Otolith shape analyses were conducted on three different
species of Mullidae (Mullus barbatus barbatus, M.
b. ponticus and M. surmuletus). The otolith
shape was described by 19 harmonics from elliptic Fourier descriptors. In
a first step, their comparison through canonical discriminant analyses
(CDA) was run for all fish with right otoliths, left otoliths and
both otoliths pooled. The latter possibility had a higher discriminating
power and allowed much more visually explicit results. This implied
that the two otoliths were not similar as often claimed, and had
each their specific information. In a second step, the CDA demonstrated
strong spatial discrimination of local populations from various
areas within the Mediterranean basin, i.e. NW Mediterranean, Aegean
Sea and Black Sea, and between sites within each area. The percentage
of well classified individuals of M. barbatus in
predefined groups varied between 78 to 100% depending on sites,
and even reached 100% for each site for M. surmuletus.
These spatial patterns were most likely linked to differences in
environmental conditions between areas and sites, such as effects
of strong river runoffs and differences in depths and/or habitat
types. In a third step, CDA also evidenced ontogenetic discriminations
of mullet populations that could be linked (i) to influence of diet
of fish of various sizes and (ii) to changes in physiological conditions
according to the stage of development of the fish.