Aquaculture and Fisheries News => Aquaculture News => ข้อความที่เริ่มโดย: mei ที่ มกราคม 13, 2010, 03:29:37 AM

หัวข้อ: Fish behaviour and welfare
เริ่มหัวข้อโดย: mei ที่ มกราคม 13, 2010, 03:29:37 AM
Applied Animal Behaviour Science 104 (2007) 173–175
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Fish are commercially important in both fisheries and aquaculture and their use is widespread
in experimental studies. This special issue of Applied Animal Behaviour Science is dedicated to
contentious topics in fish behaviour and welfare. Our use of fish as a foodstuff in fisheries and
aquaculture generally involves procedures that impact upon fish wellbeing and natural behaviour.
Human diets have historically included fish as an important foodstuff and the nutrients obtained
from fish have been important in our neural development.We have to catch fish and we do this by
hook and net on either a small scale of the individual catching few fish or on a larger scale in
fisheries where thousands of fish are caught by commercial means. If we eat the caught fish, then
there is a benefit to us that may outweigh the cost to the fish, however, in the recreational sport of
fishing where catch and release is practiced fish are caught for the enjoyment of angling rather
than for sustenance. Removing the fish from the water causes physiological stress and fish also
receive hooking injuries that compromise welfare. Rather than condemning this practice, Cooke
and Sneddon discuss the welfare aspects of this sport, the data on the behavioural consequences
and suggestions for the improvement of techniques that may enhance the treatment of fish during
Fish are farmed intensively in aquaculture which is an economic necessity to provide large
quantities for the food industry yet many species’ normal behaviours may be impaired by the
nature of intensive aquaculture. Recommendations have suggested that for optimum welfare,
animals should be able to express their natural suite of behaviours. Confining large migratory
species such as salmonids to relatively small tanks or cages means they are unable to perform
the extensive migrations performed by their wild counterparts so are these fish frustrated?
When considering why salmonids migrate, their motivation is to find food yet if they are well
fed by the farmer does this dampen the desire to migrate? The conflict of behavioural needs
and the major welfare issues in aquaculture highlighted by recent scientific studies are
discussed by Ashley. Species specific requirements are an important issue since fishes are one
of the most diverse vertebrate taxa on the globe. Salmonids require the ability to swim
constantly whereas flatfishes require ample space to rest on the substrate. When space is
limited for flatfish, such as the commercially important halibut, they perform stereotypical
surface swimming which has not been observed outside of the fish farm. Kristiansen and
Ferno¨ investigate individual variation in response to floating or sinking food pellets and find
that stress coping style results in some individuals showing poor growth when fed floating
food but their wellbeing improves when given food that sinks. These small changes in
aquaculture procedures can make a real difference to fish growth and hence improve welfare
and economic return.
Maintaining fish in confinement in high densities naturally leads to a high transmission
of disease and parasites yet little is know about the behavioural and physiological
consequences of these infections. Laboratory studies have shown tremendous changes in
behaviour as a result of parasitism in fish and parasites are prevalent in aquaculture systems
reducing growth and possibly wellbeing since many of these infections cause injury.
Barber discusses the impact of parasitic infection upon behaviour and suggests that their
incidence may be used as a general welfare indicator in the laboratory and by the aquaculture
Genetic manipulation of fish has been widespread since the mid 1980s and over 30 species of
fish have subsequently been altered by genetic modification. The impacts on behaviour and
welfare have become a controversial issue debated by public bodies and the media. Hallerman
et al. consider the issues associated with genetic modification in fish and provide important
examples of major changes in behaviour and wellbeing of fish subject to manipulation. Growth
hormone transgenic salmon grow 11 times faster than unmanipulated fish leading to increased
aggression but impaired swimming ability. The negative individual consequences of altering
growth hormone genes also have an impact on wild populations since wild fish may be
outcompeted by these transgenic individuals and this raises serious issues for the ecology and
survivorship of natural ecosystems.
The use of water bodies for industry has led to considerable changes in the structure and
composition of lakes and rivers. Anthropogenic activities, such as building dams or effluent
run off from mines and factories, has had considerable effects upon aquatic animals that we
are only now beginning to understand. Schilt details the consequences of dam building on fish
behaviour demonstrating that these dams act as barriers to the natural migration of
diadromous species that move between freshwater and seawater as either young going to the
rich feeding grounds of the sea or as adults returning to natal rivers to reproduce. The building
of dams has led to a decline in fish populations with ecosystem wide effects but improvements
are being made to allow fish passage with hope for recovery of these fish species. Heavy
metals from anthropogenic inputs have a profound effect upon fish since they live in such
close contact with the environment. The behavioural consequences of exposure to such
contaminants are detailed in Sloman’s work on the natural dominance hierarchies of the
highly aggressive salmonid species. These contaminants interfere with olfaction and thus
disrupt dominant-subordinate relationships as well as being relatively more toxic to the lower
ranking fish. These effects have serious welfare consequences in aquaculture where
aggression is problematic but also has important implications for the conservation of natural
Not all welfare concerns have been covered in this special issue since little work has
been conducted upon large-scale marine fisheries and the pet trade but we have attempted
to highlight some of the more controversial issues. Improvement of our use of fish will
lead to better wellbeing and as such healthier individuals. This should be the goal of
researchers since it is in our interest to conduct experiments in optimum conditions to
obtain truly meaningful results. Healthier fish grow better and thus improving welfare
conditions in aquaculture would be beneficial for this industry. In the natural environment,
sustainability of fish populations must be achieved and it is through a better understanding
of the biology of fish species that we can try to improve our treatment of fish and their