Definition of stress in fish.

[BillD]

I hear the word stress used constantly in the fishy forums. It seems everything is stressful to fish, from water changes to feeding. It got me to thinking, that perhaps a discussion of what is exactly meant by stress, might be worthwhile. I have my own opinions, and personally, I believe the term is over used. There are lots of experienced fishkeepers on this forum, and perahps with their input, we can come up with a useful definition or description, of what stress is or the symptoms of it. A scientific discourse is not necessary, but it would interest me to see what the more learned members of this forum have to say. One of the most common examples I hear is that water changes cause stress. My personal belief is that poor water quality causes more stress than a water change. Is the short term stress of a water change (if there even is any) as bad or worse than the constant stress of poor water quality? However, perhaps I am using the wrong terminology to describe what I mean. So, lets hear it.

 

[Menagerie]

IMHO, water changes do not cause stress in the fish, unless you chase them with the gravel vac If dechlor is left out, the chlorine and chloramine will stress the fish; I only use the term stress to describe when a fish is behaving oddly or if there is a sudden change in environment. If a fish is at the surface, unable to stay upright, gasping, dull/loss of color, constant hiding, if the fins are shredded, or if the fish is being harassed by other fish. Changes in the fish's environment go both ways--if long term poor water quality is the norm and one day, you do a large PWC, that will stress the fish; and on the other hand, the situation we are more familiar with is allowing a clean tank to collect pollutants due to a death or something dropped in the tank and suddenly water parameters are changed.

 

[Jchillin]

Here's my list:

1 - Loss of an established tank mate
2 - Sudden rapid change in environment (netting, bagging, etc.)
3 - Overcrowding (true overcrowding...not overstocking).
4 - Rapid change in temps, ph or other water quality issues.

A couple of others can be added.

 

[BrianNY]

Excellent topic BillD. I prefer to think of stress as not something short term (as in changing tanks or modest shifts in water params), but in long term impacts which wear away a fishes immune system. Any tank condition which inhibits a fish from either eating or breathing normally for an extended period of time is a stress factor.

 

[TomK2]

JC-

I would add beign a victim of agression. A fish that is constantly threatened by another fish is not only stressed mentally and emotionally, but physically as well. While that might go hand in hand with overcrowding, it can also exist in a large tank with only two fish in it!

And finally, poor water quality, even if consistant, would be a stressor.

But I agree, the term is over used. When a fish's health changes for the worse, the first thing said is that it was stressed. The term goes quite a way back, and if you think about it, keeping fish in captivity is probably a stress too. Fish that have had good food and good water would just up and die when captured and put in a tank, with no obvious disease or trauma. Thus, stress was to blame! Since then the idea that our pets are so delicate, and in such a tenuous balance, that non-lethal changes can tip them over the edge and kill them has taken hold.

 

[BillD]

Some good points. Water quality is probably the single most important factor in fish keeping. I have done large water changes in tanks that should have old tank syndrome (I didn't check parameters, but the water had gone perhaps several months without a change), and after the change, the fish were obviously happier(75% change) and non were lost. I guess the thrust of where I hoped this discussion would go was, that I think the concept of stress being an issue, leads to poor practices, such as changing a small amount of water so we don't stress the fish, when a larger change would have been appropriate. Since I joined a fish club about 12 years ago, I have come into contact with people that I would call expert. These people have bred literally hundreds of species of fish. Without exception, these people all changed more water than the average that is recommended. If water changes caused stress, it would stand to reason that breeding would be curtailed. We know, in fact that this is not the case. If you want fish to spawn, you do a large water change. If you want corys to spawn, you do a large water change with much cooler water. In the case of the corys, you are not only doing a large change of water, but quickly dropping the temp which could be said to be stressful, but obvoiusly isn't. I think that most of the fish we keep are more tolerant than we give them credit for. So, basically, we need to differentiate between what is actually stressful, and what isn't, so we don't perpetuate myths that are detrimental to what we are trying to do. Personally, if a tank looks like there is something amiss, the first thing I do is a large water change. If there is a problem of pathogenic bacteria in the tank, I will have reduced their numbers by 50% or more. If there are other toxins, they likewise will be reduced. It is a fair assumption that if something doesn't look right, it probably isn't. While stress can be a health factor in every living thing, I think that we need to focus on the real threats, rather than the percieved threats. To do that we need to separate the real from the false, and that may not be easy, but worthwhile.

 

[BillD]

Excellent topic BillD. I prefer to think of stress as not something short term (as in changing tanks or modest shifts in water params), but in long term impacts which wear away a fishes immune system. Any tank condition which inhibits a fish from either eating or breathing normally for an extended period of time is a stress factor.

