Loricariinae.com Loricariidae · Taxonomy
Research Article

Identification of Sturisomatichthys aureus, S. festivus and S. panamensis

The confusion of the identity of Sturisomatichthys aureus and Sturisomatichthys festivus is a common and widespread mistake. This confusion originates partly from the type locality of S. festivus (Maracaibo basin), where commercial fish trade has been lacking for years, and partly from one publication with a faulty identification of a specimen of S. festivus as S. aureus.

A very similar faulty identification is the origin of the confusion between Sturisomatichthys panamensis and Sturisomatichthys festivus.

With a closer look at all three species it is not very difficult to distinguish them clearly. Most characteristic are the differences in the pectoral and dorsal fins that everyone is able to assess.

Available in trade are the first two named species. Sturisomatichthys aureus is mostly available as wild-caught, Sturisomatichthys festivus is principally offered as captive-bred offspring. Unfortunately the impressive species Sturisomatichthys panamensis is not in trade yet.

Sturisomatichthys aureus Dorsal Fin Pectoral Fins
S. aureus dorsal fin S. aureus pectoral fins
  • Spine nearly straight, in maturity slightly bent at the tip.
  • Ratio of body height to fin size about 1:2.
  • No filamentous extension.
  • Spine slightly bent.
  • Ratio of body width to fin size about 1:1.5.
  • No filamentous extensions.
Sturisomatichthys festivus Dorsal Fin Pectoral Fins
S. festivus dorsal fin S. festivus pectoral fins
  • Sometimes slightly S-curved shape of the spine.
  • Bent from the middle of the fin.
  • Ratio of body height and fin size about 1:2.5.
  • At least a small filamentous extension of the spine.
  • More or less straight spine.
  • Ratio of body width and fin size up to 1:2.
  • At least small filamentous extensions of the spines.
Sturisomatichthys panamensis Dorsal Fin Pectoral Fins
S. panamensis dorsal fin S. panamensis pectoral fins
  • The spine is straight.
  • Ratio of body height and fin size up to 1:3.
  • No filamentous extension.
  • The spine is nearly straight.
  • Ratio of body width and fin size about 1:2.
  • No filamentous extensions.
Adolescent specimens are hard to identify correctly. Mostly the size of the dorsal fin gives a hint as to which species they belong to. From the onset of maturity, the listed differences are clearly visible in all three species.
Unfortunately Sturisomatichthys festivus is a very heterogeneous species with different types of body shape. You will find specimens with a slender body and very large, filamentously elongated fins — but also ungraceful specimens with comparatively small, non-elongated fins.