Science-based assessment of welfare: Aquatic animals

Abstract

Terrestrial animal welfare has been a matter for exploration for many years. In contrast, approaches towards improving the welfare and humane treatment of aquatic animals are relatively new, as is the thinking behind them. Several issues complicate the process of addressing the welfare of aquatic animals in a consistent manner. These include the following: - the huge diversity among aquatic animals, the majority of which are poikilothermic vertebrates and invertebrates - understanding the practices involved in fisheries, aquaculture and aquatic animal production, and their purpose - the relative paucity of scientific information - understanding the philosophical approaches, policies, guidance and regulations that may influence the provision of optimal welfare and humane practices for aquatic animals. In this paper, the authors attempt to provide an overview of all these elements, relating what is known and understood about these issues for the primary group used in aquaculture and fisheries, finfish, and exploring the factors that may influence the concepts and practices of aquatic animal welfare. These factors seem to be the foundation of all welfare approaches and include: - ethical and moral concepts of animal welfare and humane treatment - whether animals experience suffering from the potentially adverse practices used in their maintenance, management and use - the public and institutional understandings of these issues and their results. These are discussed with the hope that future developments in, and approaches to, aquatic animal welfare will be of use to society, industries and the public.

Full text

Rev. sci. tech. Off. int. Epiz.
, 2005, 24 (2), 529-547
Science-based assessment of welfare: aquatic
animals
T. Håstein
(1)
, A.D. Scarfe
(2)
& V.L. Lund
(1)
(1) National Veterinary Institute, P.O. Box 8156 Dep., N-0033 Oslo, Norway
(2) American Veterinary Medical Association, 1931 North Meacham Road, Schaumburg, Illinois, United
States of America
Summary
Terrestrial animal welfare has been a matter for exploration for many years. In
contrast, approaches towards improving the welfare and humane treatment of
aquatic animals are relatively new, as is the thinking behind them. Several issues
complicate the process of addressing the welfare of aquatic animals in a
consistent manner. These include the following:
–
the huge diversity among aquatic animals, the majority of which are
poikilothermic vertebrates and invertebrates
–
understanding the practices involved in fisheries, aquaculture and aquatic
animal production, and their purpose
–
the relative paucity of scientific information
–
understanding the philosophical approaches, policies, guidance and
regulations that may influence the provision of optimal welfare and humane
practices for aquatic animals.
In this paper, the authors attempt to provide an overview of all these elements,
relating what is known and understood about these issues for the primary group
used in aquaculture and fisheries, finfish, and exploring the factors that may
influence the concepts and practices of aquatic animal welfare. These factors
seem to be the foundation of all welfare approaches and include:
–
ethical and moral concepts of animal welfare and humane treatment
–
whether animals experience suffering from the potentially adverse practices
used in their maintenance, management and use
–
the public and institutional understandings of these issues and their results.
These are discussed with the hope that future developments in, and approaches
to, aquatic animal welfare will be of use to society, industries and the public.
Keywords
Aquaculture – Aquatic animal – Cephalopod – Crustacean – Decapod – Ethics – Finfish
– Harvest fishery – Humane practice – Ornamental – Welfare.
Introduction
Animal welfare deals with the humane treatment of
animals. Addressing the welfare or well-being of aquatic
animals is possibly one of the more complex and
challenging tasks for science, as this involves several
factors unique to aquatic animals. In contrast to terrestrial
production animals, aquatic animals encompass extremely
diverse, divergent and distantly related taxonomic groups,
of greatly varied phylogenetic ages and linkages. They
range from highly developed marine mammals to lower
invertebrates, all with very different anatomies,
physiologies and behaviour. For example, the evolutionary
history of finfish stretches back over 450 million years (96)
and more than 28,500 species currently exist (52).
Invertebrate groups have even greater evolutionary age,
adaptations and diversity. These animals are used in a
number of different ways and for a variety of reasons,
including food and other commodities, exhibition,
recreation, research, etc.

Furthermore, there is a relative dearth of scientific
information for evaluating and addressing the optimal
humane care and welfare of most aquatic animal species.
The majority of documented information refers to finfish
(41). This scarcity also applies to the ethical theory on
which aquatic animal welfare can be founded. Unlike those
approaches dealing with mammals and birds, aquatic
animal welfare is in its infancy.
In general, aquatic animal welfare involves philosophical
and ethical interpretations of humane practices. Public
understanding of these issues also influences humane
treatment of aquatic animals, and the resulting opinions or
policies expressed by many organisations. Sentience, that
is, the conscious awareness of the animal to favourable or
adverse conditions, is usually considered a precondition
for animal welfare concerns and is thus an important
question. The principles of animal welfare have emerged
primarily in terrestrial animals, many of which have similar
anatomies, physiologies and behaviours (which are often
also shared by humans). Most animal welfare principles are
based on the assumptions that these similarities indicate
that animals are sentient (i.e. are cognisant and feel
comfort and discomfort), and that it is unethical to
purposefully, or through neglect, inflict or allow animals to
experience discomfort. However, with the exception of
marine mammals (which will not be dealt with here),
aquatic animals are poikilothermic (cold-blooded)
vertebrates or invertebrates and their physiology is likely to
result in different levels of sentience.
One practical problem for science is how to deal with the
large numbers of individuals handled in aquaculture, as
the welfare of the individual animal must be protected and
monitored.
The development of approaches to aquatic animal welfare
issues is likely to be influenced by many factors. These
include the following:
– ethical and moral philosophical concepts and principles
which relate to the humane treatment of all animals
– scientific evidence that animals are capable of perceiving
and responding to human intervention and practices (i.e.
sentience)
– public understanding of these factors and perceptions of
human-animal interactions and sub-optimal husbandry
practices
– opinions expressed through the policies adopted by
governmental and non-governmental organisations, which
may result in legislative and regulatory decisions or
guidance.
These influences and constraints, along with a limited
number of publications dealing with animal welfare,
restrict an extensive discussion on all aquatic animal
species and welfare issues. This paper will therefore
attempt to provide an overview of the principles of animal
welfare that may apply to poikilothermic aquatic animals,
with an emphasis on finfish. Where applicable, the authors
will also refer to decapods. This discussion will focus on
the scientific evidence for the ability of aquatic animals to
perceive, process and respond to positive or negative
conditions imposed by human intervention. Such evidence
is usually considered fundamental in developing
approaches to optimise animal welfare and humane
treatment. The authors will also attempt to relate these
approaches to the current predominant practices used in
aquaculture, harvest, capture and wild fisheries.
