For the past couple of months Fish
Tales has strayed from its usual focus on typical reef-friendly
aquarium fish. One of these unusual subjects was a corallivore,
and another of the column's featured species would be happy
to eat other vertebrates. Switching gears this month and getting
back into a reef-friendly frame of mind, I'd like to introduce
a genus of sand or substrate dwelling gobies that generally
do not receive much attention from the hobby. Even so, these
little fish make perfect additions to mini- and possibly even
micro-reef aquariums, not to mention a biotope aquarium which
has been gaining popularity lately - mangrove tanks. So don't
let these small aquariums sit fishless; add a member of the
genus Istigobius!
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Istigobius species are wonderfully camouflaged
and thus are difficult to locate against the sand background.
The Rigilius goby, seen here, is a great example of
how these fish can blend into their native habitat.
Mimicking a sandbed that is similar to the colors of
your goby will aid in their transition into captivity
and likely allow for ease of viewing. Photo courtesy
of Mitsuaki Takata. |
Meet the Family
The Gobiidae is the largest family of marine
fish with over 2,000 members, and it is still growing. Most
Gobiidae are characterized by a few notable attributes. Other
than the few gobies that swim above the substrate, most lack
a swim bladder and lateral line. Gobies do, however, have
sensory ducts surrounding their heads that make up for the
lateral line's absence (Smith and Knopf, 1997). Another interesting
characteristic is the condition of the ventral fins, which
in most gobies are joined together and have small suction
cups on the end.
As with so many fish genera, Istigobius
was originally described as a subgenus, in this case, of the
genus Gobius (Whitley, 1932; Murdy and Hoese, 1985).
Even so, many of the current Istigobius species were not originally
placed in this subgenus, but instead were spread out among
genera such as Acentrogobius, Ctenogobius, and
Rhinogobius.
It wasn't until 1979 that Hoese and Winterbottom
reviewed the family and subsequently elevated Istigobius
to generic status. Despite most often being confused with
Acentrogobius, Istigobius was noted to differ
by having its nose extend over the top of its lower jaw. Additionally,
Istigobius was found to be most closely related to
Exyrias, though Exyrias was noted to have "fully
scaled cheeks and operculae," while these features are
lacking in all Istigobius except I. perspicillatus
(Murdy and Hoese, 1985).
The 10 species (see below) of Istigobius
all have a few traits in common. Possibly most important to
hobbyists is the sexually dimorphic nature of all species.
Although the genital papilla is the deciding factor in all
species of Gobiidae, this feature is more pronounced in Istigobius.
Additionally, several other sexually dimorphic traits are
also present such as the longer pelvic fins, darker pigmentation
in spots or blotches, and horizontal striping, found on the
males.
§
campbelli |
§
decoratus |
§
goldmanni |
§
hoesei |
§
hoshinonis |
§
nigroocellatus |
§
ornatus |
§
perspicillatus |
§
rigilius |
§
spence |
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In the Wild
Istigobius species are found throughout
the Indo-Pacific waters, but not all members of the genus
are tropical. Two species, Istigobius campbelli and,
I. hoshinonis, are restricted in distribution to the
temperate seas around Hong Kong and Japan, and another, I.
hoesei, has been found only around Sydney, Australia.
The remaining species inhabit warmer tropical waters, from
the Red Sea to Samoa. Istigobius ornatus is the most
abundant species in the genus and can be found from Taiwan
to Fiji, down to Queensland, and over to the Red Sea.
Istigobius decoratus is one of the larger members
of the genus, reaching nearly five inches. It is seen
here amongst the preferred habitat of dark sand and
coralline encrusted rubble. When threatened by a predator,
it is more likely to remain in the open and stay still
(hopefully) blending into the substrate. Photo courtesy
of Roberto Sozzani of Scubabob.
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All species of Istigobius are shallow
water sand-dwelling fish; that is, they freely roam the sand
substrate throughout the day. During their daily activities,
however, they are never far from shelter, which may consist
of rock, rubble, coral, or mangroves. For such a small fish
(reaching a maximum length of five inches), however, it is
interesting to note that they do not utilize burrows or crevices
for hiding. When burrows in the sand or rock were present
while the fish were frightened, in no instance did the fish
take refuge in the seemingly safe hideout. Instead, once they
flee to a suitable location, they attempt to camouflage themselves
by lying still among the sand and rock rubble.
Feeding in the wild will consist of sifting
through sand in search of interstitial fauna. By swallowing
a mouthful of sand, the sand-dwelling gobies begin the process
of eating. Once the fish has a mouthful of sand, it begins
to slowly expel the sand out its gills, but only after carefully
sifting through it for any small invertebrates. Of course,
the fish eats any invertebrates it is able to sift from the
sand. Generally, copepods (about 60% of the diet), amphipods,
ostracodes, nematodes, and shelled protozoa (foraminiferans)
are the main food targets. Naturally, once all the sand has
been expelled from the mouth, the fish will repeat the process.
