Estimating fish sizes in captivity

[Aurora D.]

<a href=showthread.php?s=&postid=14943687#post14943687 target=_blank>Originally posted</a> by Paul B
I disagree, Jay is a respected aquarist and his limited study makes perfect sense to me. It is a place to start and it proves
(not scientifically) how fish are stunted. Many people do not even believe the size of a tank will stunt fish. Those people have not kept fish long.

Any knowledge we gain is helpful.

I think this study is just a blind stab to try to help put some light on this subject, I doubt it was meant to be a comprehensive study. Although just because he is a respected aquarist doesn't mean he can't have a bad study either.

 

[jenglish]

<a href=showthread.php?s=&postid=14941940#post14941940 target=_blank>Originally posted</a> by Paul B
Jeremy, everything I say is an assumption.

It's in my nature to question assumptions. Get a couple of Turkey and Cokes in me and I will start questioning if I am real

 

[Paul B]

Although just because he is a respected aquarist doesn't mean he can't have a bad study either.

This is true,
I have bad studys all the time and I am not even a respected aquarist, Just kind of a radical aquarist.

 

[Aquarist007]

<a href=showthread.php?s=&postid=14943879#post14943879 target=_blank>Originally posted</a> by Paul B
This is true,
I have bad studys all the time and I am not even a respected aquarist, Just kind of a radical aquarist.

anybody that believes experience is the best teacher --respects you Paul

 

[WaterKeeper]

I have never seen an Oscar, in a tank, that grows as big as they are in the Amazon. I have seen people more radical than Paul however but not too often.

 

[Paul B]

Thanks guys, now I have to look for some more live asphalt to put in my tank. It has special bacteria that neutralizes that
tar nutrient which fuels oak tree algae. It also helps disolve any aluminum beer cans you may have inadvertantly placed in your display. :lol:

 

[wayne in norway]

So where do we stand with fishes that grow larger in captivity than in the wild. I've seen captive raised apistos, discus and a few wierd tilapiines from Central Africa that are far larger than any wild caught example I've ever seen, probably due to captive nutrition being superior to wild.

 

[WaterKeeper]

Good point Wayne. My guess is that some ornamental fish are larger in size than the wild species because of selective breeding. Breeders prize a large discus and probably select larger specimens to propagate. The result is larger fish entering the market. I would be interested to see what would happen if they were reintroduced into the wild as my bet would be they would grow larger there too.

 

[jenglish]

Larger is not always selected for. If they have the DNA to be larger they should get bigger.... if they make it A larger discus may have trouble meeting its larger food requirements. Purely speculation though.

 

[aaron1987]

In my limited experience, fish tend to show symptoms of abuse when improperly cared for. If a fish is eating, outwardly healthy, displays proper temperament, etc., who is to say that fish is "unhappy"?

Pardon me while I hop on my soapbox for a second. A state of being dependent on is goes by the term positive claim. In science, rational thought, etc., we require a positive claim to be substantiated somehow. I say a fish is "happy" and substantiate it by the fact that it shows the characteristics I mentioned above which are shared by their counterparts in the wild. Anyone can observe these characteristics. Now, to say that same fish is unhappy, one of the above must be untrue (or some other metric which I have neglected to mention). The catch is that it must be observable and claims to the contrary frequently rely on assumptions about a fish's preferences that cannot be substantiated.

 

[Aquarist007]

<a href=showthread.php?s=&postid=14950899#post14950899 target=_blank>Originally posted</a> by aaron1987
In my limited experience, fish tend to show symptoms of abuse when improperly cared for. If a fish is eating, outwardly healthy, displays proper temperament, etc., who is to say that fish is "unhappy"?

Pardon me while I hop on my soapbox for a second. A state of being dependent on is goes by the term positive claim. In science, rational thought, etc., we require a positive claim to be substantiated somehow. I say a fish is "happy" and substantiate it by the fact that it shows the characteristics I mentioned above which are shared by their counterparts in the wild. Anyone can observe these characteristics. Now, to say that same fish is unhappy, one of the above must be untrue (or some other metric which I have neglected to mention). The catch is that it must be observable and claims to the contrary frequently rely on assumptions about a fish's preferences that cannot be substantiated.

I think one could add colouration to your list of postive well being.

