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azeral26 Posted Today, 03:43 PM
I was reading on Shark Aquarium that these species can be shoaled (Serrasalmus medinei or sanchezi). Anyone tried it?

First, piranas cannot be "shoaled" in the literal sense, shoaled makes it sound like they are going to be peaceful like neon tetras or guppy's and nothing could be farther from the truth. So we come to compatibility. Most p's are not compatible because they engage in finbiting and sometimes mortal bites. This behavior is most evident with Serrasalmus species. Because some species like S. maculatus are found in small groups in the wild, it seems some hobbyists think their fish tank is the rio Guapore. It's not. Its an unnatural situation and they are confined to a small space. What does a photo op prove? nothing, except to those gullible to believe its worth a million words. Realistically, Serrasalmus species when juveniles can exist with a minimal of damage (loss of fins or eyes) for a short duration.

What constitutes a short duration? Anything from a few hours or until they reach subadult size. What happens when they are grouped together basically depends on several things, water temperature and tank size are considerations. Piranas are unpredicable and for anyone to suggest they "shoal" is either irresponsible or lack any real knowledge of the beast and what the term "shoal" actually means. Science (W.L. Fink, 1997) clearly stated they do not shoal in the literal sense. And that is the world foremost authority on these critters. I would certainly take his observations over some guy on the internet.

So does that mean you shouldn't try? As a collector, I wouldn't simply because I enjoy my fishes pristine and undamaged. So it comes down to what you are after. If it is grouping of the species then mortality or fin damage are something you'd better seriously consider. Don't be fooled into believing a photo taken at a moment of time to suggest it is long term "shoaling". It's not worth anymore than photos of BIGFOOT suggesting the species is real.

 

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This partial might be of interest to you since the term "shoal" is still evident. Its an answer that biologist seem more comfortable with.

One unresolved question about schools concerns definition. "Obviously one fish is not a school; is two fish a school?" asks Julia K. Parrish, a University of Washington zoologist who has studied schooling in various ocean species. "I, personally, do not believe that two fish is a school, but there are definitely people who put two fish together and say they're studying schooling behavior. "I think of a school as enough individuals to form a three-dimensional structure," she says," so we're in the high tens to low hundreds as a minimum number." Some schools have millions of members and span an area as large as a small town.

A number of researchers have avoided the difficulty by using the term "shoal" for all groups of fish and then classifying them as either simple aggregations or schools. "Schools would be what you probably think of as a group of fish traveling together that turn with an impressive synchrony and in unison...rather like coordinated airplanes doing those maneuvers at air shows," says Tony Pitcher, director of the University of British Columbia Fisheries Center. True schools have distinct boundaries, Parrish notes. "There are lots of fish and then no fish. It's not that they sort of peter out."

That clarifies the term "shoal" as far as science is concerned. Should hobbyist avoid it? I would simply because I stated above Piranas don't shoal in the usual sense. Let me give you an example. If you do a search in google you can come up with a lot of explanations for the term "shoal" including the one you described above. But another consideration why do fish form "shoals". Largely it is a number of young (and adult) prey fishes (for protection) that predators eat, usually found in the 100's. So what is a pirana? A predator in the literal sense. And they are territorial so when you add some other distinctive characters to define whether or not a pirana "shoals" then you can comprehend why the term doesn't fit with piranas as a whole. Most as full grown adult go off on solitary trips or can come together as a small group (20-25 individuals). That still doesn't form a shoal. If you have a 100 young fry of P. nattereri in a tank would that be a shoal? Yes until they no longer are in that number and decrease themselves through predation. Then you can understand why the term "shoal" doesn't apply to Pygocentrus either.

So if I were to define what a pirana forms it would be as follows; Group = any small number of predatory fish (ie; piranas) that consists of 50 members or less .(<<<<period).

And I would leave the term "shoal" to your feeder goldfish or guppy's. As for the S. sanchezi, that can be left open to interpretation and in order to understand what I wrote about compatibility requires you study the Serrasalmus species and its feeding habits in the wild. S. sanchezi behave as solitary individuals usually found with P. nattereri because they most resemble their sisters by the scaling, red belly and body shape. The reason why they have this wolf in sheep clothing attire, is because they feed on Pygocentrus fins. So we are back to that again and its natural behavior.

 

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PS: Since George's name was brought up. If George has a large quantity of piranas in a tank, he can call it a "shoal". It doesn't necessarily make it so by definition. So don't criticize him for using that term. I'm just trying to educate you hobbyist on proper terminology and not a dealer is right or wrong.

 

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KrazyCrusader Posted Today, 07:57 PM
Serra's live off fins until they are big enough to eat prey.

Not necessarily so. Many adult species live on fruit, seeds and never eat a whole fish just fins. Keep in mind, piranas are opportunistic feeders. If there is an opportunity to eat a whole fish, they will. Normally fins have enough renewable protein to keep them happy and lean.

 

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azeral26 Posted Today, 08:32 PM
Frank that is a red belly I have right? based on his picture?

Seems to be.