This simple app will calculate the respiratory rate of a fish (in beat per minute) by observing the movement of the fish operculum.

The operculum is a series of bones found in bony fish and chimaeras that serves as a facial support structure and a protective covering for the gills.

1. Press the button just after the end of an opercular movement (cover of the gills)
2. Press the same button again after 5 full opercular movements.