Reproduction of Oreochromis niloticus niloticus

Main Ref: Trewavas, E., 1983
Mode: dioecism
Fertilization: external
Spawning frequency: no obvious seasonal peak
Batch spawner: Ref. Trewavas, E., 1983
Reproductive guild: bearers
External brooders
Description of life cycle and mating behavior: Sexual maturity is reached at 3-6 months depending on temperature, reaching about 30 g. Reproduction occurs only when temperatures are over 20�C. Several yearly spawnings every 30 days. Females incubate eggs inside their mouths (approximately for a week) where larvae hatch and remain until the vitellus is reabsorved.Egg size 1.5 mm, larval length at hatching 4 mm. Spawns in firm sand in water from 0.6 to 2 m deep of lakes. Males set up and defend territory which are visited by the females. Courtship lasts several hours. Eggs are shed in batches in shallow nest and fertilized by male. Each batch of eggs is picked up into oral cavity by female. Females solely involved in broodcare. Female carries up to 200 eggs in her mouth where the larvae hatch and remain until after the yolk-sac is absorbed.

Reproduction of Oreochromis aureus

Main Ref: Trewavas, E., 1983
Mode: dioecism
Fertilization: external
Spawning frequency: one clear seasonal peak per year
Batch spawner: Ref.
Reproductive guild: bearers
External brooders
Description of life cycle and mating behavior: Nesting usually in shallow water weedy areas (Ref. 96). Males establish territory and dig a spawning pit (Ref. 2, 6465, 54601), using mouth and fins (Ref. 2), up to 60cm deep and 4-6m in diameter; a number of territories can often be found clustered together (Ref. 52307). Territories are defended by means of agressive behaviour (Ref. 6465), including lateral display, lateral biting and mouth-to-mouth combat (Ref. 2). Reproduction is stimulated by long photoperiods and inhibited by short daylengths (Ref. 54365). Reproduction requires a minimum temperature of about 20�C (Ref. 2). Males visit schools of females and attempt to attract a female spawning partner (Ref. 2, 52307). Courting behaviour in the nest consists of lateral display by both sexes with nipping and tail-flapping (Ref. 2). Eggs are deposited in single clutches, from several dozen to 100 eggs (Ref. 52307), and are taken into the females mouth as soon as they are fertilized (Ref. 2, 6465, 52307), with a peak spawning frequency around the 9-11th hour of light (Ref. 31140, 54365). One female may hold up to 2000 eggs in her mouth (Ref. 2). The female swims away to deeper water with the brood after spawning is complete (Ref. 2, 52307), while the male renews spawning activities with another female. Hatching occurs about 3 days after oviposition (Ref. 2). Incubation time varies with temperature, 13-14 days at 25-27�C (Ref. 2, 52307) or 8-10 days at 29�C (Ref. 144), and juveniles leave the mother's mouth when they are about 1.1cm in length (Ref. 54601). The young school near parent's head for a few days, reentering the mouth at any sign of danger or at a gesture of the female; parent-offspring relationship ceases after 5 days (Ref. 2).


Reproduction is best at water tem-
peratures higher than 80o F and does
not occur below 68o F. In subtropical
regions with a cool season, the num-
ber of fry produced will decrease
when daily water temperature aver-
ages less than 75o F. After 16- to 20-
day spawning cycles with 1/2-pound
Nile tilapia, fry recovery was about
600 fry per female brooder at a water
temperature of 82o F, but only 250
fry per female at 75o F.