Piranha identification key

[Gary Vinyard]

I have been approached by an individual in need of an identification key
which will allow discrimination between piranahas and a fish known as a
red pacu.  As this is way out from my area of expertise it seemed
appropriate to consult this group.  Anyone have any suggestions??

Thanks.

  Gary Vinyard
  Department of Biology
  University of Nevada
  Reno, Nevada  89557-0015

  gvinyard at unssun.nevada.edu