Aquaculture, harvest and
capture fisheries
The greatest number of human-aquatic animal interactions
fall principally into three broad categories:
– aquaculture fisheries
– harvest fisheries
– capture fisheries.
Aquaculture and harvest fisheries primarily involve using
animals for food and these industries rival or exceed
terrestrial animal agricultural production (Fig. 1).
However, captured aquatic animals may be cultured or
farmed and later consumed, and aquatic animals are also
captured or bred for exhibition and other reasons, such as
recreation and sport. Finfish, crustaceans and molluscs
constitute the predominant species harvested from the
wild or cultured (101). It is the largest group, finfish, that
will be the primary topic here. Many aquatic animals are
also used as companion animals or ‘pets’ (ornamentals) in
private and public displays, and in research. Although few
species are truly ‘domesticated’, they have been managed
or cultivated for many millennia (14).
The capture, breeding and care of aquatic animals has a
long tradition in society. Aquaculture is defined here as the
purposeful culture, farming or management of aquatic
animal populations for the benefit of humans or the
environment.
This definition includes the following:
– private and public, commercial and non-commercial
systems which have been specifically constructed (e.g.
tanks, ponds, etc.) to house aquatic animals
– impounded natural areas (e.g. net-pens, cages, etc.) of
readily motile animals (e.g. finfish)
– areas of naturally occurring habitats of sessile animals
(e.g. oyster and clam beds or reefs).
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It also includes hatcheries that release large numbers of fish
for restocking purposes and animals held for exhibition. In
all aquaculture, optimal survival, growth and maximal
fecundity are the primary objectives. Optimising the
conditions that meet these objectives is the primary reason
for improving the welfare of the animals.
Commercial harvest fisheries rely on capturing wild
animals primarily for food. Some of these stocks may have
been produced through aquaculture and subsequently
released to the wild. Non-commercial fishing or angling is
typically for personal food consumption and occurs
frequently throughout the world to sustain families or local
communities.
Many wild populations are managed through harvest or
catch limitations, usually imposed by government
regulation, to maintain ecologically stable or sustainable
populations (46). In all other ways, however, wild aquatic
animals are subject to the variable conditions of the
environment with no human control over their welfare
except humane treatment during their harvest and
processing.
Today, the production and trade of ornamentals is a large
and continuously developing industry (60, 61, 92), with a
very high monetary value (31). Traditionally, these aquatic
animals are captured from the wild and kept in home
aquaria or large public displays; however, the propagation
and culture of these animals over many generations is
increasing rapidly. In some countries, the popularity of
ornamentals as companion animals in homes rivals the
numbers of traditional ‘pets’ (3, 5). To satisfy welfare issues
in the ornamental fish trade, as in aquaculture, wholesalers
and aquarists must have sufficient knowledge of the basic
needs of these fish for water quality, feeding, genetics and
disease management.
Aquatic animals: their
cognisance and perception of
conditions affecting their
welfare
Applying the principles of ethics and animal welfare to
poikilothermic aquatic animals involves supplying the
things necessary for sustaining life, optimising health and
minimising visible discomfort (e.g. pain, stress and fear).
Evidence demonstrating that these animals have
sufficiently high cognitive ability to be fully aware of their
surroundings and the conditions that affect them (8) is
pivotal to animal welfare. However, the mechanisms for
providing such evidence are still highly controversial, even
in humans (9).
This higher level of cognition, frequently referred to as
‘sentience’ (27, 28) and typically attributed to the
neocortical functions in mammals, must result in conscious
awareness (including perception, memory, judgement and
possibly emotional responses to conditions), not merely
reflex actions to internal or external stimuli. Evidence on
cognitive abilities is therefore most frequently inferred from
neuro- and endocrine physiology findings, and as expressed
through behaviour. However, an objective scientific
assessment requires avoidance of anthropomorphic logic –
i.e. attributing human characteristics and emotions to
animals without a sound scientific basis.
Much of the information on the ability of finfish to
consciously perceive, experience and respond to conditions
and situations comes from their neuroanatomy and
neurophysiology, particularly the neocortex. There is no
doubt that the central nervous systems (CNS) of mammals
and poikilothermic vertebrates and invertebrates are very
different (Figs 2 and 3). However, higher-level cognitive
ability cannot be inferred from neuroanatomy alone.
It has been suggested that the supraoesophageal ganglion
of crustaceans (17) and the cerebral ganglion of molluscs
function as ‘brains’ to co-ordinate and integrate somato-
sensory and motor functions. Nevertheless, there appears
to be no information linking these organs to true cognitive
abilities. Indeed, some authors (30) suggest that this lack
of neural complexity indicates that invertebrates cannot be
cognisant of noxious stimuli and, therefore, are unable to
experience pain, fear or suffering.
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56 Mmt; 12.9%
58 Mmt; 13.3%
56 Mmt; 12.6%
150 Mmt; 34.2%
21 Mmt; 4.8%
8 Mmt; 1.7%
90 Mmt; 20.4%
Aquaculture
Poultry
Beef/veal
Pork
Lamb/mutton
Other terrestrial
animals
Harvest fisheries
Fig. 1
Current estimated global production from aquaculture and
harvest fisheries (primarily finfish, crustacea and molluscs), in
comparison to terrestrial animal agriculture commodities
Quantities shown in millions of metric tons (mmt) of protein
Sources: Bruinsma (24), FAO (47, 48, 49) and Rana (101)

While this belief may be justified for most mollusc groups,
cephalopods (octopuses, squid, etc.) have the most
complex and well-organised brains of all invertebrates.
Their CNS are well developed and include giant axons.
Furthermore, their eyes are the most complex of all
invertebrate eyes (140). They can solve maze puzzles and
remember the solutions, they have complex behaviour
patterns and they appear to show strong emotions that are
signalled by profound changes in colour. In many respects,
cephalopods appear to exhibit the higher-level cognisance
necessary to suggest they may be sentient. Boyle (20)
suggested that, ‘the neural and behavioural complexity of
the cephalopods is similar to that of the lower vertebrates,
and it is felt that their needs and welfare merit similar
consideration’. However, evidence for cephalopod
sentience is equivocal for, as stated by Williamson and
Chrachri (140), ‘there is surprisingly little known about
the operation of the neural networks that underlie the
sophisticated range of behaviour these animals display’. In
addition, Sømme (121), in a comprehensive review of
invertebrate sentience, concludes that, while it is unlikely
that most invertebrates are sentient, and, ‘although
octopuses have a high level of cognition and great ability to
learn, it is not definitely known if they can experience pain’
(one criterion thought to indicate sentience).
