Involved Methodology Statistics Comparison of Fish Vented vs. Non-Vented Vent vs.
Many fish have swimbladders or gas bladders.
As a general rule, fish with spiny fin rays have closed swimbladders and fish with soft fin rays have open swimbladders. The closed bladder acts like a balloon that has been tied off with the gas trapped inside. The open bladder acts like an untied balloon and gas is free to move in and out. You may have noticed that some fish caught at depths have their intestines coming out of their anus, eyes bulging out of their heads and stomachs protruding out of their mouths. This is because these fish have closed gas bladders that have expanded and ruptured and the gasses from the bladder have displaced the internal organs as they were brought rapidly to the surface.