Mother's Milk:
The role of brine shrimp nauplii for the fish of Lake Tanganyika
by Bob Allen
Bob is President of the Great Salt Lake Aquarium Society
Aquarticles
The discovery of brine shrimp eggs was a most fortunate gift for those who would come
along afterwards and undertake raising fish. Most species of baby fish will ravenously
devour brine shrimp nauplii.
For the fish of Lake Tanganyika brine shrimp have an even more special role. Cichlids,
for most of us, are the most interesting of the fish from Lake Tanganyika. It is useful to
compare Tanganyikan cichlids with those from the other two lakes in the African Rift
Valley, Malawi and Victoria. Virtually all of the cichlids from Malawi and Victoria are
mouthbrooders which produce fairly large fry. These fry can eat brine shrimp nauplii
eagerly as do almost all fry. It is possible, however, to raise the cichlids from Malawi
and Victoria with other foods, even such ordinary stuff as flake food which doesn't swim
at all.
Lake Tanganyika is another story. Many of the cichlids from there are cave or shell
spawners and they produce much smaller fry which are harder to nourish. And among the
Tanganyikan mouthbrooders and the non-cichlids there are species that require special
food.
Why is this so? Lake Tanganyika has a peculiar range of food organisms suitable for
fish. There are many types of crustaceans, shrimp and small zooplankton, so plentiful that
most of the carnivorous Tanganyikan cichlid species rarely eat other fish, there is enough
shrimp for everyone.
A very abundant food item in lake Tanganyika is Tropodiaptomus simplex. The
adult size of this copepod is about 1 mm., only a little bigger than newly hatched brine
shrimp 1. Tropodiaptomus is so abundant that some
species of fish rely on it as their principal source of food. An example is the
Tanganyikan sardine, Stolothrissa tanganicae. Research indicates that it would be
possible to harvest 400,000 tons per year of this sardine, an indication of the abundance
of their food source 2.
What does all this mean to aquarium keepers? Every Tanganyikan fish that I know of
produces fry that can eat baby brine shrimp, most likely because their natural food source
is similar in size to brine shrimp nauplii. There are some species that will eat baby
brine shrimp as adults. Here are some examples:
1) Neolamprologus caudopunctatus. This small cichlid species produces quite
small fry, when they first start free swimming and looking for food they appear too small
to be able to eat Artemia nauplii but they wolf 'em down from the very start just
as if they know what they are doing. (The other species of the genus Neolamprologus
also produce fairly small fry that are well matched to Artemia nauplii.)
2) Synodontis petricola. This catfish produces minute eggs, some of the
smallest I have seen. The larval stage fry are tiny and transparent but they grow a
catfish style mouth and by the time they are ready for food…….. they have no
trouble with baby brine shrimp.
3) Cichlids of the genera Cyprichromis and Paracyprichromis. These
fish are mouthbrooders which produce fairly large fry but they inhabit the open water
realm where Tropodiaptomus is abundant. Both fry and adults will eat Artemia
nauplii eagerly and seem to prefer it over any other food.
4) The Tanganyikan killifish, Lampricthys tanganicanus. Another fish with the
same food preference is It is true that adult Lampricthys will eat almost
anything but they never lose their appetite for Artemia nauplii.
A little more information on Tropodiaptomus simplex: This small creature is
described as a calanoid copepod.It resembles Cyclops, is about the same size, but
has longer antennae and doesn't move as fast as Cyclops. Most large freshwater
lakes or reservoirs worldwide contain Daphnia. Now Daphnia, as you know,
are not huge but they are quite a bit bigger than Tropodiaptomus simplex. There
are no Daphnia species in Lake Tanganyika 3. The
plankton of Lake Tanganyika are similar to those in the ocean. I recently had a chance to
tow a plankton net behind my boat in the Sea of Cortez in Mexico. The plankton that I
caught were quite small, mostly copepods very similar to Tropodiaptomus simplex.
My personal perspective on this subject is that I presently work full time breeding
aquarium fish. This is done in 250 glass aquariums, there are some 70 species in my
operation, most of them are cichlid species from Lake Tanganyika. I use brine shrimp as
the principal food for my fish, both newly hatched brine shrimp (Artemia nauplii)
and adult brine shrimp which usually is kept frozen before use. I am located in Utah,
about 75 miles from the Great Salt Lake which makes it convenient to harvest brine shrimp
and eggs. I usually use shrimp and eggs which I harvest myself. At present I am getting
good results with commercially harvested brine shrimp eggs from North American Brine
Shrimp I hatch 6 tablespoons of brine shrimp eggs daily which totals ca. 7,000,000 nauplii
. I am not aware of any suitable food that is actually available that could replace these
baby brine shrimp as a food for my Tanganyikan cichlids.
References
1) Lake Tanganyika and Its Life
Edited by G.W. Coulter
Oxford University Press 1991 p. 240
2) Ibid. p. 150
3) Ibid. p. 239
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