There is continuous debate (7, 107) on whether finfish are
sufficiently cognisant of noxious stimuli (119, 120) to
perceive these as pain or fear and thus experience
emotional responses akin to suffering. Southgate and Wall
(122) and others (119, 120) demonstrated that fish have
nociceptors (receptors capable of sensing noxious stimuli).
Many also suggest that, because A-delta and C fibres are
present in the trigeminal and afferent somato-sensory
neural pathways, similar to those found in mammals, fish
may have some ability for a certain level of cognitive neural
processing. It is also suggested that A-delta and C fibres
present in the peripheral nerves simply modulate pain
(71). Furthermore, substance P, which is implicated in pain
transmission in mammals, has been found in the
hypothalamus and forebrain of fish (74). However, Rose
(107) argues that nociceptive-based behaviour of fish can
occur in the absence of pain, and that these behaviours are
not dissimilar to the adaptive reflex behaviour of all
animals, including protozoans which simply avoid noxious
stimuli. The discussions of Chandroo et al. (27, 28)
complicate this still further. Using information from other
studies, Chandroo et al. speculate that fish may have
neuro-functional similarities to other animals that suggest
sentience and an appropriate level of cognisance, which
may indicate that fish are capable of suffering. However,
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A: mammal
B: teleost (trout)
C: crustacean (lobster)
D: mollusc (snail)
Fig. 2
Comparative complexity of the central nervous systems of the primary aquatic animals used in aquaculture and harvest fisheries, in
comparison to that of a mammal
Sources: A and B from Rose (107), C and D from Sømme (121)
A
Cerebrum
Diencephalon
Brainstem
Supraoesophageal
ganglion
Cerebral ganglion
Pleural ganglion
Visceral nerve cords
Pedal ganglion
Supra-intestinal
ganglion
Visceral ganglion
Suboesophageal
ganglion
Thoracic
ganglia (5)
Abdominal
ganglia (6)
Circumoesophageal
B CD

evidence for the cognitive ability of fish to interpret
noxious stimuli as pain or discomfort is equivocal and
subjective (21, 108), and must undergo rigorous
examination. Similarly, as no neurological or other
evidence is available concerning the higher-level cognitive
abilities of lower invertebrates, such as crustaceans and
molluscs, that would identify them as being sentient (121,
140), more in-depth research is also needed in this area.
Nevertheless, as has been suggested by Cawley (26) and
others, and eloquently articulated by Rose (108), ‘the
improbability that fish can experience pain in no way
diminishes our responsibility for concerns about their
welfare. Fish are capable of robust, unconscious,
behavioural, physiological and hormonal responses to
stressors, which if sufficiently intense or sustained, can be
detrimental to their health’.
Applying the principles of ethics
and welfare to poikilothermic
animals
The philosophical and ethical principles that apply to the
well-being of all animals are fundamental to the
development and application of welfare standards for
aquatic animals. Ideally, they should underlie the policies,
guidance and regulations established by both
governmental and non-governmental bodies.
Animal welfare science is emerging as a research field in its
own right (82). It explores how animals are affected by their
environment, and qualitatively and quantitatively assesses
conditions imposed on them that may affect their welfare.
The concept of animal welfare also has an ethical dimension
(50, 127), which deals with the underlying values involved
in the relationship between humans and animals. Animal
ethics asks whether humans have any moral responsibilities
towards animals and, if so, what the quantity and quality of
animal welfare practices provided by humans should be.
This approach requires some brief remarks.
A basic question is whether animals deserve any welfare
considerations at all. This is a central issue in relation to
poikilothermic aquatic animals. Concerns about animal
welfare are very often based on the belief that it is wrong to
inflict pain or suffering on other sentient beings (117).
From this point of view, the welfare of poikilothermic
animals must be considered only if they are sentient.
Hence, the question as to whether they can experience
mental states is crucial. However, it is a matter of debate
whether the existence of a subjective state such as animal
suffering can actually be proven by science (70, 87).
Philosophers have also articulated arguments on grounds
other than that of suffering, offering further reasons for
handling poikilothermic animals humanely. One such
ground is that animals, when domesticated, become part of
the ‘moral community’. That is, they become included
among those to whom humans have a special
responsibility (83). This view also makes it relevant to
consider the welfare of farmed fish.
A third argument for considering animal welfare can be
found in the proposed Norwegian animal welfare
ordinance. This ordinance, which includes aquatic
animals, states that animals have intrinsic value and,
therefore, should be handled with ‘care and respect for the
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OB
OB
MM
CB
CB
CC
C
C
MB
CB
CB
MB MB
MB
Electric ray Goldfish Trout Lungfish
C : cerebral hemisphere
CB : cerebellum
M : medulla
MB : midbrain (the optic tectum is the only midbrain structure visible
in this dorsal view)
OB : olfactory bulb
Structural specialisations are most pronounced in the brainstem, which
consists of the medulla, cerebellum and midbrain. The elasmobranches,
represented by the ray
Raja clavata
, have a large electromotor nucleus
on the dorsal surface of the medulla (shown by the upper arrow
pointing to the medulla). Among the more highly evolved teleosts
(bony fishes), brain anatomy varies according to dominant sensory
systems. For example, the goldfish
(Carassius auratus)
has a large
vagal lobe (upper arrow pointing to the medulla), due to its extensively
developed chemosensory system for taste, while the rainbow trout
(Oncorhynchus mykiss)
has a relatively large optic tectum of the
midbrain, due to its visual specialisation, and the South American
lungfish
(Neoceradotus forsteri)
, regarded as an unspecialised species,
has a slender brain lacking structural exaggerations
Fig. 3
Comparative anatomy of the brain of four diverse finfish types,
illustrating both the basic similarity of brain structural
organisation and striking differences related to predominant
sensory functions, making comparison of neurosensory and
cognitive abilities difficult
From Rose (107)

animals’ distinctive character’ (90). Furthermore, many
aspects of this thinking, specifically related to aquaculture,
are articulated in the Holmenkollen Guidelines (125),
which suggest that ethical principles ensuring the health
and welfare of fish, including humane slaughter, should
govern the industry. While the concept of intrinsic value
has been applied within the policies and legislation of
several countries, and is often referred to in the public
debate about higher animals, it is still the subject of much
philosophical debate (36), and may also be less intuitively
appealing when applied to lower animals, such as
poikilothermic animals.
