Which of the following is a sign of stress in fish after electrofishing?

The correct answer highlights that rapid gill movement and erratic swimming are indicators of stress in fish following electrofishing. After experiencing electrofishing, fish may react to the disturbance caused by the electrical current in a variety of ways.

Rapid gill movement is often a sign that the fish is trying to get more oxygen due to the stress of the shocking procedure, which can lead to elevated metabolic demands. Erratic swimming behavior can indicate disorientation or heightened stress levels, as the fish may struggle to regain its bearings after being stunned. These behavioral responses are physiological adaptations to stressors, allowing the fish to try to escape or stabilize themselves.

In contrast, increased color brightness can sometimes indicate health or excitement in certain species, rather than stress. Calm and steady swimming usually suggests that a fish is comfortable and not under stress. Excessive hiding behavior might occur after a stressor, but it is not directly indicative of immediate physical stress symptoms when compared to the more acute signs exhibited through erratic swimming and rapid gill movements. Thus, the behavioral symptoms captured by the correct choice provide a clearer more immediate response to stress from electrofishing.