Silver arowana, the most common aro in the hobby
The black arawana (Osteoglossum ferreirai Kanazawa 1966) from the Rio Negro is distinctively colored as a juvenile; however, adults are "nearly identical" in coloration to the arawana (Howells 1992). The two species can be distinguished by meristics (especially fin-ray counts), as follows (from Kanazawa 1966):
- O. bicirrhosum - Dorsal fin 42-50; anal fin 49-58; lateral-line scales 30-37; vertebrae 84-92.
- O. ferreirai - Dorsal fin 52-58; anal fin 61-67; lateral-line scales 37-40; vertebrae 96-100.
Does this help?
http://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=799
The black arawana (Osteoglossum ferreirai Kanazawa 1966) from the Rio Negro is distinctively colored as a juvenile; however, adults are "nearly identical" in coloration to the arawana (Howells 1992). The two species can be distinguished by meristics (especially fin-ray counts), as follows (from Kanazawa 1966):
- O. bicirrhosum - Dorsal fin 42-50; anal fin 49-58; lateral-line scales 30-37; vertebrae 84-92.
- O. ferreirai - Dorsal fin 52-58; anal fin 61-67; lateral-line scales 37-40; vertebrae 96-100.
Does this help?
http://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=799