General Considerations in the Transportation

of Live Fish

J M Little, Syndel International Inc.

Table of Contents:

• Introduction
• Oxygen
• Water temperature
• pH
• Ammonia
• Carbon dioxide
• Loading density
• Use of anesthetics
• Use of salt
• Removal of ammonia
• Control of pH
• Stocking fish
• Conclusion

Introduction

In aquaculture, transporting fish from one location to another is inevitable. Fry and fingerlings are moved from hatchery to fish farms, adult fish are moved from fish farms to market and processors, etc. Very often large numbers of fry, fingerlings, and adult fish are being transported.

It is imperative that proper steps and precautions are taken to ensure that there is no mortality resulting from the transportation. To achieve this, the following criteria should be satisfied: good water quality, healthy fish, proper loading density, and good capture and handling methods.

To improve the transport conditions, an understanding of the factors which cause death or distress to fish is essential. Several factors can become lethal agents during transportation. These can act individually, or more frequently in combination, and thus with increased capacity to cause mortality. The most obvious factors are dissolved oxygen, water temperature, pH, ammonia level, carbon dioxide, and loading density. Oxygen

The most important factor in transportingfish is to provide an adequate level of dissolved oxygen (DO). However, the presence of a high level of DO does note necessarily indicate the fish are in good condition. The ability of fish to use oxygen depends on their tolerance to stress, water temperature, pH, carbon dioxide level, and metabolic products. Failure to provide sufficient quantity of oxygen to fish in distribution tanks will result in hypoxic environmental conditions that may cause death from anoxia and from increased blood lactic acid levels due to anaerobic metabolism by the fish. Ample oxygen will help to suppress the harmful effects of ammonia and carbon dioxide.

During the initial handling and loading, oxygen consumption of fish increases dramatically. Hence it is necessary to provide additional oxygen during the initial period of handling. Oxygen can be supplied directly from pressurized cylinder or through aeration. When this is not possible or available, hydrogen peroxide can be added to the water to increase the dissolved oxygen level (Marathe, et al 1975). It has been estimated that one drop (1 ml = 20 drops) of hydrogen peroxide of known strength (6 percent) yields approximately 1-5 parts per million oxygen when added to 1 litre of water. However, it should be noted that hydrogen peroxide could be harmful to fish fry if used indiscriminately.

Oxygen consumption is affected by the water temperature, anaesthetics, starvation, and age and weight of the fish. Lower water temperature, anaesthetics, and starvation reduces the metabolic rate and thus reduces the oxygen consumption. Oxygen consumption rate is also reduced with increase in age and body weight of fish.

Water Temperature

Water temperature is an important factor as it determines the dissolved oxygen (DO) level and oxygen consumption rate. The lower the temperature, the higher is the DO level, and the lower is the oxygen consumption. Also, lower temperatures reduce stress to fish. Water temperature will also determine the appropriate loading density in distribution tanks. For each 10 F decrease in temperature, loading density can be increased by 25% for channel catfish (Piper, et al 1982, Wellborn 1983). This guideline may be used for other warmwater fish like carps. Thus, it is advantageous to haul fish in colder water.

pH

pH of water between 6.5-8.5 is ideal for most fish. High and low pH are detrimental to fish. At high pH the un-ionized ammonia level increases, thus increasing the toxicity (Trussell 1972). High C0₂ concentration will reduce the pH value. Extreme low pH will cause interference of respiration in fish. A rapid but relatively small increase in blood hydrogen ion concentration, caused by a rapid decrease in external pH, can cause severe acidosis in fish leading to death.

Ammonia

As a result of metabolism of protein, excretory products are being discharged by fish to the water where they are being held. In the case of fish transport, excretory products accumulate in distribution tanks. Metabolic products are excreted primarily through the gills. The products discharged through gills include ammonia, carbon dioxide, urea, amine, and amine-oxide derivatives. The remaining products, which include creatinine, and uric acid are excreted through the kidney. Ammonia is the major excretory product.

Excretion of ammonia increases with the activity of the fish and with a rise in water temperature, as well as with the feeding ration. A rise of 13°F in water temperature (47 to 60°F) may cause a tenfold increase in the rate of excretion (Brockway 1950).

The aqueous solution of ammonia consists of the un-ionized form NH₃ and the ionized form NH₄. The toxicity of ammonia is attributed mainly to NH3 and this toxicity to fish depends on many factors, including pH, temperature, ionic strength, dissolved oxygen, carbon dioxide, and alkalinity. The percentage of un-ionized ammonia in aqueous ammonia solution increases with pH and temperature (Trussell 1972). A reduction of dissolved oxygen concentration (generally more than 30% below saturation) increases in both acute and chronic toxicity of ammonia. The toxicity of ammonia decreases with rise in salinity up to 30% sea water (.9% salt).

The toxicity of ammonia to fish is complex and research underway is still making clear some of the inter-relationship between ammonia concentration, other aspects of water quality, and effects on fish.

