The Biology and Culture of Tilapias

Reproductive Physiology in Cichlid Fishes, with Particular

Reference to Tilapia and Sarotherodon

B. JALABERT AND Y. ZOHAR

Institut National de la Recherche Agronomique

Labomtoire de Physiologic des Poissons

Campus de Beaulieu 35042

Rennes-Cedex, France

JALABERT. B. AND Y. ZOHAR. 1982. Reproductive physiology in cichlid

fishes, with particular reference to Tilapia and Sarotherodon, p. 129-140.

In R.S.V. Pullin and R.H. Lowe-McConnell (eds.) The biology and culture

of tilapias. ICJARM Conference Proceedings 7, 432 p. International

Center for Living Aquatic Resources Management, Manila, Philippines.

Works dealing with the external and internal factors which regulate repro-

ductive efficiency in Tilapia and Sarotherodon are reviewed. Gametogenesis,

although presenting the same general features as in most other teleosts is

characterized by a low production of gametes related to the high efficiency

of parental care: in, substrate-spawners (Tilapia) the number of small sticky

eggs is approximately related to the cube of body length, whereas in mouth-

brooders (Sarotherodon), eggs are bigger, not sticky, and their number is

related to the square of body length.

Both groups seem to exhibit a capacity for precocious sexual maturation,

the reason for which is not clear. There is also unlimited successive breeding

through whole populations in equatorial areas and an increased tendency for

seasonal breeding with increasing latitude, with maximum activity during

maximum temperature and light intensity. When temperatures exhibit seasonal

variations of large magnitude, low temperature (15 to 22'~) inhibits repro-

duction during part of the year. Social factors have been shown to enhance

spawning frequency and might also influence sexual precocity through mech-

anisms which need further work.

Despite some attempts, specific tilapia gonadotropins have not yet been

satisfactorily purified; the ubiquity of specific prolactins in controlling both

osmoregulation and parental care behavior must be confirmed, and their pos-

sible inhibitory action on gametogenesis need investigation. The precise

nature of steroids which mediate the pituitary action during different phases

of the reproductive cycle also needs more research.

Introduction

The efficiency of reproduction in Tilapia and Sarotherodon has paradox-
ical consequences: on one hand, this aptitude which allows easy and rapid
propagation in various tropical and subtropical environments, partially
explains the economic interest in these species for fish culture; on the other
hand this reproductive efficiency can be a source of problems because

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