In a world of limited resources, one crucial question is how
much welfare it is reasonable to provide. It may be difficult
or very costly to avoid all of the negative consequences of
aquaculture for animal welfare. Often, it is argued that
these consequences must be accepted to provide people
with food. In ethics, such dilemmas are often dealt with by
arguing that different interests or rights can be weighed
against each other. Thus, an infringement upon the
interests of animals may be accepted if humans have strong
reasons for it. Production of the food necessary for human
sustenance may qualify as a reason for certain
infringements. Which compromises are morally acceptable
depends on the philosophy being applied (113). For
example, fishing for subsistence might be acceptable, while
angling, including ‘catch and release’, may not be.
Although there is general agreement that animal welfare
concerns the quality of life for the animal (112), there has
been considerable debate among scientists and
philosophers about how this concept should be
understood in practice. The following three general
approaches have emerged:
– one approach focuses on the feelings of the animal, such
as pain, pleasure or suffering (33, 37)
– another approach considers welfare as being of a
sufficient standard when the biological systems of the
animal are functioning satisfactorily and it can cope with
its environment (23)
– the third approach defines welfare as being dependent
on the ability of the animal to express natural behaviour
and live a natural life according to its genetically encoded
nature (106).
Although there is considerable overlap among these
definitions, this is to be expected in an ethical discussion
of what constitutes a good life for the animal. As in most
philosophical approaches, there is no absolute ‘right’ or
‘wrong’ answer. What is important is to be explicit about
the choice of definition. The ‘Five Freedoms’ of Brambell
(22), in the World Organisation for Animal Health (OIE)
principles of animal welfare (91), can be seen as a complex
approach which tries to combine all three of the above
approaches, with the emphasis on biological functioning.
However, there has been little discussion of how to
understand the concept of welfare in relation to aquatic
poikilothermic animals.
The definition of animal welfare is important because it
determines how welfare should be measured and what
indicators should be used. For example, if feelings are
considered essential for defining welfare, methods for
registering and quantifying pain and discomfort must be
developed, whereas choosing biological functioning as a
criterion of welfare may only require health and
production records to reveal welfare status.
A major difficulty when trying to develop welfare
standards for aquatic animals is how to understand and
quantify the concept of ‘a good life’ for animals which are
so different that any analogies with any human
understanding of welfare seem to have little relevance.
However, Fraser et al. (51) described two types of welfare
problems in animal production:
a) challenges for which animals lack adaptations
b) adaptations that no longer serve an important function.
Welfare problems are reduced when the discrepancy
between the adaptations of an animal and its
environmental conditions is as small as possible. This
approach may possibly form the foundation for welfare
guidelines in aquaculture systems, until more sophisticated
knowledge on aquatic animal needs has been gained.
Current conditions and practices
in aquatic animal production
The conditions experienced by aquatic animals used in
aquaculture and harvest fisheries, and those captured for
ornamental or display purposes, which are relevant to their
welfare are outlined below. Many have been previously
addressed by Håstein (62) and others, and the examples
mentioned are intended only to briefly illustrate some
issues of possible importance to welfare. These include the
following:
a) environmental conditions, such as water quality
b) predominant industry practices, including:
– stocking densities
– handling, grading and tagging individuals
– nutrition
– genetic selection and modification
– occurrence of and responses to diseases
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– capture techniques
– trade in ornamental fish
– transportation and shipping
– methods of slaughter and euthanasia, with an emphasis
on finfish.
Conditions and practices that may indicate physiological,
behavioural or other stresses are also emphasised, as in
Conte (30). These may be useful as indicators or indices
for assessing and evaluating optimal or sub-optimal animal
health and welfare. However, it should be emphasised that
all of these elements probably interact in complex ways, as
indicated in Figure 4, and that the overall stressors
affecting the health and welfare of aquatic animals are
multifactorial.
Environmental and water conditions
Aquatic species are physiologically well adapted to specific
ecological niches, defined by the physical, chemical and
biological parameters of the water in which they normally
live, with preference and tolerance limits for temperature,
salinity, pH, dissolved oxygen, organic and inorganic
substances, light, etc. Conditions outside the optimal
preference or tolerance ranges may result in stress, distress,
impaired health and mortality, all of which are often
associated with the intensive rearing conditions that cause
poor water quality (130, 136). The deterioration of water
quality is directly proportional to biomass and animal
metabolism, with the resulting oxygen, carbon dioxide and
nitrogenous waste levels, and water volume or turnover.
Thus, careful observation of animal behaviour and water
quality is required to maintain optimal conditions for
health and welfare.
Chronic stress from poor water quality may result in loss of
homeostasis, reduced growth and reduced disease
resistance (89). Reduced water circulation may induce
aggression, heterogeneous growth and increased
susceptibility to disease (122, 136). Photoperiodicity and
artificial light, used to increase production and observe the
animals, often result in a reduced feed uptake in Atlantic
salmon (Salmo salar) during the first 6 to 12 weeks after
the lighting change, suggesting stress. Power failure and
sudden transitions from light to dark may induce stress
responses, panic reactions and mortality (85). The position
of the lighting influences swimming depth and fish density,
and darkness may result in crowding, sub-optimal oxygen
levels and fin erosion (72).
Stocking density and social stress
Stocking density affects productivity and economic
returns, and excess density beyond a biological optimum
may negatively affect health and welfare. However, this
area is complex and depends on many interrelated factors
(40), the mechanisms of which are only partly understood
and appear to be species-specific.
Behaviour and water quality are important elements in this
specificity. Bottom-dwelling species, such as halibut
(Hippoglossus hippoglossus) and turbot (Psetta maxima),
require a larger surface area but lower volume, whereas, for
pelagic schooling species like cod (Gadus morhua), volume
is important. High stocking densities are known to reduce
Production
Physiological stress
Health
Stocking density
Production system
Life cycle stage
Genetics
Water quality Behaviour
Fig. 4
Factors influencing the appropriate stocking density of fish in cages and tanks

growth and increase stress levels (77, 134). Skin or fin
damage may occur from aggression or abrasion, resulting
in possible infections and disease. High stocking rates may
constrain swimming behaviour (16), feed intake and the
ability to digest food (40). In some species, such as
rainbow trout (Oncorhynchus mykiss) and African catfish
(Clarias gariepinus), low densities encourage territoriality.
In intensive systems that use cages or tanks without acute
corners, high feed levels and higher densities induce
schooling behaviour (13, 64) and decreased aggression.
Understanding such behaviour is therefore important in
developing fish farming systems and equipment. Tank
colour should mimic the natural environment of the
species. For example, in species adapted to dark
surroundings, bright colours will induce stress, associated
with a higher risk of predation.
