
Consult with the veterinary if 
emaciation persist in time. 

In case of observing high 
erosion of fins or physical in-
jures in the fins and skin, as 
well as signs of skeletal or 
vertebral deformities, eye 
damage or lesions, or poor 
opercular and gill condition, 

High stocking density reduce the 
available space and affect social in-
teractions, inducing physical inter-
actions, high competition and other 
agonistic behaviours, thereby in-
creasing fin erosion and dangerous 
or lethal injuries in the skin and fins 

62 

 
General fish welfare indicators for stocking density 

Swimming activity 

Normal / Al-
tered 

Respiration rate 

Regular-normal 
rate / High or 
increased rate 

adjust the stocking density 
by reducing the number of 
fish within the affected rear-
ing unit. Consult with the vet-
erinarian to prevent or palli-
ate potential health issues. 
Checking other indicators 
listed in this table may add 
valuable information. 

If normal group swimming 
behaviour is not observed for 
a prolonged period, farmers 
must adjust or reduce the 
stocking density. Checking 
other indicators listed in this 
table may add valuable infor-
mation. 

of the fish. Additionally, such condi-
tions may contribute to the develop-
ment of skeletal or vertebral de-
formities, eye damage or lesions, 
and poor opercular and gill condi-
tion, all of which are important indi-
cators of compromised fish welfare. 

Inadequate stocking densities (too 
high or too low) can have direct ef-
fects on fish behaviour, mostly 
linked to stressful conditions due to 
social interactions or unavailable 
space. Fish can shoal, school or 
disperse, but alterations of their 
natural or regular behaviour may in-
dicate some negative effects of fish 
density. 

Farmers can make a com-
parative estimation of respi-
ration rate during daily rou-
tine practices, with marked 
increases in it being used as 
an advance warning for more 
detailed monitoring of other 
finer indicators. In case of 

Assessing this indicator involves re-
cording the number of respiratory 
movements of the opercular bone 
per unit of time. Oxygen demand in-
creases when organisms are under 
stress or at high densities. This 
may be reflected in a rapid increase 
in respiration rate. Respiration rate 

63 

 
General fish welfare indicators for stocking density 

persistent high respiration 
rate, stocking density must 
be reduced.  

can be used as a non-specialised, 
non-invasive stress indicator. In 
particular, increase in respiration 
rate may be a consequence of poor 
water quality or low oxygen satura-
tion due to high stocking densities. 
A further difficulty lies in the fact 
that measuring respiration rate re-
quires the animal to be stationary or 
slow moving.  Therefore, it might be 
not applicable in all farming sys-
tems (e.g. sea-cages). 

(APROMAR, 2022; Noble et al., 2020, 2018; Pavlidis and Samaras, 2020; Roque et al., 2020; Saraiva et al., 2022) 

References 

5.4.5. 

Mortality removal 

General fish welfare indicators for mortality removal  

Indicator 

Metrics 

Dissolved oxygen 

High (above 
100% sat.) / 
Medium (about 
70% sat.) / Low 

Operational recommenda-
tions 

Dissolved oxygen must be 
measured during and after 
removal mortality, when fish 
may increase oxygen con-
sumption, making sure the 

Comments and rationale 

A minimum concentration of dis-
solved oxygen (above 70%) is cru-
cial for farmed fishes, especially un-
der stressful conditions. Sufficient 

64 

 
General fish welfare indicators for mortality removal  

(below 70% 
sat.) 

Feeding behaviour 

High / Medium / 
Low 

diluted oxygen in the water is a cru-
cial welfare need for fish. It is es-
sential to keep the highest concen-
trations of dissolved oxygen during 
the whole rearing process. Mortality 
removal may increase the stress of 
fish within the rearing unit, due to 
the extraction procedure, but also 
due to the presence of dead ani-
mals. The stressful situation may 
lead to an increase of oxygen con-
sumption during and after the pro-
cedure, threatening the welfare 
conditions of fish. The failure of an 
oxygen supplementation system 
can lead to fish mortalities due to a 
rapid reduction of available dis-
solved oxygen. 

Observing daily feeding response 
indicates fish have appetite or inter-
est for food, a good sign of welfare 
in a short time. Feeding response 
refers to foraging behaviour and 
food intake during feeding. It is es-
sential to check feeding response 
after mortality removal, observing if 
fish show appetite or interest for 
food in a short and long time. Non-

water contains the highest 
possible concentration. 
Farmers must secure with a 
back-up aeration or oxygena-
tion system ready to be used 
in any rearing unit if neces-
sary.  In any case, mortality 
removal must be carried out 
by an adequate method and 
trained personnel. Checking 
other indicators listed in this 
table may add valuable infor-
mation.  

When feeding response is 
not observed, fish may be 
stressed, and farmers must 
check other indicators for a 
better welfare assessment in 
a short term. If feeding re-
sponse is not present for a 
long period, farmers must 
consult with the veterinarian 
since health issues may be 

65 

 
General fish welfare indicators for mortality removal  

Swimming activity 

Normal / Al-
tered 

involved. In any case, mortal-
ity removal must be carried 
out by an adequate method 
and trained personnel. 
Checking other indicators 
listed in this table may add 
valuable information. 

Normal group swimming be-
haviour must be observed af-
ter mortality removal proce-
dure in a short time. If it is 
not observed, fish are sub-
jected to stress, and other in-
dicators listed in this table 
must be checked. If fish do 
not recover normal swim-
ming activity in a long time, 
farmers must consult the vet-
erinarian since health issues 
must be involved. 

stressed fish will show appetite 
quickly, but lack of feeding re-
sponse may be a consequence of 
inadequate mortality removal pro-
cedure.   

Inadequate mortality removal pro-
cedure can have direct effects on 
fish behaviour, mostly linked to 
stressful conditions due to the ap-
plied methodology or the presence 
of dead fish in the rearing unit. Fish 
can shoal, school or disperse, but 
alterations of their natural or regular 
behaviour may indicate some nega-
tive effects of mortality removal. 

Use of space 

All space used 
(high) / Some 
parts avoided 
(low) 

After mortality removal, if fish 
is widely dispersed, using 
most of the space of the 
rearing unit, is a sign of good 
welfare conditions. In con-
trast, if low use of space is 
observed for a long period, 

Inadequate mortality removal may 
cause stress in fish due to inade-
quate methodology or untrained 
personnel, and therefore, alter fish 
behaviour. Stressed fish may con-
centrate in certain parts, only using 
some parts of the rearing unit, but a 

66 

 
General fish welfare indicators for mortality removal  

Respiration rate 

Regular-normal 
rate / High or 
increased rate 

farmers must consult with the 
veterinarian since health is-
sues may be involved. In any 
case, mortality removal must 
be carried out by an ade-
quate method and trained 
personnel. Checking other 
indicators listed in this table 
may add valuable infor-
mation. 

Farmers can make a com-
parative estimation of respi-
ration rate during and after 
daily routine practices, such 
as mortality removal. Respi-
ration rate should be rec-
orded for the retrospective 
assessment of operations. If 
respiration rate remains high 
long time after the mortality 
removal, farmers must con-
sult with the veterinarian 
since fish health issues may 
be involved. In any case, 
mortality removal must be 
carried out by an adequate 
method and trained person-

wide dispersion can be later ob-
served if fish cope with the stressor. 
Observing the fish distribution or 
use of space is crucial to under-
stand the welfare state of fish within 
the rearing environment after any 
procedure.  

Assessing this indicator involves re-
cording the number of respiratory 
movements of the opercular bone 
per unit of time. ODs increase when 
organisms are under stress. This 
may be reflected in a rapid increase 
in respiration rate. Respiration rate 
can be used as a non-specialised, 
non-invasive stress indicator. In 
particular, increase in respiration 
rate may be a consequence of 
stress due to inadequate methodol-
ogy or untrained personnel during 
mortality removal. A further difficulty 
lies in the fact that measuring respi-
ration rate requires the animal to be 

67 

 
General fish welfare indicators for mortality removal  

nel. Checking other indica-
tors listed in this table may 
add valuable information. 

stationary or slow moving.  There-
fore, it might be not applicable in all 
farming systems (e.g. sea-cages). 

References 

(APROMAR, 2022; Noble et al., 2020, 2018; Pavlidis et al., 2023; Pavlidis and Samaras, 2020; Saraiva et al., 2022)  

5.4.6. 

Transport  

Indicator 

Metrics 

Operational recommenda-
tions 

Comments and rationale 

General fish welfare indicators for transport 

Skin and/or fin condition 

Presence / Ab-
sence 

In case of observing high 
erosion of fins or physical in-
jures in the fins and skin of 
some fish, adjust and im-
prove the loading/unloading 
procedure (pumps or nets). 
Consult with the veterinarian 
to prevent or palliate poten-
tial health issues. Checking 
other indicators listed in this 
table may add valuable infor-
mation. 

