Reducing
Losses Associated with Transport & Handling in Marine
Teleost Fish
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Improving the
survival rates of fish during and after transport is of interest
to hobbyists and ornamental fish business alike. While hobbyists
want their new acquisitions to arrive in good condition and
to survive, they are also interested in keeping their cost
down. Retailers have a need for quality fish and reducing
post shipment losses to a minimum. At the same time, exporters
seek ways to maintain water quality and control stress with
the goal of reducing mortalities and enhancing profitability.
Fish farmers and importers can also contribute along the way
to everyone's benefit. We all share a mutual interest in quality,
healthy fish.
The ornamental
fish industry has a standard for acceptable losses during
air transport. Exporters are expected to compensate their
customers when the dead on arrival (DOA) rate exceeds 5% (Lim,
et. al, 2003). Please note that the overall losses of fish
between capture through the first week post shipment is significantly
if not unreasonably higher. This is why it is important that
changes be implemented beginning with capture all the way
to the marine aquarist. Each aspect of commercial ornamental
fish enterprise should do their part to minimize these losses.
Hobbyists have
an essential role in helping their stock to recover from the
stress of capture, transport and handling. This begins with
being informed. Learning and gaining knowledge about the hobby
should be a priority. Research the compatibility, natural
habitant and dietary needs of each specimen prior to purchase.
To ensure the health of the fish it is advisable to wait until
after having long-term success with "easy-to-keep" species
before attempting more difficult or sensitive animals. Quarantine
newly acquired fish for several weeks before placing them
into the display aquarium so that the established stock is
not at risk of contagious disease.
Packaging
Protocol
The use of modern
packaging technology to increase fish loading density and
post shipment survival is critical to the industry. The accumulation
of metabolic waste limits fish loading density. Several methods
are available to reduce this build-up. These include starving
the fish for a day or so prior to transport (Phillips &
Brockway, 1954.), reducing water temperature (Lim & Chua,
1993. Teo & Chen, 1993.) and treating the fish with anesthetics
(Chen, 1995b). Buffers (Amend et. al, 1982.) and drugs are
often added to the transport water as well.
Fish are conditioned
for packaging in three stages. These include prophylactic
treatment, starvation and pre-packaging. The three stages
of conditioning help reduce the amount of stress on the fish
during transport, but they do not eliminate it.
Parasitic infection
is common in ornamental fish. Infection may go undetected
until the fish are weakened by the stress of transport and
handling. Specimens weakened by disease or infection are less
likely to survive transport stress. Prophylactic treatment
(preventing or contributing to the prevention of disease)
is usually performed on fish that may be infected with pathogens.
However, the short duration of these treatments (1 to 7 days)
may not be long enough to affect a cure.
Bacterial growth
during transport produces ammonia, competes for the available
oxygen supply and can potentially cause disease. Bacterial
growth is controlled in transport water by the addition of
dyes and antibiotics such as methylene blue, acriflavine and
neomycin. .
Fish are inspected
during the screening process for clinical signs of disease.
These include external parasites, cloudy eyes, lack of appetite,
dark body color, closed finnage and lethargy. Fish that exhibit
indicators of disease or distress should not be packed for
shipping. Four to six hours after pre-packaging the fish they
should be checked again for signs of distress. Suspect fish
should be removed from pre-packing to reduce the risk of mortality.
Those fish can then be treated with the appropriate therapy.
These fish can be re-evaluated, after allowing time for recovery,
for future shipment.
Fish are starved
for one to two days prior to shipment. This prevents the regurgitation
of partially digested foods and reduces the volume of excreta
during transport that would otherwise have a negative impact
on water quality. Generally, small fish are starved one day
and large fish for two.
Fish metabolism
is three times higher than normal during transport (Froese,
1988). Ammonia and carbon dioxide are the two major metabolic
wastes produced during shipping. Reducing the water temperature
helps to minimize oxygen consumption and control the accumulation
of acidity, carbon dioxide and ammonia in transport water.
Typically, tropical species are shipped at 22C. In cold weather
conditions, many exporters attach a heat pack to the inside
of the lid before sealing to prevent a rapid drop in temperature.
Cold packs may be used during warm weather conditions.
Some exporters
use ammonia detoxifiers in the shipping bag. Ammonia detoxifiers
can be incompatible with dyes such as Methylene blue and acriflavine.
These dyes are commonly used as prophylactics in transport
water. When the alkalinity of the water is not high enough,
ammonia detoxifiers can cause a sudden drop in pH. To counteract
this, a buffer that is compatible with the ammonia detoxifier
should be used. A buffer mixture containing 80% sodium bicarbonate
and 20% 5-mole borate is compatible.
