Is the fish we commonly call the black piranha a Serrasalmus Niger or a Serrasalmus Rhombeus with the latter two being its scientific names?

HISTORY:
Most of the popular piranha books prior to Gery's "Charocoids of the world" and many magazine articles on piranhas had delineated the two fishes, the Black Piranha (S.Niger) and White Piranha (S.Rhombeus) as being two different fish based on their founders (Schomburgk In Jardine, 1864) and (Linnaes,1766) respectively. Therefore, any piranha subsequently caught that needs to be classified and resembles or seemes to resemble the above two species must have all the necessary traits characteristic of that species. This seems simple enough but unfortunatedly the very name of a fish can become quite problematic. Let's try to make some sense of all this. We'll revisit what we do know as being common and accepted knowledge. Without going into any names, we do know there exist a particular species of piranha reputedly to have the following characteristics based on the experiences of pet store staff, fish wholesalers and most importantly piranha keepers themselves; (physical: strong high backed rhombusoid shape body with red lake eyes and colour ranging from steely blue,silver, charcoal grey, flat black and sometimes with a touch of noticeable yellow or orange around the gill area.

We previously thought the fish to grow up to one foot in size though now we know that indeed they grow closer to 2 feet in size. But it is not the physical characteristics that so piques our interest in the black piranha. It is the behaviour aspects of this species of fish that most of us find to be utterly fascinating. It is the behaviour of this particular species that most come to recognize as being synonymous with the fish called the "black piranha". The traits are legendary and well documented: totally solitary fish; accepts no tank companion large or small, stronger or weaker than itself; extremely difficult and dangerous piranha to handle and well capable of jumping right out of the aquarium with or without an aquarium top in place. With the combination of size, strength and a powerful body with, most importantly, a relentlessly aggressive demeanor, the black piranha is indeed a fish that is unique and one where care and handling must be at a premium.

Its legendary aggression and ferocity is its trademark and the main reason so many piranha keepers seek to own one. So what does all this have to do with names? Simple, when someone seeks out the black piranha, they would be asking for the fish called "black piranha" which was also called S.Niger scientifically. Is the S.Niger's description that of the fish we commonly call the black piranha? As far as I know, I have yet to see any published work detailing what Schomburgk had described as a Serrasalmus Niger piranha. Moreover, most if not all of the current scientific writers on piranhas agree that the "black piranha" that we have come to know is in fact belonging to species described as Serrasalmus Rhombeus. In other words, based on Linneaus's description of what he had described as Serrasalmus Rhombeus, the defining physical characteristics of that fish coincides with that we commonly know as the "black piranha".

Using scientific ichthylogical taxomic identification methods, piranha experts like Prof. Fink et al has come the conclusion that indeed what we come to know as the black piranha is still the black piranha in the non-scientific sense but a serrasalmus rhombeus in the scientific sense. So why is the white piranha synonymous with serrasalmus rhombeus, yet we hear now that the black piranha is serrasalmus rhombeus? Serrasalmus rhombeus is called the white piranha because when it is small in size, say 4 inches or smaller, it is much lighter in colour and mostly silver. Hence the name white piranha. As everyone knows, black piranhas become darker, thicker and pretty well loses most of its previous small size colours. Hence the applicable name black piranha though neither common name is truly reflective of what the true colour of the fish is.

Going back to Schomburgk's Serrasalmus Niger, we have yet to see someone come out and say here is what Shomburgk's S.Niger looks like and here is a sample of that fish. For all we know and this is a pure quess on my part but niger may mean black and thus the relationship between S.niger and black piranha. For example, native fisherman in the amazon may described the black piranha using the term black fish or niger, possibly meaning black though I am not sure niger means black. Anyhow, scientifically speaking, the overwhelming concensus today is that Serrasalmus Niger does not exits in sofar as it was described by Schomburgk and what does exits is serralsalmus rhombeus which scientifically describes the fish we commonly call the "black piranha".

Two other problems need mentioning now that we can say that the black piranha as we know it is Serrasalmus Rhombeus. 1) the black piranha or serrasalmus rhombeus has slight to moderate variations in body shape and colour due to the various different geographical water systems they originate from. For example, Brazilian blacks are a little more elonogated and thicker than Peruvian blacks which tend to be vertically taller and a little thinner than the Brazilians. Therefore, due to geographical considerations, there could be several slightly different looking black piranhas which makes identifying them a little more difficult for those without scientific expertise like myself. 2) the other major problem with with identification is that the fish/pet industry and especially the fish wholesalers in South America continue to call the black piranha S.Niger which isn't too bad as long as the fish they claim to be a black piranha is what we come to understand to be the black piranha based on physical and behaviour characteristics and not on name only.

The black piranha which we commonly associate with base on its somewhat infamous physical and behaviour traits should now be best described as "true black piranha" or scientifically serrasalmus rhombeus. What is the single biggest problem for those who seek to obtained the so called "true black piranha" is that several species of piranhas have in the past and continue today to show up in the trade as either Black piranha, S.Niger, S.rhombeus, and white piranha. One of the most frequent species that show up as any of the four mention is the various species of the spilopleura complex form of piranhas including the red throated piranha which is often called the white piranha or s.rhombeus. These spiropleura complex form species display very similar traits of being overly aggressive and indeed most of them are solitary by nature because they are relentless fin biters. This aggressiveness mimics that of the "true black piranha" and hence we often mistakingly confuse the two because even their shape, and colour is very similar at the size most of these fishes arrive from South America, which is from 2 to 6 inches. If you seen pictures of a two to six inch true black piranha(s.rhombeus) and that of the various types of spilopleura like the black diamond, the gibbus and the red throated piranha, you will find it difficult at time to tell them apart right away. To make matters even more confusing, I have seen a fish I consider to be either a serrulatus or a striolatus come in as black piranhas. Again the body is somewhat similar and the constant banging into the glass fools people into beleiving that this is a black piranha because the fish looks like it wants to come out and bite you. Infact, this constant pressing against the glass with its mouth is not aggression but instead it is actually nervous condition that makes the fish want out of the tank. One thing, this fish is considered a little more aggressive in nature than say your typical red piranha and thus people may conclude that it is a "true black piranha" when it is not.

Conclusion:
After thoroughly confusing everyone, understandably, lets review what has been said upto this point. That black piranha as we have come to know based on physical and especially behaviour traits has been scientifically classiffied as Serrasalmus Rhombeus. Serrasalmus Niger is scientifically inaccurate description of the black piranha as we know it. A better term I would like to use to describe the black piranha as we know it would be the "true black piranha" so that we can separate the "true black piranha (s.rhombeus)" from the several different species of piranhas that come identified as s.niger, s.rhombeus, black piranha and white piranha, but are none of the above. For references, please review the piranha literature section of aquaria central. You will find the latest pictures of small and large "true black piranhas" in the book by David M.Schleser and another nice picture of a large true black piranha in Prof.Pinkguni's Book. As well there is a couple of nice pictures of a Peruvian Black in one of the articles i listed in the tropical fish hobbyist magazine. Remember, the black piranha we have come to know and appreciate and admire is still out there, but under a different name.

" True Black piranha or serrasalmus rhombeus"
Note: the term "true black piranha" is my own term and may not be scientifically correct, Black Piranha and Serrasalmus Rhombeus are synonymous terms.