Loading/unloading fish before and 
after transport may affect the condi-
tion of fins and skin due to mechan-
ical frictions or physical interactions 
with the tools applies (pumps or 
nets). Physical contact between fish 
and other surfaces, dropping fish 
from pumps or elevators, handling 
before loading, and the loading it-
self cause poor welfare. Inadequate 
pumping and handling may result in 
physical injuries, particularly to the 
fins, but also disrupting the protec-
tive mucous coating and fish 

68 

 
General fish welfare indicators for transport 

Dissolved oxygen  

High (above 
100% sat.) / 
Medium (about 
70% sat.) / Low 
(below 70% 
sat.) 

scales. Therefore, fin erosion and 
dangerous or lethal injuries in the 
skin and fins of the fish can be ob-
served if the procedures are not ad-
equately carried out. 

A minimum concentration of dis-
solved oxygen (above 70%) is cru-
cial for farmed fishes before and 
during transport. Sufficient diluted 
oxygen in the water is a crucial wel-
fare need for fish. It is essential to 
keep the correct concentrations of 
dissolved oxygen during the whole 
loading/unloading and transport 
process, since both high and low 
oxygen levels are particularly dan-
gerous in combination with high lev-
els of metabolites in the transport 
water. High fish stoking densities 
increase the oxygen consumption 
due to a high number of animals in 
the transport unit, threatening the 
welfare conditions of fish. The fail-
ure of an oxygen supplementation 
system can lead to mortalities due 
to a rapid reduction of available dis-
solved oxygen. 

Dissolved oxygen must be 
measured regularly during 
the whole transport duration 
and loading process, making 
sure the water contains satu-
ration percentages above 
100%, but avoiding too high 
concentrations. Farmers 
must secure a monitoring 
system and back-up aeration 
or oxygenation system ready 
to be used in any rearing unit 
if necessary. Checking other 
indicators listed in this table 
and water quality parameters 
(carbon dioxide or ammonia) 
during transport may add val-
uable information.  

69 

 
General fish welfare indicators for transport 

Use of space  

All space used / 
Some parts 
avoided 

Feeding behaviour 

High / Medium / 
Low 

If fish are widely distributed 
in a short time after transport 
(in the new rearing environ-
ment), using most of the 
available space, the proce-
dure was carried out cor-
rectly. If fish are not widely 
distributed in the new rearing 
unit after transport in a short 
time, fish may be still under 
stress. Farmers must then 
consult with the veterinarian 
given that stress after 
transport can lead to fish 
health issues. In case of poor 
welfare, loading and 
transport protocols must be 
checked and update. Train-
ing of personnel is required, 
and checking other indicators 
listed in this table may add 
valuable information. 

Observing the fish distribution or 
use of space during and after 
transport is crucial to understand 
how the fish cope or recover from 
the stress induced by the whole 
transport procedure. Loading, con-
finement and high densities during 
transport can cause stress to fish. 
Monitoring the spatial use or distri-
bution of fish during and after 
transport, indicates the reaction of 
fish to the stress. After transport, 
stressed fish may concentrate in 
certain parts, only using some parts 
of the new rearing unit. If fish are 
widely distributed and use most of 
the space of the transport or new 
rearing unit is a sign of good wel-
fare conditions.  

Low or lack of feeding re-
sponse the following days af-
ter transport may indicate 
stress or poor welfare condi-
tions. In this case, consult 
with the veterinarian and 

Loading, confinement and high 
densities during transport can 
cause stress to fish. Monitoring the 
feeding behaviour reflects the reac-
tion of fish to the potential stress in-
duced by transport. After transport, 

70 

 
General fish welfare indicators for transport 

check potential health-re-
lated issues. In case of poor 
welfare, loading and 
transport protocols must be 
checked and update. Train-
ing of personnel is required, 
and checking other indicators 
listed in this table may add 
valuable information.  

stressed fish may loss appetite, 
whereas observing feeding re-
sponse in a short time after 
transport is signed of fish appetite, 
and indicates fish coped or recov-
ered from the stress induced by the 
whole transport procedure. High 
feeding response in the new rearing 
unit is a sign of good welfare condi-
tions. 

References 

(APROMAR, 2022; Noble et al., 2020, 2018; Pavlidis and Samaras, 2020; Saraiva et al., 2022, 2021) 

5.4.7. 

Stunning and slaughter 

General fish welfare indicators for stunning and slaughter 

Indicator 

Metrics 

Dissolved oxygen 

High (above 
100% sat.) / 
Medium (about 
70% sat.) / Low 
(below 70% 
sat.) 

Operational recommenda-
tions 

Dissolved oxygen must be 
measured during the ma-
noeuvre, making sure the 
water contains the highest 
possible concentration. 
Farmers must secure a mon-
itoring system and stop 

Comments and rationale 

Monitoring the dissolved oxygen 
concentration in water is crucial 
during crowding. This pre-slaugh-
tering procedure can cause stress 
and impaired welfare of fish. Suffi-
cient diluted oxygen in the water is 
a crucial welfare need for fish, 

71 

 
General fish welfare indicators for stunning and slaughter 

Surface activity  

No surface 
breach / fins 
appearing / 
bodies emerge 

crowding in case of low con-
centrations of dissolved oxy-
gen (to avoid mortality by as-
phyxia). Checking other indi-
cators listed in this table may 
add valuable information. 

therefore, it is essential to keep the 
highest concentrations of dissolved 
oxygen during crowding, given the 
stressful situation fish experience. 
The lack of sufficient dissolved oxy-
gen during crowding can lead to 
mortalities due to asphyxia.  

Observing burst swimming 
next to the surface, or fish 
exposing the dorsal fin above 
water are the first signs farm-
ers can observe during 
crowding. Such behaviours 
indicate stress, and their ap-
pearance is to be avoided or 
reduce as much as possible 
in time. No surface breaches 
are desired, and if fish bod-
ies emerge from the surface, 
crowding must be modified 
or stopped. Training of per-
sonnel is required, and 
checking other indicators 
listed in this table may add 
valuable information. 

Crowding procedures expose fish 
to high densities, and therefore high 
stress, being concentrated next to 
the surface for a certain period of 
time. Crowed fish can be observed 
from the surface showing diverse 
behaviours such as ripples in the 
water or surface breaks (rolling, 
jumping etc.). Fins out of the water 
across the crowding surface and 
belly sides at the surface can be 
also observed due to high densities 
at crowding.  

Body injures 

Presence / Ab-
sence 

In case of observing physical 
injures in the fish body check 

Crowding may result in physical in-
juries due to high densities for long 

72 

 
 
General fish welfare indicators for stunning and slaughter 

periods, particularly to the fins and 
skin, but also to eyes or gills. Fins 
and gills can get entangled, skin 
and eyes can be rubbed. Addition-
ally, inadequate long fasting peri-
ods may lead to aggressive attacks 
among fish, which may also cause 
physical injures in the fins and skin. 
In all cases, causing external 
wounds and injures that are easily 
and quickly visible. These wounds 
can also lead to the entry of infec-
tions and diseases, or even mortal-
ity.  

Inadequate pre-slaughtering fasting 
periods can lead to poor growth 
performance or nutritional status of 
fish which can be monitored 
through the body condition factor 
(K). Reduced condition factor can 
lead to emaciated fish. As condition 
factor is variable and changes with 

operational protocols for 
crowding (e.g. fish density 
crowded, time of procedure, 
number of fish captured at 
the same time in a hand-net, 
during brailing, or speed of 
pumping). Also check the 
condition of the equipment 
used, in case there are pro-
trusions, holes or any need 
for repair. In case of high 
prevalence of injures, farm-
ers must consult with the vet-
erinarian to prevent or palli-
ate potential health issues. 
Training of personnel is re-
quired, and checking other 
indicators listed in this table 
may add valuable infor-
mation. 

Fish with stunted growth or 
emaciated are sings of inad-
equate pre-slaughtering fast-
ing periods. Check fasting 
strategies applied and adjust 
if necessary for future proce-
dures.  Emaciated fish 
should be removed from the 

73 

Condition factor 

High / Medium / 
Low 

 
 
General fish welfare indicators for stunning and slaughter 

Respiration rate 

Presence / Ab-
sence 

stock much earlier than har-
vesting. Checking other indi-
cators listed in this table may 
add valuable information.  

species, life stage and season it is 
difficult to define exact values that 
are indicative of reduced welfare, 
but exceptionally low condition (< 
0.9) is usually indicative of emacia-
tion. 

