The true size of Arapaima gigas

Acheloos

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Polish, you should read my first post again (please do it). I wrote there from where the nearly always repeated claim of the 4m+ arapaimas come, from ONE SINGLE SECOND HAND claim from the first half of the 18th century. But this claim, which was probably even based on a translation error, found its way in literature, and that´s the reason why you can find it so often. There are many similar cases, for example the great white shark, for which you can find in many old books a maximum length of 11-12m (again based on a single unauthenticated record).
Furthermore I showed by simple caculations, that the stated dates are in no possible relation, as a hypothetical 4m+ arapaima would be much much heavier than only 200kg.
A weight of 200kg seems not impossible for an arapaima, but not 4m as length. That´s the reason why I named this thread "The TRUE size of arapaima gigas". If you read or hear about 4,5m or even 5m, you will probably think this is a normal length, but this is miles away from being true. Same thing with the wels catfish. A lot of people think they grow usually up to 5m, what´s again just a result of a handfull of very old big-fish-stories which were never proven but found their way in literature.
Today you won´t hardly ever find 11 or 12m as maximum length for the great white shark in a good book, so why is it so hard to accept that there is a very similar situation in Arapaima gigas?

Just look at the photos you posted. They are all very big specimens, but none is just close to at least 3m. The 2,65m specimen is more or less official world record. Don´t you think this is not a bit strange? If this species could easily reach lengths of around 4m, why is the official record so much smaller? Why could an expert which studied thousands of them in their original habitat not find at least one of more than 2,40m?
I have looked for photos of the arapaimas in the Dallas aquarium. They are big by no means, but surely not as big as claimed. A lot of aquariums around the world keep arapaimas, and they often grow to a length of more than 2m. But hardly ever over 2,5m. So why should they grow there so much bigger?
 

polish

Jack Dempsey
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Well written but and I can understand what you mean but there is no proof either way and you can't tell me that last Arapaima (In the photos I posted) isn't every bit of 3 meters. At least I think so. The width of that mans shoulders compared to the fish speaks volumes, as does the fact that the fish isn't even straight and the tail is curled. That thing is a monster.

It's arguing semantics at this point. I just don't see the point but I know the first place I post if I ever see proof. :)
 

Acheloos

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The arapaima has a comparably round body (at least in the first third of the body), so it looks very compact. And take a closer look at the photo. The guy is a good bit behind the fish (just look how big his hand looks compared to his head), which causes a forced perspective, so the fish looks much bigger than it is. If you take his fingers as comparison, you will see that it is actually not that big, and surely not in the 3m range.
 

Arowana1

Candiru
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Acheloos what would you estimate the Arapaima length to be if I was wrong about the man in the photo and was actually between 5'6" to 6ft tall? As well with some species of fish (especially wild fish) when they are old they tend to become lean and long and girth isn't an appropriate scale to use. I live on a ranch here in California and my family has a fifteen acre pond and I see this once in a while when I catch older largemouth bass. They're long however no where near as robust as young adult fish. I've had old 22 inch bass that weigh as much as a robust young 18.5 inch young adult. Maybe this might be the case with the Arapaima in the photo that its just an old fish.
 

Acheloos

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If you will take a closer look to the photos you will see that the guy on the first photo is the same as the one on the last photo, so it is possibly even the same fish. If you look at the size of the size of the pectoral fin and the size of the head compared to the fingers (4 fingers are together roughly 7-9cm wide), you will see that the head is well within the dimensions of the comparably common arapaimas in the upper range of 2,20m or possibly a bit more.
If you look at record fish, you will often see that many fish become stockier and plumper when they grow larger. A lot of very large record fish are proportionally heavier than average sized fish. When fish grow older, the length growth slows down, and they will convert additional growth not only for length but also for a more robust body. Only if fish are already very old, and no more able to get enough food, they will become slimmer. But at this stage, there was no length growth since a long time. A fish will only grow longer, if it has enough energy resources to support at least its basal metabolism. If this is not the case it will loose weight and there won´t be any length growth anyway.
 

Arowana1

Candiru
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When looking at these big fish photos, keep in mind that when wild fish grow older and are more worn out providing a meal becomes tougher and they slowly start to become leaner and look long. As well comparing these older wild fish to older captive fish isn't accurate since captive fish don't have to worry about catching a healthy amount of food each day.
 

Acheloos

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But this is only the fact if this fish are already very old. If they are still healthy, they are in general stockier and plumper than smaller fish of the same species (the same can be found in big snakes and crocodiles as well). Record specimens (if you count weight) are not always extremely old. They have to be healthy and well-feed for several (or even many in some species) years, but if they have good genetic conditions and good natural conditions as well (food and temperature) record specimens in general reach a big size within a comparably short time. Some of the species which will live for a long time will in any case need many years to reach record sizes (like sturgeons and some catfish), and during this time they need a lot of food. If you catch an old perch which seems to be slim, then you have to keep in mind that it was once much stockier at this size.
And in general the largest perches (as well as other record fish) are normally very stocky and far away from being slim: http://images.google.de/images?hl=de&q=record%20perch&um=1&ie=UTF-8&sa=N&tab=wi
 

Acheloos

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I made a picture to show the size comparisons between a big arapaima of 2m, the confirmed record specimen from Thailand which was 2,63m and one with the alleged size of 4,5m. As you can see the difference between 2,63 and 4,5m is quite massive, and it would weigh more than a ton. If 2,63 and 185kg is already extemely unusual, why do really so many people believe that 4,5m are possible only because there was this single acount from the first half of the 19th century?

Hypothetic 4,5m Arapaima and actual record specimen of 2,63 and 2m specimen.jpg
 

Zoodiver

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I'm still not convinced the 2.63 meters (roughly 8 feet) is going to be record size.... mabe in Thailand.
Look around the US and you'll find arapaima that size.
 
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