Despite the habitat preference of some
species for mangroves and others for coral rubble, all species
prefers water less than 20 feet deep. These shallow waters,
combined with silty-sand substrate, typically yield water
visibility of less than 20 feet. Perhaps this limited visibility
is a major reason the fish never move further than several
inches from suitable cover.
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The perfect option to add fish life to your mangrove
sump is Istigobius ornatus because it is rarely
found outside of the shallow, silty mangrove coastal
areas. Only keep one per tank, however, as with most
members of this genus, the Ornate goby is found as a
single individual in the wild. Photo courtesy of Robert
A. Patzner, Austria. |
In the Home Aquarium
Maintenance of these sand-dwelling gobies
is rather simple, provided the aquarist offers them the proper
habitat. Small, peaceful aquariums often provide the optimum
environment for these gobies' long-term care. One major consideration,
however, is the temperature of the aquarium. Maintaining any
of the aforementioned temperate sea species will require an
aquarium cooler than a typical reef aquarium. Otherwise, a
sooner-than-should-be-expected-death will result from the
increased water temperature.
The aquarium mates of Istigobius
should be restricted to peaceful fish. Other gobies that maintain
territories in the middle of the water column would be good
choices. These would obviously include Wormfish and cleaner
gobies. Gobies that maintain a territory within rocks, corals
or burrows are also good choices.
Of course, predatory fish such as lionfish,
groupers, or moray eels should be avoided. The gobies will
become a quick snack for most any predatory fish. Additionally,
predatory invertebrates such as brittle starfish from the
genus Ophiarachna
should also be avoided. Small gobies such as Istigobius
are an easy meal for these aggressive predators. Likewise,
anemones such as the Stichodactyla
species should be avoided. All too often fish will fall victim
to these anemones.
An aquarium photo of Istigobius decoratus. The original
type specimens
collected in 1927 were lost from Manila as a casualty of World
War II.
Photo courtesy of Erik Schloegl.
Compatibility
chart for Istigobius:
Fish
|
Will Co-Exist
|
May Co-Exist
|
Will Not Co-Exist
|
Notes
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Angels, Dwarf
|
|
X
|
|
A larger aquarium will contribute to greater success.
|
Angels, Large
|
|
|
X
|
Large size and aggressive feeding nature.
|
Anthias
|
X
|
|
|
Provided the aquarium is large enough for Anthias and
direct feeding is administered to the goby.
|
Assessors
|
X
|
|
|
Excellent choice.
|
Basses
|
|
|
X
|
May consume Istigobius species.
|
Batfish
|
|
|
X
|
Large size and aggressive feeding habits.
|
Blennies
|
|
X
|
|
Most blennies should do well; larger ones may harass
smaller gobies.
|
Boxfish
|
|
X
|
|
The smaller members of the genus are the best options.
|
Butterflies
|
X
|
|
|
Excellent choice.
|
Cardinals
|
X
|
|
|
Excellent choice.
|
Catfish
|
|
|
X
|
May consume Istigobius species.
|
Comet
|
X
|
|
|
Excellent choice.
|
Cowfish
|
|
X
|
|
The smaller members of the genus are the best options.
|
Damsels
|
|
X
|
|
Most damsels can be incredibly abusive to tank mates.
|
Dottybacks
|
|
|
X
|
Most dottybacks will hunt and kill small gobies - Pseudochromis
fridmani and P. springeri are possible exceptions.
|
Dragonets
|
X
|
|
|
Excellent choice.
|
Drums
|
X
|
|
|
Excellent choice.
|
Eels
|
|
|
X
|
May consume Istigobius species.
|
Filefish
|
X
|
|
|
Excellent choice.
|
Frogfish
|
|
|
X
|
May consume Istigobius species.
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Goatfish
|
|
|
X
|
May consume Istigobius species.
|
Gobies
|
X
|
|
|
Excellent choice.
|
Grammas
|
X
|
|
|
Excellent choice, if Gramma is added after goby.
|
Groupers
|
|
|
X
|
May consume Istigobius species.
|
Hamlets
|
|
|
X
|
May consume Istigobius species.
|
Hawkfish
|
|
|
X
|
May consume Istigobius species.
