Numerous fish at Cairns Aquarium in Australia have shown signs of depression after the facility was closed to the public in mid-March because of the COVID-19 pandemic crisis. Marine biologists said that the fishes became lethargic and disinterested in their environment without human visitors to engage through the glass.

Some fishes decided to hide in the dark corners of their tanks. But most notable of them all is the Queensland grouper named Chang, who stopped eating for several weeks, according to the Daily Mail.

Depressed fish

Cairns Aquarium's curator and marine biologist, Paul Barnes told ABC News that fishes are curious animals and appreciate having new things to look at and explore. So, even the mere presence of people walking past their tanks is a form of stimulation for these animals.

Even though humans do not realize that animals can see outside of the tank and see the people looking at them, fishes actually enjoy the interaction between them and the humans, Barnes told the ABC News. They enjoy watching new faces and the different colors that humans wear.

So, the aquarium management thought of hiring a new diver to swim with them and keep them company and help them deal with their depression. The chief executive of Cairns Aquarium, Daniel Leipnik, told AAP that the leopard sharks were like puppy dogs who like being cuddled.

After hiring one more diver, the aquarium now has three divers adding a bit to the human contact going on in to create that extra stimulation that the fishes were used to before the lockdown.

In a report by the New York Times in 2017, Troy University's Julian Pittman explained that fishes are sensitive in part because of how their neurochemistry closely resembles those with the humans. Just as how humans get depressed, the serotonin and dopamine levels of the fish are also fluctuating.

Pittman uses fish to test the effectiveness of an antidepressant medication, which, according to him, can measure how active the fish becomes in the tank. The fish would swim to the top of the tank and begin exploring if the medication is proven effective. However, if it does not work, it will remain motionless and inactive in the bottom corner.

Depression in Animals

According to the National Geographic magazine, certain aspects of depression may be measured in animals. One of its core symptoms is anhedonia or the decrease and loss of interest in pleasurable activities.

Scientists measure depression in animals based on the food if they like it a lot or in motivation for sexual activity. Additionally, they also look at how the animals interact socially with other animals in the group and the changing patterns of their sleep. An animal is also likely to be depressed if they easily give up when exposed to a stressful event.

Trained observers can say that a monkey is depressed based on behavioral observations. Just by looking at their facial expression, it can indicate that the primate is experiencing sadness.