Carbon Dioxide

Fish transported in distribution tanks are subjected to increased carbon dioxide concentration as a result of metabolic excretion. High concentration of C0₂ can be tolerated if the build-up is slow. When C0₂ increases rapidly, as it does when loading density is high, the fish become distressed due to upset of the acid/base equilibrium.

The toxic effects Of C0₂ are related to both the water pH and internal blood pH. An increase in dissolved C0₂ concentration in water will reduce blood pH of fish. The reduction in blood pH decreases haemoglobin oxygen carrying capacity and therefore reduces arterial blood oxygen content. High dissolved carbon dioxide level imposes stress on the oxygen transport system of fish.

Also, a significant effect of C0₂ is its interaction with ammonia toxicity. As the C0₂ concentration increases, the pH decreases and the percent of toxic un-ionized ammonia decreases. However, if the concentration of un-ionized ammonia is held constant, increases in C0₂ level increases the toxicity of ammonia.

Loading Density

It has always been the desire of fish culturists to transport as many fish per load as possible without incurring losses of fish. This naturally is to keep the cost down. Loading density in transport is determined by many factors such as the respiration rate of fish, water temperature, transport duration, size of fish, etc. The factors are, in turn, related to the metabolism of the fish.

With an increase in temperature, metabolic rate increases, and loading density should be reduced. Safe loading density is inversely proportional to water temperature. The reduction of safe loading density will be as much as 25% with a rise of 10 F in water temperature (Piper et a] 1982, Wellborn 1983).

Duration of transportation affects loading density which is inversely proportional to transport duration. It is recommended that loading density for channel catfish (Ictalurus punctatus) should be reduced by 25% if transportation time exceeds 12 hours. If transport time exceeds 24 hours, loading density should be reduced by 50% or a complete water change should be carried out (Piper, et al 1982, Wellborn 1983).

On the other hand, loading density increases with the increase in fish size. This is because the metabolism of small fish is always greater than that of large fish. A general rule for channel catfish is to decrease the loading density by 50% for each decrease in fish length of 50% i.e., haul only 2 pounds of ' 8-inch fish per gallon of water, instead of 4 pounds of 16-inch fish. However, different species of fish will have varying safe loading density even though they are of the same size. These rules on loading density for channel catfish can be used as a guide to determine the loading density for other warmwater fish.

Use of Anaesthetics

When fish are captured and loaded into fish distribution tanks or bags, they become hyperactive. This hyperactivity results in increased oxygen consumption and excretion of metabolic products.

When using anaesthetics, extreme

It should be noted that low temperature, darkness, and gentle motion during transportation are in themselves factors calming to fish, and represent a cost effective means of reducing fish stress during hauling operations.

Use of Salt

Capture and hauling produce stress in fish, and fish experience osmoregulatory problems (Hattingh and Van Pletzen 1974). This may lead to mortality of fish during and after transport. Hattingh and Van Pletzen (1974) observe a decrease in blood pH in the mudfish (Labeo umbratus) after capture and transport. A severe depression in blood pH may result in mortality and it has been shown that sublethal depressions in blood pH due to elevated environmental C0₂ may result in decreased disease resistance in channel catfish (Ictalurus punctatus). Thus, it is desirable to minimize all physiological disturbances associated with hauling to reduce long-term mortality. Common salt may be used to this end.

Sodium chloride of 0.5 percent concentration had been employed successfully, together with TMS (MS222), to transport threadfin shad (Dorosoma petenense; Collins and Hulsey 1963), and gizzard shad (Dorosoma cepedianum; Anderson 1968). Similarly, air shipment of striped bass (Roccus saxatifis) in 1 % salt solution (Powell 1970), and

transport of young American shad (Alosa sapidisma; Chittenden 1971), and transport freshwater drum (Aplodinotus grunniens; - Johnson and Metcalf 1982) in 0.5% salt solution demonstrated the benefit of sodium chloride. However, Chittenden contended that salt solution will not prevent mortality due to intense stress.

In their work, Hattingh, et a] (1975) demonstrated again the beneficial value of adding salt to water for transportation and also keeping fish in salt water after transportation to decrease the incidence of skin infections. Similar work involving small scale study carried out by Long, et al (1977) again indicate that adding salt (0.5% concentration) to the water during handling and hauling increased the survival of Chinook salmon (Oncorhynchus tshawytscha) smolts and protect the test fish against Saprolegnia spp., a fungus which commonly infects weakened fish.

It is evident that the addition of sodium chloride in hauling water appears to provide a means of protection against depression of blood pH, thus helping to ameliorate the acid-base disturbances associated with handling and hauling (Haswell, et al 1982). other sodium salt, sodium sulfate (Na₂S04) and sodium bicarbonate (NaHC03) can be employed as well.