Handling, grading and tagging
Handling during grading, tagging and other maintenance or
management operations usually requires concentrating and
removing animals from the water, and escape attempts,
struggling and other behaviours suggest acute stress. The
degree of stress is dependent on the life stage (fry or adult) of
the animal, handler skill and equipment, and, for many
routine tasks, automated equipment has been designed for
rapid and minimal handling of animals. Many of these
routine tasks are necessary for optimal production and
animal health and welfare, but have disadvantages. For
example, in hatcheries rearing salmon and other species,
cannibalism is common if fish are not graded by size;
however, handling during grading is not only stressful but
may cause skin damage (6). Stressful handling of the female
may increase fry mortality and deformities and reduce
growth. Tagging to identify individuals is becoming more
important for a variety of reasons, including health and
disease surveillance, and several methods are used, including
fin clipping, a variety of different metal or plastic external
and internal tags, and thermal branding. Internal tags require
minor abdominal surgery and external tags, which penetrate
the skin, may result in chronic wounds and secondary
infections. External tags may also physically disrupt
swimming and other behaviours.
Feeding and nutrition
Farmed fish rely heavily on rations that are specifically
formulated and include omega fatty acids, usually from
fish meal. Nutritionally imbalanced feeds or food not
natural to the species may result in malnutrition and
nutritional deficiencies. Phosphorus deficiency results in
scoliosis and other skeletal deformities (11) and rancid
feed may cause fatty liver syndrome and liver
degeneration. Immune systems are often impaired before
malnutrition affects growth (135). Using dry feed at low
temperatures may result in ‘water belly’ (ascites) and
mortality, as the fish are unable to maintain fluid and
electrolytic balance.
Improper feeding routines and technology may induce
stress and aggression. Starvation and/or reduced feeding
are occasionally used to reduce growth to adjust to market
demands and improve flesh quality (39). While the welfare
aspects of stress from reduced feeding have not been fully
investigated, aggression increases among fish that are fed
sub-optimally and some fish show behavioural
abnormalities (‘eye snapping’ or ‘bum eye disease’). Tail
biting, cannibalism and physical fin or eye damage may
occur (59).
Genetics
Genetic selection and improvement of farmed fish have
mostly focused on improving production, including:
– growth rate
– feed conversion rates
– flesh quality
– genetic disease resistance
– fecundity.
Genetic manipulation has been conducted on a wide
variety of aquatic species for production purposes,
including the development of transgenics (2), for sex
reversal, and polyploids, which result in sexual sterility
and increased growth rates. High reproductive capacity,
short generation times and high survival of offspring in
hatcheries have allowed rapid selection of phenotypes and
genotypes. For example, over four generations of breeding,
the feed conversion in farmed salmon increased by 80%,
when compared to that of wild salmon (56), due mainly to
higher feed intake and better feed use (129). It is not
known if these changes will challenge the biological limits
of the animals, become stressors and consequently cause
welfare concerns, but selective breeding has been shown to
have positive welfare effects. Selective breeding of
Norwegian Atlantic salmon and rainbow trout has
produced less-aggressive, less-excitable fish, which are
better adapted to artificial rearing conditions and handling.
Selection has also produced fish that are resistant to several
diseases, including the following:
– vibriosis (57, 102)
– furunculosis (58)
– infectious salmon anaemia (102)
– infectious pancreatic necrosis (T. Åsmundstad, personal
communication)
– sea lice infestation (75)
– Saprolegnia toxicity (88).
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The effects of genetic engineering on welfare depend on
the genes which are modified. There is some concern
about unforeseen phenotypic consequences (109),
including cranial, jaw and opercular deformities in
transgenic coho salmon (Oncorhynchus kisutch) (35) and
carp (Cyprinus carpio) (29, 38), that affect feeding and
respiration. Altered allometry in transgenic coho salmon
results in reduced swimming ability (44, 80, 93) and some
behavioural changes have also been reported (1, 34).
Disease problems related to farming
Intensive farming conditions may physiologically stress
fish, increasing their susceptibility to disease (122, 124),
and a close relationship has been observed between
husbandry practices and disease incidence (116). Diseases
associated with aquacultural production include skeletal or
soft tissue malformations, eye lesions, etc. (10, 19, 25, 42,
76, 98, 100), and increases in the number of such
deformities suggest sub-optimal conditions (11) that may
affect the welfare of the animals. The so-called ‘gaping jaws’
syndrome, an abnormality caused by infection during
development, is a common problem in cultured halibut
larvae (86). It causes the fish to be unable to close their
jaws adequately and feed properly, and can also result in
head abrasions with additional secondary infections of
bacteria and fungi (86).
Cardiac anomalies, including total or partial lack of septum
transversum, hypoplasia and situs invertus, have been
reported in farmed Atlantic salmon (73, 97, 98), leading to
reductions in size and tolerance to stress, and heart failure.
Cataracts causing blindness are reported to be an increasing
problem (19, 137, 139), some of which may result from
organophosphate treatment or ultraviolet light (78).
While the use of vaccines for treating bacterial disease is
increasing (63), and effectively reducing infectious disease,
adjuvants may cause local inflammatory responses and
granulomas. Intra-abdominal vaccination may result in
peritoneal adhesions and other side effects, such as growth
retardation and spinal deformities (18). In some cases (e.g.
Atlantic salmon), severe vaccination-related reactions are
reduced when fish weigh at least 70 grams and the water
temperature is 10°C or below. Ultimately, the goal is to
develop vaccinations which produce good immunity with
few side effects (84).
Treatment against parasites such as sea lice in salmonids is
important as infestation can lead to scale loss and skin
lesions that cause osmotic disturbances. Damage to the
head may be so severe that the skull bones are exposed – a
condition referred to by Lymbery (79) as ‘death crown’.
Using ballan wrasse (Labrus bergylta) to control lice
infestations may also involve welfare considerations in
regard to the biological needs of the wrasse (131).
Capture fisheries
The history of fishing for wild fish is about as long as the
history of humankind. In recent years, questions have been
raised regarding aquatic animal welfare and human-animal
interactions. The question of whether fishing for pleasure
through ‘catch and release’ is ethically acceptable has also
been raised. For welfare purposes, the use of wild fish can
be divided into two categories, as follows:
– fish caught to be killed
– fish caught to be kept alive for further rearing.
Traditional commercial fisheries and ‘put-and-take’ fishing
(angling on private farms for a fee, based on what is
caught) come into the first category, while capture-based
aquaculture and catch-and-release fishing belong to
the second.
