The Biology and Culture of Tilapias

The Use of Predators to Control Recruitment

Effective predators on young tilapias include many piscivorous fishes,

such as Elops hawaiiensis, Megalops cyprinoides, Micropterus salmoides,

Ophicephalus striatus, Cichla ocellaris, Lates niloticus, Clarias lazera, Hemi-

chromis fasciatus and Cichlasoma manguense. In most cases, predator-prey

stocking ratios have been determined (Table 3). Where effective predators

are used, high yields of harvestable-size tilapia are reported (Swingle 1960;

Lovshin 1975; Dunseth and Bayne 1978). Total production of tilapias,

however, is significantly reduced as the recruits are eaten (Maar et al. 1966;

Lovshin 1975). Moreover, difficulty in obtaining stocks of the desirable

predator has limited application of this population control method (Balarin

and Hatton 1979).

Table 3. Fish predators used for the effective control of recruitment of tilapias.

Stocking Ratio

Predator (Predator:Prey) References

Sarotherodon mossambicus Elops hawaiiensis 1:10 and 1:20 Fortes (1979)
Megalops cyprinoides 1:10 Fortes (1979)
Micropterus salmoides Swingle (1960)

S. niloticus

S. shiranus

T. rendalli

S. aureus

Not specified

Cichla ocellaris 1:15 Lovshin (1975)

Clarias lazera 1:lO Bard et al. (1976)

Lutes niloticus 1:20-1:84 Planquette (1974)

Clarias sp. 1:lO-1:20 Meecham (1 97 5)

Cichlasoma managuense 1:4-1:8 Dunseth and Bayne (1 97 8)

Hemichromis fasciatus 1:48 Bardach et al. (1972)

The Use of Stock Manipulation Methods

Reproduction of tilapias appears to be inhibited by high stocking densities

(Allison et al. 1979). Swingle (1960) reported that increasing stocking rates

of fingerlings decreased rates of reproduction. He suggested the presence of a

repressive factor affecting reproduction. In S. mossambicus, a substance

believed to be present in the mucus has been found to cause an autoallergic

response at high densities (Henderson-Arzapalo et al. 1980).

Culture of tilapia in cages at high densities has limited reproduction

(Pagan 1975; Coche 1979; Guerrero 1980a). Pagan (1969) suggested that

failure of tilapia to reproduce in cages is due to an alteration of reproductive

behavior that prevents fertilization or that the eggs pass through the cage.

The Use of High Stocking Densities

The continuous hamesting of tilapias from ponds to reduce their popu-

lation has been proposed by Hickling (1960). A similar method suggested