Fish Behavior for the Exotic Pet Practitioner

Key points
• When evaluating fish behavior, veterinarians can use three models to categorize the possible cause of behavior—natural history (species typical modal action patterns), medical (disease state), and learning experience (classical and operant conditioning).
• Natural history model: The fish may be exhibiting normal, species-appropriate modal action patterns related to natural history. Common behaviors seen in pet fish are related to resource competition, breeding behavior, social interactions, and grooming (parasite removal).
• Medical model: The fish may be exhibiting behaviors in response to a medical condition. It is critical to consider water quality and other environmental factors as part of evaluating disease state. Common signs of disease include color change, pruritus, lethargy, erratic swimming, isolation, fin clamping, and tachypnea or dyspnea. Common causes include parasitic disease (particularly protozoal ectoparasites), buoyancy problems, poor nutritional condition, trauma, neoplasia, ocular changes, and poor water quality.
• Learning model: The fish may be exhibiting a learned behavior. Fish readily learn and this should be taken into account when evaluating fish behavior. Positive reinforcement training can be used to deliberately train behavior in fish. Although uncommon, fish may present for problem behaviors.
• These models are useful for ensuring clinicians take a holistic approach to fish behavior. They are not mutually exclusive and integrate naturally. Models help clinicians formulate appropriate differentials, ensuring they do not exclusively consider disease, particularly in unfamiliar species.