If respiration/opercular move-
ment is not observed, the 
fish is likely approaching to 
unconsciousness, previous 
to the absence of eye roll. If 
opercular movement is ob-
served, the fish is conscious, 
and farmer must stun the fish 
again with a spare method 
before killing, in order to get 
a humane slaughtering. 
Check stunned protocols and 
modified if necessary. Other 
indicators (e.g. VOR) may 
add valuable information. 
Training of personnel is re-
quired. 

Previous to slaughtering, fish must 
be successfully stunned, this is, los-
ing consciousness during killing 
procedure. Losing respiration is one 
of the indicators towards losing 
consciousness. However, the ces-
sation of opercular movement cou-
pled with the loss of eye roll are, to 
the best of our knowledge, the top 
operational indicators towards loss 
of consciousness that are measura-
ble in farming context.  

Vestibulo-Ocular Reflex (VOR) 

Presence/Ab-
sence 

If VOR is observed, the fish 
is likely to be conscious, and 
farmer must stun again the 

The VOR, known as “eye roll”, is a 
test that consist on rotating the fish 
and observing any eye movements. 
In an unconscious fish the eye is 

74 

 
General fish welfare indicators for stunning and slaughter 

fish with a spare method be-
fore killing, in order to get a 
humane slaughtering.  If 
VOR is not observed, the fish 
is likely to be approaching 
unconsciousness. Check 
stunned protocols and modi-
fied if necessary. Training of 
personnel is required. 

fixed in the skull when the fish is 
rocked from side to side. In a fish 
retaining some brain function, the 
eye rotates dorso-ventrally when 
the fish is rocked. VOR test is con-
sidered a good on-farm indicator of 
state towards loss of conscious-
ness for many species as this is 
one of the last things to be lost dur-
ing anaesthesia and one of the first 
to appear upon recovery.  

References 

(APROMAR, 2022; EFSA, 2009d; Kestin et al., 2002; Morzel et al., 2003; Noble et al., 2020, 2018; Pavlidis and Samaras, 2020; 
Saraiva et al., 2022; Stien et al., 2024) 

5.4.8. 

Environmental enrichment 

General fish welfare indicators for environmental enrichment 

Indicator 

Metrics 

Condition factor 

High / Medium / 
Low 

Operational recommenda-
tions 

Comments and rationale 

Inadequate EE may lead to 
fish with stunted growth or 
emaciated, which are most 
likely near-dead, and should 
be removed from production 

Condition factor (K) is a well-estab-
lished indicator of the growth per-
formance. Reduced condition factor 
can result from stressful stimuli or 
inadequate EE strategies, leading 

75 

 
General fish welfare indicators for environmental enrichment 

Feeding behaviour 

High / Medium / 
Low 

when possible. Checking 
other indicators listed in this 
table may add valuable infor-
mation. Consult with the vet-
erinarian in case of observed 
recurrent emaciation and 
modify EE strategy. 

When feeding response is 
not observed, fish may be 
stressed due to inadequate 
EE, and farmers must check 
other indicators for a better 
welfare assessment in a 
short term. If feeding re-
sponse is not present for a 
prolonged period, farmers 
must consult with the veteri-
narian since health issues 
may be involved. In any 
case, EE strategy must be 
checked and modified if nec-
essary. Checking other indi-
cators listed in this table may 
add valuable information. 

to emaciated fish. As condition fac-
tor is variable and changes with 
species, life stage and season it is 
difficult to define exact values that 
are indicative of reduced welfare, 
but exceptionally low condition (< 
0.9) is usually indicative of emacia-
tion. 

It is essential to check feeding re-
sponse during the whole rearing 
process, especially if EE strategies 
are implemented or modified in the 
rearing unit, observing if fish show 
appetite or interest for food in a 
short and long time. Non-stressed 
fish will show appetite quickly, but 
lack of feeding response may be a 
consequence of inadequate EE 
strategy implemented.  

76 

 
General fish welfare indicators for environmental enrichment 

Use of space 

All space used 
(high) / Some 
parts avoided 
(low) 

Swimming activity 

Normal / Al-
tered 

When EE is implemented, 
observing widely dispersed 
fish using most of the space 
of the rearing unit (including 
additional structures) is a 
sign of good welfare condi-
tions. In contrast, if low use 
of space is observed for a 
long period, farmers must 
consult with the veterinarian 
since health issues may be 
involved, and the imple-
mented EE strategy must be 
checked and modified. 
Checking other indicators 
listed in this table may add 
valuable information. 

Inadequate EE may cause stress in 
fish due to inadequate stimuli, ma-
terials, or methodology, and there-
fore, alter fish behaviour. Stressed 
fish may concentrate in certain 
parts, only using or avoiding some 
parts of the rearing unit, but a wide 
dispersion can be later observed if 
fish cope with the stressor or are in 
good welfare conditions. Observing 
the fish distribution or use of space 
is crucial to understand the welfare 
state of fish within the rearing envi-
ronment during the whole produc-
tion procedure, as well as the po-
tential effects of the EE on farmed 
fish.  

When EE is applied normal 
group swimming behaviour 
must be observed in a short 
time. If it is not observed, fish 
are subjected to stress, and 
other indicators listed in this 
table must be checked. If 
farmed fish do not recover 
normal swimming activity in a 

Inadequate EE strategy can have 
direct effects on fish behaviour, 
mostly linked to stressful conditions 
due to the applied methodology, or 
the presence of inadequate struc-
tures or stimuli in the rearing unit. 
Fish can shoal, school, or disperse, 
but alterations of their natural or 
regular behaviour may indicate 

77 

 
General fish welfare indicators for environmental enrichment 

Body injures 

Presence / Ab-
sence 

Dissolved oxygen 

High (above 
100% sat.) / 
Medium (about 
70% sat.) / Low 
(below 70% 
sat.) 

some negative effects of the ap-
plied EE. 

Inadequate materials used as struc-
tural EE may result in physical inju-
ries, particularly to the fins, eyes, 
and/or skin. Additionally, inade-
quate environmental stimuli may 
lead to stressful conditions, promot-
ing aggressive attacks among fish, 
which may also cause physical inju-
ries. In all cases, causing external 
wounds and injures that are easily 
and quickly visible. These wounds 
can also lead to the entry of infec-
tions and diseases, or even mortal-
ity.  

Inadequate EE can cause stress 
and impaired welfare of fish due to 
stressful stimuli or inadequate ma-
terials or methodology. Sufficient di-
luted oxygen in the water is a cru-
cial welfare need for fish, therefore, 
it is essential to keep the highest 

long time, farmers must con-
sult the veterinarian since 
health issues must be in-
volved, and the implemented 
EE strategy must be checked 
and/or modified. 

In case of observing physical 
injures in the fish body, farm-
ers must check, the EE strat-
egy, such as the materials 
used or the stimuli imple-
mented. In case of high prev-
alence of injures, consult 
with the veterinarian to pre-
vent or palliate potential 
health issues, and modified 
the EE applied. Checking 
other indicators listed in this 
table may add valuable infor-
mation. 

Monitoring the dissolved oxy-
gen concentration in water is 
crucial during the whole rear-
ing process, especially if EE 
is applied in the rearing unit, 
making sure the water con-
tains the highest possible 

78 

 
General fish welfare indicators for environmental enrichment 

concentrations of dissolved oxygen 
during the whole rearing process, 
especially when EE is implemented 
to avoid undesired negative effects. 
The lack of sufficient dissolved oxy-
gen during farming can lead to mor-
talities due to asphyxia.  

concentration. Farmers must 
secure a monitoring system, 
and EE implemented must 
be checked and modified if 
necessary in case of low 
concentrations of dissolved 
oxygen (to avoid dead by as-
phyxia). Checking other indi-
cators listed in this table may 
add valuable information. 

References 

(Arechavala‐Lopez et al., 2022; Jones et al., 2021; Kleiber et al., 2023; Näslund and Johnsson, 2016; Saraiva et al., 2022; 
Zhang et al., 2023) 

79 

 
 
6. 

References 

AAC (2017). Farmed fish welfare during slaughter. Retrieved from https://aac-
europe.org/wp-content/uploads/2017/11/Slaughter_report__AAC_report.pdf  

AAC (2019). Recommendation on Fish Welfare at Slaughter. Retrieved from 
https://aac-europe.org/wp-content/uploads/2019/07/AAC_recommenda-
tion_Fish_Welfare_at_Slaughter_July_2019.pdf  

AAC (2022). Recommendation on Fish Welfare in Live Fish Transport. AAC. 
Retrieved from https://aac-europe.org/wp-content/uploads/2022/03/7.AAC_Rec-
ommendation_-_Fish_Welfare_in_Live_Fish_Transport_2022_07.pdf  

AAC (2024). Code of Good Practices on Fish Welfare among Aquaculture Pro-
ducers.  

