Geographical Forms of S. rhombeus

FROM FRANK MAGALLANES - May 22, 2007

One of the many questions I receive about Serrasalmus rhombeus is...What kind is it? An ichthyologist would immediately look at the hobbyist with an incredulous look, probably followed with an answer/question that would go with something like this? What do you mean? What kind is it?

So what is the real answer? They are all Serrasalmus rhombeus for the following systemic reasons, they all possess a distinctive red eye when full grown adult. They all have nearly the same number of skeletal bones within its geographical range and lastly, there has been nothing yet via DnA that has proven them to be anything else other than Serrasalmus rhombeus.

While it is true that some look different based on the small size to sub-adult, once they reach full maturity they are indeed difficult to tell apart other than some minor, nearly obscure features to the trained eye. But that alone will not hold up to the fish being from a particular country as these fish are variable depending on the water.

Use the photos below cautiously. The species photographs shown here are not to be considered scientific representations, unless noted. They are specimens collected and photographed by George Fear in the area of collection. Some of the species were collected by other people and so credited.

From Belem probably from Rio Araguaia resembles S. gibbus.

Rio Araguaia Adult

Rio Araguaia juvenile

Rio Araguaia, sub adult

Upper Rio Araguaia collected from a pond

Rio Araguaia Adult

Marbled S. rhombeus

Rio Iriri

Darker Adult

Rio Iriri

Both are the same fish, in the water and outside. Notice the difference in
color. The fish outside the water looks olive green, whereas in the
photo tank it looks more silvery. These fish have a beautiful humeral
torquoise band that did not show well in the pictures -P. Petry

Jet Black High Back

Rio Nanay, Iquitos, Peru

Jet Black High Back

Rio Nanay, Iquitos, Peru

Jet Black High Back

Rio Nanay, Iquitos, Peru

Jet Black High Back

Rio Nanay, Iquitos, Peru

Photo by D.M.Schleser, Natures Images

UNKNOWN LOCALITY

Juvenile and sub-adult, possibly wrong species might be a variation of S. altuvei.

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