The precarious temperature regime, associated with the negative influence of other environmental and biotic factors, represents a major risk for the survival of the thermal rudd from the lake Ochiul Mare, located in the Pârâul Peţea natural reserve. Therefore, a complex morphometric and body geometry analysis was conducted on specimens collected in 2013 in order to define the variability of the present population. The relatively small sample size is due to legislative restrictions on collecting endangered species, so statistical methods of analysis were applied to increase confidence in the assertions.