What makes transporting live fish, shellfish and crustaceans so difficult are the specific needs of aquatic organisms. Only a few species such as oysters, mussels or lobster can survive for a longer period of time in the air and can thus be dispatched “dry”. In contrast, fishes can only be transported in water, which makes the process very expensive and complicated. Expensive, because water is relatively heavy (one cubic metre weighs at least a tonne), and complicated, because complicated technology is required to keep the water quality constantly at the optimal level for the fishes during transport. Although temperature is one of the decisive factors here, it is not the main problem. Carriers face a considerably greater challenge with regard to the fishes’ respiration and excrement. Aquatic organisms require oxygen during transport, of course, and during respiration they release carbon dioxide and ammonia through their gills. Both these gases accumulate in the water and it is necessary to bind or remove them so that they do not become toxic. The fishes thus constantly influence the quality of the water in which they live via their metabolism. This can pose a risk during transportation because for economical reasons the aim is mostly to carry a maximum number of fish in a minimum amount of water.
The success or failure of live transportation mainly depends on the following factors:
• Oxygen supply (Freshwater fish usually utilise the available oxygen more efficiently that marine species)
• Increase of carbon dioxide in the water
• Changes in pH value and temperature
• Accumulation of fishes’ excrement in the water
• Loss of slime on the skin surface due to high fish density in the transport container (this can lead to an increase in susceptibility to bacterial infections)
• Mechanical injuries, increased mortality
Every journey constitutes a source of stress for the fishes. For this reason alone it is clear that only perfectly healthy fishes can be considered for live transportation. A sick or dead fish within the transport container could endanger the whole batch. On top of this careful selection, the fishes are frequently “conditioned” prior to transportation, i.e. prepared for transport. This is even sometimes the case with shellfish. Oysters, for example, undergo special training to strengthen the muscle which holds the two parts of the shell closed. The aim here is to rid them of their natural habit of opening and closing their shells to coincide with the rhythm of the tides. To achieve this they are put into shallow water or tanks with a controllable water level where they are left for a longer period in the open air (French: “au grand air”). In this way the oysters learn to remain closed during transport. Where fishes are concerned, feeding is stopped several days prior to transport to empty the fish’s gut before the journey and thus reduce the number of impurities added to the water during transport. Often the temperature is also decreased to reduce the fishes’ activity and decelerate their metabolism. Some fish species go into a cold shock, an extremely energy-saving state, the physiology of which is similar to hibernation. However, this temperature point has to be approached with great care and considerable experience to make sure the temperature does not go below the tolerance limit of the species concerned.
Air transport is the cheapest solution
Live transportation is difficult but nevertheless possible. This can already be seen in the aquaculture sector where every day fry are carried over large distances for stocking purposes or salmon are transported live in well boats to the processing plants. And this is often even possible without complicated technical equipment or the use of the latest technologies. How otherwise could it be explained that in Asia, in spite of insufficient logistics, nearly every better restaurant offers live fish and seafood and gets regular supplies to fill up its stock? So it is not only technical equipment that makes live transport possible but also the knowledge and experience of the people involved. It is not so much a question of how expensive or complex the know-how is but solely a question of whether the conditions and duration of transport are suitable for the specific species of fish.
A good example of this “reductionist“ approach is the transport of live lobsters. The large defensive crustaceans are lone creatures that already perceive stress when they are kept in groups. In spite of this they can be transported “dry” under relatively simple conditions in a box if certain conditions are fulfilled. The temperature in the container should be about 4°C (range of 1-7°C) and humidity should be around 70%. Good air circulation is important so that the lobsters can get sufficient oxygen during transportation. Prior to dispatch the lobsters are not fed for several days so that they can start the journey with an empty gut. It is also important to fix the lobsters’ claws with elastic bands to stop them harming one another. Prepared in this way lobsters can be transported without water for about 24 hours. The simplest (but also least favourable) way is to place the lobsters loose in layers in a film coated moisture-resistant carton or polystyrene box. A better and less stressful method, however, is to place a few layers of damp newspaper between the lobsters. Some carriers use sea grass or algae but this is rather risky because some of these release gases which could damage the lobsters. It is better for lobsters if the boxes have separate compartments in which they can spend the journey on their own to reduce stress.
Live shrimps are occasionally transported in pre-cooled damp wood shavings or woodwool. The preferred packaging material is Japanese cedar which is said to have anti-bacterial properties and also absorbs the shrimps’ excrement effectively. The live shrimps are layered loosely between the wood shavings but firmly enough to prevent them from freeing themselves and harming themselves or one another. The transport packaging should be damp but not wet.
Freshwater crustaceans like Procambarus clarkii are also frequently transported live in plastic sacks with 15 to 20 kg content for processing. Compared to rigid transport containers the flexible sacks have the advantage that the crustaceans lie compactly and immobile on top of one another and are thus unable to do harm to each other. To keep them cool during the journey ice is poured onto the plastic sacks. The crustaceans can survive for several days in this kind of packaging at temperatures of 3 to 8°C and a high humidity level.
