Most fish can swim backward. However, they don’t display their reverse swimming trait unless it’s necessary. In the wild, fish swim backward to catch prey. Triggerfish, Eels, and Blue Gill Sunfish are some fish that swim backward very well, while the Shark is one fish that can’t swim backward.
Let’s learn more about the reverse swimming abilities of fish.
Can All Fish Swim Backward?
The majority of the fish can swim backward. However, they don’t display this ability unless there’s a need.
Swimming backward is a skill that requires a lot of energy and strength.
So fish mostly swim backward while they are moving against the flow of the water, in search of food, or to inspect their surroundings.
Also, it’s an important survival technique for many fish as they avoid predators by swimming backward.
Which Fish Can Swim Backward Very Well?
Fish in home aquariums usually don’t swim backward.
However, many fish swim backward in their natural environment when the situation demands.
While swimming backward, these fish move their anal and pectoral fins to generate sufficient force for moving in the reverse direction.
As per a research, the anal and dorsal fins assist these fish in swimming backward with ease.
The most common fish that swim backward very well are given below.
1. Blue Gill Sunfish
Blue Gill Sunfish have an exceptional ability to swim backward.
They use their flexible fins for swimming backward without rotating the body position.
Blue Gill Sunfish alternate their movements between the pectoral, dorsal, anal, and caudal fins.
They use their dorsal and anal fins to propel themselves in the reverse direction while stiffening their pectoral and caudal fins for precise control.
These fish don’t reverse their fin motions like they do while swimming forward.
Triggerfish are another fish that are capable of swimming backward with ease.
They mostly use their top and bottom fins to swim around, unlike other fish that use their whole body.
So these fish manoeuver their bodies very precisely while swimming backward.
3. Black Ghost Knifefish
Black Ghost Knifefish move backward by swirling the fins on their bellies.
They swim backward mainly to hunt prey and lunge on it without having to circle around.
If these fish swim forward, the prey will end up on their tail. So they won’t be able to eat it.
That’s why swimming backward and catching the prey is essential for them.
Eels are popular for reverse swimming.
They can swim forward and backward with ease, making them one of the most sought-after fish species.
Eels generate waves that travel the length of their bodies. They reverse the direction of the waves during reverse swimming.
While swimming backward, eels use their anal and pectoral fins to move against the flow.
Why Do Electric Fish Swim Backward?
Electric fish like electric eels swim backward to detect prey. This ability helps them to catch the prey efficiently.
They are good at reverse swimming as they can undulate the fin on their bellies.
In addition, they possess an elongated fin that allows them to send electric discharges toward potential prey.
When electric eels swim backward, they create a current in the water.
This current creates an electromagnetic field that attracts nearby prey.
They keep their mouths open to hunt the potential prey while swimming backward.
Furthermore, these fish release low currents to detect their prey in the water.
Once they sense the prey nearby, they start swimming in reverse so that their mouth stands behind the prey.
After that, they generate high voltage currents to stun their prey.
Eels then back up and lunge forward on the prey to grab and eat it.
If these fish don’t swim backward to hunt their prey, they can miss the prey.
Which Fish Can’t Swim Backward And Why?
While all electric eels or electric fish can swim in reverse, Rhabdolichops Troscheli is an exception.
Rhabdolichops Troscheli fish don’t swim backward because their environment is unsuitable for reverse swimming.
They majorly inhabit areas that have strong water currents.
So they constantly swim in a forward direction for survival.
If these fish try to swim backward, they may disappear downstream due to the strong water currents.
The other fish that can’t swim backward is Shark.
Sharks’ streamlined body enables them to move forward at high speeds.
However, when it comes to reverse swimming, sharks can’t do it due to their biological design.
Unlike other fish that can swim backward, sharks have pectoral fins that don’t curve upward.
So their swimming is limited to forward movement.
Any backward movement from sharks can prove fatal to them.
If the sharks attempt to move backward, water can enter their gills, thus hindering their breathing.
As a result, they can suffocate.
Apart from the limitation of swimming backward, sharks can’t even stop if they find an obstacle in front of them.
So instead, they just swerve to the side to avoid a collision.
Is there any harm if aquarium fish swim backward?
There’s no harm if an aquarium fish swims backward for a short duration.
However, if the fish continues to swim in reverse for a prolonged duration, it can suffocate because the gills of most aquarium fish are designed for forward movement.
So when they swim backward, they can’t breathe properly.
How long can an aquarium fish swim backward?
Aquarium fish can’t swim backward for too long.
This is because swimming backward is complex and consumes a lot of energy.
Besides, reverse swimming also reduces their swimming pace, and the chances of dashing on the aquarium decorations and tank walls also increase.
Which aquarium fish can swim backward?
Aquarium fish like goldfish, bettas, and clownfish can swim backward.
However, they often don’t swim backward as it requires more energy.
Aquarium fish usually swim backward when they want to back off from a fight with tankmates, catch food, or have some illnesses like swim bladder disorder.