Shoal leaders and their numbers

[Otherone]

I was reading an article about Piranha shoals and came across a paragraph that stood out to me;

"Previously it was thought piranhas shoaled as it enabled them to form a co-operative hunting group. However we have found that it is primarily a defensive behavior, and quite a complex one. The bigger, older fish tend to swim in the middle as they are reproductively mature and need to keep safe, whereas the outer layer of the shoal is made up of smaller, younger piranhas. Being at the edge of the group means they can get access to food sooner - essential if they are to grow more quickly and mature."
http://news.softpedia.com/news/Uncovering-the-Myth-of-the-Piranha-58952.shtml

Just curious - has anyone noticed this behavior in their captive shoals?
Also would this explain why Piranha shoals are best kept in "odd" numbers so the dom. male feels comfortable with an equal amout of mates on either side?

 

[jp80911]

I don't think my "shoal" is big enough to have a center/outer layer.

Piranha shoals are not best to kept in "odd" numbers, from what I know that piranhas do not know how to count. that pretty much only applies to people that want either 2 or 3 piranhas, 3 is of course better than 2, but if they can get more then 4 would be better than 3; 5 will of course better than 4...and it goes on and on and on.

 

[ballinouttacntrol]

but is 6 better then 5? lol, i'm kidding

 

[jp80911]

but is 6 better then 5? lol, i'm kidding

not necessary if the tank isn't big enough

 

[frontosablkrhom]

I was reading an article about Piranha shoals and came across a paragraph that stood out to me;

"Previously it was thought piranhas shoaled as it enabled them to form a co-operative hunting group. However we have found that it is primarily a defensive behavior, and quite a complex one. The bigger, older fish tend to swim in the middle as they are reproductively mature and need to keep safe, whereas the outer layer of the shoal is made up of smaller, younger piranhas. Being at the edge of the group means they can get access to food sooner - essential if they are to grow more quickly and mature."
http://news.softpedia.com/news/Uncovering-the-Myth-of-the-Piranha-58952.shtml

Just curious - has anyone noticed this behavior in their captive shoals?
Also would this explain why Piranha shoals are best kept in "odd" numbers so the dom. male feels comfortable with an equal amout of mates on either side?

that sounds cool , i dont see it at all in my shoal and theres 20 some are 2 years old the bigger ones just punk the smaller ones in my shoal. the small ones hang out as far away as possible from the big guys.