When fish are caught to be killed, the aim from a welfare
point of view must be to kill the animals as quickly and
painlessly as possible. Depending on the method of
capture, the process of killing and exsanguination may take
from a few minutes to 24 hours or more.
In commercial ‘Danish seining’ (also known as ‘Scottish
seining’ and Japanese ‘bull-trawling’), which uses trawls,
purse seines and hooks, death may typically take one hour
(trawls), from one to four hours (seines), and from four to
six hours (hooks), depending on the species, while nets
may take up to 24 hours (I. Huse, personal
communication, 2004).
At present, there is no knowledge to judge whether
crowding, choking or hooking is the most painful
procedure for the fish. Although welfare issues should be
considered, even for capture fisheries, it will take time and
probably political incentives to introduce alternative
catching methods.
Capture-based aquaculture, in which young fish are caught
and reared in pens or enclosures, is an old tradition for
several fish species, such as cod, eel (Anguilla anguilla),
groupers (Serranidae), tuna (Thunnus spp.) and yellowtail
(Seriola quinqueradiata) (68). However, it has been shown
that the catching methods used involve stress, as well as
external and internal lesions in the fish and subsequent
mortality (67, 126). It is clear that some equipment,
particularly nets, causes mortality due to choking because
of impaired gill movement. Mortality figures are usually
lower when fish pots or hooks are used, but the latter do
wound the fish. The use of trawls and Danish seining, in
which the fish are heavily concentrated as the nets are
hauled in, results in squeezing, choking and gill irritation
from particles adhering to the gills. When cod are captured
at depths of 15 metres to 30 metres or more, nearly 100%
of the swim bladder of the animal will rupture from
Rev. sci. tech. Off. int. Epiz.,
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pressure de-compensation and possible eversion of the
peritoneum in the vent region (68). The lesions are
normally reported to heal within one week and the fish will
start feeding within four weeks (68). However, in some
fish, gas may be trapped in the abdominal cavity when they
surface and these fish will subsequently die, unless a
needle is used to drain the gas. Exophthalmia from
pressure de-compensation has also been reported.
Danish seining is recognised today as the method of choice
for capture-based cod aquaculture, while trawling is
recognised as unsuitable from a welfare point of view. In
trawling, studies have shown that, even though the fishing
gear used does not cause mortality, discarded fish may die
later due to behavioural impairment, resulting in increased
predation (32, 110).
Although the fish in ‘put-and-take’ fisheries are killed
quickly and humanely, immediately after capture, the
practice has welfare implications. Catch-and-release
fishing has become increasingly common in many
countries in recent years, not only for sport but also as a
tool to reduce the pressure on fish stocks in rivers with
small and vulnerable local populations. Being caught
probably inevitably results in stress and pain, suggested by
the production of lactic acid and increased cortisol levels.
Although a high proportion of fish may survive, high
mortalities are occasionally reported. Factors such as
temperature, catch-and-release time and handling methods
are important to the survival rate. In some countries, catch-
and-release fishing is prohibited since it is not considered
to fulfil animal welfare criteria.
Factors affecting welfare in ornamental fish
Breeding and caring for ornamental aquarium fish has a
long tradition and these days the production and trade in
ornamentals is a rapidly developing sector. With
industrial-scale production of ornamentals, welfare issues
related to breeding, transportation and killing for disposal
are of concern. It is reported that, in some cases, less than
50% of bred fish survive the first six months, while wild
captured ornamentals may suffer losses as high as 75%
between capture and retail sale (99). To satisfy welfare
issues in the ornamental fish trade, wholesalers and
aquarists must have sufficient knowledge on the basic
needs of these fish with regard to water quality, feeding,
genetics and disease management. The attention given to
welfare in the ornamental fish industry must be similar to
that given in aquaculture.
Transportation of fish
Transportation routines for live fish depend on the reason for
shipping, size of consignment and species to be transported.
For restocking purposes, buckets and/or sealed plastic bags
with excess oxygen are used. Sealed bags are also the most
common method for compartmentalising ornamental fish,
traded over long distances.
Lorries or well boats are the most common way of
transporting fish from hatcheries or nurseries to grow-out
farms. The type of vehicle used depends on whether the
fish are bound for sea-water cage-culture or inland
pond-farming.
Containers for transporting fish must be designed to
eliminate harm to the fish during transportation. Adverse
conditions during movement, such as overcrowding or
unacceptable water quality due to low oxygen, may result
in irreparable damage to the fish and mortality.
Transportation of coho salmon yearlings by truck has been
reported to cause a marked physiological stress response
and reduced relative fitness, as well as a lower survival rate
and reduced ability to tolerate any additional stressing
agent (69, 114, 123). Conditioning has been shown to
improve the ability of juvenile chinook salmon
(Oncorhynchus tshawytscha) to withstand transportation
stress (115). Mortalities in large captive broodstock of
milkfish (Chanos chanos) can be minimised if the fish are
transported and handled in sealed oxygenated bags with
chilled sea water (53). Sedation combined with a recovery
period appears to lessen the stress burden associated with
hauling and transport (111).
Slaughter and euthanasia
As in terrestrial animal production, aquatic animals are
purposefully killed for two main reasons:
– for animal or human food
– to control or eradicate devastating diseases in both wild
(managed and unmanaged) and farmed populations.
Secondary purposeful human activities, such as sport
fishing, may result in the death of animals. However, sport
fishing frequently combines this recreation value with
harvesting animals for human consumption, or the control
of animals unsuitable for consumption.
The term ‘slaughter’ will be used for terminating an animal
life for immediate human consumption or use, as with
terrestrial animals, whereas ‘euthanasia’ is applied to
animals that are humanely killed but not consumed. Many
of the principles underlying euthanasia are outlined in the
American Veterinary Medical Association (AVMA) Report
of the AVMA Panel on Euthanasia (4). However, many of
the recommended methods for finfish are mainly
applicable to ornamental or research animals.
To ensure ethical slaughter, acceptable methods of killing
should be in place. However, since there are differences
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538

between species, establishing universal methods is difficult.
While carp and eel are tolerant to hypoxia, salmonid fish are
sensitive in this respect. Thus, the oxygen level in the
holding units must be optimal for the particular species.
Various methods are used to slaughter fish (103) and there
is no doubt that many of them can be considered totally
unsatisfactory from an animal welfare point of view.
Exsanguination without stunning causes aversion reactions
in fish (106).
Whatever method is used for sedation, it is important that
the personnel at the slaughterhouses are skilled and
dedicated to their work, to reduce the levels of stress and
avoid external and/or internal traumatic lesions to the
animals during the slaughter process.
