Materials and methods
2.1. Historical background and fish production
All experimental procedures were conducted at
The World Fish Regional Centre Experimental Station
at Abbassa. Grandparents of the experimental fish
were produced in spring of 2000 from all possible
diallel crosses between four local Egyptian strains
(Rezk et al., 2002, 2004). 108 brooders from the
grandparental stock were randomly mated in 2002 to
produce the parental fish. Grand-sires were each
mated to either one or two females. The experimental
fish were produced in a full-sib/half-sib mating design
in which each sire was mated to two dams and each
dam mated to only one sire. A total of 80 full-sib
families were produced from 43 sires and 80 dams.
These consisted of 37 paternal half-sib families, six
sires having been mated to one dam each. The pedigree
of all the individuals was known and was used to
construct a relationship matrix. The number of individuals
used in the pedigree and the fish production
scheme is shown in Fig.