uncontrolled multiplication within a limited environment in situations of
food competition is liable to produce dwarf fish populations, of little value.
The behavioral patterns which occur after spawning and which charac-
terize substrate-spawners (Tilapia) and mouthbrooders (Sarotherodon) have
been described and discussed by numerous authors (Lowe-McConnell1959;
Perrone and Zaret 1979). Whatever the role of each sex in brood care, which
differs among species, this care provides an efficient protection for eggs and
fry against predators, and contributes greatly to the reproductive efficiency
of these species. However, the physiological mechanisms which control
parental care behaviour are poorly understood.
Another aspect of the reproductive efficiency of tilapias is precocious
sexual maturation which can occur as early as 3 months in some species
(McBay 1961; Arrignon 1969) and depends probably, in addition to genetic
factors, on environmental factors like temperature. (Hyder 1970a; Siddiqui
1979a), food availability, social factors, etc. Precise data based on exper-
imentation are generally lacking.
As soon as sexual maturity is attained, and provided temperature is
suitable, most cichlid females are able to undergo successive breeding cycles,
producing new broods at 4 to 6 week intervals. This usually results in a con-
tinuous production of fry throughout a population, with the exception of
certain environments subject to substantial seasonal variations (Moreau
1979). But the relative asynchrony between the sexual cycles of individual
females can be a problem when mass production of homogenous fry is
required for intensive fish farming.
Thus, for practical reasons dictated by fish farming conditions, it would
often be advantageous either to inhibit or delay sexual maturation, or in
some cases to favor synchronous spawning and breeding for mass production
of fry.
This paper reviews the external and internal factors which seem to be
involved in the control of different stages of the reproductive cycles of
cichlids, to suggest practical means for artificial control. As literature in the
field of cichlid reproductive physiolo& is scattered, references will be made,
when necessary, to the present state of knowledge in other teleosts. For
more detailed information concerning reproductive physiology and endo-
crinology in fish, see recent reviews by Dodd (1975), Fontaine (1976),
Jalabert (1976), Olivereau (1977), Callard et al. (l978), Peter (1978), Billard
et al. (1978) and Breton et al. (1980).
General Characteristics of GametogenesisSexual differentiation of the gonad into a juvenile testis or ovary with a
characteristic morphology occurs very early in Tilapia (Yoshikawa and Oguri
1978) and in Sarotherodon (Nakarnura and Takahashi 1973), around 15 to
30 days after fertilization (at 23 to 25°C). Sexual maturity can be then
completed after a few months.
Gametogenesis in cichlids appears to present the same general features
as in most other teleosts and lower vertebrates, whether in males or in
females (Barr 1968; Hoar 1969). Thus some stages in the following de-