Reproduction
is one of the basic drives of all life. Having fish reproduce in
the aquarium is one of the basic drives of many aquarists. In keeping
members of the catfish genus Synodontis a great many aquarists
(and probably even more Synodontis) have been hindered
in pursuit of this natural drive.
In performing literature searches and having personal communications
with aquarists it quickly becomes evident that very little aquarium
spawning has taken place with Synodontis have gone unreported,
but as a whole this event seems to be at best quite uncommon.
The few literature references to successful aquarium spawnings of
Synodontis involve two species. The first of these is S.
nigriventris and a few articles on spawning this species have
been published. The second, with which the largest amount of success
has been reported, is the Lake Tanganyikan species S. multipunctatus.
But before we look at these two species it would be fitting to take
a general look at a little of what is known about the reproduction
of the genus in it’s natural habitat.
All species of Synodontis are known to be egg layers. The
eggs appear to be scattered and no parental care of the eggs has
been reported in any species. To give a general picture of reproduction
in the Synodontis it might be best to take a look at most
studied member of the genus.
One of the first considerations to take into account, if attempting
to spawn Synodontis, is sexual maturity. It appears from
the literature that different species of Synodontis attain
sexual maturity at varying rates. Some species appear to show total
sexual maturity in all individual by the time they reach sexual
maturity might even come earlier. In S. schall, which is
a large species, the time is somewhat extended. A study of this
species in the Sudan Nile showed the following maturity rates: During
their first year of life all individual of S. schall are
sexually immature. By the end of the second year all females were
still immature, but approximately 32% of the males had achieved
maturity. At the end of the third year all males are sexually mature.
At this same time approximately 60% of the females have achieved
maturity. By the end of their fourth year all individuals examined
are sexually mature. Size correlation showed that the youngest males
to reach maturity (by the end of their second year) were around
16 cm in total length. The youngest mature females (end of their
third year) were around 18.5 cm in total length.
The fecundity (egg production) of the females of S. schall
can generally be taken as a factor of size. As the females grow,
larger amounts of eggs are produces. Those females in the size range
of 25-30 cm show egg numbers from 4,500 to almost 12,000.
Large females in the 55-56 cm class have eggs which number up to
almost 150,000! Ripe females of smaller species show proportionally
smaller amounts of eggs. For example, an 8 cm ripe female S.
migriventris will produce in the vicinity of 350 to 500 eggs.
The females of S. schall tend to be larger than males at
the same age. This is apparently not true with all Synodontis
species. In some species the males appear to make up the greatest
percentage of large individuals. Another interesting figure is the
ratio of males to females in S. schall. In the area studied
females were more common and outnumbered males on an average percentage
of 57 to 43. In other species it appears that such as those on S.
schall are generally not available on other species, but this
information does five the aquarist something to think about and
to take into consideration when purchasing stock.
The spawning of S. schall coincides with the heavy rains
and flood season. The spawning is extended over a period of two
to three months, but many exact details are lacking. Studies in
West Africa show similar results with some species, but in these
studies show an apparent extended breeding period for some of the
Synodontis species. Ripe and ripening S. multipunctatus
have been observed over a period of at least 5 months. Some other
Lake Tanganyikan species also appear to show similar extended breeding
periods.
In looking at why very little captive breeding has taken place with
members of this genus one consideration stands out strongly. Most
Synodontis species are generally maintained in very low
group density numbers. Many aquarists will keep an interesting Synodontis
or two in their tanks for their attractiveness or only to serve
a scavenging function. Other aquarists may have a collection of
Synodontis that is large, but it may contain only one or
two individuals of each species. It appears that relatively few
attempts to purposely spawn Synodontis catfish, by the
accumulation of large groups of one species, have been made. This,
at least to some degree, appears to be one of the main reasons for
lack of breeding success. With some species of Synodontis,
such as the earlier mentioned S. schall, size may be a
problem in this somewhat neglected approach. But there are a number
of smaller Synodontis species, which would be quite satisfactory
for this type of breeding approach.
Synodontis nigriventris, which has been spawned on occasion,
is an ideal choice to start with. It’s small adult size and
general availability offers good potential for someone desiring
to spawn Synodontis. Another similar species with which
I have worked is S. contractus. To the best of my knowledge
this species has not yet been spawned in captivity. I think that
these two species offer some of the best potential for the aquarist
wishing to spawn Synodontis. Their small adult size together
with ease of maintenance makes them excellent candidates. Of great
interest is the fact that S. multipunctatus now easily
rates as the most commonly spawned of the Synodontis catfish
that are available to the aquarist. There are a number of spawning
reports, both verbal and written, from the United States. Success
has also been reported from England. Not only are some aquarists
being successful with spawning this fish, but a pattern of very
interesting form of reproductive behavior has become evident. There
is rapidly increasing evidence that S. multipunctatus is,
at least in part, a cuckoo spawner. This term is used in reference
to the bird of the same name who lays its eggs in the nests of other
species of birds. This is evidenced by the fact that the great majority
of the aquarium spawnings of this fish have produced young Synodontis
by way of oral incubation of the Synodontis eggs and fry
by maternal mouthbrooding rift lake cichlids. Even in cases where
this method has not been definitely observed evidence points towards
it.
What has been observed with S. multipunctatus is that they
appear to coincide their spawning act with that of mouthbrooding
cichlids. Most of the reported aquarium spawnings have taken place
with cichlids of the Mbuna complex from Lake Malawi, although spawnings
of Lake Tanganyikan mouthbrooders have also been reported. The Synodontis
generally appear to spawn in a gang fashion, although there is a
report of a single pair spawning. They intervened into the spawning
act of the cichlids, constantly moving in and out of the spawning
arena. As they do this they lay and fertilize their own eggs while
eating at least some of the cichlid eggs. The female cichlids who
are not too fussy about what they pick up will take some of the
Synodontis eggs into their mouth where they are incubated.
Observations on the finding of Synodontis multipunctatus
fry in the mouths of female mouthbrooding cichlids have been reported
in the wild by Pierre Brichard. Aquarium observations back these
up and offer more information about the mechanisms of this interesting
situation. I have written an in-depth article on this topic and
it was published in June 1984 (FAMA).
A brief word should be added on the sexing of Synodontis.
As with many catfish, a well conditioned female Synodontis will
tend to be thicker and more rounded than a male, especially when
viewed from above. Another sexing method which works well on some
species, especially S. multipunctatus, is examining for
the genital papilla. Many male Synodontis show a well developed
genital papilla anterior to the anal fin. This structure, when present,
is usually well developed, pointed and usually tipped somewhat to
the rear. It is similar to that seen on many male cichlids. Females
of many species usually show only a slight rounded protrusion in
this area.
I am very interested in hearing from anyone who has had experiences
with the spawning, or near spawning, of any Synodontis
catfish. I plan to write some articles on this topic which will
incorporate what is available from the scientific literature together
with aquarium experiences.
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