The Biology and Culture of Tilapias

A Study of the Problems of the Mass Production of

Hybrid Tilapia Fry

Chief Extension Worker in Fish Culture

Ministry of Agriculture

Kibbutz Ein Hamifrats D.N. Ashrat. 25210.

Israel

MIRES. D. 1982. A study of the problems of the mass production of hybrid

tilapia fry, p. 317-329. In R.S.V. Pullin and R.H. Lowe-McConnell (eds.)

The biology and culture of tilapias. ICLARM Conference Proceedings 7,

432 p. International Center for Living Aquatic Resources Management,

Manila, Philippines.

Comparative data on the spawning capacity and spawning frequency

of female tilapias demonstrate successful spawning in intraspecific and

interspecific crosses. There is, however, great variability in the fecundity of

individual females. Spawning incompatibility exists between tilapia species,

the degree of incompatibility varying with the species combination. The

influence of the sex ratio of the parental stock and other factors which

reduce male aggressiveness are discussed. There are three main influences on

the production of tilapia fry: genetic, behavioral and environmental.

Introduction

For the last ten years or so, fish farmers in various parts of the world have
searched for efficient ways of rearing all-male broods of tilapias (Hickling
1960; Fishelson 1962; Pruginin 1967; Chen 1969; Mires 1973; Lovshin and
Da Silva 1975; Mires 1977), yet the problem of mass-rearing these fish
remains. After many years of hard work, some of the Israeli fish hatcheries
have succeeded in making a major breakthrough in this field (Mires 1977)
but this young industry still has to overcome the problem of the low fry
production from interspecific spawns. This paper discusses various aspects of
this problem.

Possible Reasons for the Low Production

of Tilapia Fry in Spawning Ponds

There are quite a few possible reasons for the low production of tilapia fry

in commercial spawning ponds. The main ones are probably: too low a

density of broodstock; incompatibility in interspecific crosses; inappropriate

broodstock sex ratios; inadequate spawning techniques and high fry mortal-

ity. More information is needed on each of these possibilities.