TRANSPORTATION OF LIVE FISHES 357 



Ammonia 



When fish are transported in distribution tanks, their excretory products 

 accumulate in the water. Ammonia is the main metaboHc product of fish 

 and is excreted through the gills. Total ammonia concentrations can reach 

 10 parts per million (ppm) or higher in fish distribution tanks depending 

 on the fish load and duration of the haul. Exposure to 11 to 12 parts per 

 million total ammonia (0.13 to 0.14 ppm un-ionized ammonia) for 6 hours 

 and longer adversely affects trout and can reduce stamina. 



Temperature and time of last feeding are important factors regulating 

 ammonia excretion. For example, trout held in water at 34°F excrete 66% 

 less ammonia than those held in 51°F water, and fish starved for 63 hours 

 before shipment produce half as much ammonia as recently fed fish. Small 

 fish should be starved for at least two days prior to shipping. Fish larger 

 than 4 inches should be starved at least 48 hours; those 8 inches and larger 

 should be starved 72 hours. If they are not, large losses may occur. 



Water temperature during shipping should be as low as can be tolerated 

 by the fish being handled. Low temperatures not only reduce ammonia 

 production, but oxygen consumption as well. 



The effects of metabolic waste products and related substances on warm- 

 water fish during transportation have received little attention, but most fish 

 culturists agree that excretory products, mucus, and regurgitated food de- 

 grade water quality and stress the fish. Cannibalistic species, such as large- 

 mouth bass, walleye, and northern pike, obviously should not be starved. 

 Although proper grading for size of fish will reduce cannibalism, it does 

 not eliminate it. 



Carbon Dioxide 



Elevated carbon dioxide concentrations are detrimental to fish and can be 

 a limiting factor in fish transportation. A product of fish and bacterial 

 respiration, CO2 acidifies transport water. Although this reduces the per- 

 centage of un-ionized ammonia in the water, it also reduces the oxygen- 

 carrying capacity of fish blood. Fish may succumb if CO^ levels are high, 

 even though oxygen levels are seemingly adequate. Trout appear to 

 tolerate carbon dioxide at levels less than 15.0 parts per million in the 

 presence of reasonable oxygen and temperature, but become distressed 

 when carbon dioxide levels approach 25.0 parts per million. 



Fish transported in distribution tanks are exposed to gradually increas- 

 ing concentrations of carbon dioxide. Unless aeration is adequate, CO^ lev- 

 els may exceed 20-30 parts per million. In general, for each milliliter of 

 oxygen a fish consumes, it produces approximately 0.9 milliliters of CO2. 

 If the CO2 level increases rapidly, as with heavy fish loads, fish become 



