Crescent Grunter (Terapon jarbua)

Crescent Grunter (Terapon jarbua)

A school of Crescent Grunters investigating a fallen snake shed in Berlayer Creek.

Family: Terapontidae

Species Name(s): Terapon jarbua

Common Name(s): Crescent Grunter, Target Fish, Spiky Trumpeter, Tiger Perch
Presence in Singapore: Native

Habitat: Freshwater to Marine.
Conservation status: Least Concern (Red Data Book 3)

The Crescent Grunter is a euryhaline fish that can be found in a wide range of salinities from full marine to freshwater. It spawns in saltwater, where juveniles hang out in intertidal zones but also swim up estuaries and rivers alongside adults. This commonly sighted fish can grow to a maximum known length of 36cm but usually average around 25cm. This species' distinctive patterning especially from the top gives it one of its many common names - the Target Fish.

This fish is mostly carnivorous, hunting invertebrates and smaller fish near the bottom but will also eat algae. They are also known ectoparasites, feeding on the scales of larger fishes which makes them horrible community fishes in most aquariums. Commercially, this fish is sold usually fresh or dry and salted.

Adult males guard and fan their eggs. Juveniles are also known to be territorial and establish territories via excavating craters. The name "Grunter" and "Trumpeter" comes from their ability to make noise using their swim bladder, which they use for communication.



References

• FishBase. Terapon jarbua (Fabricius, 1775) – (Jarbua terapon). Retrieved from https://fishbase.se/summary/Terapon_jarbua.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.
• National Parks Board (NParks). Marine Fishes. Retrieved from https://www.nparks.gov.sg/nature/species-list/marine-fishes.

Grey Knight Goby (Stigmatogobius sadanundio)

Grey Knight Goby (Stigmatogobius sadanundio)

A pair of Grey Knight Gobies hovering in a mangrove creek in Pasir Ris. (Photograph by: Lumin Ong)

Family: Oxudercidae: Gobionellinae

Species Name(s): Stigmatogobius sadanundio
Common Name(s): Grey Knight Goby

Presence in Singapore: Native
Habitat: Brackish and freshwater. Mangrove creeks and pools.
Conservation status: Least Concern (Red Data Book 3)

This is one of the more prominent mangrove gobies one will spot from above water due to its size! The Grey Knight Goby is decently-sized compared to its neighbours and grow to a maximum known length of 9cm. It is common and often seen hovering in shallow mangrove creeks and pools during low tide. 

It is known to prefer lower salinity levels and are more abundant in the back mangroves, with younger individuals being spotted in freshwater. This carnivorous species is an active predator which feeds on smaller fish and invertebrates. Its rarer cousin, the Peach Knight Goby (Stigmatogobius pleurostigma) can look similar and would require a clear view of the tail for identification. A solid spot would be present at the bottom of the tail for that species! 

The Grey Knight Goby is also a commonly sold aquarium fish and is frequently included in brackish community tanks.

A large Grey Knight Goby - note the lack of solid spot at the bottom of the tail.

A small juvenile found in a freshwater drain on Pulau Ubin.

References

• FishBase. Stigmatogobius sadanundio (Hamilton, 1822) – (Knight goby). Retrieved from https://www.fishbase.se/summary/Stigmatogobius-sadanundio.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.
• National Parks Board (NParks). Marine Fishes. Retrieved from https://www.nparks.gov.sg/nature/species-list/marine-fishes.