Slaughter for consumption
According to the Humane Slaughter Association (66),
millions of fish are reared for food on a global basis and these
must be slaughtered in such a way that unnecessary pain and
suffering are avoided. Any handling before the slaughtering
process involves an increase in the level of stress to the
animal, such as the handling stress that occurs when fish are
transferred from the transporting vehicle (well boat, lorry,
etc.) to the holding units where they are to be kept until
slaughter.
Starvation before slaughter to empty the gut is considered
acceptable from a welfare point of view. The starvation
period should, however, be as short as possible (122). The
maximum starvation period for salmonids is normally one to
three days, depending on water temperature (122, 138).
Handling and crowding can occur in the holding units before
the fish are brailed (netted) or pumped into the killing
facility. Rough handling during such procedures leads to
additional stress in the fish and is an important welfare
concern. The cortisol level of roughly handled fish may reach
700 nanograms per litre. Such rough handling may also lead
to abrasions and mortality (138). It has been suggested that
it is optimal if fish do not spend more than 15 seconds out
of the water, whatever handling methods are used (122).
The guiding principle for optimal slaughter is to avoid
unnecessary stress and pain to the animal during
the slaughtering process. Thus, sedation should cause
instantaneous unconsciousness lasting until death (133).
Methods that only gradually result in unconsciousness may
be allowed if the method does not, in itself, cause pain or
stress (55).
In commercial fish slaughter, several methods have been
used for sedation, as follows:
– employing CO
2
– cooling the animal down to 0°C, using ice slurry alone
or in combination with CO
2
– stunning by a blow to the head
– automated percussive stunning
– electro-shocking, using the same principles as electro-
fishing gear
– using approved chemicals.
All sedation methods should be followed by
exsanguination.
Suffocating fish in air or crushed ice before exsanguination
and slaughter may take as long as 15 minutes before trout,
for example, become unconscious (79). Using crushed ice,
it is possible to calm the fish and keep it alive for several
hours until osmoregulatory problems and exhaustion
occur. Pre-chilling fish before slaughter has been shown to
be a minor stressor, compared to handling and crowding
prior to slaughter, but a low chilling temperature may
provoke ‘water belly’ (ascites), especially in rainbow trout,
due to inadequate osmoregulation (118). Asphyxiation in
air or chilled water is a common method for killing fish
and is highly stressful (12, 103). Such methods have thus
been deemed unacceptable from an animal welfare point of
view (43).
Interestingly, Parisi et al. (94) found that ice water is the
preferred method for killing edible-portion-sized sea bass
(Dicentrarchus labrax) (of about 250 grams to 300 grams),
for which individual killing is not feasible.
Sedation by CO
2
, followed by cutting the gills for
exsanguination, is a widely used method for commercially
slaughtering salmonids. As CO
2
creates an adverse
environment for the fish, they show stress reactions and
erratic swimming behaviour, trying to escape before losing
consciousness (106). Although the fish stop moving after
30 seconds, they may not lose consciousness until after 4 to
5 minutes and thus, if removed too early from the sedation
tank, they may still be conscious when the bleeding process
starts (106). The use of CO
2
is probably the best method for
sedating flatfish and Parisi et al. (94) reported that this
method was less stressful to sea bass than electrocution
because of more rapid stunning. However, in general, the use
of CO
2
for euthanasia is not considered humane.
Certain chemicals, including anaesthetics such as
methoxypropenylphenol (isoeugenol, clove oil), have been
approved in some countries for sedating fish before
slaughter, with no withholding period for drug residues.
Stunning fish before slaughter is also used. The Farm
Animal Welfare Council (43) suggests that stunning must
cause immediate loss of consciousness that lasts until
death. Percussive stunning and spiking results in a rapid
loss of consciousness, without aversion reactions, if
applied correctly (106), while a lesser blow to the head
generally provides momentary sedation. This method is
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539

normally used on large fish. Although percussive stunning
by a hand-held club is useful from a technical point of
view, the method must become automated if it is to be
useful for slaughter under industrial conditions. Pneumatic
devices suitable for industrial conditions have been
developed, but care must be taken to ensure sufficiently
high pneumatic pressure or the fish may not be adequately
sedated before bleeding. Different fish shapes, i.e. flat fish
as compared to salmonids, may make percussive stunning
of some species difficult.
Electric stunning is another possible and practical method
for sedating fish (105, 132). However, effective
electrocution depends on providing an electric current
which is high enough to achieve complete sedation,
otherwise the fish will only be paralysed. Problems may
also occur if the current is too high, the most frequently
observed being backbone fracture and flesh haemorrhages.
Another problem which has recently come under
discussion is the electric stunning of Atlantic salmon
without subsequent exsanguination, to keep slaughter
costs down. Since fish may have individual tolerances to
electric current, some may survive the stunning procedure
and suffer unnecessarily before dying of suffocation.
Whereas salmonids are relatively easy to kill, killing eels is
difficult. The traditional method used (removing the
mucus from the fish with ammonia or dry salt, followed by
evisceration) has now been banned in many countries for
welfare reasons (122). The decapitation method proposed
for killing eels is also unacceptable. As spinal transection
does not cause visible injuries to the brain, the eel may
suffer for some time if this method is used. Thus,
immediate destruction of the brain is required in the
slaughtering process, if ‘neck cutting’ is to be used on these
animals (45). According to van de Vis et al. (133), the
humane slaughter of eels in fresh water is possible through
the combined use of electrical stunning and nitrogen gas,
which result in unconsciousness and death.
Slaughter for disposal
When aquatic animals must be killed in an organised
manner to control a disease – which may be either exotic
or of socio-economic importance due to mortality,
infectivity or its being untreatable – welfare criteria must
be considered. The methods used must be the same as
those accepted for slaughter for human consumption.
To prevent the spread of disease to the environment or
neighbouring aquaculture establishments, killing for
control purposes should preferably occur on the site.
Measures should be taken to ensure that the infected
animals are collected and treated in an optimal way to
prevent further spread of the disease/disease agents.
Crustacean slaughter and euthanasia
Although the higher-level cognitive ability (and,
consequently, sentience) of crustaceans has recently been
called into question (121), several different methods have
been described as ‘humane’ for killing them. There are
several important studies that suggest that lobsters do
suffer stress (95) and that their physiology and welfare are
affected by live transportation (65, 128).
