Question

How can I calculate the flight initiation distance in fish?

Answer 1

When threatened with a predator or encroachment by other species (including humans), animals become alarmed and an escape response is triggered within them. The flight distance is described as the willingness of an animal to take risks. The flight initiation response is a measure of animals' fear responses to human activity. It is the distance at which an animal will leave its original habitat when approached by a human.

During experiments on fishes, often scuba-divers (the human element) are use to collect data. The divers usually swim slowly to a site where the fishes are foraging, until the time the diver is a position to approach the fishes directly, and at the same depth as the fishes, perpendicular to them. The speed at which the diver approaches is noted by another diver, who does not approach the fish.

When the fish start to flee, as indicated by an increase in speed, often accompanied by a change in direction, the diver would drop a weighted marker. A second weighted marker would be placed at the position of the fish when it initiated flight. The distance between the two markers would then be measured with a graduated chain, and the distance between the diver’s head and waist was subtracted so that the recorded FID was the distance between the fish and the closest part of the diver’s body.