Possible behavioural characteristics to look for in infected or diseased fish

  • Fish stop eating
  • Juveniles (less than 25 mm) often swimming in disorientated fashion at surface
  • Feeble swimming action
  • Separation from shoal (rest of the group)
  • Lethargy
  • Fish congregate in the upper water levels
  • Fish gasp at the surface
  • Inappetence
  • Lethargy
  • Swimming at outer edges
  • Lingering
  • Swimming with rotating movement around body axis (e.g. spinning)
  • Fish lie still on bottom
  • Fish swim with a spiralling, corkscrew motion

Important: animals with disease may show one or more of the signs below but disease may still be present in the absence of these characteristics