Yes, fish captured at the bottom of the ocean can experience expansion when they are brought to the surface. The phenomenon is known as barotrauma or "the bends." It occurs due to the rapid change in pressure as the fish is brought from high-pressure deep waters to low-pressure surface waters.
In deep waters, fish are subjected to high pressure, which compresses their swim bladders (an internal air-filled sac that helps with buoyancy control). When they are rapidly brought to the surface, the pressure decreases quickly, causing the gas inside their swim bladders to expand. This expansion can lead to various physiological problems and injuries in the fish.
The swim bladder may rupture, causing the fish to lose its ability to control buoyancy. The expanded swim bladder can also push against other internal organs, potentially leading to damage. Additionally, the rapid expansion of gases can cause bubbles to form in the fish's bloodstream, similar to the bends experienced by scuba divers.
To mitigate the effects of barotrauma, some fishing practices, such as catch-and-release in recreational fishing or commercial fishing with certain regulations, emphasize techniques to minimize the pressure change for captured fish. These techniques may involve venting the swim bladder or using specialized devices to help fish safely return to deeper waters.