Organic buffers
such as Trizma™ or tris buffer may work best for maintaining
the pH of water when fish density is high such as during shipping
(Spotte, 1979). However, tris buffers are incompatible with
some products used to control ammonia build-up. Tris is an
amine and some ammonia detoxifiers react with ammonia and
amines. Therefore, tris buffers should not be used in conjunction
with these products.
Anesthetics are
sometimes used to slow the metabolism of fish during transport.
Tricaine or MS-222 is one of the most commonly used anesthetics.
It is the only anesthetic fully licensed for use with fish
(Stoskopf, 1993). Fish rapidly clear residues of MS-222, usually
within 24 hours. However, the activity of MS-222 varies considerably
with water quality, water hardness, fish species, fish size
and fish density. This makes administering the correct dosage
difficult.
The packaging
process causes severe stress in fish (Barton & Iwama,
1991). Stress and the subsequent release of stress hormones,
primarily cortisol, into the bloodstream suppresses immune
function making fish more suceptible to pathogenic disease
(Barton & Iwama, 1991). Acute, prolonged stress also causes
osmotic or osmoregulatory dysfunction. If the fish are not
able to recover normal homeostasis, it can lead to mortalities.
Osmoregulatory dysfunction is counteracted by salinity manipulation.
The addition of
salt to freshwater, or conversely reducing the salinity for
marine species, is effective in controlling osmoregulatory
dysfunction and other physiological responses to stress (Johnson
& Metcalf, 1982. McDonald & Milligan, 1997). This
will reduce mortalities caused by shipping stress (Tomasso
et.al, 1980. McDonald & Milligan, 1997).
Fish are prepared
for transport by packing them in polyethylene bags with little
water. The cost of shipping limits the volume of water used
in transport. The most important factor is an adequate supply
of oxygen. The transport water is oversaturated with oxygen
and usually pretreated with chemicals or drugs. Typically,
the volume of oxygen to water in transport is three or four
to one. The fish are then pre-packed and placed in an air-conditioned
room so they can acclimate for 4 to 6 hours to a lower water
temperature, confinement, crowding and high pressure prior
to shipping.
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Delayed Mortality
Syndrome
Delayed Mortality
Syndrome or DMS is associated with losses that occur in recently
transported fish (Noga, 2000. Stoskopf, 1993). Fish suffering
from DMS experience osmotic dysfunction and inhibited immune
system response. Transport stress is diagnosed clinically
by a decrease in plasma osmolarity in freshwater fish or an
increase in osmolarity in saltwater species (Carmicheal et.
al, 1984. Robertson et. al, 1988). Severely stressed fish
can lose up to 10% of their body weight in 9 to 49 hours.
This weight loss is attributed to osmotic dysfunction leading
to dehydration (Sleet & Weber, 1982). These fish are susceptible
to opportunistic pathogens, especially bacteria that take
advantage of stress-weakened hosts (Mazeaud et. al, 1977).
Infections caused by DMS usually become apparent within the
first week after shipping. However, the critical period is
longer extending to several weeks.
Steps to treat
or reduce acute stress and DMS (Noga, 2000).
Prophylactic
treatment with antibiotics
Frequent, small
water changes.
Reduce stress
during transport and other manipulations such as netting.
Stress Management
The mean cumulative
mortality at 7 days post shipment is approximately 11% (Lim,
et. al, 2003). This does not include all losses that occur
during the "chain of custody" between capture and final destination.
Handling, capture and transport causes severe stress in fish
making stress resistance an important factor in determining
post shipment survival. Assuming that low stress resistance
is partially responsible for mortalities that occur during
and post shipment, the use of stress resistance techniques
before transport may reduce mortalities. Current ornamental
fish packaging focuses on minimizing stress and controlling
the water quality during transport. More emphasis must be
placed upon enhancing stress resistance prior to transport
and post-shipment recovery of osmotic balance and normal homeostasis.
Fish are subjected
to a series of stressors beginning with their capture in the
wild or harvesting from a fish farm all the way to and including
their final destination in a display aquarium. During collection
for shipping, precautions should be taken to prevent injury,
exposure to the air and overcrowding (Bartelme, 2003b). These
stress factors can be more severe than the effects of transport
(Iverson et.al, 1998). Netting and handling causes severe
stress in fish, especially when they are removed from their
native environment (water) during these processes (Bartelme
2003b, Carragher & Sumpter 1990, Klontz 1995, Kreiberg
1994, Rottmann et al 1992, Spotte 1993, Spotte 1979).