APROMAR (2022). A guide on fish welfare in Spanish aquaculture - Volume 1: 
Concepts and generalities. Retrieved from https://apromar.es/wp-content/up-
loads/2024/04/guia_wellfare_eng_web.pdf 

APROMAR (2024a). A guide on fish welfare in Spanish aquaculture - Volume 2: 
Welfare of European sea bass. Spanish Aquaculture Business Association. 

APROMAR (2024b). A guide on fish welfare in Spanish aquaculture - Volume 3: 
Welfare of gilthead sea bream. Spanish Aquaculture Business Association. 

APROMAR (2025). A guide on fish welfare in Spanish aquaculture - Volume 4: 
Welfare of rainbow trout. Spanish Aquaculture Business Association. 

Aquaculture Welfare Standards Initiative (ITA). Recommendations on animal 
welfare in aquaculture. Retrieved from https://www.aquaculture-welfare-stand-
ards.net/en/downloads-2/translations-of-awsis-basic-recommendations/ 

Aquatic Life Institute (2023). Stunning and slaughter: Best practices for animal 
welfare in aquaculture. Retrieved from https://www.ali.fish/welfare-guides/stun-
ning-and-slaughter-best-practices-for-animal-welfare-in-aquaculture  

Arechavala-López, P., Cabrera-Álvarez, M., Maia, C., & Saraiva, J. (2022). En-
vironmental enrichment in fish aquaculture: A review of fundamental and practi-
cal aspects. Reviews in Aquaculture, 14, 704-728. doi:10.1111/raq.12620 

Arechavala-López, P., Díaz-Gil, J., Saraiva, J., Moranta, D., Castanheira, M., 
Nuñez-Velázquez, S., Grau, A. (2019). Effects of structural environmental en-
richment on welfare of juvenile seabream (Sparus aurata). Aquaculture reports. 

 
 
Retrieved from https://digital.csic.es/bitstream/10261/201504/4/environmen-
tal_enrichment_welfare_juvenile_seabream.pdf  

ASC (2019). ASC Freshwater Trout Standard. Retrieved from https://www.asc-
aqua.org/wp-content/uploads/2019/09/ASC-Freshwater-Trout-Stand-
ard_v1.2_Final.pdf  

Attia, J., Millot, S., Di-Poï, C., Bégout, M., Noble, C., Sánchez-Vázquez, F., 
Damsgard, B. (2012). Demand feeding and welfare in farmed fish. Fish Physiol. 
Biochem. https://link.springer.com/article/10.1007/s10695-011-9538-4  

Barreto, M.O., Rey Planellas, S., Yang, Y., Phillips, C., Descovich, K. (2022). 
Emerging indicators of fish welfare in aquaculture. Rev. Aquac. 14, 343–361. 
https://doi.org/10.1111/raq.12601 

Bermejo-Pozo, R., et al. (2017). Determination of optimal degree days of fasting 
before slaughter in rainbow trout (Oncorhynchus mykiss). Aquaculture. Re-
trieved from https://www.sciencedirect.com/science/arti-
cle/abs/pii/S0044848616307001  

Best Aquaculture Practices (2023). BAP Salmon Farm Standards. Global Sea-
food Alliance. Retrieved from https://www.bapcertification.org/Down-
loadables/pdf/GSA%20-%20Salmon%20Farm%20Standard%20-%20Is-
sue%202.4%20-%2007-February-2023.pdf  

BIM (2022a). Certified Quality Aquaculture Standards. Retrieved from 
https://bim.ie/aquaculture/sustainability-and-certification/certified-quality-aqua-
culture-cqa-programme/#certified-quality-aquaculture-(cqa)-standards  

BIM (2022b). Fish Welfare During Handling. Retrieve from https://bim.ie/wp-
content/uploads/2024/05/BIM-Fish-Welfare-During-Handling.pdf 

BIM (n.d.). Operational welfare indicators. A brief overview. Retrieved from 
https://bim.ie/wp-content/uploads/2021/11/Operational-Welfare-Indicators-Fish-
Health-Guide.pdf 

Boissonnot, L., Austad, M., Karlsen, C., Reynolds, P., Stensby-Skj, S., Sakari-
assen, T., Imsland, A. (2022). Welfare assessment of lumpfish in sea cages - 
Manual -. 

Bosakowski, T., & Wagner, E. (1995). Experimental use of cobble substrates in 
concrete raceways for improving fin condition of cutthroat (Oncorhynchus 
clarkii) and rainbow trout (O. mykiss). Aquaculture. doi: 
https://doi.org/10.1016/0044-8486(94)00223-B  

Browning, H. (2023). Improving welfare assessment in aquaculture. Front. Vet. 
Sci. 10. https://doi.org/10.3389/fvets.2023.1060720  

 
 
Ceinos, R., Chivite, M., López-Patiño, M., et al. (2019). Differential circadian 
and light-driven rhythmicity of clock gene expression and behaviour in the turbot 
(Scophtalmus maximus). PLoS One. doi:https://doi.org/10.1371/journ 
al.pone.0219153  

CIWF (2018). Improving the welfare of European seabass and gilthead sea-
bream. Retrieved from https://www.compassioninfoodbusiness.com/me-
dia/7436996/the-science-driving-change-for-gilthead-sea-bream-and-european-
sea-bass.pdf  

CIWF (2018). The welfare of farmed fish during slaughter in the European Un-
ion. Retrieved from https://www.compassioninfoodbusiness.com/me-
dia/7434891/ciwf-2018-report__the-welfare-of-farmed-fish-during-slaughter-in-
the-eu.pdf  

CIWF (2023). Improving the welfare of farmed rainbow trout at rearing. Re-
trieved from https://www.compassioninfoodbusiness.com/me-
dia/7436980/126879_ciwf_trout_insert-3_rearing.pdf  

Costache, M., & Dobrota, R. (2020). Guide of good practice for farming fresh-
water fish species for aquaculture (in Romanian). NUCET fish research and de-
velopment station, NUCET (SCDP). 

Council of Europe (2005). Recommendations concerning farmed fish. Retrieved 
from https://www.coe.int/t/e/legal_affairs/legal_co-operation/biologi-
cal_safety_and_use_of_animals/farming/rec%20fish%20e.asp  

Currie, A., Cockerill, D., Diez-Padrisa, M., Haining, H., Henriquez, F., & Quinn, 
B. (2022). Anemia in salmon aquaculture: Scotland as a case study. Aquacul-
ture. doi:10.1016/j.aquaculture.2021.737313  

Ebbesson, L., & Lal, P. (2024). Revolutionary lighting, technologies, and ma-
chine vision in aquaculture: Enhancing efficiency and cutting costs – But what 
about the fish? (Sessions on Light and aquatic animals at AQUA 2024). 

EFFAB (2023). CODE EFABAR. Retrieved from https://urlde-
fense.com/v3/__https:/www.effab.info/modern-animal-breeding/responsible-
breeding/how-to-adopt-it/__;!!EJ3n55FBLexp1rhr!4gZ7tO_LPNnhjyN-
kHPq0BB36j3BG2gqK5sdf3ptVGSzuDVxrwNqzcS-
kNlOWYBHXY9q9hD_hD7a5tGgxhd-lA0SkVAUMYL1BaA63aAy2e6FPh$  

EFSA (2004). Opinion of the Scientific Panel on Animal Health and Welfare 
(AHAW) on a request from the Commission related to welfare aspects of the 
main systems of stunning and killing the main commercial species of animals. 
Retrieved from https://efsa.onlineli-
brary.wiley.com/doi/epdf/10.2903/j.efsa.2004.45  

 
 
EFSA (2008a). Animal welfare aspects of husbandry systems for farmed Atlan-
tic salmon. Scientific Opinion of the Panel on Animal Health and Welfare. doi: 
https://doi.org/10.2903/j.efsa.2008.736  

EFSA (2008b). Animal welfare aspects of husbandry systems for farmed Euro-
pean seabass and gilthead seabream. Scientific Opinion of the Panel on Animal 
Health and Welfare.  

EFSA (2008c). Animal welfare aspects of husbandry systems for farmed fish: 
carp. Scientific Opinion of the Panel on Animal Health and Welfare. EFSA. 

