Mediterranean
Farmed Fish Welfare. How good are we ?
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Invited lecture by Dr. PANOS VARVARIGOS |
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CONTENTS |
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VETCARE Ô Copyright (c) Dr. Panos
Varvarigos. Athens, Greece. |
Perception and expression of fish
welfare
Fish are sentient animals, capable of
suffering pain, fear, frustration and even boredom. Fish feel distress by
hunger, heat or cold, confinement, crowding and handling. They are also able of
experiencing comfort and well-being as well as expressing preferences and
learning. We do not know how fish experience the world and how they
communicate, but we study how they adapt their physiology and observe their
behavioural reactions. The continuous addition of new species in aquaculture
furthers the knowledge gap for species specific information necessary to define
and document welfare status.
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The main fish species grown in the
Mediterranean are:
Sea bass (Dicentrarchus labrax, family Serranidae)
Sea bream (Sparus auratus, family Sparidae). |
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Other farmed species comprise:
Sharp snout sea bream (Diplodus puntazzo), White bream (Diplodus sargus), Red porgy (Pagrus pagrus), Striped sea bream (Lithognathus mormyrus), Dentex (Dentex dentex), Pandora (Pagellus erythrinus), Corb or Shi drum (Umbrina Cirossa), Dover sole (Solea solea), Meagre (Argyrosomus regius).
Although physiological parameters
(e.g. stress hormones) may be measured and correlated with external stimuli,
thus indicating the status of wellbeing, it is the behavioural changes and the
tendency to escape danger or seek comfort (fight for space, shelter and food)
that actively express the will to satisfy needs. Despite not being quantifiable,
it is these reactions that drive the need to secure a better living standard
for the fish in culture.
Feelings and emotions (e.g. pain,
fear, agony, sense of care), cannot be adequately assessed, so fish welfare
is perceived as the fulfilment of biological needs for proper body functions
(maintaining homeostasis) away from adverse environmental conditions and danger.
Life in captivity comprises an artificial existence, to which the fish have to
adapt.
In the field, we evaluate what we
are able to observe, such as behavioural change, growth and health. Obscure physiological parameters,
which, if measured, could have shown that homeostasis is upset, are not taken
into account unless they express themselves as disease, awkward behaviour,
reduced growth, inferior body condition, or bad FCR. Visible changes in colour,
schooling and swimming behaviour, respiratory rate, response to feeding,
presence of skin ulcers, fin erosion, haemorrhage, exophthalmia, abdominal
distension, etc, are regarded as visible ill-signs associated with impaired
welfare. If the faltering parameter is not rectified and welfare upgraded,
disease outbreaks follow, due to compromised immune defences.
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Farmed fish
are forced to live in artificial confinement, far from their natural habitat. Despite
efforts to ensure adequate water quality and suitable feed it is hard to
prove whether they are “happy animals”. Example: Intensive sole (Solea solea)
rearing in land-based stacked tray-like basins. |
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Behind welfare ethics
Maintaining acceptable welfare
status for the farmed fish is considered important because it safeguards fish
health and efficient growth. It is seen as an insurance policy for profits.
Only as such, the associated costs for upgrading technology and management may
be justified.
For example, the agony of a painful
death at harvest, past any moral standpoint, inflicts self-injuries and
degrades the product (loss of scales, bleeding, abnormal skin colour as well as
adverse muscle biochemical reactions reducing storage life). Therefore, it
makes sense to try hard to minimise, or even avoid stress at harvest, by means
of procedures that render fast insensitivity.
It seems that Mediterranean farmers
treat their fish well because there are benefits to be gained (a
‘contractarians’ approach).
As regards the consumers’ point of
view, animal welfare has gradually become part of the total quality concept. It
is not enough to produce high-quality meat unless it is documented and labelled
that officially recognised welfare/ethical norms have been observed throughout
production as well as harvest. This consumer driven necessity to treat fish
“humanely” is strong in the Mediterranean countries where the fish are
presented for sale mainly fresh, in the round and skin on. The consumer buys
a whole dead animal, not just a skinless (or featherless) and/or boneless
piece of its musculature.
Current practice
Question: Do Mediterranean aquaculturists
practice environmentally sustainable and ethically sound fish farm management ?
Answer: Yes. Despite minor and ever
diminishing exceptions, common sense management sustaining fish wellbeing,
according to current knowledge is routine (expressed as good growth and
health).
But more
is needed:
There are
gaps in the legislation and a profound lack of state interest and official
controls.
There are
only few, scattered and inadequate efforts in order to:
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Establish sound, workable welfare indicators.
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Devise a system for on-farm welfare assessment.
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Draft and propose acceptable codes of practice.