Good point, Brian. I agree with that, as I see that as one of the real threats. It is interesting to me to see the different attitudes towards common practices on different forums. Water changes shouldn't be a topic of disagreement in the hobby in this day and age; the hobby didn't just start. If you go to an Angel forum, you will see a different attitude towards water changes. Anyone who has bred angels knows that you have to change lots of water, because they grow so fast, and failure to do so will show immediately. The same thing applies to other fish as well, but is more quickly noticed with angels.

 

[7Enigma]

I'll throw my 2cents in, for what its worth coming from a more scientific side with little experience. Take it with a grain of salt.

My field of expertise is cell and molecular biology, and I'm a research scientist for a biopharm company. I focus primarily on small proteins and interaction....so not with fish.

In my job, difficulties constantly arise when trying to work with these and the best way I've always overcome them is to "think like the protein". So I will "think like the fish".

As the fish, drastically reducing the total volume (lets say greater than 30%, most normally found during acclimation period or when getting lazy and doing 50% change when the fish are already stressed from being in a new environment/establishing territory) of water would be a stressful experience due to the closing-in feeling, especially in tanks with large amounts of vegetation or more importantly lots of fish. Those invisible boundaries that many fish spend so much time setting up and "protecting" are dissapearing. Top dwellers have all but lost their space, and bottom dwellers have suddenly got a lot of playmates they might otherwise have tried to avoid.

Now compound this with the addition of water that "tastes" differently (due to lost salts, chlorine, or byproducts of the dechloronation process).

Now compound that with the possible temperature difference of the newly added water. While I feel the closer proximity of fish will cause a lot of stress, I would imagine as a fish the temp change would be cause for the most stress (if not temp matched before addition). Remember 2 things about fish, 1 they are tiny compared to humans, so their surface area to volume ratio is greatly increased. Imagine putting your bare hand out a car window in the dead of winter while your driving. Now compare that to sitting on the roof of the same car NAKED. That's a completely non-scientific analogy to how quickly heat changes occur in small animals, but it serves the purpose.

And 2, we are dealing with water not air. Water has the heat capacity of something like 600times that of air (don't quote me ). That means it can add or leech heat from an object MUCH faster than that of air. Think of when someone flushes the toilet when your taking a hot shower. That's shock, and while it may not cause you to go into cardiac arrest, imagine if you had the same surface area to volume ratio as a fish!? That would be quite stressful.

So like anything its a balancing act. Balancing the stress of everything mentioned above from water removal, with the benefit of removing contaminants from the water. What's the best choice? Probably a compromise between the 2. Once my tank is up and running I'll be doing PWC's of max 25% with the same temperature of water (probably aiming for 1-2 degrees above tank temp to account for the heat lost during syphoning back into the tank at a slow rate), but instead of dumping a bucket of new water in, or removing a bucket full in a short time, I'll set up some type of drip-syphon so no water gets added/taken out too quickly. I think doing something like this will limit the amount of stress on the fish. But who knows...

justin

 

[BrianNY]

I've always said that trying to think like a fish gives me a headache 7Enigma. Although your points are logical, they come from a human perception. We cannot begin to think how something as different from us as a fish perceives comfort. As I've stated in another thread, the reason penguins winter in Antarctica and not a Park Av condo is because they're penguins.

IME fish adapt very quickly to even 100% water changes. That is providing there are no chemical poisons, or drastic swings in pH, temp and the like. I do daily 50% pwcs on most my tanks. I use the feel method to determine temp closeness and have never sent a fish into stress by doing so.

I'm no expert in fish biology but I do know that healthy fish can harbor some nasty diseases in the form of parasites and bacteria. Healthy fish have a way of keeping these in balance in their own systems. When a fish becomes stressed it loses that ability and will succumb.

 

[Devilishturtles]

7Enigma, When I first read the initial post in this thread, I thought the same thing. Done correctly, a water change should not be stressful, but I think it some minute way, it is. That's just my opinion though.

 

[TomK2]

Well, if you do water changes frequently, and the water is near the same temp as the tank, your tank water will not be that different from your replacement water, so there is no percieived difference on the fish's part? Brian changes the water so much, his fish think they live in the sink!

 

[mattrox]

I used to do 80% pwcs on occasion (after weekends away and such like) with my discus when i had them. When the water level was low they showed clear signs of discomfort. However, after the pwc they seemed more relaxed and far more active than before the pwc. The large change seemed to stimulate them into more activity. I never worried about how much water was changed, rather the overall quality of the water.