EFSA (2008d). Animal welfare aspects of husbandry systems for farmed trout. 
Scientific Opinion of the Panel on Animal Health and Welfare. doi: 
https://doi.org/10.2903/j.efsa.2008.796 

EFSA (2009a). Species-specific welfare aspects of the main systems of stun-
ning and killing of farmed Seabass and Seabream. European Food Safety Au-
thority. EFSA J. 7, 1010. https://doi.org/10.2903/j.efsa.2009.1010  

EFSA (2009b). Species-specific welfare aspects of the main systems of stun-
ning and killing of farmed Carp. European Food Safety Authority. EFSA J. 7, 
1013. https://doi.org/10.2903/j.efsa.2009.1013  

EFSA (2009c). Species-specific welfare aspects of the main systems of stun-
ning and killing of farmed Eels (Anguilla Anguilla). European Food Safety Au-
thority. EFSA J. 7, 1014. https://doi.org/10.2903/j.efsa.2009.1014  

EFSA (2009d). Species-specific welfare aspects of the main systems of stun-
ning and killing of farmed Atlantic Salmon. European Food Safety Authority. 
EFSA J. 7, 1011. https://doi.org/10.2903/j.efsa.2009.1011  

EFSA (2009e). Species-specific welfare aspects of the main systems of stun-
ning and killing of farmed fish: Rainbow Trout. European Food Safety Authority. 
EFSA J. 7, 1012. https://doi.org/10.2903/j.efsa.2009.1012  

EFSA (2009f). Species‐specific welfare aspects of the main systems of stunning 
and killing of farmed turbot. European Food Safety Authority. EFSA J., 7(5), 
1073. https://doi.org/10.2903/j.efsa.2009.1073 

EFSA (2013) Testing the effectiveness of stunning includes both laboratory 
tests, testing of equipment and of slaughterhouse practice https://efsa.onlineli-
brary.wiley.com/doi/pdf/ 10.2903/j.efsa.2013.3486 

EU Platform on Animal Welfare Own Initiative Group on Fish (2020). Guidelines 
on water quality and handling for the welfare of farmed vertebrate fish. Re-
trieved from https://food.ec.europa.eu/document/download/b94c2fe0-2c04-
48c9-801b-281778bc716c_en?filename=aw_platform_plat-conc_guide_farmed-
fish_en.pdf  

 
 
Eurogroup for Animals (2022). On-farm Welfare Standards in Aquaculture: An-
nex to White Paper – No animal left behind: The need for a new Kept Animals 
Regulation. Retrieved from https://www.eurogroupforanimals.org/library/farm-
welfare-standards-aquaculture  

Eurogroup for Animals (2024). Transport regulation: Due time to change the 
rules. White paper on the revision of Council Regulation (EC) 1/2005. Retrieved 
from https://www.eurogroupforanimals.org/files/eurogroupforanimals/2024-
06/2024_06_efa_MAY%20UPDATE_live%20ani-
mal%20transport%20due%20time%20to%20change%20the%20rules_white%2
0paper_eng.pdf  

European Commission (2018). Report from the Commission to the European 
Parliament and the Council on the possibility of introducing certain requirements 
regarding the protection of fish at the time of killing. Retrieved from https://eur-
lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:52018DC0087  

European Commission (2017). Welfare of farmed fish: Common practices dur-
ing transport and at slaughter. Retrieved from https://publications.europa.eu/re-
source/cellar/facddd32-cda6-11e7-a5d5-01aa75ed71a1.0001.01/DOC_1  

European Commission (2022). Communication from the Commission to the 
Council and the European Parliament a Strategy for the Sustainable Develop-
ment of European Aquaculture. Retrieved from https://eur-lex.europa.eu/LexUr-
iServ/LexUriServ.do?uri=COM:2002:0511:FIN:EN:PDF  

FAO (1989). Report of the EIFAC working party on prevention and control of 
bird predation in aquaculture and fisheries operation. Rome. 

FAO (2005). Responsible use of antibiotics in aquaculture. FAO Fisheries Tech-
nical Paper No. 469. Rome. Retrieved from 
https://www.fao.org/3/a0282e/a0282e.pdf  

FAO (2011). Better management practices for carp production in Central and 
Eastern Europe, the Caucasus, and Central Asia. Retrieved from 
https://www.fao.org/fishery/docs/DOCUMENT/aquacul-
ture/aq2010_11/root/2011/t566e.pdf  

FAWC (2014). Opinion on the Welfare of farmed fish at the Time of killing. Re-
trieved from https://assets.publishing.service.gov.uk/government/uploads/sys-
tem/uploads/attachment_data/file/319331/Opinion_on_the_wel-
fare_of_farmed_fish_at_the_time_of_killing.pdf 

Folkedal, O., Pettersen, J.M., Bracke, M.B.M., Stien, L.H., Nilsson, J., Martins, 
C., Breck, O., Midtlyng, P.J., Kristiansen, T. (2016). On-farm evaluation of the 
Salmon Welfare Index Model (SWIM 1.0): theoretical and practical considera-
tions. Anim. Welf. 25, 135–149. https://doi.org/10.7120/09627286.25.1.135  

 
 
Fraser, D. (2009). Assessing animal welfare: different philosophies, different 
scientific approaches. Zoo Biol. 28, 507–518. https://doi.org/10.1002/zoo.20253  

García-Ortega, A., & Calvario-Martínez, O. (2003). Manual de Buenas Prácticas 
de Producción Acuícola de Trucha para la Inocuidad Alimentaria (in Spanish). 
Retrieved from https://www.researchgate.net/publication/236159561_Man-
ual_de_Buenas_Practicas_de_Produccion_Acuicola_de_Trucha_para_la_Ino-
cuidad_Alimentaria  

GLOBALG.A.P (2024). Integrated Farm Assurance Smart/GFS. Principles and 
Criteria for Aquaculture – Finfish, Crustaceans, Molluscs, Seaweed. Retrieved 
from https://documents.globalgap.org/docu-
ments/240902_IFA_Smart_GFS_P_Cs_AQ_v6_0_Aug24_en.pdf  

GSA (2023). Best Aquaculture Practices Farm Standard. Retrieved from 
https://www.bapcertification.org/Downloadables/pdf/GSA%20-
%20Farm%20Standard%20-%20Issue%203.1%20-%2007-February-2023.pdf 

Gutierrez Rabadan, C., Spreadbury, C., Consuegra, S., Garcia de Leaniz, C. 
(2021). Development, validation and testing of an Operational Welfare Score In-
dex for farmed lumpfish Cyclopterus lumpus L. Aquaculture 531, 735777. 
https://doi.org/10.1016/j.aquaculture.2020.735777  

Humane Slaughter Association (2016). Humane Harvesting of fish. Retrieved 
from https://www.hsa.org.uk/downloads/publications/harvestingfishdownload-
updated-with-2016-logo.pdf 

Huntingford, F.A., Adams, C., Braithwaite, V.A., Kadri, S., Pottinger, T.G., 
Sandøe, P., Turnbull, J.F. (2006). Current issues in fish welfare. J. Fish Biol. 68, 
332–372. https://doi.org/10.1111/j.0022-1112.2006.001046.x  

Hyvärinen, P., & Rodewald, P. (2013). Enriched rearing improves survival of 
hatchery-reared Atlantic salmon smolts during migration in the River Torni-
onjoki. Canadian Journal of Fisheries and Aquatic Sciences. doi: 
https://doi.org/10.1139/cjfas-2013-0147     

ICWDM (2024). Heron Damage Prevention and Control Methods. Retrieved 
from https://icwdm.org/species/birds/herons/heron-damage-prevention-and-con-
trol-methods/  

IFA Aquaculture (2017). The farmed salmonid health handbook. Retrieved from 
https://www.fishhealth.ie/fhu/health-surveillance/aquaplan-fish-health-manage-
ment-ireland/farmed-salmonid-handbook 

Jarvis, S., Ellis, M.A., Turnbull, J.F., Rey Planellas, S., Wemelsfelder, F. (2021). 
Qualitative Behavioral Assessment in Juvenile Farmed Atlantic Salmon (Salmo 

 
 
salar): Potential for On-Farm Welfare Assessment. Front. Vet. Sci. 8, 702783. 
https://doi.org/10.3389/fvets.2021.702783  

Jones, N., Webster, M., & Salvanes, A. (2021). Physical enrichment research 
for captive fish: Time to focus on the DETAILS. Journal of Fish Biology, 99(3), 
704-725. https://doi.org/10.1111/jfb.14773  

Kalleberg, H. (1958). Observations in a stream tank of territoriality and competi-
tion in juvenile salmon and trout (Salmo salar L. and S. trutta L.). Institute of 
freshwater research. Drottningholm. Report No 39. Fishery Board of Sweden. 
Retrieved from https://www.joacimnaslund.com/hard-to-find-papers  

