Commerson's Glassy
Ambassis commersoni
Type: estuarine, saltwater, freshwater
Physical Characteristics
Oval, compressed body with a silver to transparent appearance. It features a deeply notched dorsal fin, large eyes, and a prominent lateral line. Adults may show a faint yellowish tint.
Habitat & Distribution
Found in coastal waters, estuaries, and lagoons in the Indo-West Pacific, including Sri Lanka. They are often associated with mangroves and can tolerate varying levels of salinity.
Size & Weight
Usually reaches a maximum length of about 15-16 cm; typical weight is very small, often less than 50-100 grams.
Similar Looking Species
Gymnochanda species (filamentous glassy perchlets) which lack the same dorsal fin structure, or other Ambassis species. Ambassis interrupta lacks the continuous lateral line.
Ecological Role
Acts as a primary consumer of zooplankton and small invertebrates while serving as a significant prey source for larger piscivorous fish and birds.
Diet
Carnivorous, primarily feeding on small planktonic crustaceans, fish larvae, and small insects.
Behavior
Highly social and schooling fish that are most active during the day. They often congregate near structures or vegetation for protection.
Reproduction
Engages in external fertilization where eggs are scattered in aquatic vegetation or sheltered areas. Spawning typically occurs in estuarine conditions.
Conservation Status
Data Deficient/Least Concern (not currently listed on IUCN Global Red List as threatened).
Identification Tips
Look for the transparent body where the internal skeletal structure is visible, and the distinctive notch between the two parts of the dorsal fin.
Interesting Facts
These fish are so transparent when young that they are often called 'glassfish'; they use this transparency as a form of camouflage against predators in open water.
User Notes
From lagoon in Sri Lanka
Identified on: 5/20/2026
Mode: Standard