Dropping live crustaceans (e.g. lobsters, shrimp crabs) into
boiling water has been the most common method of killing
decapods (lobsters, crabs, shrimps) for human
consumption. This method is not considered inappropriate
as it is questionable whether decapods have the ability to
feel pain when boiled (121). Whether the vigorous
whipping of the tail of the lobster when being boiled is the
result of pain or a reflex reaction is still not known.
However, if such behaviours do indicate stress or pain of
which the animals are cognisant, it may be appropriate to
make them incapable of feeling pain before boiling.
Crustaceans have been effectively anaesthetised or
euthanased with chemicals and cold. An injection of
potassium chloride (15), immersion in saturated sodium
chloride for 1 minute or refrigeration (cooling) for at least
20 minutes are assumed to be humane killing methods.
The use of commercial anaesthetics, such as tricaine
methanesulfonate, methoxypropenylphenol (isoeugenol)
and CO
2
, have also been described (54). In giant crabs, the
use of CO
2
may result in stiffness and loss of limbs. Robb,
as cited by Mejdell (81), however, did not observe any
effect in edible crabs after exposure to CO
2
for 1 hour.
Mechanical stunning devices used to destroy the
supraesophageal ganglion in large crustaceans, such as
lobsters, have also been developed for euthanasia. Robb
(81) reported that electricity at 50 Hz and 240 V for
1 second immediately anaesthetises or stuns crustacea.
Equipment for this purpose has been developed both for
small-scale situations (single stunner) and for industrial
purposes (batch stunner).
Conclusions
In summary, the authors believe that it is essential to
improve the welfare of poikilothermic animals by:
– increasing understanding of the quantitative and
qualitative aspects of welfare in relation to poikilothermic
vertebrates and invertebrates
– increasing understanding of their cognitive abilities,
motivational systems and behavioural needs, and
the relationship between environmental parameters
and welfare
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– developing a more humane technology
– developing validated welfare indicators for on-farm
welfare assessment (risk analysis, surveillance, etc.) and
monitoring systems
– increasing awareness and promoting education on the
welfare needs of poikilothermic vertebrates and
invertebrates and humane practices for handling and
managing these animals.
Rev. sci. tech. Off. int. Epiz.,
24 (2)
541
Évaluation scientifique du bien-être appliquée aux animaux
aquatiques
T. Håstein, A.D. Scarfe & V.L. Lund
Résumé
Le bien-être des animaux terrestres est un sujet d’étude depuis de nombreuses
années. Par contre, les approches visant à améliorer le bien-être et le traitement
décent des animaux aquatiques sont relativement nouvelles, tout comme l’est la
réflexion sous-jacente. Plusieurs aspects compliquent la démarche de la prise
en compte systématique du bien-être des animaux aquatiques :
–
l’extraordinaire diversité caractérisant le monde des animaux aquatiques, qui
sont, en majorité, des invertébrés et des vertébrés poïkilothermes ;
–
la connaissance des pratiques appliquées dans le domaine de la pêche, de
l’aquaculture et de la production d’animaux aquatiques et leur finalité ;
–
la relative rareté des informations scientifiques ;
–
la connaissance des approches philosophiques, des politiques, des
orientations et des réglementations susceptibles d’influer sur la mise en place de
pratiques optimales assurant le bien-être et le traitement décent des animaux
aquatiques.
Dans cet article, les auteurs fournissent un aperçu de tous ces éléments, en
rapportant ce que l’on connaît et comprend sur ces questions concernant les
poissons, le principal groupe utilisé en aquaculture et par l’industrie de la pêche,
et en étudiant les aspects susceptibles d’influer sur les concepts et les pratiques
liés au bien-être des animaux aquatiques. Ces aspects, qui semblent être le
fondement de toutes les approches axées sur le bien-être, sont les suivants :
–
le concept éthique et moral de bien-être et de traitement décent des animaux ;
–
la question de savoir si les animaux souffrent des pratiques potentiellement
néfastes utilisées pour l’élevage, la gestion et leur utilisation ;
–
la conception du public et des institutions sur ces questions et les résultats
qui en découlent.
Ces points sont examinés dans l’espoir que les progrès dans le domaine du bien-
être des animaux aquatiques et les approches axées sur ce bien-être seront
utiles à la société, aux secteurs industriels et au public.
Mots-clés
Aquaculture – Animal aquatique – Bien-être – Céphalopode – Crustacé – Décapode –
Éthique – Pêche traditionnelle – Poisson – Poissons d’ornement – Pratique décente.

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Evaluación por métodos científicos del bienestar de los animales
acuáticos
T. Håstein, A.D. Scarfe & V.L. Lund
Resumen
Hace muchos años que se viene estudiando el bienestar de los animales
terrestres. En cambio, la voluntad de aportar un mayor nivel de bienestar a los
animales acuáticos y de tratarlos con decencia es algo relativamente nuevo,
como lo son las ideas que subyacen a tales planteamientos. Hay varios factores
que dificultan un trabajo coherente al respecto, entre ellos los siguientes:
–
la enorme diversidad de animales acuáticos, que en su gran mayoría son
vertebrados poiquilotermos o invertebrados;
–
la insuficiente comprensión de los métodos y fines propios de la actividad
pesquera, la acuicultura y la producción de especies acuícolas;
–
la relativa escasez de información científica;
–
la insuficiente comprensión de las concepciones filosóficas, los programas y
pautas de actuación y los reglamentos que pueden influir en la prestación de un
nivel óptimo de bienestar y un trato decente a los animales acuáticos.
Los autores tratan de ofrecer una visión general de todos esos elementos,
exponiendo lo que de ellos se sabe y comprende en relación con el principal
grupo objeto de acuicultura y pesca, que es el de los peces, y examinando las
cuestiones susceptibles de influir en los conceptos y métodos relacionados con
el bienestar de los animales acuáticos. Entre esas cuestiones, que parecen
constituir el eje de todo planteamiento en la materia, figuran las siguientes:
–
conceptos éticos y morales del bienestar animal y el tratamiento decente;
–
determinación de si los animales sufren cuando se aplican sistemas de
alimentación, gestión y explotación que puedan resultarles perjudiciales;
–
percepción de estas cuestiones y sus consecuencias por parte del gran
público y las instituciones.
Los autores examinan todos estos elementos con la esperanza de que el futuro
depare mejoras técnicas y nuevos planteamientos en la materia que resulten
útiles a la sociedad, la industria y el gran público.
Palabras clave
Actividad pesquera – Acuicultura – Animal acuático – Bienestar – Cefalópodo –
Crustáceo – Decápodo – Especie ornamental – Ética – Pez – Práctica decente.

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