Which symptom is NOT typically associated with copper toxicity in fish?

Copper toxicity in fish is known to induce a range of symptoms as it affects their physiological and neurological functions. Erratic swimming is often a response to distress caused by copper exposure, where fish show abnormal swimming patterns due to stress or neurological impairment. Gill hyperplasia is a noted pathological change, with copper exposure leading to irritation and inflammation of the gills as the fish attempt to detoxify the metal, resulting in the overgrowth of gill tissue. Loss of equilibrium is another common symptom, as copper can affect the inner ear balance mechanisms in fish, leading to difficulty maintaining orientation in the water.

On the other hand, increased appetite is not typically associated with copper toxicity. Instead, fish exposed to high levels of copper usually exhibit signs of stress, which can lead to decreased feeding behaviors rather than an increase in appetite. Stress from toxicity often results in lethargy and a lack of interest in food, as the fish's body prioritizes dealing with the toxic exposure rather than engaging in feeding behaviors. Therefore, increased appetite stands out as the symptom that does not align with the expected clinical signs associated with copper toxicity in fish.