Asterropteryx ovata
A 2cm goby logged mostly in Apra Harbor, Guam, in warm 25-29C water year-round. Here's how to spot one.
A tiny goby, barely 2 cm long, that perches motionless on rubble, coral debris or the seafloor rather than swimming freely in open water. Look for a slender, tapered body typical of gobies, with the oval-shaped markings that give the species its name showing along the flanks under close inspection. At this size you will need a macro lens or a very close, patient look to pick up any pattern detail at all.
Expect to find it sitting still on rubble or open sand-and-rock patches rather than darting around, which is standard goby behaviour: perch, watch, dart for cover if approached too fast. Divers report it as an uncommon find even at the sites where it does turn up, so this is more a
Like most gobies, this species almost certainly lacks a swim bladder, which is why it rests on the substrate instead of hovering in midwater like many other small reef fish.
Sightings show no clear seasonal pattern, and the water temperature range recorded, 25.3 to 29.0 C, sits comfortably within tropical norms year-round, so there is no obvious best month to target. Treat this as a species you look for on any warm-water dive in Guam rather than one tied to a particular season.
Every logged sighting of this goby comes from Guam, making it essentially a Guam specialty for divers chasing it specifically. Apra Harbor is by far the most reliable spot, with the Southern Coast a secondary option, though at these tiny sizes it takes a dedicated macro dive rather than a casual reef cruise to actually find one.
Mapping where Oval-spot Goby is logged…
Guam is the only place with confirmed sightings, and within Guam, Apra Harbor is the strongest spot, with a smaller number of sightings along the Southern Coast.
There's no detected season for this species. It's recorded in water from about 25 to 29 C, which holds steady year-round in its known range, so any time of year is fair game.
Look for a very small goby, around 2 cm, perched still on rubble or bare substrate rather than swimming in the open. The oval markings along its body that give it its name are only visible on close macro inspection.
They stay tiny, topping out around 2 cm, which puts them firmly in macro-photography territory rather than something you'll spot from a distance.
No. It poses no threat to divers and is far too small and non-aggressive to be a concern; the only real challenge is spotting it.
Its conservation status has not yet been formally evaluated, so there's no listed threat level to report at this time.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Slender Goby
803 sites