Kause, A., Ritola, O., Paananen, T., Wahlroos, H., & Mäntysaari, E. (2005). Ge-
netic trends in growth, sexual maturity and skeletal deformations, and rate of in-
breeding in a breeding programme for rainbow trout (Oncorynchus mykiss). Aq-
uaculture, 247, 177-187. https://doi.org/10.1016/j.aquaculture.2005.02.023  

Kestin, S.C., Robb, D.H., Van De Vis, J.W. (2002). Protocol for assessing brain 
function in fish and the effectiveness of methods used to stun and kill them. Vet. 
Rec. 150, 302–307. https://doi.org/10.1136/vr.150.10.302  

Kleiber, A., Stomp, M., Rouby, M., Ferreira, V., Bégout, M.-L., Benhaïm, D., 
Colson, V. (2023). Cognitive enrichment to increase fish welfare in aquaculture: 
A review. Aquaculture, 575, 739654. https://doi.org/10.1016/j.aquacul-
ture.2023.739654  

Kristiansen, T., Madaro, A., Stien, L., Bracke, M., & Noble, C. (2020). Theoreti-
cal basis and principles for welfare assessment of farmed fish. in: Fish Physiol-
ogy. Elsevier, pp. 193–236. https://doi.org/10.1016/bs.fp.2020.09.006 

Lieberman, D.A. (2000). Learning: Behaviour and Cognition. Wadsworth Publis-
ing Co. 

Lines, J.A. & Spence, J. (2002). Safeguarding the welfare of farmed fish at har-
vest. Fish Physiology and Biochemistry, 38, pp. 153-162. 
https://link.springer.com/article/10.1007/s10695-011-9561-5  

Maia, C.M., Saraiva, J.L., Gonçalves-de-Freitas, E. (2024). Fish welfare in 
farms: potential, knowledge gaps and other insights from the fair-fish database. 
Front. Vet. Sci. 11, 1450087. https://doi.org/10.3389/fvets.2024.1450087  

Manfrin, A. (2022). Manual for use on field Operational Welfare Indicators 
(OWIs) of Sea bass (D. labrax) and Sea bream (S. aurata) breeding in sea 
cages. AdriAquaNet project - Enhancing Innovation and Sustainability in Adri-
atic Aquaculture. Deliverable WP4, Activity 4.3.2  

 
 
Martínez, A., et al. (2025). Seasonal comparison of uniform pre-slaughter fast-
ing practices on stress response in rainbow trout (Oncorhynchus mykiss). Aqua-
culture. Retrieved from https://www.sciencedirect.com/science/arti-
cle/pii/S0044848624012122?via%3Dihub  

Marzano, M., & Carss, D. (2006). INTERCAFE Case Study report, Hula Valley, 
Israel. Retrieved from https://nora.nerc.ac.uk/id/eprint/505253/1/5.%20INTER-
CAFE%20Israel%20Case%20Study%20report.pdf  

Ministerio de Agricultura Pesca y Alimentación (MAPA) (2019). Estrategias nu-
tricionales para la mejora en el rendimiento productivo: uso de piensos funcio-
nales y dietas salud en acuicultura (DIETAplus) (in Spanish). Convocatoria 
2016. Madrid. 

Ministero della Salute. (2017). Manuale per la gestione del controllo del 
benessere dei pesci durante il trasporto su strada (in Italian). Retrieved from 
https://www.salute.gov.it/imgs/C_17_pubblicazioni_2848_allegato.pdf 

Morzel, M., Sohier, D., Van De Vis, H. (2003). Evaluation of slaughtering meth-
ods for turbot with respect to animal welfare and flesh quality. J. Sci. Food 
Agric. 83, 19–28. https://doi.org/10.1002/jsfa.1253  

Müller-Belecke, A. (2020). Neues Analyseinstrument für mehr Tierwohl in der 
Aquakultur. Die Innovationsförderung des Bundesministeriums für Ernährung 
und Landwirtschaft: Förderverfahren, Themenfelder und Beispiele aus der 
Nutztierhaltung, Broschüre der Bundes-anstalt für Ernährung und 
Landwirtschaft. 

Näslund, J., & Johnsson, J. (2016). Environmental enrichment for fish in captive 
environments: effects of physical structures and substrates. Fish and Fisheries, 
17(1), 1-30. https://doi.org/10.1111/faf.12088  

Näslund, J., Rosengren, M., Del Villar, D., Gansel, L., Norrgard, J., Persson, L., 
Kvingedal, E. (2013). Hatchery tank enrichment affects cortisol levels and shel-
ter-seeking in Atlantic salmon (Salmo salar). Canadian Journal of Fisheries and 
Aquatic Sciences. doi:https://doi.org/10.1139/cjfas-2012-0302  

Nilsson, J., Gismervik, K., Nielsen, K.V. (2022). Standardisert operasjonell 
velferdsovervåking for laks i matfiskanlegg. 

Noble, C., Cañon Jones, H.A., Damsgård, B., Flood, M.J., Midling, K.Ø., Roque, 
A., Sæther, B.-S., Cottee, S.Y. (2012). Injuries and deformities in fish: their po-
tential impacts upon aquacultural production and welfare. Fish Physiol. Bio-
chem. 38, 61–83. https://doi.org/10.1007/s10695-011-9557-1  

 
 
Noble, C., Gismervik, K., Iversen, M.H., Kolarevic, J., Nilsson, J., Stien, L.H., 
Turnbull, J.F. (Eds.). (2020). Welfare Indicators for farmed rainbow trout: tools 
for assessing fish welfare. 

Noble, C., Gismervik, K., Iversen, M.H., Kolarevic, J., Nilsson, J., Stien, L.H., 
Turnbull, J.F. (2018). Welfare indicators for farmed Atlantic salmon: Tools for 
assessing fish welfare. 

Noble, C., Iversen, M.H., Lein, I., Kolarevic, J., Johansen, L.-H., Berge, G.M., 
Burgerhout, E., Puvanendran, V., Mortensen, A., Stene, A., Espmark, Å.M., 
(2019a). An introduction to Operational and Laboratory-based Welfare Indica-
tors for lumpfish (Cyclopterus lumpus L.). RENSVEL OWI FACtsheet series. 

Noble, C., Iversen, M.H., Lein, I., Kolarevic, J., Johansen, L.-H., Burgerhout, E., 
Puvanendran, V., Kousoulaki, K., Aas, G.H., Stene, A., Espmark, Å.M. (2019b). 
An introduction to Operational and Laboratory-based Welfare Indicators for bal-
lan wrasse (Labrus bergylta), RENSVEL OWI FACtsheet series. 

North, B.P., Ellis, T., Bron, J., Knowles, T.G., Turnbull, J.F. (2008). The Use of 
Stakeholder Focus Groups to Identify Indicators for the On-Farm Assessment of 
Trout Welfare, in: Fish Welfare. John Wiley & Sons, Ltd, pp. 243–267. 
https://doi.org/10.1002/9780470697610.ch15 

Odegard, J., Baranski, B., & Gjedrem, T. (2011). Methodology for genetic evalu-
ation of disease resistance in aquaculture species: challenges and future pro-
spects. Aquaculture Research. Retrieved from  https://onlineli-
brary.wiley.com/doi/10.1111/j.1365-2109.2010.02669.x  

Pavlidis, M., Papaharisis, L., Adamek, M., Steinhagen, D., Jung-Schroers, V., 
Kristiansen, T., Otero, F. (2023). Research for PECH Committe - Animal welfare 
of farmed fish. Brussels: European Parliament, Policy Department for Structural 
and Cohesion Policies. Brussels, Belgium. 

Pavlidis, M., Samaras, A. (2020). Mediterranean Fish Welfare: Guide to Good 
Practices and Assessment Indicators. 

Pavlidis, M., Samaras, A., Papaharisis, L. (2024). Welfare assessment study for 
European sea bass: A scientific approach towards improvement of welfare sta-
tus and welfare assessment of on-growing European sea bass (Dicentrarchus 
labrax). https://doi.org/10.26248/4V5N-7V19  

Pedrazzani, A.S., Quintiliano, M.H., Bolfe, F., Sans, E.C.D.O., Molento, C.F.M. 
(2020). Tilapia On-Farm Welfare Assessment Protocol for Semi-intensive Pro-
duction Systems. Front. Vet. Sci. 7, 606388. 
https://doi.org/10.3389/fvets.2020.606388  

 
 
Pettersen, J.M., Bracke, M.B.M., Midtlyng, P.J., Folkedal, O., Stien, L.H., Stef-
fenak, H., Kristiansen, T.S. (2014). Salmon welfare index model 2.0: an ex-
tended model for overall welfare assessment of caged Atlantic salmon, based 
on a review of selected welfare indicators and intended for fish health profes-
sionals. Rev. Aquac. 6, 162–179. https://doi.org/10.1111/raq.12039  

Reiser, S., Teitge, F., Klase, K., Lugert, V., Steinhagen, D. (2024a). Farming, 
transport, and slaughter rainbow trout: survey guidelines., Consortium of the 
National Animal Welfare Monitoring (NaTiMon) project. 

