Tvopical Fish— Keeping a Giant Industry Healthy by John B

TVopical Fish— Keeping a Giant Industry Healthy By John B. Gratzek

"W'he tropical fish industry fish, are reared entirely in ■ is large and complex. It is aquariums or vats in heated estimated that the on-farm buildings. Such facilities may value of goldfish alone is $21 be found scattered throughout million. Tropical varieties the United States. raised in Florida are worth at About 45 percent of the least $15 million. Current imported fish sold by whole- data supplied by wholesalers salers originate in the Far of tropical fish shows that 30 East, 20 percent in South to 40 percent of ornamental America, and 5 percent in Af- fish sold in the United States rica. are produced in the United Points of origin from the States. Far East in order of volume of Of these domestically pro- fish include Singapore, Thai- duced fish, 20 percent are land, Hong Kong, Indonesia goldfish while 80 percent are and Taiwan. Fish from these warm water varieties produced areas may primarily be mainly in South Florida caught wild as in Indonesia where production may consist and Thailand or produced in of pond culture and vat cul- ponds and vats as in Singa- ture or combinations of each. pore, Hong Kong, or Taiwan. A small percentage of domest- Principal exporters of ically raised ornamental fish. tropical fish from South Amer- such as angelfish and discus- ica—in order of the volume of fish suDDlied—are Brazil John B. Gratzek is Professor and Peru, Colombia and Vene- Head, Department of Medical Mi- zuela, Fish from these areas crobiology. College of Veterinary are caught wild. Points of ex- Medicine, University of Georgia, port in Africa include Zaire Athens, Ga, and Tanzania that serve as

Tropical Fish 347 ANIMAL HEALTH

M. Knox More than 200 tropical fish farms such as this one are part of an ornamental fish industry that airfreights more than 4 million live fish from Florida each week.

Tropical fish originated from many different parts of the world. The kribensis cichlid (Telvicachromis pulcherj is a species that came originally from tropical west Africa. This popular small freshwater fish is often kept in community aquariums.

348 Keeping Fish Healthy ANIMAL HEALTH sources of unique species such tremely susceptible to the cil- as Reedfish (Calamoichthys iated protozoan, while orna- calabaricus), mormyrids, and mental catfish such as various species of Cichlids. species of Corydoras are rela- It is estimated that 20 tively resistant. miUion American homes have Some species are very tol- aquariums at any given time. erant of shipping stress. Oth- However, there is a considera- ers such as the lemon tetra ble turnover of individuals or are less tolerant. famihes who keep fish as pets. Some species of ornamental fish tend to have a higher Unique Aspects incidence of diseases caused Innate factors make the tropi- by specific organisms than do cal fish industry most inter- other species. For example, esting but also contribute to species of the intestinal proto- the problem of keeping fish zoan, Hexamita, have been healthy. These include: frequently associated with an- Diverse Species. It is gen- gelfish, goldfish, and various erally accepted that the pet species of anabantids and industry distributes about 500 cichlids. The organism is to 600 species of fish. Within a rarely if ever found in tetras single genera such as the an- or livebearing fish. gelfish or swordtails there Anabantids such as the may be numerous varieties Siamese fighting fish or dwarf based on color patterns. The gouramis, in our experience, end result is that the con- have a high incidence of my- sumer has a very wide selec- cobacterial infections. One can tion of fish available for pur- only speculate that the higher chase. incidence of infectious agents Similar to other animals, results from a fortuitous com- there are considerable vari- bination of factors. For exam- ances among species in dis- ple, the anabantids take air ease resistance. For example, from the water-air interface while the channel catfish is where there may be a higher very susceptible to nitrite tox- concentration of acid-fast my- icity, the serpa tetra is practi- cobacterial organisms. cally insensitive to high con- centrations of nitrite. Diverse Origins Scaleless species such as Since tropical fish are pro- the clown loach and various duced using commercial fish species of catfish are ex- farming methods as well as

Tropical Fish 349 ANIMAL HEALTH

The pet industry distributes about 500 to 600 species of fish. Within a single genera such as the angel fis h there may be numerous varieties based on color patterns, and so there is a very wide selection of fish available to the consumer. This queen angelfish rHolan- canthus ciliarisj, is a marine fish found from the tropical western Atlantic to the Gulf of Mexico.

