Current issues in fish welfare

TLDR: This paper focuses on welfare as the absence of suffering in fish, arguing that complex animals with sophisticated behaviour, such as fish, probably have the capacity for suffer ing, though this may be different in degree and kind from the human experience of this state.

Abstract: Human beings may affect the welfare of fish through fisheries, aquaculture and a number of other activities. There is no agreement on just how to we igh the concern for welfare of fish against the hum an interests involved, but ethical frameworks exist th at suggest how this might be approached. Different definitions of animal welfare focus on an animal's condition, on its subjective experience o f that condition and/or on whether it can lead a natu ral life. These provide different, legitimate, pers pectives, but the approach taken in this paper is to focus on welfare as the absence of suffering. An unresolved and controversial issue in discussion s about animal welfare is whether non-human animals exposed to adverse experiences such as physical injury or confinement experience what humans would call suffering. The neocortex, which in huma ns is an important part of the neural mechanism tha t generates the subjective experience of suffering, i s lacking in fish and non-mammalian animals, and it has been argued that its absence in fish indicates that fish cannot suffer. However, a strong alternative view is that complex animals with sophisticated behaviour, such as fish, probably have the capacity for suffer ing, though this may be different in degree and kind fro m the human experience of this state. Recent empirical studies support this view and show that painful stimuli are, at least, strongly avers ive to fish. Consequently, injury or experience of othe r harmful conditions is a cause for concern in term s of welfare of individual fish. There is also growing e vidence that fish can experience fear-like states a nd that they avoid situations in which they have experience d adverse conditions.

Figures

Table 3. Possible easily-measured indices of welfare and examples of their use. We list only those based on direct observations of fish rather than the systems in which they are held.

Table 5. Examples of scientific studies of the impact of various aspects of aquaculture on fish welfare.

Table 1. Some human activities that could potentially compromise fish welfare

Table 2. Natural threats to the welfare of wild fish

Table 4. Examples of scientific studies of the impact of various aspects of angling on fish welfare.

Table 6. Examples of scientific studies of the impact of various aspects of ornamental fish keeping on fish welfare.

Full text

university of copenhagen
Current issues in fish welfare
review paper
Huntingford, F.A.; Adams, C.; Braithwaite, V.A.; Kadri, S.; Pottinger, T.G.; Sandøe, Peter;
Turnbull, J.F.
Published in:
Journal of Fish Biology
DOI:
10.1111/j.0022-1112.2006.001046.x
Publication date:
2006
Document version
Publisher's PDF, also known as Version of record
Citation for published version (APA):
Huntingford, F. A., Adams, C., Braithwaite, V. A., Kadri, S., Pottinger, T. G., Sandøe, P., & Turnbull, J. F. (2006).
Current issues in fish welfare: review paper. Journal of Fish Biology, 68(2), 332-372.
https://doi.org/10.1111/j.0022-1112.2006.001046.x
Download date: 10. Aug. 2022

Danish Centre for Bioethics and Risk Assessment
This is a post-print version of an article published in
Journal of Fish Biology by Wiley-Blackwell
For more articles on animal ethics, see www.animalethics.net
Review paper: Current issues in fish welfare
1
F. Huntingford*, C. Adams*, V. A. Braithwaite+, S. Kadri*, T. G. Pottinger++, P. Sandøe** & J. F.
Turnbull***
*Fish Biology Group, Institute of Biomedical & Life Sciences, Graham Kerr Building, University of
Glasgow, Glasgow, G12 8QQ, UK. +Institute of Evolutionary Biology, University of Edinburgh, Kings
Buildings, Edinburgh. EH9 3JT ++ NERC Centre for Ecology & Hydrology, Lancaster Environment Centre,
Library Avenue, Bailrigg, Lancaster, LA1 4AP ** Centre for Bioethics and Risk Assessment, Royal
Veterinary and Agricultural University, Copenhagen ***Institute of Aquaculture, University of Stirling,
Stirling, FK9 4LA
Abstract
Human beings may affect the welfare of fish through fisheries, aquaculture and a number of other
activities. There is no agreement on just how to weigh the concern for welfare of fish against the human
interests involved, but ethical frameworks exist that suggest how this might be approached.
Different definitions of animal welfare focus on an animal’s condition, on its subjective experience of
that condition and/or on whether it can lead a natural life. These provide different, legitimate, perspectives,
but the approach taken in this paper is to focus on welfare as the absence of suffering.
An unresolved and controversial issue in discussions about animal welfare is whether non-human
animals exposed to adverse experiences such as physical injury or confinement experience what humans
would call suffering. The neocortex, which in humans is an important part of the neural mechanism that
generates the subjective experience of suffering, is lacking in fish and non-mammalian animals, and it has
been argued that its absence in fish indicates that fish cannot suffer. However, a strong alternative view is
that complex animals with sophisticated behaviour, such as fish, probably have the capacity for suffering,
though this may be different in degree and kind from the human experience of this state.
Recent empirical studies support this view and show that painful stimuli are, at least, strongly aversive
to fish. Consequently, injury or experience of other harmful conditions is a cause for concern in terms of
welfare of individual fish. There is also growing evidence that fish can experience fear-like states and that
they avoid situations in which they have experienced adverse conditions.
1
The reference of the printed version is:
Felicity Huntingford, Colin Adams, Victoria A. Braithwaite, Sunil Kadri, Tom G. Pottinger, Peter Sandøe & James F.
Turnbull. (2006): Review paper: Current issues in fish welfare. Journal of Fish Biology 68: 332-372.
The definitive version is available at
http://onlinelibrary.wiley.com/doi/10.1111/j.0022-1112.2006.001046.x/abstract