Reiser, S., Teitge, F., Steinhagen, D., Lugert, V. (2024b). Farming, transport, 
and slaughter common carp: survey guidelines, Consortium of the National Ani-
mal Welfare Monitoring (NaTiMon) project. 

Roque, A., Castanheira, M.F., Toffan, A., Arechavala-Lopez, P., Brun, E., Villa-
rroel, M., Gisbert, E., Mylonas, C., Muniesa, A., Estevez, A., Dalmau, A., Ba-
surco, B. (2020). Report on fish welfare and list of operational welfare indicators 
in sea bream. MedAID. 

RSPCA (2020). Welfare standards for farmed rainbow trout. Retrieved from 
https://science.rspca.org.uk/documents/1494935/9042554/RSPCA+Trout+Wel-
fare+Standards+2020.pdf/3f74881f-577b-d4bb-22f0-
a9792a298db6?t=1618819287216  

RSPCA (2024). RSPCA welfare standards for farmed Atlantic salmon. Re-
trieved from https://science.rspca.org.uk/documents/d/science/rspca_wel-
fare_standards_for_farmed_atlantic_salmon  

Salvanes, A., Moberg, O., Ebbesson, L., Nilsen, T., Jensen, K., & Braithwaite, 
V. (2013). Environmental enrichment promotes neural plasticity and cognitive 
ability in fish. Proceedings of the Royal Society B. Biological Sciences. 
doi:10.1098/rspb.2013.1331  

Sánchez-Vázquez, F., López-Olmeda, J., Vera, L., Migaud, H., López-Patiño, 
M., & Míguez, J. (2019). Environmental cycles, melatonin, and circadian control 
of stress response in fish. Front Endocrinol. doi: 
https://doi.org/10.3389/fendo.2019.00279    

Sánchez-Vázquez, F.J., López-Olmeda, J.F., Vera, L.M. (2019). Fish welfare 
and biological rhythms: time to regulate. dA. Derecho Animal (Forum of Animal 
Law Studies) 10/4. doi: https://doi.org/10.5565/rev/da.461  

Saraiva, J., Arechavala-López, P., Cabrera-Álvarez, M., & Waley, D. (2021). 
Research for ANIT Committe - Particular welfare needs in animal transport: 
aquatic animals, European Parliament, Policy Department for Structural and 
Cohesion Policies. Brussels. Retrieved from https://www.europarl.eu-
ropa.eu/RegData/etudes/STUD/2021/690875/IPOL_STU(2021)690875_EN.pdf 

 
 
Saraiva, J.L., Arechavala-Lopez, P., Castanheira, M.F., Volstorf, J., Heinzpeter 
Studer, B. (2019). A Global Assessment of Welfare in Farmed Fishes: The 
FishEthoBase. Fishes 4, 30. https://doi.org/10.3390/fishes4020030  

Saraiva, J.L., Volstorf, J., Cabrera-Álvarez, M.J., Arechavala-Lopez, P. (2022). 
Using ethology to improve farmed fish welfare and production. (Report pro-
duced for the AAC). Aquaculture Advisory Council. 

 Saraiva, J., Brijs, J., Cabrera-Álvarez, M. J., Arechavala-Lopez, P., & Gräns, A. 
(2024). Blueprint for research to detect loss of consciousness and/or sensibility 
of fish at slaughter. Zenodo. https://doi.org/10.5281/zenodo.15592691 
(EURCAW-Aqua) 

Saura, M. (2021). Estimates of recent and historical effective population size in 
turbot, seabream, seabass, and carp selective breeding programmes. Genetics 
Election Evolution, 53-58. doi: https://doi.org/10.1186/s12711-021-00680-9   

Scottish Salmon Producers Organisation (2015). Scottish Salmon Farming. 
Code of Good Practice. Retrieved from https://thecodeofgoodpractice.co.uk/  

Skjermo, J., Salvessen, I., Oie, G., Olsen, Y., & Vadstein, O. (1997). Microbially 
matured water: a technique for selection of a non-opportunistic bacterial flora in 
water that may improve performance of marine larvae. Aquaculture 
International. doi: 10.1007/BF02764784 

Spezzani, C., Manfrin, A., Franzago, E., Dall Pozza, M., Mordenti, O., 
Roncarati, A., Fabris, A., Ruffo, G., Petochi, T. (2025). Welfare manual for 
farmed fish species: operator´s guide. 94 pp. (In Italian). 

Stien, L.H., Bracke, M., Noble, C., Kristiansen, T.S. (2020). Assessing Fish Wel-
fare in Aquaculture, in: Kristiansen, T.S., Fernö, A., Pavlidis, M.A., van de Vis, 
H. (Eds.), The Welfare of Fish, Animal Welfare. Springer International Publish-
ing, Cham, pp. 303–321. https://doi.org/10.1007/978-3-030-41675-1_13  

Stien, L.H., Bracke, M.B., Folkedal, O., Nilsson, J., Oppedal, F., Torgersen, T., 
Kittilsen, S., Midtlyng, P.J., Vindas, M.A., Øverli, Ø., others. (2013). Salmon 
Welfare Index Model (SWIM 1.0): a semantic model for overall welfare assess-
ment of caged Atlantic salmon: review of the selected welfare indicators and 
model presentation. Rev. Aquac. 5, 33–57. 

Stien, L.H., Nilsson, J., Noble, C., Izquierdo-Gomez, D., Ytteborg, E., Timmer-
haus, G., Madaro, A. (2024). Evaluating a crowding intensity scale and welfare 
indicators for Atlantic salmon in sea cages. Aquac. Rep. 37, 102211. 
https://doi.org/10.1016/j.aqrep.2024.102211  

Strauch, S. (2023). Light plays an important role in fish development. EU-
ROFISH Magazine. 

 
 
Subasinghe, R., Alday-Sanz, V., Bondad-Reantaso, M., Jie, H., Shinn, A., & 
Sorgeloos, P. (2023). Biosecurity: Reducing the burden of disease. World Aqua-
culture Society. doi: https://doi.org/10.1111/jwas.12966   

Sun, B., Van Dissel, D., Mo, I., Boysen, P., Haslene-Hox, H., & Lund, H. (2022). 
Identification of novel biomarkers of inflammation in Atlantic salmon (Salmo 
salar L.) by plasma proteomic approach. Dev. Comp. Immunol. doi: 
10.1016/j.dci.2021.104268 

Toni, M., Manciocco, A., Angiulli, E., Alleva, E., Cioni, C., Malavasi, S. (2019). 
Review: Assessing fish welfare in research and aquaculture, with a focus on 
European directives. Animal 13, 161–170. 
https://doi.org/10.1017/S1751731118000940  

Tschirren, L., Bachmann, D., Güler, A.C., Blaser, O., Rhyner, N., Seitz, A., 
Zbinden, E., Wahli, T., Segner, H., Refardt, D. (2021). MyFishCheck: A Model 
to Assess Fish Welfare in Aquaculture. Animals 11, 145. 
https://doi.org/10.3390/ani11010145  

UNE. (2016). UNE 173300:2016. Piscicultura. Guía de prácticas correctas para 
el sacrificio (in Spanish). Retrieved from https://www.une.org/encuentra-tu-
norma/busca-tu-norma/norma?c=N0057508 

Van de Vis, H., et al. (2003). Is humane slaughter of fish for industry?. Aquacul-
ture Research. https://onlinelibrary.wiley.com/doi/abs/10.1046/j.1365-
2109.2003.00804.x  

Van de Vis, J.W., Poelman, M., Lambooij, E., Bégout, M.-L., Pilarczyk, M. 
(2012). Fish welfare assurance system: initial steps to set up an effective tool to 
safeguard and monitor farmed fish welfare at a company level. Fish Physiol. 
Biochem. 38, 243–257. https://doi.org/10.1007/s10695-011-9596-7  

Wedekind, H., Harrer, D., Geiser, M., & Kraus, G. (2020). Praktische und 
rechtliche Aspekte beim Transport lebender Fische (in German). LfL. Retrieved 
from https://www.lfl.bayern.de/mam/cms07/publikationen/daten/informatio-
nen/praktische-rechtliche-aspekte-transport-lebende-fische_lfl-information.pdf 