Removal of Ammonia

As ammonia is harmful to fish, it is necessary to reduce its concentration in transport water. There are various ways of achieving this. Keeping water temperature low, use of anaesthetics, and starving fish before transport all result in lower metabolic rate. Hence, there is a lower ammonia excretion and ammonia concentration is reduced. Removal of ammonia can be accomplished by biological means through nitrifying bacteria, and ion exchange method with natural zeolite.

Clinoptilolite, a natural zeolite, is found to be effective in removing ammonia from water. The absorption efficiency of clinoptilolite is influenced by chemical characteristics of water (water hardness and pH) and its granule size. A study by Marking and Bills (1982) showed that:

• absorption efficiency is not affected by temperature variation;
• efficiency of clinoptilolite decreased as water hardness increased;
• efficiency of clinoptilolite decreased in water of low pH;
• large granules are less efficient than smaller ones.

Efficiency is found to be optimum in water of 44 mg/L or less total harness, near neutral pH, and for granules of 20 x 30 mesh size. Absorptive capacity ranged from 3.42-9.12 mg of ammonia per gram of clinoptilolite. Amend, et al (1982) showed that clinoptilolite reduced ammonia in proportion to the amount used.

Bower and Turner (1982) carried out a study by adding clinoptilolite to a polyethylene bag containing goldfish (Carassisus auratus) and found that it substantially reduced the ammonia concentration in the water during 24 hours of simulated transport. This method of ammonia removal by ion exchange augment methods that reduce the rate of ammonia excretion (water cooling anaesthetization, and starvation) and is not stressful to fish. Although small granules of clinoptilolite remove ammonia more effectively than larger granules (Smith, et al 1981; Marking and Bills 1982), larger granules are preferred for transport purposes because they do not cause the water to become turbid.

Bower and Turner (1982) contended that transport water containing clinoptilolite should not be buffered to counteract the accumulation of respiratory carbon dioxide as recommended by McFarland and Norris (1958) because the potential for toxic effects from un-ionized ammonia increase dramatically at higher pH. However, Amend, et al (1982) dispelled this fear. They demonstrated that clinoptilolite can be used along with buffer satisfactorily, if water is buffered at pH of 8.0 or below.

Clinoptilolite also has reduced affinity to other ions and this may result in an initial reduction of water hardness. The effective use of clinoptilolite is limited to freshwater application because the ammonia removal capacities of natural and synthetic ion exchangers are reduced considerably by competing cations in sea water (Johnson and Siburth 1974). Removal of ammonia from transportation of marine fishes in sea water can be effectively carried out by introducing nitrifying bacteria cultivated on a solid substrate into the sea water (Turner and Bower 1972). Thin pads of polyurethane foam seems to be an ideal substrate for the attachment of ammonia-oxidizing bacteria.

Control of pH

Rapid changes in pH stress fish, but buffer can be used to stabilize the water pH during fish transport. Tris buffer (tris-1 hydroxymethal amonomethane) is effective as a buffer and safe for fish. Morpholoinopropane sulfonic acid and imidazole both had excellent buffer capability, but they were toxic to fish in 24-hour exposure (Amend, et al 1982).

The actual amount of buffer which will be consumed during any transport operation is dependent upon the pH, the natural buffering of the transport water, the temperature, and the duration of transport.

Stocking Fish

When the transported fish reach their destination, a few precautions have to be taken before the fish are released into rearing or holding ponds. Care must be taken to avoid temperature shock to fish. A rapid change of water temperature greater than 10°F (5-6°C) can cause stress that can lead to an infectious disease or, if the change is great enough, kill the fish in a few minutes (Wellborn 1983). Fish being handled should be tempered slowly to acclimatize them to the temperature of receiving water.

Fish being hauled may suffer from osmotic shock if there is great difference in water chemistry and dissolved gases level between the hauling water and receiving water. It may be necessary to add receiving water to distribution units slowly to allow fish to adjust to the new water environment.

Transportation also reduces the ability of fish to tolerate a second stressing agent, e.g. severe and prolonged crowding (Specker and Schreck 1980). Hence, it is absolutely necessary to ensure that the receiving environment will be void of stressing agents, e.g., holding ponds shall be free of crowding.

The osmoregulatory disturbances resulting from handling in fish may be partially offset by temporarily holding the fish in hypo- to isotonic saline-adjusted environment (Mazeaud, et al 1977).

Conclusion

Fish can be transported with little or no mortality when the water quality parameters (dissolved oxygen, temperature, pH, ammonia, carbon dioxide) are properly controlled, and the appropriate loading density is employed. Adequate oxygen supply, lower water temperature, use of tris-buffer, use of clinoptilolite, use of anaesthetics, and starvation all contribute to improvement of water quality. This, in turn, can lead to higher safe loading density. Use of salts and anti-bacteria drugs will alleviate some of the problems associated with stress in fish. Precautions taken in stocking fish will minimize post-transport mortality.