 

[Jerry W]

I recall reading studies (don't ask for a link as it was a long time ago) about the effects of confinement stress as it applied to captive marine fish. The gist of the read was that confinement released a constant stream of stress hormones which in fact inhibited immune function and stunted growth. I think it's quite reasonable to say that a potentially large marine fish like an angel of the holo/pomacanthus genus, or one of the larger surgeon fishes would never reach near adult size in a tank that was too small. I've heard (and repeated), that saltwater fish will not simply grow to the size of their tanks as many believe, but will continue to grow out, albeit slowly, in spite of being cramped. My concern is that if it becomes widely held that marine fish will not grow to their maximum sizes in home aquaria, then a lot of large fish are going to be kept in tanks that are much too small to house them. I had kept a blackback butterfly fish in my 120 for seven years. Purchased it at the size of a silver dollar and it grew to about 4 inches in the time I had it. Sources say this fish tops out at around 5-6 inches and I always wondered if the fish had stopped growing or just began tapering off and would hit it's full size over the next few years, just growing at a much slower pace. I think the tank was of sufficient size. The fish had an excellent diet, no overly aggressive tankmates and was always healthy/active/vibrant. I know hobbyists who kept blueface angels in 75's for 8-9 years and the fish never exceeded 5 inches. Clearly a symptom of crowding?
Regardless of the conclusions you draw from the study, given it's obvious limitations, Jay is a good example of a conscientious hobbyist and someone who's knowledge is worthy of consideration. I enjoy topics like this and this thread could generate a lot of interesting ideas/theories.

 

[Aquarist007]

<a href=showthread.php?s=&postid=14951870#post14951870 target=_blank>Originally posted</a> by Jerry W
I recall reading studies (don't ask for a link as it was a long time ago) about the effects of confinement stress as it applied to captive marine fish. The gist of the read was that confinement released a constant stream of stress hormones which in fact inhibited immune function and stunted growth. I think it's quite reasonable to say that a potentially large marine fish like an angel of the holo/pomacanthus genus, or one of the larger surgeon fishes would never reach near adult size in a tank that was too small. I've heard (and repeated), that saltwater fish will not simply grow to the size of their tanks as many believe, but will continue to grow out, albeit slowly, in spite of being cramped. My concern is that if it becomes widely held that marine fish will not grow to their maximum sizes in home aquaria, then a lot of large fish are going to be kept in tanks that are much too small to house them. I had kept a blackback butterfly fish in my 120 for seven years. Purchased it at the size of a silver dollar and it grew to about 4 inches in the time I had it. Sources say this fish tops out at around 5-6 inches and I always wondered if the fish had stopped growing or just began tapering off and would hit it's full size over the next few years, just growing at a much slower pace. I think the tank was of sufficient size. The fish had an excellent diet, no overly aggressive tankmates and was always healthy/active/vibrant. I know hobbyists who kept blueface angels in 75's for 8-9 years and the fish never exceeded 5 inches. Clearly a symptom of crowding?
Regardless of the conclusions you draw from the study, given it's obvious limitations, Jay is a good example of a conscientious hobbyist and someone who's knowledge is worthy of consideration. I enjoy topics like this and this thread could generate a lot of interesting ideas/theories.

Jerry--those are great thoughts. I hope that reefers will not use the material on this post to stretch the envelop on keeping larger tangs in smaller tanks.
Rather, be on the look out for signs that is time to find an new home for your favorite tang whether it be upgrade or adoption.
I personally see nothing wrong with keeping larger tangs while they are infants in our tanks.
With more knowledge of the signs of stress hopefully the majority of hobbyists will the make the right decision at the right time that it is time to upgrade the home for their fish
This is what I hoped would come out of this thread when I started it.

 

[jenglish]

THe term "happy" is anthropomorphizing (the 5 dollar word for assigning human traits to non humans) and can't really be substantiated. Stressed can be substantiated by measuring cortisol levels in the brain. They see that they correlate positively with breaths per minute, so the faster above baseline a fish is breathing, we can pretty accurately predict stress. Happiness is a more complex emotion. I think before Jay started looking at this project he was asking about the term "happy" in regards to fish. What chemicals in what parts of the human brain are the physical hallmarks of happiness I do not know. I meant to look it up when Jay was discussing it months ago but that got lost in the shuffle.

So happy is still up in the air but stressed is something that has observable signs.