Avoid using nets and exposing fish to the air during transfer
whenever possible. Products such as StressGuard™ or
Pro Tech Coat Marine™ can serve as a temporary barrier
when the mucus/skin/scale barrier is compromised during handling
and transport.
Significant portions
of post shipment losses are due to osmoregulatory dysfunction
and stress-mediated diseases occurring within the first week
after transport (Johnson & Metcalf, 1982. Carmicheal et.
al, 1984). Stress in fish causes osmoregulatory dysfunction
(Harrell & Moline, 1992. Weirich et. al, 1992). This can
lead to mortalities (Tomasso et. al, 1980). Reducing the gradient
(difference in salinity) between the internal fluids of fish
and the surrounding ambient water alleviates water and ion
disturbance ((Wedemeyer, 1996). Manipulating the salinity
of the transport water upward for freshwater fish and conversely
downward for saltwater fish is effective for controlling osmoregulatory
disturbances and reducing losses (Carneiro &Urbinati,
2001). Fish held in water that is close to isotonic (the salinity
of the surrounding ambient water is close to the internal
fluids of the fish) have increased stress resistance (Lim
et. al, 2000). These fish also display a significantly lower
mortality rate at 7 days post shipment.
Marine teleost
fish typically adjust to hyposaline conditions quite readily.
An article in Drum and Croaker reported on thirty-two species
of marine teleost fish maintained in a Specific Gravity of
1.010 for six to twelve weeks (Goodlett & Ichinotsubo,
1997). One study was performed using thirteen species of marine
fish (Wu & Woo, 1983). Another was performed using Emperor
angelfish Pomacanthus imperator. The angelfish were
kept in salinities as low as 7ppt for 30 days without any
apparent ill effects (Woo & Chung, 1995). While marine
teleost fish adjust rapidly to salinities lower than natural
seawater, the transition back from hyposaline conditions to
NSW levels must take place slowly over several days. Fish
with a different osmoregulatory strategy such as sharks and
rayfish cannot withstand hyposaline conditions.
The optimal salinity
for shipping saltwater fish has not been determined and may
vary with the species. However, it is reasonable to assume
that a salinity that is close to isotonic would work well
for marine teleost fish. The cooperation of those at all points
of handling is necessary. Ideally, marine teleost fish would
be held in hyposaline conditions beginning with the exporter
all the way to the hobbyist's quarantine tank. This will help
the fish quickly recover osmotic balance and it helps to control
some types of external parasites as well. Hyposalinity therapy
can be extended for several weeks as a proactive approach
for dealing with some types of parasitic infection such as
Cryptocaryon irritans (saltwater ich).
Acclimation to
hyposaline conditions should begin two days prior to shipping.
The fish should be acclimated in steps using two water changes
per day for two days. Reduce the salinity 5ppt with each water
change. I suggest a salinity of 14ppt, not to be confused
with Specific Gravity, for transporting marine teleost fish.
Hyposaline conditions should be maintained for 7 days or longer
post shipment.
Maintaining the
temperature of transport water during shipping is difficult.
The temperature of transport water can rise or fall to dangerous
levels leading to mortalities (Chow et. al, 1994b. Froese,
1998). Styrofoam boxes 2cm in thickness are generally used.
It has been recommended that these boxes should be a minimum
of 2.5cm thick (Froese, 1998) to reduce heat loss. .
Some exporters
use buffers when transporting marine fish. Shipping fish in
sealed plastic bags with oxygen can result in hypercapnia
and mortalities unless the water is buffered to prevent a
dangerous rise of carbon dioxide (Spotte, 1979). Organic buffers
such as Tris buffer or Trizma™ do a better job of maintaining
the pH than inorganic buffers such as NaHCO3 when the fish
density is high (Spotte, 1979).
Fish that have
been exposed to low pH will recover more quickly if they are
acclimated slowly back to a normal pH. The pH of shipping
water may drop below 7.0 so abruptly raising it into the 8.0
to 8.3 range is stressful to fish. This should be taken into
consideration when acclimating fish into holding tanks. Raise
the pH slowly over a period of a couple of days.
Do not float the
shipping bags to equalize the temperature with the holding
tank. The pH of transport water can rise quickly when the
shipment bag is opened. This can lead to a rapid rise in toxic
ammonia in the transport bag. Remove the fish quickly from
the shipment bags into dimly lit holding tanks. The pH and
temperature in the holding tank should be similar to that
of the transport water. Then slowly adjust the water parameters
to optimal levels. The salinity of the water should remain
low for one week or longer.