Polyethylene transport bags and “breathable“ membranes
One of the best known seafood products which is carried “dry“ by air is oysters. If prepared thoroughly and treated with care these bivalve molluscs can survive “au grand air” for about a week without water. The preparation process includes the cleaning of the shells to remove oxygen-eating growths. Care has to be taken during packaging that the oysters are placed into the container with the cupped shell on the underside. It is also important not to seal the packages tightly so that air can circulate between the oysters. The same applies to other crustacean species that are traded live. When transporting blue mussels from aquaculture farms particular care is necessary because they have relatively thin shells that are very susceptible to mechanical damage.
It is not only shellfish and crustaceans that can be transported without water. This mode of transport is also possible with some fish species – at least over short periods. Eels, for example, can satisfy up to 90% of their oxygen requirements and release carbon dioxide via the skin provided humidity is sufficient. This enables the fishes to get around weirs and other obstacles during their migration by covering short distances on land. In the air the eels suffer from an oxygen debt and the lactic acid content in their bodies rises but this debt is repaid later on in the water. If during short transports it is not possible to supply sufficient oxygen in the water it can thus sometimes be better to carry the eels moist but otherwise without water.
A no less practical and also inexpensive solution for transporting fishes is the plastic bag. This must not be filled to more than one third with water. As soon as the fishes have been put into the water the remaining two thirds are filled up with pure oxygen. The oxygen in the gas bell diffuses gradually into the water (this process is intensified by hefty movements within the water during transport) and supplies the fishes with air to breath over a longish period of time, sometimes even for two or three days. The time it will last naturally depends on the size of the fishes, their density within the bag and the external conditions. This transport method is so safe and reliable that ornamental fishes are nearly always transported in this way when exported. Postlarvae for stocking shrimp ponds are also normally carried in these kinds of bags. It is really only very large fishes that cannot be transported in this way (with the exception of valuable koi carp which are also transported in plastic sacks) and sensitive species whose gills might “burn” on the surface through contact with pure oxygen when breathing.
There are also “breathable“ transport bags made of a special membrane that is absolutely waterproof but allows gases such as oxygen and carbon dioxide free passage. The higher the temperature the more gas is allowed to pass through. These breathable bags are more expensive than conventional polyethylene sacks but to make up they can be re-used. Apart from that they reduce transport volume because the whole bag can be filled with water and an oxygen bell is not necessary. One disadvantage of these bags, however, is that they are difficult to insulate because the contact surface to the surrounding air has to be as large as possible in order to guarantee reliable oxygen supply.
New systems increase spectrum of possible transport methods
Over the past few years the market for live fresh fish and seafood has expanded strongly so that conventional transport methods are no longer able to sustain supply. The response to these developments has been to devise new transport systems that enable the sensitive creatures to be transported not only on land and sea but also over great distances as air cargo. In spite of certain constructional differences nearly all of these systems have similar components whose purpose it is to ensure the survival of the fishes during transport:
• Aeration systems that work with air or pure oxygen
• Diffusers for introducing air or oxygen into the water as effectively as possible
• Absorbers, which bind the carbon dioxide that arises, thereby making it harmless
• Thermostats to keep the water temperature within a given range.
An example of this new transport philosophy is the Live Seafood Transport System (LSTS) of the Canadian company BioNovations which was developed for long-distance transport over land. The LSTS is built into a 53 foot standard transport trailer and can carry up to 11 tonnes of fish and seafood irrespective of the species concerned. The programmed temperature is maintained to within one degree and internal filter units guarantee constant water conditions during transport. All system-relevant components are integrated at least in pairs so that if one instrument fails its job can be taken over by its partner, thereby ruling out risks to the valuable freight. The diesel-driven electricity generator beneath the trailer means that the LSTS is independent of the vehicle’s electricity network. Integrated computers measure all the important water parameters constantly and keep the conditions within the desired range. Monitoring of transport positions per satellite is optional. The LSTS is mainly used by wholesalers, hotels and restaurants, and fishermen who then get higher prices for live fresh products.
The Danish company Aqualife Logistic offers similar technology. Their system is suited in particular to shellfish and crustaceans which mostly used to be carried as air freight. It consists of cylinder shaped plastic containers that are equipped with filter units for the water. The containers’ dimensions enable them to be set up in two rows in conventional containers. Lobsters, oysters, blue mussels and other seafood products are placed in wire baskets that are stacked on top of one another in the containers in layers. During transport the control technology ensures that all the essential water parameters (temperature, oxygen, salt and ammonia content) are maintained within an optimal range. This system is thus also suitable for longer-distance sea transport that is considerably less expensive than air freight. Depending on the type of products being transported the costs are reduced by 30 to 80% compared to air freight. Apart from that the CO2-balance is better: whilst 3,600 kg CO2 per tonne are produced during transport as air freight, container transport by sea produces only 120kg CO2/t. Maersk already offers this transport service for live lobsters on its scheduled services from Halifax to Rotterdam.
The Australian company Live Aqua has developed its own system for transporting fishes live in containers. According to their own statistics more than 250t coral trout (Plectropomus leopardus), a high-value grouper species have already been transported with minimal losses of less than 0.5%.
Despite these new developments which enable inexpensive live transport in containers over the sea the share of air freight is likely to rise further in the coming years. At present already 5% of global fish and seafood is already transported by air. Live transportation accounts for only a small percentage of this but it is expected to grow further, too. Constant improvements in airline networking (leading to shorter transport times) will contribute towards this development. The IATA guidelines prohibit transports of live fish and seafood products that take more than 48 hours.