Nile tilapia growth and reproduction a dynamic energy budget approach

Nile tilapia is a widely introduced fish and quantitative knowledge about its life history is essential for ensuring high fish yield and preventing deleterious effects on water quality and native fish communities. Here, we extracted several attributes of Nile tilapia populations from tropical lakes and reservoirs reported in literature to model the dynamics of individuals based on resource level using a dynamic energy budget model (DEB). Our findings show that asymptotic size, size-at-maturity, and maximum fecundity are positively related to the lake area, likely due to competition for food or space. Tilapia asymptotic length varied from 11.6 to 55 cm and size-at-maturity from 9 to 27 cm. The model provided good estimates of growth and fecundity, suggesting high investment in growth and a comparatively low investment in reproduction. The success of tilapia appears to result from parental care and low juvenile mortality. The DEB model assumes a fixed allocation of energy for growth and reproduction, and at low food availability first the growth ceases, and the reproduction remains until the amount of food is low enough to cover only the maintenance costs. This explains well the variation in tilapia size. The model demonstrates that tilapias survive and reproduce even with 70% reduction in food, highlighting the risks of introducing tilapia to increase fishing earnings. Such introductions can lead to overpopulations of small-adult tilapias, especially in shallow and productive lakes, where abundant food for adults boosts reproduction but increases competition among juveniles, reducing their growth rates with minimal impact on overall reproduction.