Biology Reference
In-Depth Information
(RF) and egg size. From their data, it is possible to calculate the rate of egg
production (number of eggs per gram fi sh per day) as function of body
weight. Figure 27 shows the established positive correlation between body
weight-BF relation. In the natural but man-made lakes of Cote d'Ivoire,
the fecundity of the Nile tilapia O. niloticus also increases from 149 to
2,797 eggs for fi sh weighing 36 g to 975 g (Duponchelle et al., 2000). In
fact such a positive relation between fecundity and body weight has been
observed even among sea-run and resident strains of S. leucomaenis , who
produce larger and smaller eggs, respectively (Morita and Takashima, 1998).
However, the body weight-RF relationship in T. zilli clearly shows that the
RF holds a negative relation to body weight (Fig. 27). Even more revealing
is the relation between body weight and egg production rate (RFR), which
Fig. 27. Fecundity (F), relative fecundity (RF), relative fecundity rate (RFR) and egg weight
(Ew) as function of body weight of substratum repeat spawner Tilapia zilli (compiled from
Coward and Bromage, 1999)
Search WWH ::




Custom Search