The
scarcity of funding local Institutions to carry-out species-specific research
means that rules may relate to salmonid based research with inherent
species-related flaws.
Fish
welfare at present depends on the initiatives taken by individual companies,
but there is no co-operation or consultations across companies, even among
those operating sites on a single bay.
The
pro-welfare actions that are in place:
Infrastructure
and water (farm environment)
• Deep waters with adequate sea currents (sea).
• Modern spacious circular net cages (sea).
• Suitable borehole water, sometimes geothermal
(land-based).
• Automated controls and water sanitation
systems (land-based).
Feeds
• Proper quality/size of dry diets for each
species and age class.
Health
management
• Prophylaxis (e.g. vaccination).
• Veterinary consultations (but there is scope
for improvement).
• Disinfection (biosecurity) (but occasionally
with outdated products).
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Modern,
spacious circular cages in open, deep waters. Smaller
rectangular cages are used as “helper cages” (arrows) for fish manoeuvring, partial
harvest and handling (grading, treatments, etc.) |
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Stock
management in need of more attention:
Stocking
densities
The majority
of the Mediterranean fish species are harvested at much smaller weights than
salmon (350g to 650g), thus the number of fish per volume unit for a given biomass
is much higher in comparison. While an acceptable upper limit for stocking
salmon is 4 fish or 15-20 kg per m3, the respective limit for sea
bream or bass is 20 fish or 7.5-10 kg per m3.
Smaller fish
and fry do not utilise the space available to them but shoal and compete
fiercely for food, necessitating wide dispersion of food, or multiple feeding
points. Putting too many young fish in a large cage or nursery tank should be
avoided. Despite a low biomass per volume ratio, crowding ensues, resulting in
self injuries, fin erosion and skin lesions with opportunistic bacterial
colonisation.
Handling and treatments:
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Fry transportation (weighing, loading, transporting, delivering).
· Grading and counting.
· Bath treatments (crowding).
· Vaccination.
· Handling brood-fish.
Handling of
brood-stock is performed only for brood-stock selection, because spawning is
spontaneous under controlled conditions (photoperiod, water temperature) and
fertilisation is natural in the brood-stock tank. There are no stripping or milking
procedures for spawning and fertilisation of sea bass and sea bream.
Fish are
sedated and subsequently anaesthetised for tagging, by means of microchips in
the dorsal muscles, or by subcutaneous polymer colour tags. Mutilations (fin clipping)
is impractical.
Examples
of handling stress:
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Bream and bass fry grader |
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Fry transport pump |
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Fry counter |
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Grading eels |
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Sea bass
enclosed in a tarpaulin and sedated prior to complete anaesthetisation and
injection vaccination |
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Anaesthetic
overdose in the tarpaulin. The common
anaesthetic used is phenoxy-2-ethanol, which
despite being safe and effective, has to be gradually added in the water,
otherwise it irritates fish gills and skin hence, panic ensues among the
enclosed sea bass. |
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Immersing
sea bass in anaesthetic dilution until completely immobile (deep
anaesthetisation) prior to injection vaccination. |
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Injection
vaccination of sea bass under deep anaesthesia. |
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The most controversial welfare issue
Harvesting / killing
Procedures prior to killing include
severe handling, such as partial netting, or swimming the fish into a smaller
‘helper’ cage and crowding. Such handling, no matter how gentle, invariably results
in welfare degradation. If performed haphazardly, it has a negative impact on
quality (abrasions, haemorrhage, muscle biochemistry leading to shorter time to
rigor mortis).
During crowding panic ensues,
characterised by strong escape attempts and mainly burrowing (sea bass),
resulting in snout and/or eye damage. Partial cage harvest, or release of
crowded fish back to their cage, after an aborted harvest attempt, should be
avoided.
A three day fasting period should
normally precede harvest. It may be stressful, but partly offsets the stress
and hardship of harvest itself. (It also enhances product quality and prolongs
storage life).
No stunning or sedation is performed
prior to lifting the fish out of the water. Fish are killed by means of a cold
shock, by immersing them in an ice-water slurry mixture (2:1:1 -
Ice/Water/Fish) with temperature no higher than 4oC.
Killing by cold shock
On-farm experiments by the GMA
(Greek Maricultures Association) have indicated that the abrupt drop in
temperature by more than 16oC, shocks the fish in ~10 seconds. A
state of apparent unconsciousness (complete immobility and lack of any
reactions to external stimuli) is evident after 3-5 min. Sea bream is more
susceptible to cold shock than sea bass of the same body weight and age and
under similar field experimental conditions. Sea bream collapses completely
after 3-4 min as opposed to 4-5 min for sea bass. Under no circumstances
are live fish packed in ice.
