Working with a fish health specialist to identify and solve disease problems is highly recommended but this is not always possible. In many cases, two or more factors, such as changes in water quality, handling, parasites or bacteria, will have contributed to the disease outbreak, and each must be corrected.
Records of water quality and management actions should be reviewed for early warning and any problems should be
corrected (see table below). We cannot stress enough the importance of record keeping as this will aid you in determining any changes made to the management of your system that can provide important insight into what needs to be changed to correct problems in your system.
Nutritional programs should be examined for completeness (this will vary depending upon the species requirements and life stage), and storage of feeds should be evaluated to ensure feeds are stored properly (cool temperatures, low humidity, and for minimal periods).
Fish should be evaluated, preferably with the assistance of a fish health specialist. Early warnings will include behavioural changes, lack of feeding, and any obvious external signs of disease (e.g., ulcerations, white spots, hemorrhages,or presence of fungi). A representative sample of sick fish should be sacrificed for necropsies. Necropsies should include examination of all tissues for appearance and presence of abnormalities; search for external and internal parasites; microbiological culture of pertinent organs; histopathology; and virology, if warranted. Any necessary treatments should then be based on findings from all pertinent tests.
The following general guidelines in the table highlight common problems with water quality that often contribute to disease.
Roy P.E. Yanong – University of Florida