Everybody who has ever caught a fish has taken a fish out of the water. While taking a long time to remove a stubborn hook or to get the right pose for a picture, most of you have probably wondered, “how long can this fish safely stay out of the water?” Well, this is my area of research expertise: fish out of water! Some fish can survive for a few minutes out of water, some for a few hours, and some for even a few months! This mostly depends on the species of fish, the habitat/environment, and how long you fight the fish.

 A surprising number of fish that you may catch around the world actually have air-breathing organs or can breathe air through their skin! This includes tarpon, arapaima, walking catfishes, snakeheads, eels, bowfin, lungfishes, gars, and more! Some of these fish are limited in their air-breathing, like tarpon which will gulp air from the surface during long fights to get extra oxygen and bursts of energy. Others like snakeheads and walking catfish have well-developed air-breathing organs that allow them to survive many hours out of water.

Many killifish can breathe air through their skin quite efficiently, and are tolerant of low-oxygen conditions (hypoxia), which is why they survive quite well in bait buckets when other baitfish (minnows, shad, etc.) do not. Furthermore, the most extreme of killifish, like the mangrove rivulus, can survive out of water for over a month at a time (Bressman et al., 2018; Taylor et al., 2007)!

A large American eel I caught comfortably slithers around on the grass due to its air-breathing capabilities.

If a fish can’t breathe air, though, it doesn’t necessarily mean it’ll die right away out of the water. Your usual catfish species (channel, blue, etc.) are particularly tolerant of low-oxygen conditions, and I have seen them alive out of the water for multiple hours! However, some fish are less tolerant of being out of the water than others. In particular, trout fair particularly poorly when out of the water for even a few minutes.

Fish with slow metabolisms and those that live in cold water can usually survive a good bit of time as long as it’s cool; metabolic rates and oxygen demand are generally lower for fish in cold water, so they can survive without breathing longer. For instance, I caught pike while ice fishing and immediately put it on ice. When I opened my cooler a few hours later, it was still movie! Conversely, many fish caught in very warm water require a lot more oxygen and likely will not survive as long out of the water.

Most importantly, the longer you fight a fish, the more oxygen it’ll need to recover, so the quicker it needs to go back in the water. Just imagine running a marathon and then immediately trying to hold your breath underwater – you won’t last long. After a long fight with a fish, it is important to get it back in the water ASAP so that it can “catch its breath” and recover. Sometimes, the fish will need some help if it’s very tired, and you will need to perform fish CPR – moving water over the fish’s gills or moving the fish through water to help increase its oxygen uptake, so that it can safely recover.

What about the average, non-air-breathing fish that didn’t spend a long time fighting on a moderate-temperature day? Fish like bass, perch, and drum that don’t have any air-breathing adaptions are usually fine being out of the water for a few minutes out of the water, but it’s best to return fish to water as soon as possible to reduce their stress! If it takes several minutes to get a stubborn hook out, these fish should still be fine if you release them, but keep an eye on them when you put them back in the water. If they are struggling, you may need to perform fish CPR on them until they can swim away on their own.

Interested in learning more about fish out of water and amphibious fishes? Check out my current project that I am crowdfunding on the terrestrial orientation and behavior of invasive walking catfish: https://experiment.com/projects/how-do-amphibious-fishes-find-their-way-around-on-land, or feel free to reach out to me on social media to ask a

IG: noahwithfish

Twitter: noahwithfish

Noah Bressman is a PhD candidate studying fish biology, behavior, and biomechanics at Wake Forest University. Below is Noah with a Blue Catfish (Ictalurus furcatus), caught on cut bait while night fishing in the Pee Dee River in NC.

References

Bressman, N. R., Simms, M., Perlman, B. M., & Ashley‐Ross, M. A. (2018). Where do fish go when stranded on land? Terrestrial orientation of the mangrove rivulus Kryptolebias marmoratusJournal of Fish Biology, doi: 10.1111/jfb.13802.

Taylor, D. S., Turner, B. J., Davis, W. P., & Chapman, B. B. (2007). A novel terrestrial fish habitat inside emergent logs. The American Naturalist171(2), 263-266.