Federal, state, and private fishery workers were asked which anesthetics they used and for which fish species; how the materials were used; the disadvantages or problems associated with their use; and the desired characteristics of an ideal anesthetic. Responses were received from 66 state or provincial hatcheries, 40 federal hatcheries, 3 private hatcheries, and 74 others who did not identify themselves by category. Tricaine methanesulfonate (MS‐222) was by far the most commonly used anesthetic (145 users), followed by quinaldine (41), and carbon dioxide (18). Carbon dioxide and MS‐222 are the only registered fish anesthetics. The most cited limitation on the use of MS‐222 was the 21‐day withdrawal period required after treatment. The ideal anesthetic should permit a reasonable duration of exposure, produce anesthesia within 3 minutes or less, allow recovery within 5 minutes or less, cause no toxicity to fish at treatment levels, present no mammalian safety problems, and leave low tissue residues after a withdrawal time of 1 hour or less.

Disease problems constitute the largest single cause of economic losses in aquaculture. In 1988, channel catfish producers lost over 100 million fish worth nearly $11 million. Estimates for 1989 predict even higher losses. The trout industry reported 1988 losses of over 20 million fish worth over $2.5 million. No data are available on losses sustained by producers of shellfish. Bacterial infections constitute the most important source of disease problems in all the various types of production. Gram-negative bacteria cause epizootics in nearly all cultured species. Fungal diseases constitute the second most important source of losses, especially in the culture of crustaceans and salmon. External protozoan parasites are responsible for the loss of large numbers of fry and fingerling fin fishes and are a cause of epizootics among young shellfish. The number of therapeutants approved by the Food and Drug Administration is limited. Research to support the registration of promising therapeutic agents is urgently needed.

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Infections in channel catfish (Ictalurus punctatus, Rafinesque) induced by the sporozoan Henneguya (Protozoa: Myxosporidea) result in seven known and diverse disease manifestations. Most outstanding is an interlamellar branchial form responsible for significant losses among immature catfish, and a unique papillomatous form. The question of whether or not the species of Henneguya involved in these cases is H. exilis remains to be resolved.