Telescope Cardinalfish
Sphaeramia orbicularis
Type: Reef fish / Brackish / Lagoon
Physical Characteristics
Deep, compressed orbicular body shape with two separate dorsal fins. Translucent yellowish-green or grey with dark spots and a prominent dark vertical bar from the first dorsal fin to the pelvic fins. Large prominent eyes. Small, fine scales. Distinctive rounded profile.
Habitat & Distribution
Commonly found in mangroves, lagoons, and sheltered coastal reefs. Prefers brackish water environments across the Indo-Pacific, specifically around Sri Lanka and Southeast Asia.
Size & Weight
Typically reaches 8 to 10 cm in length. Maximum weight is small, usually only a few grams.
Similar Looking Species
Pajama Cardinalfish (Sphaeramia nematoptera) which has much brighter coloration and red eyes; Orbiculate Cardinalfish (Sphaeramia orbicularis) is the specific name, often confused with other Apogonidae.
Ecological Role
Mesopredator in lagoon ecosystems; serves as important prey for larger reef and lagoon piscivores while controlling planktonic populations.
Diet
Carnivorous, primarily feeding on small planktonic crustaceans, tiny fish larvae, and benthic invertebrates.
Behavior
Nocturnal by nature, hiding among mangrove roots or coral during the day. Often forms small groups or schools. Territorial during breeding periods.
Reproduction
Paternal mouthbrooders; the male carries the eggs in his mouth until they hatch to protect them from predators. Spawning typically occurs in sheltered waters.
Conservation Status
Least Concern (IUCN); however, habitat loss in mangrove regions can impact local populations.
Identification Tips
Look for the distinctive round, orbicular body shape, the vertical dark bar through the eye/mid-body, and the large eyes characteristic of nocturnal cardinalfish. Found specifically in lagoon-mangrove interfaces.
Interesting Facts
These fish are paternal mouthbrooders, meaning the father does not eat for several days or weeks while holding the developing eggs in his mouth for protection. They are highly adapted to the low-visibility waters of Sri Lankan lagoons.
User Notes
From Sri Lankan lagoon waters
Identified on: 5/30/2026
Mode: Standard