The protozoan, Hexamita, is shown lodged on the surface of the intestine of an angelfish. The scanning electron micrograph magnifies the parasite 4,800 times.

350 Keeping Fish Healthy ANIMAL HEALTH caught in the wild, the types ers use various invertebrates of problems encountered in such as Cyclops, daphnia, and wild-caught fish vary from tubificid worms as "natural" those raised under intensive foods. These frequently are in- conditions. Our experience termediate hosts of various with fish captured in areas of fish parasites such as nema- South America suggests that todes, acanthocephalans, tape- protozoan parasites infecting worms, and in some cases gills are extremely rare, but small groups of internal proto- that infestations with meta- zoans called sporozoans. cercariae of digenetic trema- For example, some groups tode worms as well as various of neon tetras imported from types of nematode worms are Hong Kong will be severely common, especially towards afflicted with the sporozoan the end of the collecting Plistophora hyphessobryconis. season. Since all neon tetras in Hong Another example of the Kong are tank-reared it is influence of location on inci- reasonable to assume that in- dence of parasitism is our re- fections are introduced by the cent finding that various spe- feeding of various live orga- cies of livebearing fish nisms, some of which carry originating from some loca- parasites. tions in Florida are heavily In general, fish reared infested with worm-like lin- and maintained in aquariums guatulid larvae {Arthropoda: without exposure to parasites Pentistomida). Distribution of carried by live food are devoid this larval form in fish de- of many parasites compared to pends on the presence of alli- those captured in the wild or gators or possibly turtles pond-raised. which are hosts for the adult worms. Transport, Handling Feed Diversity, Salmonid An axiom in producing any and channel catfish fry are kind of fish is to avoid unnec- able to prosper on commer- essary handling or transporta- cially produced diets. In the tion. The ornamental fish in- commercial production of or- dustry is absolutely dependent namental fish, brine shrimp on airfreight transportation are indispensable to raising for its existence. Packing of many types of larval tropical fish for transport can result in fish. many problems. Some tropical fish produc- Fish are placed in plastic

Tropical Fish 351 ANIMAL HEALTH bags of water which then are Common Diseases filled up with oxygen and Problems associated with trop- shipped in insulated boxes. ical fish can be divided The number offish packed per broadly into noninfectious and bag depends on the size and, infectious. Infectious diseases to some extent, the relative are directly related to the tolerance of a particular spe- habitat from which fish were cies to shipping stress. collected, feeding practices, During transportation, shipment and handling fish may be subjected to oxy- stresses, and problems result- gen depletion, accumulation of ing from poor water quality. carbon dioxide and ammonia, Lastly, there are potential in- and temperature variations. terchanges of infectious dis- To some extent carbon dioxide ease agents at wholesale and can be controlled by adjust- retail establishments. ment of pH while ammonia Disease problems which can be removed by addition of occur at each location—pro- natural zeolites. ducer, collector, exporter, im- Fish shippers naturally porter-wholesaler, retailer, tend to pack the highest den- hobbyist—tend to be different sity possible to minimize air or may not be manifest. freight costs. The fact that For example, a recently most tropical fish can tolerate arrived fish shipment from the physiologic rigors of ship- some foreign country may be ment testifies to their natural infected with a bacterium durability. Nevertheless, causing columnaris disease. stress following shipment is a These fish are not salable un- well recognized problem fac- til the infection has run its ing wholesalers. course naturally or with re- Most often stress is fol- covery assisted by antibiotic lowed by outbreaks of bacte- therapy. Columnaris disease, rial diseases. Examination of therefore, tends to be less of a gills of recently unpacked fish problem at the retail level often reveals the presence of than at the wholesale level, gill pathology as evidenced by and is rare in well maintained clubbing of the lamellae of the home aquariums. gill filaments, or by aneur- Another example is pro- isms. Refusal of recently vided by sporozoan diseases shipped fish to eat is probably such as neon tetra disease. At associated with oxygen defi- the wholesale level, the fish ciency caused by damaged gills. may not be visibly afflicted;

