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Coral reef of the Red Sea is an extraordinary,
diverse ecosystem, shining with all colors of the rainbow.
Thousands of divers come here every year,
attracted by colorful fish and corals.
I carry out my research here for two years now,
and I'm interested in fish
which are often overlooked by the divers,
because they are small and inconspicuous.
PRIVATE LIFE OF BRYANINOPS NATANS A small gobiid fish from the Red Sea
We are in Dahab, Egypt,
on the outer side of the coral reef called “The Islands”.
Near the sandy bottom, at a depth of about 16 meters,
grow numerous bushes of the Acropora corals.
This is the habitat of an unusual species of fish,
belonging to the Gobiidae family.
Bryaninops natans
Body length of adult fish does not exceed 4 cm,
so it's easy to overlook them on the reef.
Their coloration is quite unusual: a transparent body,
yellow internal organs and big, pinkish-violet eyes.
Natans is a very specialised species.
It inhabits only few particular species of Acropora corals.
The name “natans” in Latin means “floating”.
The fish usually hover above the coral,
catching plankton carried with water.
This hovering is unique among gobiids,
because most members of this family
spend their lives sitting on the substrate.
The aim of my research is to determine
if Bryaninops natans are suitable for keeping in aquaria,
and what conditions do they need
to reproduce in captivity.
Last year I described in detail the habitat of the gobies.
This year I began preliminary monitoring of their behavior.
For two weeks, every morning
I set up the recording equipment
in front of the Acropora inhabited by gobies.
A small tripod with some weights attached,
and a small camera fitted with an additional power supply.
Original battery of the camera lasts for one hour of recording.
For my purposes it was far too little.
The underwater housing of the camera had to be modified,
so that external power source can be connected.
12V gel battery with AC car adapter,
locked in a piece of a PVC pipe
perfectly fulfilled their task.
With this additional power supply
the camera could record constantly
for more than 12 hours.
Dozens of tourists dive every day on the Islands reef.
I used a piece of strong chain, and two padlocks
to prevent any non-planned changes
in the ownership of my equipment.
Every day I repeated the same procedure.
In the morning I set up the equipment,
and in the afternoon I dived again,
to stop the recording and remove the equipment.
Just some minor adjustments of the camera position,
and I can start another day of recording.
Here is a typical view from the monitoring camera.
In total, I managed to record about 90 hours of video.
For most of the time gobies hover above Acropora,
and feed on minute plankton carried by water current.
However, there are more dramatic moments in their lives.
This is probably the worst danger – attack of predators.
The dark fish with whiskers on its chin
is a goatfish Parupeneus cyclostomus.
It is accompanied by 2 wrasses Gomphosus caeruleus.
Their elongated snout is perfect for capturing prey
among the branches of the Acropora corals.
These two species often hunt together,
terrorizing small inhabitants of the reef.
Please note the reaction of the gobies.
Panic-stricken, they hid in the Acropora,
so there is not a single trace of them left.
Another case.
Again, contact with the larger fish, but this time
it is one of the damselfish Pomacentridae.
There is a difference in the behavior of the gobies.
They flee, but do not hide between the branches of Acropora.
Apparently they know that the intruder
doesn't feed on small fish.
And finally – swapping of the roles.
Now the goby will be an aggressor.
A pair of butterflyfish Chaetodon paucifasciatus enters the stage.
One of them is too inquisitive, it swims too close...
...and gets a slap from the goby!
Let's look at this scene in slow motion.
The goby sticking close to the left side of the Acropora
behaves as if guarding something,
and that is why it drives away the butterflyfish.
Apparently the gobies can very well recognize
various species of reef inhabitants,
and change their behaviour accordingly.
After watching this scene I realised
that I saw more of those single gobies across the reef,
each guarding its own branch of Acropora.
Why are they doing it?
I started to look closer at such natans-guarded branches.
With the unaided eye, however, not much could be seen.
After applying macrophotography I discovered eggs,
laid on such single Acropora branches.
Those eggs are probably laid by the gobies.
I was lucky to record the moment of hatching:
one little fish escapes quickly into the water.
Let's see this moment again, in slow motion.
For now, I'm not sure if the eggs indeed belong to the gobies.
Perhaps it is some other species
which lays its eggs on Acropora branches,
and gobies treat such places only as a snack bar.
To find the answer to that question
I will have to catch the gobies at the time of spawning.
I'm sure that there are many interesting facts
still to be discovered about Bryaninops natans.
So next year I will surely return to Dahab
to continue the observations
of those small gobies from the Red Sea.
Research, filming and editing
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