Depression in Fish

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Seawitch submitted a new Article:

Depression in Fish

The photos included in this article are not depicting depressed fish, but rather they are just some good fish photos from the Reef2Reef archives showing different species that we commonly see in saltwater tanks. ©2019, All Rights Reserved.

We often set up aquariums for the joy that they bring us, the soothing feelings we get watching colorful fish flit around beautiful coral displays and the deep satisfaction the aquarist gets from having built and cultivated something impressive. With all the happiness that can be created by an aquarium have your thoughts ever drifted to the emotions of the little finny friends that occupy that gorgeous tank?

powderbluetang1.jpg

Powder blue tang photo by @ChristopherKriens.

While fish are not often thought of as very emotive animals they are actually quite emotionally complex possessing very similar neurochemistry to humans and are often used in trials for psychiatric drugs. This means that yes, fish can get depressed just like their owners. But how do you recognize depression in fish and what can a concerned aquarist do about it?

As fish cannot sit down with a therapist and discuss their concerns and worries we can identify depression in fish by observing their behaviour. One of the most notable indicators which should be easy for most aquarists to identify is the degree to which a fish explores his or her tank. Depressed fish tend to linger in one spot, usually near the bottom and will rarely move around the entire tank. The key element here is inactivity as depressed fish will just let the currents of the water move them around, allowing themselves to sink to the bottom and not swimming to the top for mealtimes.

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Starry blenny photos by @MJC.

There are some fish species that stay in one small territory as part of their normal behavior. That's not what we're talking about here. We're talking about the fish that would and should normally swim around but chooses not to.

One test that aquarists can perform in order to see if their fish is depressed is to introduce it to some new surroundings, as most fish are naturally curious they will, when in a healthy state of mind, immediately begin to explore the new environment or feature whereas a depressed fish will often allow itself to sink to the bottom and remain there.

royalgramma.jpeg

Royal gramma photo by @Joey Bekius.

What causes a fish to become depressed? According to Victoria Braithwaite, a professor of Biology and Penn State University, some of the most likely causes are a lack of stimulation or insufficient oxygen in the water. Another cause can be chronic stress, which can come from and be enhanced by a variety of sources.

Some of the most common stressors to occur in an aquarium environment include overcrowding, inability to avoid aggressive fish, a struggle for food and changes in lighting and currents. Thankfully, unlike humans, genetic causes of depression are rare in fish, usually only occurring in selectively bred fish used for laboratory research so you shouldn’t need to worry about having to flood your tank with Prozac or put your fish on medication to deal with their depression.

In situations where you aren’t dealing with a genetic mutation that requires chemical correction of the issue there are steps an aquarist can take to improve the livelihood of your fish and mitigate the effects of stress and depression. As fish can become bored with their surroundings one of the simpler solutions to ichthyoid depression involves enriching their environment, doing things like adding some new marine flora or some interesting decorations and ensuring that more nervous fish have plenty of places to hide and plenty of room to get some safe space. It might also be prudent to check your filtration system to ensure water quality.

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Purplelined wrasse photo by @Acorral
Remember that the warmer your water is, and the saltier it is, the lower the oxygen saturation. The solubility of oxygen decreases as temperature increases, and dissolved oxygen decreases exponentially as salt levels increase. (1)

For increasing oxygen in the tank, sometimes something as simple as opening a window in the room where the tank is helps the oxygen uptake in the water. More surface agitation will help with gas exchange, and that's easy to accomplish with changing the direction of a powerhead or adding another one or adding a small air pump and bubbler or adding a skimmer.

You could also observe your depressed fish and determine if it is being harassed by any other fish and take steps to separate them or give them space apart from each other. Another simple solution is making sure that when feeding your fish you spread the food around, reducing competition for food among tank denizens. In extreme cases where your fish are being crowded your options are a lot more limited: get a bigger tank, get a new tank, or get rid of some fish.

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Harlequin tusk fish photo by @OrionN
We recognize that discussing the emotional lives of your fish is a new concept and one that will likely bring about some debate and disbelief. However, the fact that fish are intelligent and have emotional lives is what the recent peer-reviewed research is concluding, so as aquarists, it's something we need to be aware of. In humans, untreated depression shortens life expectancy, so it's not a big step to suggest that untreated depression may shorten life expectancy in other species as well.

It probably doesn’t come as a surprise to experienced aquarists that fish are more emotionally complex than many people give them credit for. Fish have been observed exhibiting complex emotions such as joy, relaxation and playfulness and as we’ve already noted, depression and stress. Hopefully with our discussion above we’ve given you some solid strategies to minimize the stressful and depressing elements in your fish's lives and to bring out the best emotions in them, so you and your fish can both enjoy each others company to the fullest.

* * *

Sources

· (1) Fondriest Environmental, Inc. “Dissolved Oxygen.” Fundamentals of Environmental Measurements. 19 Nov. 2013. Web. < https://www.fondriest.com/environmental-measurements/parameters/water-quality/dissolved-oxygen/ >.

