Culture Shock! Understanding and Managing Stress Among Globetrotting Ornamental Fish
Tropical aquarium fish and ornamental pond fish such as koi are bred in aquaculture facilities all around the world. Some tropical aquarium fish are still collected from the wild, especially in Africa, Asia and South America. These fish are transported by trucks, boats and planes long distances, shipped in Styrofoam-insulated boxes containing the fish in plastic bags filled with water and oxygen.
The distribution network for tropical fish industry is a complex network of businesses:3
Breeders/fish farmers/wild collectors
Retail pet stores
Home aquarium keeper
Stress occurs during the capture and transport of fish. An increase in plasma cortisol levels is the primary response to adverse stimuli; alterations in blood glucose and electrolytes can also occur.1 Stress is the term used to describe the sum of the biological and physiological changes in an organism in response to adverse external influences.4 Those external influences include injury, illness, environmental contamination, fear, medications, nutritional deficiency, overcrowding, parasitism, predation, reproduction, temperature extremes, transportation, or other similar factors. In many instances, more than one stressor is present at the same time. While causing an initial increase in protection, long-term effects of stress are a decrease in immune response (decreased antibody production and reduced phagocytosis ability) and therefore a decreased resistance to disease.
To reduce stress, always handle the fish safely during transport. Be sure it is netted carefully, using a net of appropriate size and mesh, or a one-way sock net for large fish such as koi. Do not frantically chase the fish with the net; use two nets if possible, one to guide the fish into the other. Once netted, place the fish into a plastic bowl or bucket of shipping water with a minimum amount of time out of the water. Try not to carry the fish in the net in the air, but place the net of fish in a bowl or bucket of water to move it if necessary. Gently pour the fish into the shipping bag.
The fish should be placed into the plastic bags with enough water to comfortably accommodate all the fish so they are not injuring each other from crowding. The remainder of the bag is filled with air for trips of short duration (a few hours maximum), or pure oxygen for longer time in transport. Non-iodized salt can be added to the transport water at one teaspoonful per gallon (1 gram per liter). One aspirin tablet (325 mg) per gallon of water can also be added to reduce transportation shock. If the trip is extensive or more than one fish is placed in a bag, adding an ammonia detoxifier (sodium hydroxy methanesulfonate, HOCH2SO3-Na+) will help to reduce ammonia toxicity by binding ammonia as nontoxic aminomethanesulfonate.
The plastic bags of fish should then be placed on their sides in a cardboard box and insulated with styrene sheeting to help maintain constant temperature and packed with newspapers to prevent the bags from rolling around in the box. In hot weather, frozen gel-packs, or frozen plastic bottles of water can be placed outside of the bag in the boxes to keep the temperature cool. In cold weather, heat packs can be added into the box to help maintain the water temperature. Handle these boxes carefully to avoid dropping them or jarring unnecessarily. Label the boxes as live fish to hopefully ensure they are handled gently and not left out in extreme temperatures during vehicle transfers.
Shipping of live fish can lead to high mortality if not planned carefully, due to changes in temperature, high stocking densities, poor water quality and physical trauma.6 During transport, it is sometimes helpful to add a tranquilizer to the water to calm the fish. This will reduce transportation-related physical injury from active fish or when many are packed together. It also lowers the respiration rate so the fish do not use as much oxygen or produce as much carbon dioxide and ammonia.
Newly arrived fish are often stressed from transportation. In many freshwater fish species, using salt in the water will reduce the osmoregulatory effort needed by these fish. Use 1–3 grams of salt per liter of water, depending on species, to produce 0.1–0.3% salinity. Maintain this level during the quarantine period, adding the appropriate amount of salt to the new water when doing the partial water changes.
The use of preventative medications after arrival during the quarantine period is recommended. Perform frequent water changes, measuring ammonia, nitrite, nitrate, and pH to determine how often. Remember to use a dechlorinator when adding new water to the quarantine facility. Maintain the salt concentration up to the 0.2–0.3% level during the quarantine period, which should run a minimum of 2 weeks, ideally 4 or more. The word "quarantine" originally meant 40 days' isolation.
1. Carneiro PCF, Urbinati EC. Salt as a stress response mitigator of matrinxa, Brycon cephalus (Guenther) during transport. Blackwell, Aquaculture Research; 2001;32:297–304.
2. Dixon BA. Stress and fish disease. In: Aquarium Fish Magazine. Irvine, CA: Fancy Publications; 1990:2(4).
3. Miller-Morgan T. A brief overview of the ornamental fish industry and hobby. In: Roberts H, ed. Fundamentals of Ornamental Fish Health. Ames, IA: Wiley-Blackwell; 2010.
4. Saint-Erne N. Advanced Koi Care. 2nd ed. Glendale, AZ: Erne Enterprises; 2010.
5. Stoskopf MK. Tropical fish medicine. Vet Clin North Am Small Anim Pract. 1988;18(2):331–348.
6. Tlusty M, et al. Shipping Cardinal tetras from the Amazon - understanding stressors to decrease shipping mortality. OFI Journal 48, Jubilee Issue, 2005:21–23.
7. Wedemeyer GA, et al. Diseases of Fishes, Book 5: Environmental Stress and Fish Diseases. Neptune, NJ: TFH Publications; 1976.