352 Keeping Fish Healthy ANIMAL HEALTH but after some time at the re- Management Lapses tail level the disease will have Another feature of infectious progressed to a point where diseases of aquarium fish is clinical signs are obvious. A that disease problems often third example is provided by are related to lapses in good mycobacterial infections aquarium management and which may not be apparent at husbandry techniques, leading both the wholesale and retail to stressful conditions such as level, only to become clinically ammonia and nitrite accumu- apparent after some weeks or lation, or a radical pH drop. months in the display aquar- The resulting stress on the ium. fish is thought to depress its In general, classes of in- natural capacity for resisting fectious disease agents which disease, resulting in sick and can affect ornamental fish are dying fish. identical to those that affect In home aquariums para- other species. Because of their sitic and bacterial disease diverse geographical origins problems often occur during and requirements for trans- the stressful first 30 to 45 portation, tropical fish may be days when ammonia and ni- exposed to a wider spectrum trite levels may be high. Fre- of parasites and bacteria than quently, parasitic diseases fol- fish raised for food. low introduction of a disease- A very important point is carrying but apparently that there appear to be no healthy fish into the aquar- parasites or bacteria unique to ium. The husbandry lapse in tropical fish. For example, this instance is the failure to Hexamita infections have been isolate and observe new fish reported in trout as causing before adding them to a com- either no distinct clinical dis- munity of healthy fish. ease or a syndrome referred to Diet. It is becoming in- as "pinhead". In various tropi- creasingly apparent that a cal cichlids, Hexamita are as- well balanced diet with suffi- sociated with emaciation and cient vitamins A, C, E, and B death of fish. Possibly the dif- complex is essential for fish to ference is due to the parasite maintain their natural disease load and rate of infection, resistance mechanisms. Stor- which would be greater in a age of food over a long period closed aquarium system. can result in food essentially depleted of some B vitamins, vitamins A, C, and E.

Tropical Fish 353 ANIMAL HEALTH Other nutritional prob- rahymena pyriformis is an ac- lems arise when only beef tively invasive carnivorous heart or liver are fed fish. protozoan which can infect in- Also, feeding some species of ternal organs of various tropi- raw fish to tropicals can lead cal (and wild) fish. Because of to a deficiency of vitamin B its invasive properties, treat- (thiamin) due to an enzyme ment usually is not successful. (thiaminase) present in the iíexamiía are flagellated uncooked fish. protozoans found in many Despite all precautions, tropical fish and can be associ- tropical fish may be afflicted ated with wasting and ema- with infectious disease orga- ciation. Treatment with 5 nisms including various types parts per million metronida- of protozoans, worms, para- zole in water is effective. sitic copepods, bacteria and viruses. Some of these infections Velvet Disease can be treated while others The flagellated protozoan Oo- are essentially untreatable at dinium frequently is a prob- the time when fish appear lem of tropical fish. There are clinically sick. at least three species associ- Protozoan infections that ated with this condition, com- are very common are Ichth- monly called "velvet disease." yopthirius multifiliis which Low levels of copper (.11 to causes "white spot" disease of .18 parts per million) for a pe- fish. Other protozoan parasites riod of 10 days have been used which cause serious disease to cure the problem; however, and deaths of fish are/cAiyo- metronidazole may be a good 6oiio necatrix and species of candidate as a treatment. Chilodonella. These organisms Other protozoans such as are found on gills and skin members of the genera Tri- and cause death by gill chodina, Glossatella and Am- damage. biphrya are seen in pond- A variety of chemicals raised ornamental fish, but such as formaldehyde, ma- rarely at the wholesale or re- lachite green, copper, salt, tail level. Stalked ciliated pro- quinine, potassium permanga- tozoans, of the genus Epistylis, nate and méthylène blue have occasionally are seen on tropi- been used to remove external cal fish in poorly maintained parasites. These chemicals aquariums. The colonies ap- vary in effectiveness and po- pear as localized tufts resem- tential damage to the fish. Tet- bling fungal growths.

