Cypholtilapia frontosa is one of the most commonly occurring
cichlids in Lake Tanganyika. Were it not for their existence in
very deep water, this type of fish would be just as simple
to catch and export as, for example, Tropheus moori. Catching
frontosa at great depths comes with many problems which
is difficult, time-consuming and expensive. The biggest problem
is decompressing the fish. Most fish have a closed swim bladder
that controls the specific gravity of the fish which allows it
to remain at certain depths without using up energy. The pressure
in the swim bladder is regulated by a gas gland. This gland ensures
that the pressure remains stable when the fish swims up or down.
If the difference in depth increases to several meters, the gas
gland requires relatively more time to do its job. The decompression
time between catching and bringing fish to the surface differs
among species. For example, shell dwelling cichlids
can be brought to the surface within an hour from a depth of 10
meters without a problem. The most difficult species of fish is
Neolamprologus furcifer; under stress, it cannot tolerate
a single meter of difference in pressure without suffering permanent
damage to the swimbladder. After being caught at depths of 15
to 20 meters, frontosas need two to three days to be able
to reach the surface without consequence. By remarkable coincidence
the most beautiful and thus most desired color variant of C.
frontosa, the Blue Zaire, actually lives deeper than the other
sorts at 40 meters depth. For this reason it takes 4 to 5 days
to bring a Blue Zaire to the surface.
My explanation for the fact that these fish live at such great
depths is the absence of human settlements in this region. This
became obvious to me in a whole other part of Lake Tanganyika,
the Kavalla islands. In this location frontosas occur at
very shallow depths. Frontosas are particularly intelligent
fish and adapt 
very quickly according to the local circumstances
and availability of food. Around the Kavalla islands there is
a high frequency of fishing by the locals for kapenta, a sort
of anchovy. The boats and nets are cleaned on these islands which
causes a great deal of fish waste to end up in the water. The
Kavalla frontosa lies there in wait of his daily meal,
and has thus come to live at a much more shallow depth. The Zaire
frontosas are not as lucky, and must really hunt for their
food. They are specialized in hunting in groups and at greater
depths. Frontosas have a special ability to perform better
than other fish at depths where oxygen is scarcer, giving them
an advantage over their prey. Through organized hunting practices,
they are able to rapidly exhaust and overcome their prey. The
Zaire frontosa lives thus, the most naturally and also
possesses the best predatorial characteristics. This is also easy
to observe in the aquarium. They are harder to keep together with
smaller fish, and much more difficult to get to breed. This is
all a result of their being less domesticated than, for example,
the Kavalla frontosa.
The high price of the Zaire blue is determined by a series of
factors. First and foremost is the fact that a great distance
must be covered to reach the closest airport. The fish must be
caught twice as deep 
and are much wilder and thus more vulnerable
to stress. Moreover the geographic region in which they occur
is politically very unstable. Catching and thus diving to depths
of 40 meters carries with it much greater risks for the divers
and the bottom time is much shorter. For this reason, twice as
many people are involved in this effort. When you add all these
factors up, it surprises me every time when wild-caught Zaire
blue frontosas are available for sale. At one point I calculated
what it would cost if a fish such as this were to be caught in
Europe under these conditions, including personnel costs, insurance,
fuel, and costs of the risk involved, and it worked out to NLG
1700 to 2000 (approx. US $740 to $865 at the current exchange
rate) per fish!
Frontosas are caught in the following manner: A team of
experienced divers goes to the assigned catching location, and
the boat goes to the right spot with the assistance of a depth
gauge. Then a bag of fish waste (chum) is thrown overboard to
attract 
the frontosas. About three hours
later, the first dive team is allowed to descend. They then place
a 20 x 3 meter net weighed down with lead to the place where they
observed the first frontosas. A large cage measuring 1x1x1
meter is placed in this area. The frontosas are then chased
into the net and are then caught one by one with a hand net and
brought to the cage. The greater the depth at which they must
be caught, the shorter the bottom time, and the longer the decompression
time for the diver. After several teams have caught fish, the
cage is moved upwards to a shallower depth. At this point the
fish are closely observed. When one of the fish begins to float,
in other words, to continuously swim in a downwards direction
in order to maintain a constant depth, then it is determined that
maximum ascension has been reached for the day.
