The length of time a fish can survive out of water depends on the species of fish. There is a species of climbing fish that can survive without water for six days while crossing land. There are several other types of amphibious fish, meaning that they live both in water and on land. For the fish that must live in water most of the time, they can survive minutes to hours, depending on how well they can breathe oxygen through their skin and other factors.

I recently answered a similar question from a student interested in catch-and-release fishing. The short answer is that being out of the water for more than 30 seconds increases the chance a fish will die.

Being hooked and handled creates stress, causing fish to have a higher metabolic rate and need more oxygen and energy, just like how your heart beats faster when you’re scared. We don’t know if the fish are actually scared, but they produce the same stress hormones that we do, and these can be measured. Another issue is that the fish will probably be warmer in the air. Warmer temperatures speed up chemical reactions, like the metabolic reactions in bodies. This would create a higher demand for oxygen and energy. This is also the reason that it is better not to catch fish when water temperature is high.

Basically, the less the fish is tired out by being played, the less time it is handled, and the less time it is out of the water, the better. If you use a hook that you can remove quickly—like a hook without barbs, the fish will spend less time in the air. If you can remove the hook with the fish underwater, that’s even better. But one study showed that using a lip grabber on the fish when removing the hook can damage its mouth.

Holding the fish (gently) in the water until it has a chance to get oxygen into its blood can help it avoid being hurt while it’s recovering. When it has recovered enough, it will swim away.

There are many kinds of fish, though. Lungfish live in places where the water dries up. They stay in muddy, mucus cocoons breathing air with a sort of lung until the rains come again. Mudskippers live in the “intertidal zone,” which is underwater or not, depending on the ocean’s tides which change throughout the day. They actually need to breathe air sometimes. To really appreciate them, you have to see them in action.

A spokesman for the Association of Midland Goldfish Keepers said: "Fish can survive quite a while out of the water, as long as their gills remain moist, allowing them to breathe. But this is the longest I've heard of a goldfish staying alive. It's quite astonishing."Dec 27, 2008

Goldfish leaves owner gasping by surviving 13 hours out of water ...

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It depends on the fish. Most can live for minutes, but some can live for months.