Danish Centre for Bioethics and Risk Assessment
This is a post-print version of an article published in
Journal of Fish Biology by Wiley-Blackwell
For more articles on animal ethics, see www.animalethics.net
Human activities that potentially compromise fish welfare include anthropogenic changes to the
environment, commercial fisheries, recreational angling, aquaculture, ornamental fish keeping and scientific
research. The resulting harm to fish welfare is a cost that must be minimised and weighed against the
benefits of the activity concerned.
Wild fish naturally experience a variety of adverse conditions, from attack by predators or conspecifics
to starvation or exposure to poor environmental conditions. This does not make it acceptable for humans to
impose such conditions on fish, but it does suggest that fish will have mechanisms to cope with these
conditions and reminds us that pain responses are in some cases adaptive (for example, suppressing feeding
when injured).
In common with all vertebrates, fish respond to environmental challenges with a series of adaptive
neuro-endocrine adjustments that are collectively termed the stress response. These in turn induce reversible
metabolic and behavioural changes that make the fish better able to overcome or avoid the challenge and
are undoubtedly beneficial, in the short-term at least.
In contrast, prolonged activation of the stress response is damaging and leads to immuno-suppression,
reduced growth and reproductive dysfunction. Indicators associated with the response to chronic stress
(physiological endpoints, disease status and behaviour) provide a potential source of information on the
welfare status of a fish. The most reliable assessment of well-being will be obtained by examining a range
of informative measures and statistical techniques are available that enable several such measures to be
combined objectively.
A growing body of evidence tells us that many human activities can harm fish welfare, but that the
effects depend on the species and life history stage concerned and are also context-dependent. For example,
in aquaculture, adverse effects related to stocking density may be eliminated if good water quality is
maintained. At low densities, bad water quality may be less likely to arise whereas social interactions may
cause greater welfare problems.
A number of key differences between fish and birds and mammals have important implications for their
welfare. Fish do not need to fuel a high body temperature, so the effects of food deprivation on welfare are
not so marked. For species that live naturally in large shoals, low rather than high densities may be
harmful. On the other hand, fish are in intimate contact with their environment through the huge surface
area of their gills, so they are vulnerable to poor water quality and water borne pollutants.
Extrapolation between taxa is dangerous and general frameworks for ensuring welfare in other
vertebrate animals need to be modified before they can be usefully applied to fish.
The scientific study of fish welfare is at an early stage compared with work on other vertebrates and
a great deal of what we need to know is yet to be discovered. However, it is clearly the case that fish,
though different from birds and mammals, are sophisticated animals, far removed from unfeeling
creatures with a 15 second memory of popular misconception. A heightened appreciation of these points

