Giant Shrimpgoby
Amblyeleotris fontanesii
The Giant Shrimpgoby
Amblyeleotris fontanesii
(Bleeker, 1853)
Description
Body Design The largest of the partner gobies, growing to 20 cm. They are pale gray with five brown bars which have indistinct edges.
The head is plain white save for small orange spots between the eye and the gill cover, and a reflective blue line below the eye.
Fin design The dorsal pectoral and `pelvic fins are gray, with a brown blotch at the base of the first dorsal fin in immature individuals. The pelvic fin is plain with a yellow tinge. The anal fin is yellow-grey with a blue border decorated by two purple lines. The caudal fin is oval in shape, grey with a purple lower and distal edge.
Juveniles may be much smaller and it may not be apparent at first that one is looking at a Giant goby. They have a narrow band made up of many brown spots between the broad bands and the first brown bar extends into the base of the first dorsal fin.
They are not necessarily paired up with Violet shrimps.
Diagnostic features
The adults can be distinguished by size alone. They are twice the size of other partner gobies. The five bars are pale with soft edges and the intervening spaces are undecorated.
Similar species
There are no other partner gobies of this size. A callopareia are also large but readily distinguished by the gold bars on the gill cover.
Juveniles can look like a different species and indeed have erroneously called the Five bar goby in the past. The facial markings are consistent in adult and juvenile.
Not all shrimpgobies associated with Violet shrimps are Amblyeleotris fontanesii.
Natural History
Habitat
Found mostly at around 20 metres depth, but with a recorded range of 5 to 30 metres. Usually in relatively protected very fine silty sand with small shell fragments and not much rubble. Well away from reefs in areas of bare sand.
Sometimes seen on extensive sand
flats at 10 to 20 metres with patchy growth of Halophila minor and Halophila spinulosa seagrasses
Also described from deep coastal mud slopes and muddy channels in estuaries.
Behaviour
A wary fish, probably because its size makes it more visible and of more interest to foraging predators. We have the impression that this includes dolphins. It will allow a cautious approach but remains constantly ready to flee into its burrow and takes pains to restrict its shrimps to the burrow until it has fully assessed the disturbance.
We have not observed two of these fish together at the burrow entrance. Obviously they must pair up for breeding so this behaviour remains unexplained. Perhaps they are too big and clumsy for a simultaneous emergency retreat!
We have rarely observed Giant shrimpgobies away from the burrow, though this may simply be because they are a cautious species that lives in a habitat with not much cover. Possibly for the same reason we have not observed them eating.
The areas occupied are often murky thanks to the bulldozing activities of the pairs of large partner shrimps so the gobies take the form of a single dimly perceived figure in a cloud of silt. When an area of the seabed is taken up by a colony of these gobies it is unusual to find any other species present.
One aspect of their cautious behaviour is sensitivity to the strobe pre flash resulting in a contorted image although the fish has resumed its steady posture afterwards.
Usually found with Violet Shrimp even in areas where other large shrimps occur. Juveniles are more often found with smaller shrimp such as the Red-Speckled Shrimp, but probably change partners when they are too large for the smaller shrimp’s burrow. This may account for juveniles sharing habitat with other shrimpgobies while adults are often in monospecific colonies.
Distribution
Published distribution: Andaman Sea to New Caledonia and north-eastern Australia to Ryukyu Islands. Palau.
Our records: Papua New Guinea, Solomon Islands and Australia: North East Percy Island, Fantome Island, Fitzroy Island and Low Isles.
Associated Shrimps
2 species
Associated Shrimps (two shrimps)
Red-Speckled Snapping Shrimp, Alpheus species 10
Violet Snapping Shrimp, Alpheus fenneri