Thomas C. Ardelt
Recent interest in stress and disease in fish parallels the continuing worldwide increase in fish farming. Intensive fish culture increases potential risk of environmental stressors (e.g., poor water quality, low dissolved oxygen, and temperature fluctuations and/or extremes). In addition, behavioral stressors such as crowding and territorial behavior are also present. An investigation was carried out to examine the effects of behavioral stress in the form of male territoriality on fish suffering from bacterial infection. An initial experiment (Experiment I) was performed to determine if Aeromonas hydrophila could be incorporated into a carrier state in the convict cichlid (Cichlasoma nigrofaciatum) and then recrudesced at a later time following behavioral stress. A final experiment (Experiment II) was carried out to observe the effects of behavioral stress on acute A. hydrophila infection in C. nigrofasciatum.
Fish in Experiment I did not develop a latent carrier state of A. hydrophila and fish were not tested for recrudescence of disease. Experiment II fish showed a significantly higher mortality when inoculated with A. hydrophila and exposed to behavioral stress, in comparison to infected non-stressed controls.