Danish Centre for Bioethics and Risk Assessment
This is a post-print version of an article published in
Journal of Fish Biology by Wiley-Blackwell
For more articles on animal ethics, see www.animalethics.net
in those who exploit fish and in those who seek to protect them would go a long way towards improving
fish welfare.
Key words: Fish, welfare, stress, pain, fisheries, aquaculture, ornamental fish.
Introduction
The aim of this review, which arose from a briefing paper prepared for the Fisheries Society of the British
Isles (http://www.le.ac.uk/biology/fsbi/briefing.html), is to give a broad overview of current understanding
on a number of issues relating to fish welfare, an area of increasing public concern. The term “fish” includes
animals of very different taxonomic status and in this review we mostly consider teleost fish, since these
have been the subject of almost all recent research into fish welfare. A broad approach necessarily precludes
in-depth, exhaustive coverage of all the relevant issues, but many of these issues have been the subject of
recent published reviews and we cite these in the relevant sections. We briefly address what welfare means,
why it matters and how welfare science relates to the philosophical discipline of ethics, before considering
human activities that may compromise fish welfare and how welfare might be measured. We concentrate on
the impact of human activity on welfare at the level of individuals, as opposed to populations, species or
ecosystems and address the experiences of living animals (up to and including the point of slaughter) and not
the question of whether it is right to kill animals.
To discuss animal welfare objectively, we need a definition and this is not easy to produce because the
concept is complex and the word is used in a number of different ways (Dawkins, 1998; Appleby, 1999).
Most definitions fall into one of three broad categories (Duncan & Fraser, 1997; Fraser et al., 1997), none of
which is right or wrong from a scientific point of view; rather they express different ideals about what we
should be concerned about in our dealings with animals:
Feelings-based definitions are set in terms of subjective mental states. Here, the requirement for good
welfare is that the animal should feel well, being free from negative experiences such as pain or fear and
having access to positive experiences, such as companionship in the case of social species. This use of the
term welfare obviously depends on the animal concerned having conscious subjective experiences and our
ability to interpret such experiences, controversial points (Dawkins, 1998) that are discussed below.
Function-based definitions centre on an animal’s ability to adapt to its present environment. Here good
welfare requires that the animal be in good health with its biological systems (and particularly those involved

Danish Centre for Bioethics and Risk Assessment
This is a post-print version of an article published in
Journal of Fish Biology by Wiley-Blackwell
For more articles on animal ethics, see www.animalethics.net
in coping with challenges to stasis) functioning appropriately and not being forced to respond beyond their
capacity. This definition is based on things that are relatively easy to observe and measure.
Nature-based definitions arise from the view that each species of animal has an inherent biological nature
that it must express. Here good welfare requires that the animal is able to lead a natural life and express its
natural behaviour. This approach, which reflects a view that what is natural, is inherently good, focuses on
something we can measure, namely what animals do in the wild and in captivity.
Because suffering, health problems and impairment of natural behaviour often accompany each other, in
many cases these three approaches will reach the same conclusions. Chickens (Gallus domesticus) are
strongly motivated to build nests (as opposed to having access to a completed nest) and will work hard for
the opportunity to build (Hughes et al., 1989); arguably then, nest-building reflects a behavioural need that
must be met if the chicken’s welfare is not to be compromised. However, in some cases different
conclusions about whether welfare is compromised will follow from the different definitions. For example,
much behaviour of wild animals is shown in response to adverse conditions (as when fleeing from a
predator), but it is hard to argue that feelings of suffering will occur if these responses are not evoked. In
other cases, animals may be highly motivated to perform an action independent of its consequences. Their
welfare may be compromised if they are deprived of the opportunity to do so, but this is not necessarily the
case and it may be difficult to decide whether the different approaches lead to the same conclusion. For
example, wild Atlantic salmon (Salmo salar) migrate long distances at sea. If this happens because fish leave
an area when the local food supply is poor and stop swimming when they find food, there is no reason to
believe that farmed salmon will be frustrated when they are prevented from migrating, provided they have
plenty of food. If they are simply motivated to swim, then swimming in large circles may be sufficient to
avoid such frustration. On the other hand, if they have an instinctive drive to move to new areas regardless of
food supply, confinement in cages might well lead to suffering, even though fish are able to swim
continuously.
It is, therefore, important to state clearly what definition of animal welfare is being used (Appleby & Sandøe,
2002). In this article, we adopt a feelings-based approach that focuses on animal suffering that is on more-or-
less intense unpleasant mental or physical states felt by the animal. One important complicating factor is that
the occurrence of unpleasant states does not by itself imply suffering. Such states are an unavoidable part of
normal animal life and often serve as signals or behavioural prompts that help the animals satisfy their
biological needs. Sometimes, negative experiences are compensated for by corresponding positive
experiences, so suffering may be defined as prolonged experience of unpleasant mental states.