· https://www.huffingtonpost.ca/2013/08/09/depressed-fish-study-new-drug-treatments_n_3714691.html

· https://www.jhunewsletter.com/article/2017/11/research-shows-that-fish-can-also-get-depressed

· https://www.sciencedaily.com/releases/2010/11/101116101736.html

· https://www.the-scientist.com/news-...ressants-span-three-generations-in-fish-65193

· https://www.animalsaustralia.org/features/fish-in-farms-are-depressed.php

· https://www.hartz.com/en-ca/stress-in-fish-symptoms-and-solutions/

· https://www.upi.com/Science_News/20...-salmon-suffer-from-depression/5391464194628/

· https://www.fetchpetcare.com/blog/facts-fish-depression/

· https://www.animalsaustralia.org/features/fish-facts.php


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Author Profile: Peter Steckley

Peter Steckley is a freelance science writer based in Calgary, Alberta, Canada. When he's not studying reef aquariums or testing out new recipes on his family, he's usually reading or enjoying the latest video game releases.
 

ngoodermuth

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I think the most notable experience I've had with "fish depression" was when I tried to add a small tusk to my 120g... it was miserable in my tank, and did nothing but quickly pace the glass back and forth all day long. I told my husband, that just watching him made me anxious... not peaceful and serene like a fish tank should be. So, I found someone with a nice, big tank (much bigger than mine) and gave him away. The new owner reported that the pacing had stopped completely, and he seemed quite content :)
 

Daniel@R2R

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I wonder if research looks into varied differences between species? I'd imagine that some types of fish have far more developed neurology than others. So for example, should a bangaii cardinal be considered as being similarly developed neurologically as some other species like an angler fish or a tang? I would imagine there's variance there.

I do think it's easy to note that most fish do exhibit some type of anxiety-like behavior when placed in certain conditions.
 

Seawitch

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I wonder if research looks into varied differences between species? I'd imagine that some types of fish have far more developed neurology than others. So for example, should a bangaii cardinal be considered as being similarly developed neurologically as some other species like an angler fish or a tang? I would imagine there's variance there.

I do think it's easy to note that most fish do exhibit some type of anxiety-like behavior when placed in certain conditions.

Yes, well, there's no doubt that some are more developed than others. I don't know if there's much research (yet) comparing species with octopusses at the top (but they aren't fish either). But I can take a look and try to contact some of the scientists. Most of the published research to date is on freshwater fish, and most of that is on the zebrafish, Danio rerio. I can try to do something more in depth in the future. I recall one experiment in which fish that were (purposefully) injured clearly preferred being in tank that contained morphine (for pain relief) than a tank without it. It's extremely difficult and challenging to design experiments on fish since they can't walk or talk and don't have opposable thumbs, for example.

There's probably a difference between species and probably a difference even within the same species. Remember, all dogs are the same genus and species, Canis familiaris but there's a tremendous variation within the same species, and my French Bulldogs are definitely neither as intelligent or trainable as a Border Collie.
 

ngoodermuth

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If my clown fish has depression he definitely takes it out on my hand every chance he gets.

Ocellaris? Every female oc. I’ve ever owned has attacked my hand in the tank [emoji23] Territorial little buggers. My clarkii and perculas don’t do it...
 

actik

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yup Oc, strange thing is it should still be a male i would assume, its been alone now for about 4 months since i got it. so soo aggressive lol
 

ngoodermuth

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yup Oc, strange thing is it should still be a male i would assume, its been alone now for about 4 months since i got it. so soo aggressive lol

A lot of times if a clown is kept singly for a period time, they will turn female by default... I would guess your “he” is a “she” based on her behavior [emoji23]
 

actik

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ugh :( hahah i was hoping to avoid the whole aggressive female thing, thats why i thought just 1 clown was the way to go. haha thanks for the info might as well just get her a mate now
 

ngoodermuth

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ugh :( hahah i was hoping to avoid the whole aggressive female thing, thats why i thought just 1 clown was the way to go. haha thanks for the info might as well just get her a mate now

Might as well...maybe she won’t be as mad at your hand with a little hubby to push around [emoji23][emoji23]
 

ca1ore

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Stressed …. yes; depressed …. not so sure. Anthropomorphism at work perhaps :D:D. Added a gam tang to my tank with a resident purple. Latter beat up the former which hid and would not eat. Removed latter and former came out and within a day was eating and swimming normally. Reintroduced the latter after 6 weeks and former beat up latter which would hide and not eat. Stress ….. not depression. I don't think I have ever seen a fish that didn't recover from a stress event when the stress vector was removed. I'm not buyin' it.
 

Seawitch

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Stressed …. yes; depressed …. not so sure. Anthropomorphism at work perhaps :D:D. Added a gam tang to my tank with a resident purple. Latter beat up the former which hid and would not eat. Removed latter and former came out and within a day was eating and swimming normally. Reintroduced the latter after 6 weeks and former beat up latter which would hide and not eat. Stress ….. not depression. I don't think I have ever seen a fish that didn't recover from a stress event when the stress vector was removed. I'm not buyin' it.

@ca1ore with all due respect, my friend, I beg to disagree. Depression is fish is described in the literature as a specific constellation of behaviors including little movement, apparent apathy, staying at the bottom. There is research on and examples of "stressed" and "frightened" fish, but those fish demonstrate a different group of behaviors like what you describe here--hiding, unwillingness to eat, etc.
 

ca1ore

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@ca1ore with all due respect, my friend, I beg to disagree. Depression is fish is described in the literature as a specific constellation of behaviors including little movement, apparent apathy, staying at the bottom. There is research on and examples of "stressed" and "frightened" fish, but those fish demonstrate a different group of behaviors like what you describe here--hiding, unwillingness to eat, etc.

I remain unconvinced ...... I think we see what we want to see.
 

EmptyWallet

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I think my Moorish Idol is on the Spectrum. I have no doubt saltwater fish at least have the basic emotions and 'suffer' when put in tiny tanks and crappy conditions, not unlike animals at the zoo or people in big cities!
 

Peach02

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Thanks for the great article!! I always suspected it could happen but was never sure thanks for the advice would coral ‘stimulate’ fish?
 

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