Inter- and intraspecific crossbreeding
experiments were conducted to evaluate the aquaculture potential
of hybrids in the genus Dicentrarchus, focusing
on fertilisation and hatching success. The experimental design
consisted of 24 controlled crosses in which individual and pooled
fertilisations were made between wild D. labrax individuals
(8 dams and 5 sires originating from West Mediterranean and Atlantic
populations) and wild D. punctatus (6 sires). Three
experiments were successively performed: (1) dams from the Mediterranean
population, individually considered to have good egg quality, (2)
dams from Mediterranean population, individually considered to have
poor egg quality and (3) crossbreeding using pooled eggs from the
Atlantic population. In each case, batches of these eggs were fertilized
by sperm from males of the two species. Sperm cell quality (concentration
and motility) was verified before experimentation in all cases and
equal numbers of sperm cells from each male were used to individually
(without inter-sire competition) fertilise egg batches. Through
the repeated artificial crosses between female common sea bass Dicentrarchus
labrax (Linnaeus 1758) and male spotted sea bass D.
punctatus (Block 1792), these experiments showed that no
post-zygotic reproductive barriers exist to interspecific hybridisation
between these two species when using D. labrax as
dams and D. punctatus as sires. Phenotypically,
the F1 hybrids were easily recognisable: they inherited the characteristic
black spots of D. punctatus. Furthermore, embryo
survival was significantly higher in interspecific crosses compared
with intraspecific controls, showing increased fitness for this trait
(increased performance at early life stage). Then, the experimental
breeding design validates the observation that West Mediterranean
and Atlantic common sea bass populations are different. Indeed,
the inter-population crosses (between West Mediterranean dams and
Atlantic sires) also revealed increased fitness at early life stages
in comparison with the progeny of intra-Atlantic population crosses.
However, these individuals were still smaller than their interspecific
counterparts. The ability to produce viable F1 hybrids will have
significant implications for the practical improvement of sea bass
aquaculture.