Frequently asked questions

Q1. What future works have the authors mentioned in the paper "Review paper: current issues in fish welfare" ?

In this document a pragmatic working position has been taken on a number of important questions ( whether fish suffer and whether this matters, for example ), recognising that this position may have to be changed in the light of facts that emerge in the future. 

Q2. What contributions have the authors mentioned in the paper "Review paper: current issues in fish welfare" ?

These provide different, legitimate, perspectives, but the approach taken in this paper is to focus on welfare as the absence of suffering. This is a post-print version of an article published in Journal of Fish Biology by Wiley-Blackwell Indicators associated with the response to chronic stress ( physiological endpoints, disease status and behaviour ) provide a potential source of information on the welfare status of a fish. This is a post-print version of an article published in Journal of Fish Biology by Wiley-Blackwell Net Human activities that potentially compromise fish welfare include anthropogenic changes to the environment, commercial fisheries, recreational angling, aquaculture, ornamental fish keeping and scientific research. This does not make it acceptable for humans to impose such conditions on fish, but it does suggest that fish will have mechanisms to cope with these conditions and reminds us that pain responses are in some cases adaptive ( for example, suppressing feeding when injured ). 

Q3. What are the critical aspects of the environment for fish welfare?

Since fish are in intimate contact with their environment through the huge surface of their gills, water quality (in terms of dissolved oxygen, ammonia and pH) and the presence of contaminants (organic and inorganic pollutants) are probably the most critical aspects of the environment for fish welfare and also the best defined. 

Q4. How many larvae of the common Japanese goby die before obtaining their first food?

At least 50% of larvae of the common Japanese goby Rhinogobius brunneus die through starvation prior to obtaining their first food (Iguchi & Mizuno, 1999). 

Q5. Why have behavioural deficits been used to identify conditions that compromise welfare?

since animals may suffer if prevented from performing their full behavioural repertoire, behavioural deficits have been used to identify conditions that compromise welfare (Mench & Mason, 1997). 

Q6. What is the definition of an interest in utilitarian writings?

In utilitarian writings the notion of an interest is usually defined in terms of “the capacity for suffering and/or enjoyment or happiness” (Singer, 1989). 

Q7. What is the ideal of meaningful and transparent discussion leading to mutual understanding?

The ideal of meaningful and transparent discussion leading to mutual understanding is attainable, however, because people’s gut feelings about matters are very often based on underlying ethical assumptions and theories, which are more susceptible to rational assessment than the individual beliefs to which they give rise. 

Q8. What is the effect of food deprivation on fish welfare?

Wild fish show marked changes in appetite (some temperature-based and others depending on life history events) that determine the effect of food deprivation on welfare. 

Q9. What is the first problem of being led by one’s feelings rather than approaching matters through ethical?

The first problem of being led by one’s feelings rather than approaching matters through ethical theory is simply that people’s feelings about animal use are often unstable or ambivalent and so cannot be relied upon as a rational guide. 

Q10. What is the role of the behavioural and physiological mechanisms in salmonid fish?

Recent work with salmonid fish has shown that the integrated behavioural and physiological mechanisms that comprise the distinct “coping strategies” believed to be present in mammals (Koolhaas et al., 1999; Wingfield, 2003; Huntingford & Adams, 2005) are also evident in fish, with heritable reactive and proactive traits demonstrated in rainbow trout (Øverli et al., 2005). 

Q11. What does Narveson mean by the lack of standing of animals in the moral community?

The lack of standing of animals in the moral community does not necessarily mean that the way animals are treated is irrelevant from the contractarian point of view: if people like animals, for example, and dislike the practice of their being used in this or that way, animal use can become an ethical issue, because it is in a person’s interests to get what he or she likes. 

Q12. What is the common cause of poor welfare in fish?

Where this is not the case, for example, in brood stock or in ornamental fish, because chronic stress impairs reproductive function, failure of adult fish to breed or to display normal patterns of reproductive development when feed, light and temperature regimes are appropriate is a possible sign of poor welfare. 

Q13. What is the potential for using the full range of available indicators for fish welfare?

The potential for using the full range of available indicators will vary with the context in which fish welfare is to be assessed; fish farmers may have to rely on a few signs, but people keeping ornamental fish are well placed to use many of them, on all their fish.