It is true that small fish tend to freeze to avoid predators. So, I am sure that is part of it. As the dropping of the object was standardized to always be in the middle of the tank, there were times where the fish were very near to the center and the clip ended up less than an inch away from them. They didn't budge still. It'll be interesting to re do the experiment in a couple of months and see if they have changed in their reaction.
When I did a similar experiment with the eye biter fry, they did freeze and I used it as a measure of boldness (less time freezing = bolder fish). However, when I dropped an object they would usually dart around a bit and then freeze. The average time spent darting was about 2 seconds, but nearly all of them did it. These guys have such a different behaviours to the eye biters that I'm thinking I may have to wait until they are older and do aggression and things along those lines.
When I did a similar experiment with the eye biter fry, they did freeze and I used it as a measure of boldness (less time freezing = bolder fish). However, when I dropped an object they would usually dart around a bit and then freeze. The average time spent darting was about 2 seconds, but nearly all of them did it. These guys have such a different behaviours to the eye biters that I'm thinking I may have to wait until they are older and do aggression and things along those lines.
