Commerson's Anchovy (Larval stage)
Stolephorus commersonnii
Type: Estuarine, saltwater, lagoon ichthyoplankton
Physical Characteristics
As a larva/post-larva, it displays a slender, elongated, and nearly transparent body. It has a prominent eye, a visible straight gut, and developing vertical muscle segments (myomeres). The mouth is inferior as it transitions to the adult stage, and the fins are small and delicate at this phase.
Habitat & Distribution
Inhabits coastal waters, estuaries, and lagoons. In Sri Lanka, larvae are common in brackish lagoon systems which serve as nurseries. Distributed throughout the Indo-Indo-Pacific region.
Size & Weight
As a larva, it measures between 5mm to 20mm. Adults typically reach lengths of 8cm to 10cm, with a maximum of approximately 15cm.
Similar Looking Species
Other Stolephorus species and larval Engraulidae. Identification at the larval stage requires microscopic analysis of myomere counts and pigmentation patterns compared to Stolephorus indicus.
Ecological Role
Acts as a vital link in the trophic web, consuming zooplankton and serving as a primary food source for larger predatory fish and marine birds.
Diet
Primarily a planktivore, feeding on copepods, small crustaceans, and other zooplankton through filter feeding as it matures.
Behavior
Schooling behavior begins at a young age. They are generally diurnal and move into lagoon areas with tidal currents for protection and feeding.
Reproduction
Part of the Engraulidae family with high fecundity. Spawning occurs in coastal waters; eggs and larvae are pelagic, often drifting into lagoons to utilize the nutrient-rich environment.
Conservation Status
Least Concern (IUCN); however, populations are sensitive to environmental changes in lagoon water quality and mangrove degradation.
Identification Tips
Look for the transparent, glass-like body with a distinct silver stripe starting to develop along the midline in older larvae. The long, slender body and single dorsal fin position are key indicators.
Interesting Facts
These larvae are often part of 'whitebait' plankton communities. Their transparency is a survival mechanism to avoid predation in the open water column.
User Notes
From a Sri Lankan lagoon ichthyoplankton survey
Identified on: 5/20/2026
Mode: Standard