 

[aaron1987]

<a href=showthread.php?s=&postid=14952498#post14952498 target=_blank>Originally posted</a> by jenglish
THe term "happy" is anthropomorphizing (the 5 dollar word for assigning human traits to non humans) and can't really be substantiated. Stressed can be substantiated by measuring cortisol levels in the brain. They see that they correlate positively with breaths per minute, so the faster above baseline a fish is breathing, we can pretty accurately predict stress. Happiness is a more complex emotion. I think before Jay started looking at this project he was asking about the term "happy" in regards to fish. What chemicals in what parts of the human brain are the physical hallmarks of happiness I do not know. I meant to look it up when Jay was discussing it months ago but that got lost in the shuffle.

So happy is still up in the air but stressed is something that has observable signs.

Hence my use of quotes around happy and unhappy. Personally I suspect it's an emotional state fish don't experience (at least not in the sense we do) but that's neither here nor there. It's just an easier way of describing satisfactorily cared for, or perhaps the absence of stress.

 

[Aquarist007]

<a href=showthread.php?s=&postid=14952498#post14952498 target=_blank>Originally posted</a> by jenglish
THe term "happy" is anthropomorphizing (the 5 dollar word for assigning human traits to non humans) and can't really be substantiated. Stressed can be substantiated by measuring cortisol levels in the brain. They see that they correlate positively with breaths per minute, so the faster above baseline a fish is breathing, we can pretty accurately predict stress. Happiness is a more complex emotion. I think before Jay started looking at this project he was asking about the term "happy" in regards to fish. What chemicals in what parts of the human brain are the physical hallmarks of happiness I do not know. I meant to look it up when Jay was discussing it months ago but that got lost in the shuffle.

So happy is still up in the air but stressed is something that has observable signs.

I believe it was in his article "beware of the tang police"

Happy fish?



Driving in to work one morning, with a half a pot of strong coffee boiling through my veins, I got to pondering â€"œ when you hear somebody say, "you need to do X,Y,Z in order to keep your fish happy" or "your fish cannot be happy in that size tank" what do they really mean? Are they using the word "happy" in place of "healthy" or "proper well-being"? Or do they really mean to imply that true happiness can be identified and then quantified in fish?

I may use that term myself â€"œ "Man, that fish sure is unhappy." to identify a fish being bullied by a tankmate. What I really mean is "That fish has an ongoing territorial conflict with a tankmate, it is exhibiting a depressed demeanor and its well-being is compromised. If something isn’t done to change the situation, that fish’s health will be affected, eventually to the point of morbidity followed by mortality". It is just faster (but far less precise) to use the word "unhappy".

On the other hand, an animal rights advocate may look at a single fish in a tank and exclaim, "how unhappy that fish must be, all alone in that small tank". I suspect that in these cases, they mean not the fish’s well-being and health, but that it is truly unhappy in the mammal paradigm of how the word is generally used in English.

Now don't get me wrong, I don’t have a problem that some people do with semantics â€"œ as long as their intent is clear. Same thing could be the case with "happiness", I'm content to let the term ride unless I think the people really mean "smiley face" happy, as in "the opposite of sad" when talking about fish.

However, if for example, one of the "tang police" say, "hepatus tangs need at least a 150 gallon tank in order to be happy" they are not using the word in place of "healthy" if that same tang can be kept healthy and problem free, long term, in a 75 gallon tank. They are then adding an extra layer to the definition, one that cannot be measured or quantified. I do have a problem with that, it is misleading or ambiguous at best.

I’m not condoning keeping fish in overly small aquariums, I’m just opining that you cannot formulate tank size requirements based on intangibles such as the "happiness" of a fish. If your opinion is that this example fish is so much happier in the 150 gallon than the 75 gallon, that the smaller tank becomes a non-starter, then the fish would be whole orders of magnitude "happier" in the wild, and shouldn’t be kept in an aquarium at all.

Since 1985, I have been collecting fish respiration rate data as a means to try and identify stress in captive fishes. Certainly, I discovered that stressed fish respire at a higher rate (with temperature, species, and size all being factored in). I then collected baseline data from wild fishes in the Bahamas and the Galapagos. My hypothesis was that fish from the wild would respire at the best, most stress-free rate. Funny thing â€"œ almost all of those fishes respired faster than captive fish. It turns out that swimming against currents and waves, sculling around looking for food and out-swimming predators were all combining to cause these fish to be MORE physically stressed than captive fish by this measure. Are they less happy then?