Weirup, L., Schulz, C., Seibel, H. (2022). Fish welfare evaluation index (fWEI) 
based on external morphological damage for rainbow trout (Oncorhynchus 
mykiss) in flow through systems. Aquaculture 556, 738270. 
https://doi.org/10.1016/j.aquaculture.2022.738270  

WOAH (2012). Welfare of farmed fish during transport. In WOAH, Aquatic Ani-
mal Health Code. Retrieved from https://www.woah.org/en/what-we-do/stand-
ards/codes-and-manuals/aquatic-code-online-ac-
cess/?id=169&L=1&htmfile=chapitre_welfare_transport_farm_fish.htm  

 
 
WOAH (2015). Welfare aspects of stunning and killing of farmed fish for human 
consumption. In Aquatic Animal Health Code. Retrieved from 
https://www.woah.org/fileadmin/Home/eng/Health_standards/aahc/2010/chapi-
tre_welfare_stunning_killing.pdf 

WOAH (2024). Killing of farmed fish for disease control purposes. In Aquatic 
Animal Health Code. Retrieved from chrome-extension://efaidnbmnnnibpcaj-
pcglclefindmkaj/https://www.woah.org/fileadmin/Home/eng/Internationa_Stand-
ard_Setting/docs/pdf/chapitre_1.7.4.pdf  

Yildiz, H.Y., Chatzifotis, S., Anastasiadis, P., Parisi, G., Papandroulakis, N., 
2021. Testing of the Salmon Welfare Index Model (SWIM 1.0) as a computa-
tional welfare assessment for sea-caged European sea bass. Ital. J. Anim. Sci. 
20, 1423–1430. https://doi.org/10.1080/1828051X.2021.1961106 

Zhang, Z., Lin, W., Yunqi, L., Yuan, X., & et, a. (2023). Physical enrichment for 
improving welfare in fish aquaculture and fitness of stocking fish: A review of 
fundamentals, mechanisms and applications. Aquaculture 574, 739651. 
doi:https://doi.org/10.1016/j.aquaculture.2023.739651 

Zhu, Y., & Takemura, A. (2024). Development of aquaculture technology based 
on the potential synergistic effects of light wavelength and salinity on the Mala-
bar grouper (Epinephelus malabaricus) growth physiology (Sessions on Light 
and aquatic animals at AQUA 2024). 

Zhulay, I., Reiss, K., & Reiss, H. (2015). Effects of aquaculture fallowing on the 
recovery of macrofauna communities. Marine Pollution Bulletin, 97, 1-2. 
doi:DOI:10.1016/j.marpolbul.2015.05.064 

 
 
 
 
7. 

Annexes 

7.1. 

Annex 1 – Methodology 

This document has been prepared based on:  

●  The document on “Good husbandry practices for aquaculture” (24) devel-
oped by the EU AAM in 2024. It provides a non-exhaustive list of general 
and species-specific GHPs on key topics related to welfare and health in the 
different production techniques of some European aquaculture species. An-
nex 2 of that document describes the methodology used to select the GHPs 
and prepare the factsheets.  

●  The work of the EU AAM on fish welfare good practices and indicators. 

This work aimed to i) complement the above-mentioned GHP document by 
identifying general fish welfare good practices and indicators at all stages of 
fish life cycle, and considering different production systems, ii) produce fact-
sheets that include examples from different EU and non-EU countries. To 
provide relevant and updated information on the key topics addressed in this 
document the following data collection activities have been undertaken:  

o  Desk research and scientific literature review to analyse how fish 
welfare practices are performed and which indicators and assess-
ment protocols are used in EU MS, Norway, and UK. The main 
sources of information that have been consulted are: 

■ 

International organisations (e.g. FAO, EFSA, WOAH). 

■  Standards and codes from EU, UK, Norway. 

■  European producer’s associations guidance documents and 

handbooks. 

■  NGO’s standards. 

o  An online survey targeting EU MS, Norway, and the UK, as well as 
the AAC members through this organisation, the West MED Assis-
tance Mechanism, and the fish expert group from the European Part-
nership on Animal Health and Welfare (EUPAHW), was launched to 

(24) https://aquaculture.ec.europa.eu/key-documents/good-husbandry-practices  

 
 
 
 
identify good practices and indicators related to fish welfare. The sur-
vey run from October 22nd, 2024 to December 6th, 2024. A total of 36 
responses have been received from 21 MS, Norway, and UK. 

●  An expert consultation through a cluster meeting with representatives of 

relevant EU-funded projects (see Annex 2) and 13 experts from the Board of 
Ambassadors (BoA) (25) of the AAM. The key objectives of this meeting were 
to: i) present and discuss the preliminary list of fish welfare good practices, 
and ii) discuss the work on fish welfare indicators.  

●  This document has been reviewed by the European Commission’s Direc-

torate-General for Health and Food Safety (DG SANTE) and a group of ex-
perts from the EURCAW-Aqua prior to its final publication. 

●  The draft Code was distributed among the Member States and the AAC to 
gather their feedback and observations. Comments were received from Ire-
land and the AAC, and have been incorporated throughout the document.  

(25) Expert consultation group created ad-hoc by the EU AAM composed of 21 independent ex-

perts from all over Europe. 

 
 
 
 
 
 
 
7.2. 

Annex 2 – References to relevant EU-funded 
projects 

AQUAEXCEL 3.0 (AQUAculture infrastructures for EXELience in European 
fish): https://aquaexcel.eu/ 

AquaIMPACT (Genomic and Nutritional Innovations for Genetically Superior 
Farmed Fish): https://projects.luke.fi/aquaimpact/  

Cure4Aqua (Curing EU aquaculture by co-creating health and welfare innova-
tions): https://cure4aqua-project.eu/team/consortium/  

DIGIRAS (Optimizing land-based fish production in next generation digital recir-
culating): https://bluebioeconomy.eu/optimizing-land-based-fish-production-in-
next-generation-digital-recirculating/ 

EATFISH (European Aquaculture Training for improving Seafood Husbandry): 
https://eatfish-msc.com/ 

EUPAHW (European Partnership on Animal Health and Welfare): 
https://www.eupahw.eu/index.html 

FISHWELL(26) (Fish welfare knowledge synthesis for farmed salmon and rain-
bow trout) 

iFishIENCi (Intelligent Fish feeding) https://ifishienci.eu/ 

IGNITION (Improving green innovation for the blue revolution): https://ignition-
project.eu/the-project/  

MedAID (Mediterranean Aquaculture Integrated Development): 
http://www.medaid-h2020.eu/ 

PerformFISH (Integrating Innovative Approaches for Competitive and Sustaina-
ble Performance across the Mediterranean Aquaculture Value Chain): 
https://performfish.eu/  

SAFE (SmartAqua4FutureE): https://projectsafe.eu/  

SmartAqua4FuturE (Reducing the environmental impact of freshwater aquacul-
ture by applying circular economy approaches): https://projectsafe.eu/  

(26) Norwegian Seafood Research Fund (FHF) financed project. 

 
 
 
 
Getting in touch with the EU 

In person 

All over the EU there are hundreds of Europe Direct centres. You can find the 
address of the centre nearest you online (european-union.europa.eu/contact-
eu/meet-us_en). 

On the phone or in writing 

Europe Direct is a service that answers your questions about the EU. You can 
contact this service: 

–  by freephone: 00 800 6 7 8 9 10 11 (certain operators may charge for 

these calls), 

–  at the following standard number: +32 22999696, 
–  via the following form: european-union.europa.eu/contact-eu/write-us_en. 

Finding information about the EU 

Online 

Information about the EU in all the official languages of the EU is available on 
the Europa website (european-union.europa.eu). 

EU publications 

You can view or order EU publications at op.europa.eu/en/publications. Multi-
ple copies of free publications can be obtained by contacting Europe Direct or 
your local documentation centre (european-union.europa.eu/contact-eu/meet-
us_en). 

EU law and related documents 

For access to legal information from the EU, including all EU law since 1951 
in all the official language versions, go to EUR-Lex (eur-lex.europa.eu). 

EU open data 

The portal data.europa.eu provides access to open datasets from the EU in-
stitutions, bodies, and agencies. These can be downloaded and reused for 
free, for both commercial and non-commercial purposes. The portal also pro-
vides access to a wealth of datasets from European countries. 

 
 
Written by Pablo Manuel Xandri Royo, Tiziana Pacchiarini, Mayra Llorente Manzanares (NTT Data), David Bassett 
(EATIP) and Pablo Arechavala López (IMEDEA-CSIC) on behalf of the EU Aquaculture Assistance Mechanism 
October 2025