Fish generally
take much longer to adjust to changes in light intensity than
humans do. Their eyes can take hours to adapt to a change
from darkness to intense light. This makes it necessary to
open the transport bags in dim lighting or with the use of
red lights to avoid photo shock.
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Nutritional
Supplements
Enhancing stress
resistance in fish should begin after capture at wholesale
facilities or fish farms. Feeding fish diets supplemented
with highly saturated fatty acids such as those found in Selcon™
helps with stress resistance. Supplementing the diet with
vitamin C will improve disease resistance and help reduce
the effects of stress (Waagbo et.al, 1993).
Enhancing
Immune Function
Adding a biological
immune defense modulator such as Beta 1, 3D glucan to the
diet will help increase resistance to disease and stress.
An overall enhancement of immune response can be achieved
by the use of Beta 1, 3D glucan. It has proven in numerous
scientific studies to be an immodulating agent that can enhance
the major host defense mechanisms of the immune system (Bartelme,
2003c).
Pretreatment with
Beta glucan means that the host can activate and proliferate
defense mechanisms at a faster rate than invading organisms,
giving the fish and their immune system a head start. Beta
glucan can be administered in food prior to starving the fish
in preparation for shipping. Safety evaluations indicate that
Beta glucan is safe over a wide dose range, but a dose of
0.02% a day of body weight is recommended.
Beta glucan can
be administered orally to fish by farmers, exporters, importers,
retailers and hobbyists alike. It can be administered by exporters
24-48 hours prior to packaging. Importers and retailers can
add Beta glucan to the food while the fish are in their care.
Hobbyists can add Beta glucan to the food during the initial
quarantine period before the fish are moved to their final
destination.
Investigating
Modern Packaging Technology
Stress from low
pH is certainly a factor in transported marine fish. Although
buffers such as tris-buffer are effective in stabilizing the
pH of transport water, many exporters do not use them. There
is concern about ammonia toxicity, especially when the pH
is above 8.0. Other exporters claim that tris-buffer helps
them to reduce losses. Sigma has a product called Trizma®
"Fish" Grade Pre-set Crystal, pH 8.3, Type 8.3-FT, "Fish"
grade, pH 8.3 designed to maintain the pH and control carbon
dioxide toxicity in holding tanks and transport water. For
more information about this go to http://www.sigmaaldrich.com/suite7/Brands/Sigma.html
Clinoptilolite
(zeolite) is used to help control ammonia build up in freshwater
during transport. However, it is not effective in saltwater.
The use of ammonia detoxifiers can be problematic. They can
be incompatible with dyes used to control pathogens in transport
water. Ammonia detoxifiers can also cause a rapid drop in
pH if the alkalinity of the water is too low. The use of ammonia
detoxifiers and other means of controlling ammonia build-up
in transport water warrant further investigation.
Breathing bags
have been available for some time. These bags allow harmful
levels of carbon dioxide to dissipate into the outside air.
Despite some limitations and increased cost, they appear to
have applications for use. New technologies for improving
the practicality of breathing bags are being developed. For
more information on breathing bags, go to http://www.novalek.com/klistfr.htm.
(This is an example and not an endorsement of the product).
Notification
of Pertinent Information
Communication
between the various points of handling is essential to improving
the mortality rates of transported fish. Posting pertinent
information in a standardized location such as on the outside
of the styrofoam box on the lid will help foster this commuication.
Some suggestions for information that can be shared are:
What type of
shipping bag was used?
What type of
buffer was used if any?
What was added
to control ammonia if anything?
What is the
salinity of the transport water?
What chemicals
or drugs were added to the shipping bag?
Time and date
that the fish were packaged for shipment.
Proposed Changes
in Acclimation and Transport Procedure
Hyposaline
conditions in transport water and holding tanks for 7 days
post shipment.
Prophylactic
use of Beta 1, 3D glucan 24-48 hours prior to shipping continuous
through the first week post shipment.
Notification
of Pertinent Information.
Styrofoam boxes
2.5cm in thickness.
Further investigation
into the use of tris-buffers, ammonia detoxifiers and breathing
bags.
Concluding
Remarks
It is crucial
that scientific research continues to explore ways to reduce
losses associated with transport and handling. We have much
yet to learn. Many of the changes proposed here in procedures
for transporting and acclimating fish will likely meet with
resistance. Some may consider change to be inconvenient or
be reluctant because of a potential increase in costs. However,
if our hobby is to survive some tough choices must be made
at this time. We cannot continue with the status quo. The
responsibility to reduce fish mortalities belongs to everyone
involved. After all, we share a mutual interest in quality,
healthy fish.
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