can fish swim backwards

Can fish swim backwards?

Whether or not a fish can swim backward is probably not something that too many fish keepers have stopped to consider. After all, there are very few circumstances, especially in the wild, that one would think that a fish would need to do so. Swimming forward is definitely the direction of fish choice, with the occasional hovering thrown in.

That doesn’t mean, however, that fish cannot swim in reverse. In fact, I know they can, and have witnessed it with my own eyes. You see, I have a very shy Frontosa Cichlid who swims backward into his cave slowly every time I approach with his food.

Unfortunately, he does not do his swimming backward in a particularly graceful way, and I’m pretty sure that if he needed to do it for more than a few inches, he’d struggle. However, he isn’t the only species of fish that can swim backward, and he certainly isn’t the best.

Fish That Swim Backwards Well

Commonly the fish that swim backward the best are species such as the eel who use anguilliform (eel-like) locomotion to move their elongated bodies. They can do this due to their entire body being flexible throughout its entire length. Movement is in a sinuous wave that passes from head to tail.

It has also been found that electric fish swim backward as well as they do forwards. Black ghost knife fish, for example, swim backward by undulating the fin on their belly. They do this so they can swim over their potential prey to scan it with their electroreceptors and still be able to lunge at it without having to turn around. If they swam forwards in order to do this, their prey would end up by their tail, and they would not be able to eat it.

Other Forms Of Swimming

Of course, not all fish swim using anguilliform locomotion or are as good at swimming backward as the eel or electric fish tend to be. There are several other types of locomotion as described below.

Sub-carangiform locomotion is used by fish such as trout that generally have a stiffer body and more speed. It works by creating an increase in wave amplitude along the body with the majority of work being done by the rear of the fish.

Carangiform locomotion refers to movement sourced from the posterior of a fish. This means only the rear half of the body flexes with the passage of contraction waves in carangiform locomotion. Fish that commonly swim using carangiform locomotion include Jacks, Pompanos, Mackerel, runners, and, scads.

Not necessarily related to fishes swimming backward, but interesting all the same, carangiform locomotion is thought to be the most efficient method of swimming. This is due to it being the manner in which most of the fastest and most active fish swim.

Thunniform locomotion is used by the group of fish that contains high speed and long distance swimmers such as tuna and several lamnid sharks. Virtually all the movement, sideways, is in the tail and the area connected to it, known as the peduncle. The tails of these fish are usually large and crescent-shaped.  

Ostraciiform locomotion is the movement of fish where only the caudal fin oscillates from side to side in a manner similar to moving a boat with one oar. Boxfish, cowfish, and trunkfish all swim in this manner, mainly to avoid predators, and they are surprisingly good backward swimmers despite it.

Fish That Can’t Swim Backwards

The only fish that we are absolutely sure is completely incapable of swimming backward is the shark. This is because their pectoral fin cannot bend upwards as a fishes can. Sharks are, unfortunately for them, limited to forward movement only, although they can use gravity to sink back a little. Not related at all, but just an FYI, sharks also cannot just stop if they need to avoid bumping into something. Rather, they have to swerve to the side to avoid a collision. Weird really, when you consider that sharks are apex predators that they would have swimming or movement limitations.

There is also some debate surrounding the ability to swim backward in seahorses, Razorfish, and shrimp fish, who all swim vertically, and large fish such as marlin, tuna, and Arowana.  

Can Fish Swim Backwards For Long?

It’s hard to imagine that a fish would need to swim backward for long making whether they can or not a rather moot point. However, just for the sake of curiosity, we’ll address it.

I’m sure that you have heard tales of sharks being pulled back through the water and drowning as a result. Not only is this cruel, but it’s factually incorrect too. A shark pulled backward through the water would not drown, rather it would suffocate because it would be incredibly hard to breathe.

The reason the shark would struggle to breathe is that water needs to flow over its gills in the correct direction in order for them to do so. This is achieved for fish by water passing through the mouth and out of the gills. Pulling them backward reverses this procedure making it incredibly hard for them to breathe.

Interestingly, when catching large fish such as tuna and marlin, fishermen have been known to use backward pulling of a fish to tire them out. They equate this experience for the fish with us wearing an elevation mask then exercising heavily. You can still breathe, it’s just a bit harder.

Considering the above, it is hard to think that a fish would choose to or be capable of swimming backward for long distances.

Conclusion

It would seem that pretty much every fish, excluding the shark, can swim backward if they need to or choose to. It is hard to believe, however, because it makes breathing harder and is tiring for them that they would choose to that often. Rather, it would seem that backward swimming is used for a necessity such as avoiding predators, or in the case of electric fish catching them.

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