Spotfin Spiny Eel

Distribution

The peacock eel is native to the Mekong and Chao Phraya basins, which make up the countries of Thailand, Cambodia, Laos, and Vietnam. They are mostly found in slow-moving backwaters that have a sandy or muddy bottom, such as swamps, canals, and ponds.

There is an invasive population of peacock eels in the Everglades region of Florida, most likely being released due to the aquarium trade. The eels were first discovered in the C-111 canal in 2002, and in 2004 were also found to inhabit mangrove swamps further south.

Description

These fish lack scales and require a soft substrate to burrow into, such as sand, mud, or silt. They breed during the wet season when adjacent forests flood. Larvae reach 8 cm (3 in) in length in approximately 60 days after hatching.

This eel can grow up to 30 cm (12 in) in standard length, although 20 cm (8 in) is more common. Males and females are hard to tell apart through external means.

Additional field notes

The eye-like marks along the dorsal fin and dusk feeding behavior are useful features of the spotfin spiny eel.

Sources: Macrognathus siamensis species summary

Identification and feeding activity

FishBase describes three to six conspicuous eyespots along the base of the soft dorsal fin and 13–19 dorsal spines. It notes that the dorsal, anal, and tail fins remain separate. These features help narrow an identification among superficially similar spiny eels.

The fish often remains buried in fine bottom material with only part of the head showing, then emerges around dusk to feed. Reported prey include bottom-dwelling insect larvae, crustaceans, and worms. A hidden daytime fish and an actively foraging evening fish can therefore represent normal behavior at different times of day.

Sources: Macrognathus siamensis species summary