There’s long been a belief that fish don’t feel pain or experience emotions. However, scientific studies suggest otherwise. As fish spend all of their time with their tankmates, you may wonder if they realize if another fish dies.
While more research is needed, studies suggest that fish form attachments with familiar fish and are more likely to associate with them than other tankmates. Similarly, fish feel less afraid when they’re in schools of their kin. As a result, some fish display signs of sadness and loneliness when another dies, losing their appetite, becoming lethargic, and swimming at the bottom of a tank.
Most fish thrive when they live with companions or in small groups. If the death of a fish means that your surviving fish is alone, you might want to consider finding it a companion to reduce feelings of depression.
Do Fish Get Sad When Other Fish Die?
“Sadness” is an emotion that humans and sentient animals feel. Historically, it’s been believed that fish don’t feel pain and emotion. However, recent studies suggest that fish are sentient animals with individual personalities. They also form bonds with other fish.
In a study by Scientific Reports, researchers observed the social buffering behavior of zebrafish and discovered that they shared similar traits to humans and mammals.
By exposing zebrafish to threatening situations, researchers have found that, when zebrafish are in groups, they feel less afraid than when they are alone.
In another study by the Journal of Ethology, scientists discovered that rainbowfish were capable of identifying and distinguishing between other fish when faced with predatory situations. Those fish chose to associate with familiar fish rather than strangers.
While it’s difficult to determine whether fish feel the equivalent of human sadness when members of their group die, it certainly affects them. That’s because fewer fish in the school means there’s a higher chance of them getting eaten.
That being said, another journal by Scientific Reports discovered that fish experience emotion-like states based on their environmental stimuli. Therefore, it’s likely that fish recognize when fish familiar to them are absent from the tank. They may even experience feelings of sadness.
However, there’s a counter-argument to this. If fish in your tank all start behaving strangely after the death of your fish, it might not be due to sadness but a chemical reaction. Some fish release a chemical substance called schreckstoff when they’re distressed.
If the fish died of injury, predation, or disease, it releases the chemical, alerting its tankmates of danger. As a result, surviving fish start behaving as if a predator is nearby and will:
- Dart quickly back and forth
- Freeze in place
- Stop swimming
- Hide amongst plants
- Lose their appetite
Humans interpret this behavior as grief, but the fish are actually trying to protect themselves from whatever killed the fish.
Do Fish Get Lonely If One Dies?
In the wild, few fish species live alone. Many fish, like angelfish, catfish, and tetras, live life in large schools, gliding through the water together. As a result, fish are naturally ingrained to live in groups.
We’ve already explained how some fish can recognize their tankmates. This means that if they’ve formed an attachment to another fish, they’ll become lonely due to a lack of stimulation once their “friend” dies. If a fish is lonely, it’ll display the following signs:
- Lack of reaction when it sees you
- Lethargic behavior
- Swimming at the bottom of the tank
- Refusal to eat
Loneliness can make fish depressed. Fish need mental, social, and emotional stimulation to keep themselves happy and healthy. Without it, they’ll swim around the tank without purpose, displaying signs of boredom.
This is amplified when you only have two fish in the tank, leaving one completely alone. Worryingly, loneliness also causes stress, which kills fish.
Similar to feelings of sadness, some fish may feel lonely in a more practical sense. That’s because some fish species need to form large groups to feel safe and secure. They also enjoy swimming around together as it provides mental enrichment.
To put it simply, loneliness kills vulnerable fish and prevents them from schooling.
Which Fish Are Most Likely To Know When Other Fish Die?
We’ve already established that some fish can recognize when another dies. While more research is needed in this area, certain fish species display signs of loneliness and depression more than others when one of their tankmates dies. Fish that are most likely to mourn include:
Guppies
Guppies aren’t schooling fish, but they like company. Guppies are breeding fish that has earned the nickname “million fish” because of how fast they breed. Guppies breed all year round, mating with numerous males to produce their young.
As a result, guppies don’t do well on their own and notice when other fish aren’t around anymore. While females produce offspring for approximately 8 months with a male’s sperm stashed in her body, she’ll need a male fish to mate with after this time.
Angelfish
Angelfish don’t do well living alone and need to live in pairs or groups of even numbers. Some angelfish develop long-term partnerships and become territorial of each other. When one dies, the other becomes sad and depressed, refusing to eat.
Similarly, when an angelfish dies, the entire group notices the absence. Due to the uneven number, the dominant fish will turn on the smaller, more submissive angelfish, bullying it and engaging in a fight. This is due to their aggressive nature.
As a result, an angelfish dying allows the group to readdress the hierarchy within the tank.
Discus
Discus fish is a breed that must live in small groups of its own kind. They’re peaceful, shy fish that form attachments to other discus fish in the tank. When living alone, they become lonely and stressed. Similarly, they’re heavily affected by another discus’ death.
The only time discus fish live alone is when they’re in the breeding phase. During this time, they’ll isolate themselves. But even when the fish has given birth, it re-joins the group.
When a discus fish dies, you’re likely to notice that the rest of the group lose their appetite and become lethargic. This is a normal reaction to the fish’s death, but you’ll need to keep an eye on this behavior to ensure it naturally passes after a short time.
Platies
Again, platies aren’t schooling fish, but they enjoy living in groups. They’re peaceful and active and rarely become aggressive towards each other. They’re also very similar to discus fish in that they breed quickly and efficiently, so male and female platies spend a lot of their time mating.
Because of their social nature, platies form attachments to each other and don’t do well on their own. As a result, they’re likely to notice the absence of dead fish more than other species. When a platy dies, the surviving fish may refuse to eat for a few days, so try to hand-feed them to encourage them to feed.
Because we can’t be sure whether fish mourn, you’ll need to observe your surviving fish for any signs of depression, stress, or loneliness. If your fish lose their appetite or stop swimming, the death of their tankmate has likely affected them. In that case, provide some form of mental enrichment to try and minimize feelings of sadness.
