· Female O. nilotica  ND-2 Tilapia family line
· Male O. aurea  ND-1 Tilapia family line
 
The ND-2 Tilapia O. nilotica line, and the ND-1 Tilapia O. aurea line are a result of continuous selection and propagation within the specific families, originally obtained from nature many years ago. The original specimen are regarded as ecotypes.

The economic traits of the ND-21 Tilapia hybrids are:

All-Male population without hormonal treatment for sex reversal The ND-21 Tilapia hybrid are all males. The proportion of Tilapia males in any spawning cycle is ~ 98%, without hormonal treatment, and provided APT operational instructions are adhered to. Actually, the progeny is 100% genetic males. The lower percent reflects penetration of foreign fish, assuming stern protection methods are used.

Docile behavior ND 21 hybrids are more docile than the parental O. nilotica. This becomes evident during sampling, sorting, selective harvesting and final harvesting. Fish are calm, not jumping and cooperate in routine farm activities. This results in reduced losses of fish throughout the production cycle.

Fast growth The growth rate of All Male population of ND-21 Tilapia hybrids is comparable to pure line O. nilotica. To be specific, the ND-21 will grow slightly better in the lower temperature range (22-25 °C) and slightly lower in the high temperature range (29-31 °C).

High fecundity Parental stocks yield 300 fry per female per month, at initial phase of maturity, reaching ~500 fry per female per month at full maturity. For production of 1000 ton per year, it is recommended to use a flock of 1000 ND-2 females and 250 ND-1 males.

Sensitivity to Streptococcus infection The ND 21 is as sensitive as the pure line O nilotica.

*Note: the cross between REGULAR TYPES of O. nilotica and O. aurea will not result in meaningful increase in the proportion of males in the progeny. Crossing of other types of either O. nilotica or O. aurea with either ND-2 or ND-1 will result in the loss of the special traits of latter.