Killing by cold shock precedes
transport to the packing plants; where weighing, sorting and packing with ice
take place. However, it does represent the initiation of the ‘cold chain’ for
the harvested fish.
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Sea bass
caught from their cage with a purse net and off-loaded in ice slurry causing
cold shock and expected insensitivity within 10 sec. The “cold
chain” of the products to the market starts here. |
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Stunning/killing
alternatives
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Narcosis with CO2 causes alteration of gill coloration (brown
instead of bright red), which is unacceptable by the Mediterranean consumer.
(The fish are not bled and the bright red colour of the gills is a fundamental
characteristic of freshness.)
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Electrocution requires a vast amount of energy due to the high
conductivity of sea-water (salinity at 38-40ppt) and electric power is not
available in all cage sites (an underwater cable would be necessary).
Man made diseases
There is direct relation of husbandry with fish
welfare. Frequent repercussions of mismanagement or occasional negligence
comprise:
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Suffocation during transport (water
quality degradation).
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Skin injuries and fin erosion during transport (excessive biomass density per m3).
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Handling trauma (careless net
manoeuvres, grading, etc.).
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Over-feeding and lipoid liver degeneration (feeding ad libidum with energy rich
diets all year round).
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Sea bream winter syndrome
(feeding fatty diets during the cold season).
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Chronic copper poisoning
(careless use of copper-based antifouling agents to impregnate the pen
nets).
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Excessive antagonism for food leading to behavioural
hierarchies and marginalization of the less active fish in the cage (improper stocking).
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Gas supper-saturation (inadequate degassing of pumped
borehole water).
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Nefrocalcinosis (high biomass
density with simultaneous supply of liquid oxygen to sustain it).
Examples
of man-made problems:
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Copper and
copper compounds leach in the water from copper oxide based antifoulants which are used
to impregnate nets. These
products contain 18-20% copper oxides. Chronic copper
toxicity is frequently diagnosed by staining blood smears. Intoxicated
erythrocytes are bent or spindle shaped.
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Gas
supersaturated water on land based installations can cause gas bubble
disease, whereby bubbles are formed and trapped within soft tissues. When
gills are affected by gas bubble embolism the condition is fatal. |
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Nefrocalcinosis is induced in
nursery units when fry are overcrowded while liquid oxygen is injected in
their water to sustain respiration and metabolism. However, excessive amounts of
carbon dioxide are also produced, the water pH drops, fish blood acidifies
and renal calculi (often CaCO3) are formed. These may be diagnosed
by X-ray mammogrammes. When the kidney osmoregulatory function
is impaired, skin ulceration is provoked. |
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Overfeeding
sea bass with energy rich diets results in excessive visceral fat deposits
and fatty degeneration of the liver. Such fish
are prone to infectious diseases, such as vibriosis. |
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Sea bass
fingerling with inflamed and ulcerated skin due to deteriorated water quality
during prolonged transportation. |
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Skin wounds
and fin erosion due to hardship during partial harvesting of net pens (some fish
get trapped in the nets, or panic and collide with one another and onto the
netting.
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Other issues related to welfare
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Genetically engineered fish (transgenics).
o Questioning whether
genetic manipulation is compatible with welfare ethics.
o Concerns as regards
escapes of transgenic fish into the wild.
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Intensive phenotype-based breeding.
o Concern when traits of
highly productive fish escape.
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Organics
o Welfare
incompatibilities concerning disease treatments.
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Environmental impact of fish farms.
o Farms should not foul
their own existence (e.g. antifouling paints polluting sea and sediment with copper).
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Predator control.
o Intrusion prevention,
but with no harm to predators (sea birds, seals, dolphins).
Concluding remarks
Fish health is the central key
component of any welfare regulations, guidelines or farming codes of practice.
The EU recommendations describe common sense tactics to ensure healthy
fish and unhindered growth, considering these to be the most prominent welfare
indicators.
These
recommendations do not add much to current practice, nor to the improvements
that are being put in place for farming to remain viable/profitable.
In the lack
of solid species-specific biological evidence, perceptions of fish welfare vary
among countries, cultures and individual people.
Views are
shaped by the apparent intensity of fish reaction and sustained harm when
exposed to evidently adverse conditions.
Mediterranean
aquaculture would welcome and has the capacity to adapt to an ‘International
Code of Practice for Ethical Aquaculture’, but with species-related provisions.
Projects,
like the EU funded ‘Benefish’ are expected to provide proof that such a move is
not only theoretically desirable, but profitable and sustainable, consistent
with modern science.
VETCARE Ô
VETERINARY SERVICES TO AQUACULTURE AND
DISTRIBUTION OF FISH HEALTH PRODUCTS
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