By: Dana Sackett
The saying, ‘fish out of water’ has often been used to describe someone out of their comfort zone, because if you take a fish out of water and drop them onto land most would not be very comfortable. However, there are a number of fish across the world that would scoff at such a saying as they push or leap (that’s right I said leap) up a steep embankment to travel over land. This week we are dedicating our blog to some of these awesome amphibious fish.
1. Mudskippers are one of the most notorious land-venturing fish with some species spending more time out of water than in. They have special morphological adaptations that allow the use of their pectoral fins in terrestrial locomotion. They also can either ‘jump’ (usually away from something unseemly) or do a motion dubbed ‘crutching’ because of its resemblance to a human walking with crutches. Mudskippers carry water around in their gill chambers to prevent gills from drying, allowing the fish to breathe oxygen from the air and water, as well as through their wet skin.
2. Walking catfish are infamously invasive. Their native range spans Asia, Africa, and the Indo-Pacific. One group of walking catfish were introduced in Florida in the 1960s and quickly spread throughout the state, aided by the ability to leave the water and ‘walk’ across land to invade new waterbodies. They have been recorded to survive out of water for days and feed in the terrestrial environment. Northern snakeheads in particular are legendary in their ability to disrupt native habitats; with their massive maw, opportunistic feeding (meaning they will eat almost anything they come across) and ability to travel over land it is no wonder we have had such trouble stopping this species from spreading across the United States.
3. There are also a number of fish species called blennies that leave the aquatic environment on a regular basis. These fishes are similar to mudskippers with the exception that they primarily use their tails to jump around the intertidal rocky substrate just above the waterline. Pacific leaping blennies spend their entire adult life leaping from rock to rock just above the water, feeding on algal mats and breathing through their wet skin and gills.
4. Climbing perch are obligate air-breathers meaning they breathe oxygen from the air whether in the water or on land. They use their tail for propulsion, vaulting themselves into the air and use spiny gill covers to help stick their landing. They are commonly seen moving across grassy substrate after rainfall to move from one pond to another.
5. Mangrove killifish can survive months out of water typically spending that time in hollow fallen logs breathing air through the skin. These fish are mostly hermaphrodites that reproduce by self-fertilization.
6. Lungfish are not considered truly amphibious as they do not typically move across land. They do however use their pelvic fins to ‘walk’ while in water. These fish are also obligate air breathers (hence the name lungfish) and renowned for their ability to remain inactive in a state of dormancy (aestivation) on land for up to 4 years during periods of extreme drought. These fish burrow into the mud at the onset of the dry season and secrete a mucus cocoon that surrounds their body to prevent desiccation.
Some fish are not adapted to leaving the water but still display a ‘walking’ behavior while in the water. For instance, the ceolocanth, a living fossil that was initially thought to be extinct uses both pectoral, pelvic, and anal fins to walk along the bottom of the ocean. Just recently a group of sharks were also discovered to exhibit this ‘walking’ behavior. The most recent discovery comes just last year when a new species of walking shark was described in Indonesia.
The list above is nowhere near inclusive of all the species of fish across the world that can leave the aquatic environment and venture onto land. Eels commonly leave the water and slither over land to migrate between waterbodies and clingfishes use large ventral suckers to jump out of the water and cling to rocks, just to name a few more. Please add your own experience with land-dwelling fish in a comment below. Also feel free to enjoy some videos of fish moving over land below.
References and extra reading material:
Pace CM, Gibb AC. 2009. Mudskipper pectoral fin kinematics in aquatic and terrestrial environments. Journal of Experimental Biology 212:2279-2286.
Sayer MDJ. 2005. Adaptations of amphibious fish for surviving life out of water. Fish and Fisheries 6:186-211.
Sayer MDJ, Davenport J. 1991. Amphibious fish: why do they leave water? Reviews in Fish Biology 1:159-181.