Black vs Red Pacu: scientific names please

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reptileguy2727

Feeder Fish
MFK Member
Dec 12, 2005
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Northern Virginia
Can I get the scientific names for both black and red pacus? All I can find is Pacu Colossoma macropomum. With that name I can get sources that list it as black pacu, pacu, red pacu, and some call it both. My understanding is that pacus mimic red belly piranhas when they are small and when they get about the max size of piranhas they switch over to the black pacu coloration. I have seen this happen personally. I know that some of the black pacus at the National Zoo in D.C. were red bellies when they were young. Anybody have any other info?
 
The picture in the first link definitely matches all the pacus I have seen (the ones that start red and then switch to black). I have never seen one that looks like the one in the second link, maybe that is just a bad pic.
 
reptileguy2727;4427165; said:
The picture in the first link definitely matches all the pacus I have seen (the ones that start red and then switch to black). I have never seen one that looks like the one in the second link, maybe that is just a bad pic.


With that prognathic mandible, it looks like a piranha.
 
As rotten an answer as this is.... the answer depends on who you talk to. Scientific names change as more information is gathered. But if ___ doesn't know it was changed back in 1987 and reclassifies based on an older version of the "new classification" then there exists 2 versions of the "new classification" and then what? Do they arm wrestle to see who is right or just play rock/paper/scissors?

Anytime you find conflicting answers in researching latin names you can be sure that is a group that is currently being debated within the scientific community.

This website does a fabulous job of explaining (using a lot of scientific jargon that may make it hard to read for people that aren't taxonomists) the current confusions within the family (or subfamily) of Serrasaalmidae which inclues fish known byt he common names of pacu, piranah and tambique. http://www.opefe.com/serrasalminae.html

Fish base is not as well funded as it once was and as a result is not updated much anymore. It is often out of date when dates matter. Int he case of pacu...dates matter.

In both 1982-85 and in 1972 they were independently reclassified. But the two reasearch teams were using different pre-existing historical data and didn't come to agreement on a newer system. Neither paper was published in English which makes them harder to interpret.

Published in 2008 was a newer study that used mitochondrial DNA to try and classify this group of fish. It found there to be truth in part to each of those prior studies and cam up with a 3rd classification that was a mix of the last two.
 
Can we agree that the little 'red belly pacu' sold in most shops is indeed the same fish that turns out to be a meter long 'black pacu'?
 
Your theory of them being the same fish is a new one to me. I have always presumed two different species. I have an 18-19" Pacu that has a bright red belly, that sure would put a dent in the theory.

This pic is a bit out of focus, but there is a 12" ruler in the front.

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The fish are 18-19" long and both have red bellies, one is brighter than the other.
 
reptileguy2727;4427514; said:
Can we agree that the little 'red belly pacu' sold in most shops is indeed the same fish that turns out to be a meter long 'black pacu'?
There are different species. That doesn't change the fact that the red-bellied pacu do turn mostly black and get HUGE though
 
That's what I mean. You can see in those two how much black has already developed (although by that size they have usually dropped the red). Nice looking fish.

I know there are related species, but do people in the hobby ever actually get those relatives who are not the red/black pacu and how often?

Does anyone have a species of pacu that is not the one pictured here in this thread?

I am asking all this because on here and other forums/sites I see it all the time how people refer to red and black pacus separately. Are we really talking about different fish, or in the hobby is it just the same fish in different stages of its life?
 
Does anyone know how to tell them apart from RBP, I have 2 of what I suspect to be RBP, but are too mellow, so Im starting to suspect they're actually pacu. They're about 6 months old about 6 inches
 
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