Piaractus mesopotamicus (Holmberg, 1887)

Fig. 15

Body deep; greatest depth contained 1.5 to 2.0 and caudal peduncle depth 8.8 to 8.9 times in SL; head length 2.7 to 4.2, predorsal distance 1.6 to 1.7 and caudal peduncle length 8.8 to 9.4 in SL; snout length 2.9 to 3.3, horizontal orbital diameter 5.2 to 5.5 and least interorbital width 1.9 to 2.1 in HL. Mouth terminal; inner row of premaxilla with 2, outer row with 6-8; inner dentary row with 2, outer with 6; maxilla with 1 or 2 teeth. Lateral line complete, with 107-119 pored scales; transverse series above lateral line with 49-54 scale rows and below with 50-55 scale rows. Ventral keel with 52-54 simple spines, plus 7 pairs of spines. Dorsal fin with 15 or 16, pectoral fin with 14-17, pelvic fin with 8 or 9, anal fin with 23- 25, and caudal fin with 19 rays. Ground color greyish, darker dorsally. Dorsal and pectoral fins dark-grey; pelvic anal and caudal fins yellowish-orange (Graça, Pavanelli, 2007).

Maximum standard length. 533.0 mm (Graça, Pavanelli, 2007).

Distribution. Paraná-Paraguay system.