Glassy Perchlets/Glassfishes (Ambassis sp.) part 1: A.kopsii, A.vachellii & A.interrupta

Glassy Perchlets/Glassfishes (Ambassis sp.)

A school of Singapore Glassy Perchlets.

Family: Ambassidae

Habitat: Brackish to saltwater. Open-water but enters mangroves during high tide.

There are currently 5 species in the genus Ambassis listed in the Third Edition of the Singapore Red Data Book. However, iNaturalist records and encounters prove that there are several more, with a few possibly being undescribed or in need of review. Common names refer to them as Glass/Glassy Perchlets or Glassfishes.

They're often seen as schools in the mid- to surface-water column picking off small invertebrates and other edibles they're not picky about as they're omnivorous. During a rising-high tide, some species commonly swim into mangrove swamps to forage and shelter among the roots. Some species are seen more often in and around mangroves while other species can be found in full saltwater as well around reefs, sometimes being trapped in tide pools. They are known to tolerate freshwater but are rarely seen in it locally.

Part 1 features: A.kopsii, A.vachellii and A.interrupta*

1. Singapore Glassy Perchlet (Ambassis kopsii)

A school of Singapore Glassy Perchlets feeding near the surface in Sungei Buloh Wetland Reserve. (Photograph by: Lumin Ong Jun Xiang)

Species Name(s): Ambassis kopsii

Common Name(s): Singapore Glassy Perchlet, Kops' Glassy Perchlet

Presence in Singapore: Native

Habitat: Brackish to full saltwater. Often easily seen near the surface along the shore.

Conservation status: Least Concern (Red Data Book 3)

This is the most common species of Ambassis one would encounter. It is recognized by its deep body, yellow-edged pelvic, anal and caudal fins, alongside a black spot on the first dorsal fin's tip. Reaching a maximum length of around 10cm, a school of them is easily seen from boardwalks as they hang out near the surface. While they frequent estuaries, they are also seen further out to sea and have been known to be trapped in tidal pools.

2. Vachell's Glassy Perchlet (Ambassis vachellii)

A school of Vachell's Glassy Perchlet seen along Bedok Jetty. (Photograph by: Lumin Ong Jun Xiang)

Species Name(s): Ambassis vachellii

Common Name(s): Vachell's Glassy Perchlet, Vachell's Glassfish

Presence in Singapore: Native

Habitat: Brackish to full saltwater. Often easily seen near the surface in mangrove creeks, tidal canals and open seawater around reefs etc.

Conservation status: Least Concern (Red Data Book 3)

The second most encountered Glassy Perchlet. This is a slimmer and smaller species that reaches a maximum length of around 6.5cm. Its slimmer build makes it stand out from other Ambassis species seen locally. Healthy individuals are usually a translucent grey with a sometimes a yellow tail. Infected individuals often have pale, solid colouration with dark patches (see photo below). They are sometimes seen together with A.kopsii in the same habitats but A.vachellii are frequently encountered further out to sea as well. They have been seen following flotsam, foraging along jetties and pontoons above reefs etc.

A school of Vachell's Glassy Perchlets. Sick individuals can be seen with prominent dark patches. (Photograph by: Lumin Ong Jun Xiang)

Feeding frenzy! Vachell's Glassy Perchlets feeding below a concrete boardwalk with Javanese Ricefishes.

3. Longspine Glassy Perchlet (Ambassis interrupta)

A dead Longspine Glassy Perchlet seen in Sungei Buloh Wetland Reserve. (Photograph by: Lumin Ong Jun Xiang)

Species Name(s): Ambassis interrupta

Common Name(s): Longspine Glassy Perchlet, Longspine Glassfish

Presence in Singapore: Native

Habitat: Brackish to full saltwater. Seen more in larger channels.

Conservation status: Least Concern (Red Data Book 3)

 

The Longspine Glassy Perchlet inhabits the same habitats as the other featured two species but is seen more often in larger channels such as rivers, which it swims up during a high tide. Inferencing from local sightings, it is not photographed much in-situ.

The Longspine Glassy Perchlet looks similar to the Vachell's Glassy Perchlet at first glance but can be identified by its long dorsal spine and deep body.

References

• FishBase. Ambassis kopsii Bleeker, 1858 – (Singapore glassy perchlet). Retrieved from https://www.fishbase.se/summary/Ambassis-kopsii.html
• FishBase. Ambassis interrupta Bleeker, 1858 – (Long-spined glassfish). Retrieved from https://www.fishbase.se/summary/Ambassis-interrupta.html
• FishBase. Ambassis vachellii Richardson, 1846 – (Vachelli's glass perchlet). Retrieved from https://www.fishbase.se/summary/Ambassis-vachellii.html
• Lim, K.K.P. & Low, J.K.Y. 1998. A Guide to Common Marine Fishes of Singapore. Singapore Science Centre, 163 pp. ISBN 981-00-9904-5.
•  Lin JY, Ong JXL, Tay JX & Tan HH (2024) Biodiversity Record: Fishes and other marine life observed among flotsam at Marina South. Nature in Singapore, 17: e2024128. DOI: 10.26107/NIS-2024-0128
• National Parks Board (NParks). Marine Fishes. Retrieved from https://www.nparks.gov.sg/nature/species-list/marine-fishes.

Cantor's Gudgeon (Ophiocara cantoris)

Cantor's Gudgeon (Ophiocara cantoris)

A colourful Cantor's Gudgeon found in Berlayer Creek.

Family: Butidae

Species Name(s): Ophiocara cantoris
Common Name(s): Cantor's Gudgeon

Presence in Singapore: Native
Habitat: Brackish. Mangrove creeks and canals. Shelters among mangrove roots etc.
Conservation status: Near Threatened (Red Data Book 3)

The Cantor's Gudgeon is a commonly-seen mangrove fish that one might mistaken for a fat goby. Its usual colouration is a distinct brown with two white vertical white bands, accompanied by whitish-yellow dots throughout the body. It can also appear fully dark brown as well, which is often seen in larger individuals. The average length of this fish is around 9 to 11cm but like its relative Ophiocara ophicephalus, it can probably grow to twice the average length.

The Cantor's Gudgeon is an ambush predator, hovering slowly in the water column or among shelter such as mangrove roots and leaf litter. It waits for small fishes and invertebrates to get close before snapping them up with a burst of speed.

In the Third Edition of the Singapore Red Data Book, it is referred to as Ophiocara porocephala and it is also referred to as O.ophicephalus in past records. O.cantoris should be the current correct name for the local species as a review of all 3 species differentiates them at the genetic and morphological level (Keith & Mennesson, 2021). 

A large Cantor's Gudgeon seen in Pasir Ris. Note the faded stripes.

A juvenile Cantor's Gudgeon seen in Pasir Ris. (Photograph by: Lumin Ong Jun Xiang)

References

• Lim, K.K.P. & Low, J.K.Y. 1998. A Guide to Common Marine Fishes of Singapore. Singapore Science Centre, 163 pp. ISBN 981-00-9904-5.
• National Parks Board (NParks). Marine Fishes. Retrieved from https://www.nparks.gov.sg/nature/species-list/marine-fishes.
• Philippe Keith, Marion I. Mennesson. Review of Ophiocara (Teleostei: Butidae) from Indo-Pacific Islands. Cybium : Revue Internationale d’Ichtyologie, 2021, ⟨10.26028/cybium/2021-452-002⟩. ⟨hal-03337214⟩