354 Keeping Fish Healthy Sporozoan parasites are This monogenetic trematode worm common in tropical fish. Sev- taken from the tail fin of a gold- eral genera are involved— fish is shown in high magnifica- some are associated with mor- tion (940 X) by a scanning elec- talities while others may only tron microscope. form discrete nodules on the skin and other organs of fish. Members of the genera Plisto- fish and are one of the causes phora affect muscle tissue and of "bloat." can cause high mortalities in The intestines of goldfish affected fish. are frequently affected by coc- Other sporozoans such as cidiosis organisms {Eimeria Henneguya, Myxobolus and sp.). A therapeutic approach Myxidium frequently cause would require that infected raised white spots on the sur- fish be treated before target face of fish and may be associ- organs are invaded. Anticocci- ated with other organs. Mi- dial drugs would be potential traspora sp. are frequently drugs of choice. found in the kidneys of gold- Monogenetic trematodes

Tropical Fish 355 ANIMAL HEALTH are frequently found on gills is not possible. Treatment of and bodies of various tropical intestinal forms can be accom- fish. Signs of infection will de- plished with various antipar- pend on the numbers of para- asiticides mixed with food. sites present and can include Occasionally, tropical fish respiratory distress, frayed are infected with adult tape- fins and small ulcérations. worms in their intestines; Treatment with formaldehyde more commonly found are in- or salt baths usually are suc- termediate forms of tape- cessful- Organophosphates worms encysted in the perito- have been used; however, neal cavity. The number of some species of trematodes parasites (tapeworms, nema- have developed resistance. todes) infesting a fish will de- termine if there is any observ- Problems with Grubs able effect on the fish. Digenetic trematodes, commonly called "grubs," can Baoteria» Viruses cause severe problems—espe- Bacterial infections following cially in pond-raised or wild- transportation and handling caught fish. In most cases, at the wholesale and retail aquatic birds harbor the adult levels are common. Genera of worm parasite. Snails fre- bacteria most frequently in- quently are the first interme- volved are Aeromonas, Flexi- diate host and fish the second- bacter, Myxobacterium, Flavo- ary intermediate host where bacterium, and Pseudomonas. the parasite is known as a Typical signs of infection can metacercaria. include frayed fins, ulcers, and Many species exist and hemorrhages. Mycobacterial many have a particular affin- infections are very common in ity for a special location such home aquariums. as skin, eye, gills, or internal Treatment of bacterial in- organs. Control is best accom- fections in fish is possible. plished by eradicating snails Problems encountered are bac- in production ponds. teria resistant to common an- Nematodes are common tibiotics used, absorbability of in tropical fish and include the antibiotic, and effect of members of various genera. the antibiotic on the nitrifying They frequently are found in bacteria associated with biofil- the intestine or migrating tration of ammonia and ni- within organs of the body cav- trites. ity or muscles where removal The extent of virus infec-

356 Keeping Fish Healthy ANIMAL HEALTH tions in tropical fish is not pected. At this point in time, known. However, based on many home aquarists facing other species of fish, there are problems with fish expect as- probably numerous classes of sistance from the retail outlet viruses involved in disease ep- where the fish were pur- izootics. About five viruses chased. Only recently have have been isolated from fish some Colleges of Veterinary used for ornamental or display Medicine offered courses purposes. stressing basic principles of Our clinical experience aquariology and management suggests that many conditions of closed systems along with could be attributable to vi- the study of diseases of aquar- ruses. The one well recognized ium fish, and control meas- virus of tropical fish is lym- ures. Results of this training phocystis virus which stimu- will be an increase in the lates cells associated with ex- quality of service available to ternal surfaces of the fish's the public. body to enlarge, resulting in The diverse geographical unsightly growths. origins of fish, along with re- quired transportation, congre- Diagnostic Efforts gation and handling are tail- There are factors which dic- ormade conditions for stress tate how much diagnostic ef- as well as spread of disease. It fort should be expended to is a tribute to knowledgeable solve fish problems in home fish importers that relatively aquariums. The most impor- so few fish die. tant factor is the degree of in- Preventing problems volvement of the client, who through routine treatment may be a breeder and supplier and good husbandry at the of one exotic species and may wholesale and retail level is have numerous aquariums. important in disease control. Another type of individual is Avoiding disease in the dis- the hobbyist with an aquar- play aquarium is best done ium, ancillary equipment, and through quarantine and rou- fish worth hundreds of dollars. tine treatment of new fish, One important factor fre- water management by regular quently overlooked is the close changes, pH control if re- bond many individuals estab- quired, adequate biological fil- lish with their fish. tration, and by maintaining In any of these cases, disease resistance of fish good diagnostic service is ex- through an adequate diet.

Tropical Fish 357