 

[BillD]

mattrox, I have noticed that with all my fish to varying degrees, even on tanks that have gone for a long time without changes. Are we imbuing fish with human characteristics when we claim that certain thing cause stress? In the wild fishes have to deal with a wide variance of water conditions, including temperature changes, ph changes, TDS changes, floods, drought to name a few. They seem to deal with that and survive. So, why do we think that changing the water will cause them stress? Or, that they can't take a shift in temperature or pH? It is possible to have fish die after a watewr change. The scenario would be this; tank is acidic and cotains ammonium, replacement water is alkaline, and when added to the tank causes the ph to rise above 7, which converts the ammonia to toxic ammonia. This would only occurr in tanks that were not well maintained to begin with. Assuming that conditions are reasonably maintained, the scenario would be unlikely as ther would not be any ammonium to convert. I figure, that if fish eat right after or during a water change they aren't stressed by it. Most people would consider fish in a bag to be stressed, and anyone who has been to an auction and seen the back swimmers at the end, would definitely agree However, fish are transpoprted every day and most survive. Are the ones that die victims of stress or something else? I recently bought some Rotkeil severum babies ( back in May). & of them were in a 6 x 8 bag for 3 days with no air in the bag. There was about 10" of fish. I put them into a 35 that had been filled 2 hours earlier. I had added a netful of daphnia just prior to adding the fish. Within a minute of being in the tank, they started eating. This would lead me to believe that the 3 days in the bag were not stressful. they were moved about, subjected to varying temps, and in the same water. ithinkthe fact taht there was no air in the bag and they weren't sloshed around was of benefit. The bags were breathable ones from Kordon, so there was not build up of CO2 and the resultant pH drop. http://pricenetwork.ca/forum/showthread.php?s=&threadid=30841 is a link to a discussion of these bags. One of the two bags in the picture was one I bought. At any rate, one thing I considered to be stressful may not be if handled properly. So, maybe there are others. Thanks to all who have replied. We may not get to the bottom of this, but it should be interesting, and ultimately, worthwhile.

 

[Blucat]

Let me share my experience when I first started in this hobby. I unknowingly cycled my tank with 10 neon tetras. When the tank was established I had them happy and healthy for several weeks. I did about a 25% water change/gravel vacuum every week. One afternoon I got carried away with gravel vacuuming and accidently changed 50% of the water. The tetras usually stayed mid-to bottom so the water level didnt seem to worry them. However by that night all 10 neon tetras were dead. The old and new water would have been the same ph but the new water probably would have been a few degrees cooler.

Could the neons death be concluded as being caused by the 50% water change?

 

[mattrox]

The water change probably had something to do with it. You can't say the water change killed them, but something happened during the change. As you said there was a temperature drop. That might have done it. But without more information you just can't tell. owever I would say that the temp. change did it.

I have bought neons before and had lots drop dead soon after adding them to the tank. Then when replaced with cardinals with no difference in treatment a so called sensitive fish survived. I don't buy neons very much any more because I have had bad luck with them and would consider them a bad example of a fish to use for this because in my experience they don't really need a reason to drop dead. I know that is not scientific but with neons there are many factors that cause deaths.

 

[TomK2]

Well, I had a string of 3 neon purchases die off, despit being brought right home from the lfs and having acclimation started within 10 minutes of purchase. Acclimation was a 10 to 15 minute process, since the lfs water and my water are nearly identicle in pH and temp. For the last effort, I went to a different lfs, I increased the bag float time to over 25 minutes, while I did everything else the same (adding tank water to bag over 5 to 10 minutes). By increasing the bag float time I got 100% survival. Or was it the different lfs? If it was the bag float time, then the only difference a longer bag float time would cause is better temp stabilization between bag and tank.

 

[AmberAcid]

Hello all. I am by no means an aquarist, but I have kept tanks since the mid 70's. In my experience you can greatly reduce stress through simple routines. One example: I always run my hand across the top of the tank before I turn on the lights. The fish are waiting like begging dogs at the top of the tank for food and show no signs of even noticing the lights came on. On occasion when someone else turns on the light without running their hand across the top, the fish will scat in all directions acting disturbed. Along those lines, I use a routine to do water changes. I set the vacumn in the water then get everything ready while the fish start to assume the "water change position." I always start with the same side, end with the same side and take the same amount of water out. My fish really don't seem to mind the water changes.

As for the original question, IMHO there are different levels of stress and some low level stresses are necessary to prevent high stress situations. In keeping with using human examples, it is stressfull for us to pay our bills each month but think about what happens if we just stop doing it.