So here is my working definition of "appropriate aquarium husbandry", and I say this equates to "happy" for a captive fish:


If the fish shows no signs of chronic disease or abnormality, exhibits normal feeding and reproductive behaviors and most importantly, exhibits a normal lifespan compared to that of wild counterparts (minus the predation that wild fish incur of course!), then there is no other metric we can use to determine if a certain suite of husbandry techniques are suitable or not."

http://microcosmaqx.typepad.com/jay_hemdal/2009/01/beware-the-tang-police.html

 

[Paul B]

If the fish shows no signs of chronic disease or abnormality, exhibits normal feeding and reproductive behaviors and most importantly, exhibits a normal lifespan compared to that of wild counterparts (minus the predation that wild fish incur of course!), then there is no other metric we can use to determine if a certain suite of husbandry techniques are suitable or not."

This is true, especially the reproductive part. But unless you spend a lot of time underwater with these fish you will not know what is normal or abnormal.
Fish eat and in some fish (and people) attempt to spawn or at least get ready to spawn every day.
Some of them also "play" or at least seem to be having a good time. OK not really "play". If you watch a porcupine puffer in a tank it is usually in a horrible mood. Those fish, unless in an enormous tank never "look happy". For a chubby non aerodynamic fish, they swim large arcs around a reef. Try to keep up with one some day.
They spend most of their time blowing sand around looking for worms. In a tank they usually swim up and down the glass.
Tangs will never be "happy" unless you can provide them with 25 other tangs to form a school and a few thousand gallons of water.
All reef fish have a constant supply of snacks in the form of fry.
There are baby fish all over the place and they are there for the taking. Reef fish don't eat them all at once like they would do in a tank because on a reef, fish are well fed far unlike they could possably be in a tank. They don't eat angel diet, mysis, flakes, nori, clams squid, beef heart or brine shrimp, they eat mostly fish.
Live healthy fish.
It is the oil in their natural diet that most captive fish are missing. That oil is missing in all those foods I mentiioned. If you could get this fish oil into fish, in a week or two you would notice a big difference in the health of the animal. They may even start spawning.
I also have read like was mentioned that fish exude something that limits the size which they become. I can't prove that but I do know that the size of almost all fish is limited in a tank. I have never kept a tang in a 150 gallon tank because my tank is only 100 gallons but I have kept many tangs for many years.
I once had a remora, a shark sucker. It was about 3" long and real cute. Thsat thing grew about a foot in a couple of months. I had to give it to the NY aquarium where it grew another foot in the next few months in a million gallon tank.

Here is a recent picture taken in the Caribbean by my dive partner. Notice (no not the nurse shark) the tiny white dots which are fry all over the left side of the picture. They are all over every healthy reef and it is what fish snack on all day.

 

[LobsterOfJustice]

"if the fish shows no signs of disease or chronic abnormality"

Hmm.... like dwarfism? I'm sounding like a broken record, but:

Take a 5" tang and put it in a 4' tank. It won't grow. Take a 5" tang and put it in a 8' tank, it will grow at least a few more inches, perhaps up to full size depending on the species. That is the definition of chronic abnormality.

 

[Aquarist007]

Instead of "sounding like the same old broken record" I hope this thread has done some good by 'positively' encouraging reefers to make sure they are supply the appropriate size environment for their fish with out the label of "cops" assigned to their excellent and informed advice.

http://www.reefcentral.com/forums/showthread.php?s=&threadid=1631491

 

[JHemdal]

I would like to expound a bit on my work on maximum fish sizes in captivity. There seems to be some confusion about the study. Although only 19 fish met the criteria as outlined in the project, fully 2300 fish were analyzed as candidates, it is just that 2281 of them did not meet the strict criteria:

"None of them has grown appreciably in the past two years, and all have been in captivity at least 5 years (the range was 5 to 20 years)."

Also, the ONLY conclusion that I drew from this is that the maximum size of fish on FISHBASE tends to run larger than what is seen as a maximum size in captivity - to the extent of it being 66% of that value. Remember that FISHBASE lists the maximum recorded size for a fish - not the normal adult size. Their sample size (taken from the literature) is just ONE fish. They also tend to "round up" their numbers. Think of their max size as the record size for that species.

This was just a starting point. The problem is getting enough additional data. How many fish in your own aquariums would meet the criteria? Still, I think we can safely say that stating the Fishbase maximum size as being the "adult size" for fish (as is often done on message boards) will be less precise than using a figure of say, 75% of that value.

Finally, there is still no real way (yet) to use the size of a fish and calculate what size aquarium that fish will need....so what does it really matter if you say that a particular fish will reach the Fishbase max. size or only 66% of that value, you still don't have any real way to objectively apply that information...


Thanks,

Jay