Behavioural changes

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Behavioural changes are often the first indication that there may be a health problem with a group of fish. Observant aquarists who are attuned to the normal behaviour of their pets may recognize when they are ill several days before the fish actually begin to die. This chapter covers feeding behaviour, swimming behaviour, reproductive behaviour, aggressive behaviour and colour change.

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Image of Figure 19.1
Figure 19.1 Excess positive buoyancy in an oranda (a fancy variety of goldfish) due to a grossly dilated swim-bladder. The problem had been present for 6 months and appeared to be associated with an excessively short body. Only one swim-bladder chamber is visible on the radiograph. (© W.H. Wildgoose.)
Image of Figure 19.2
Figure 19.2 An excess amount of gas was present in the bowel of this fancy goldfish. This resulted in the fish floating at the surface when at rest, with the vent and anal fin above the surface of the water. The fish could regain its normal posture by intermittent active swimming, which also enabled it to feed. (© W.H. Wildgoose.)
Image of Figure 19.3
Figure 19.3 Excess positive buoyancy in a fancy goldfish. Abdominal swelling due to polycystic lesions in the kidney displaced the posterior chamber of the swim-bladder, which resulted in it consistently floating on one side. (© W.H. Wildgoose.)
Image of Figure 19.4
Figure 19.4 A 15-year-old fantail goldfish with a disorder that caused ‘head standing’ for over 7 years. Radiography revealed a collapsed anterior chamber of the swim-bladder, which was associated with a fibroma. In addition, a large granuloma was found in the cerebellum. (© W.H. Wildgoose.)
Image of Figure 19.5
Figure 19.5 This 9-month-old black molly developed an abnormal ‘head-standing’ posture, which deteriorated over the course of one week. The same disorder had affected the parent and another offspring. Histopathological examination revealed vacuolation and degenerative changes in the mesencephalon. (© W.H. Wildgoose.)
Image of Figure 19.6
Figure 19.6 (a) A 7-year-old fantail goldfish that developed a sudden-onset loss of balance and incoordination. The fish lay on the bottom of the aquarium in an arched position and tended to revert to the same side when physically repositioned in the water. (b) A large granuloma (arrowed) found in the cranial cavity of the same goldfish. There were multiple granulomas in other organs, including the heart, spleen and kidney. Acid-fast bacilli were found in several of these lesions. (© W.H. Wildgoose.)
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