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Jawfish
|
X
|
|
|
Excellent choice.
|
Lionfish
|
|
|
X
|
May consume Istigobius species.
|
Parrotfish
|
|
|
X
|
Overall size and aggressive swimming nature.
|
Pineapple Fish
|
X
|
|
|
Excellent choice.
|
Pipefish
|
X
|
|
|
Excellent choice.
|
Puffers
|
|
|
X
|
May harass smaller gobies.
|
Rabbitfish
|
|
X
|
|
Should be OK provided the aquarium is large enough
for the rabbitfish and enough food reaches the goby.
|
Sand Perches
|
|
|
X
|
Larger individuals may harass or consume Istigobius
species.
|
Scorpionfish
|
|
|
X
|
May consume Istigobius species.
|
Seahorses
|
X
|
|
|
Excellent choice.
|
Snappers
|
|
|
X
|
May consume Istigobius species.
|
Soapfish
|
|
|
X
|
May consume Istigobius species.
|
Soldierfish
|
|
|
X
|
May consume Istigobius species.
|
Spinecheeks
|
|
X
|
|
Adult size may be intimidating.
|
Squirrelfish
|
|
|
X
|
May consume Istigobius species.
|
Surgeonfish
|
|
X
|
|
Aggressive feeding and swimming habits will likely
require direct feeding of the goby.
|
Sweetlips
|
|
|
X
|
May consume Istigobius species.
|
Tilefish
|
X
|
|
|
Excellent choice.
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Toadfish
|
|
|
X
|
May consume Istigobius species.
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Triggerfish
|
|
|
X
|
May consume Istigobius species.
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Waspfish
|
|
|
X
|
May consume Istigobius species.
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Wrasses
|
|
X
|
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Many wrasses are best avoided. The most peaceful ones
will be good choices.
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Note: While many of the fishes listed
are good tank mates for Istigobius species, one should
research each fish individually before adding it to the aquarium.
Some of the fish listed above are better left in the ocean
or for advanced aquarists.
Another photo of Istigobius decoratus, this one
showing off the highly variable pigmentation possible
for the Decorated goby. As opposed to the previous photo
which was likely collected closer to the Eastern spectrum
of its distribution, this photo was likely taken from
waters near Taiwan or the Philippines. Photo courtesy
of Mitsuaki Takata.
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Another husbandry concern should be the
life of your sand bed. Nowadays many hobbyists are concerned
about predation upon the sand bed fauna. If this describes
you - by all means avoid these fish. As noted earlier, they
feed from the sand by sifting it and stripping the vital micro-fauna
from it. If you are not concerned about the life within your
sand bed, these sand sifters will do an excellent job of overturning
the sand and generally keeping it clean. However, you should
be concerned about where the sand gets dumped; they are indiscriminate
dumpers.
Besides sifting through the sand bed, your
new goby will require supplemental feedings of prepared foods.
It is likely, especially in smaller aquariums, that the sand
bed, by itself, will not provide enough food to sustain the
fish. Instead, expect to feed smaller foods designed for a
carnivore's diet. Such foods would include mysid shrimps,
adult enriched brine shrimp, fish roe, and any of the copious
offerings of flake foods.
The behavior of Istigobius allows
a wide latitude of potential aquarium sizes. These fish have
a tendency not to feel comfortable more than several inches
from shelter. As a result, they should do well in aquariums
as small as 10 gallons, provided predators are not present.
Larger aquariums will be more suitable for those hobbyists
wishing to maintain a pair of Istigobius, or those
planning on including several tankmates.
Meet the Species
Only two species of Istigobius are
regularly available to hobbyists, and not surprisingly, they
also have the largest distribution in the genus. I'll start
with the most abundant member, Istigobius ornatus,
also called the Ornate goby. This goby is rarely found outside
of shallow mangrove roots, and in fact is rarely spotted at
depths greater than two or three feet. It is best to obtain
a single specimen, as these fish do not relate as pairs in
the wild. Several individuals can, however, be found spread
across a small area; therefore aquariums with an ample sand
bed may maintain a small harem of these fish.
The Decorated goby, Istigobius decoratus,
differs slightly from other members of this genus. It prefers
cleaner waters than do its close cousins. Even so, these fish
are rarely found below more than five feet of depth, although
collections records do show several individuals taken from
as deep as 50 feet. The clean water is probably a direct result
of the substrate they prefer - coarse coralline-encrusted
rubble.
Another Istigobius species that
prefers clear water is I. rigilius, sometimes called
by its thoughtfully creative common name, Rigilius goby. It
is likely that this and the preceeding species are available
in the hobby solely because they make themselves available
in clearer water than do their cousins. Unfortunately for
hobbyists, this is the only species of Istigobius without
sharp sexual color distinctions of the anal or pelvic fins.
This species can, however, be sexed by its genital papillae,
and on occasion males may develop a series of vertical bars
across their abdomen.
Conclusion
In an attempt to find a fish that fits
a niche often overlooked by many in this hobby - mini-reef
and mangrove tanks - I decided to cover the sand-dwelling
species of Istigobius. Their natural instincts and
habitats lend a degree of flexibility that is not afforded
to us by most ornamental marine fish. As such, these fish
place themselves into a small, albeit focused, group of fish
that do a fantastic job of filling a niche that the vast majority
of fish cannot.
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