BIOLOGIE ET DYNAMIQUE DU SAR COMMUN DIPLODUS SARGUS SARGUS (LINNAEUS, 1758) DES CÔTES DE L’EST ALGÉRIEN
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Date
2010
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Abstract
This study, which is devoted to the biology of coastal Sparidé of halieutic and
economic interest: Diplodus sargus sargus (L 1758), made it possible to look further into
scientific knowledge on the biology and the ecology of this subspecies colonizing the coasts
of the Algerian East. The first part is devoted to the main environmental characteristics
(geomorphology, hydrobiology and physicochemical parameters) of the study environment
located between Chetaibi and El Kala, and also the various populations and its current
exploitation methods. The second part is devoted to sar common D. sargus sargus and the
main descriptors of its biology (morphology, age and growth, reproduction and food).
The morphology of the sar Diplodus sargus sargus (L, 1758) is characterized on the
basis of sixteen morphometric criterion and eight meristic characters. A very significant
correlation is highlighted for all metric parameters compared with the overall length. The
growth allometry is raising in 73.33% of the cases, whereas 20% are isometric. The
discontinuity of the growth concerns only the eye’s diameter. The numerical parameters
indicate values close to those reported by the literature. Characters of sexual dimorphism are
highlighted between males and females.
Age and growth are estimated using the scalimetric method. Only one opaque zone
separates per annum and is registered at the end of spring (June). When the first scales appear,
the size corresponds roughly to 26,9 mm. The maximum theoretical size of this species is
285,5 mm for males, 297,3 mm for females and 299,3 mm for the total population. These
sizes correspond to the maxima theoretical weights of 465,5 G, 522,6 G and 558,0 G
respectively. The index of importance of growth ( shows a relatively slow growth of the
local population. The relative growth is isometric (b = 2.987; r = 0.980), indicating a slow
growth. Longevity is approximately 10 years.
Diplodus sargus sargus is a hermaphrodite protandric. Its reproduction is seasonal and
happens only once a year, between January and May and the abrasion takes place between
March and April. The hepato-somatic ratio, the adiposity and the plumpness show variations
related to the reproductive cycle. The first sexual maturity is acquired starting from 20 cm for
females and males, corresponding to a 4 years age. The common sar is classified among fatty
fish. The sex-ratio is in favour of males which prevail in the smallest intervals of size and the
females in the biggest intervals. The type of the reproduction strategy adopted by this species
is "
lay not split"
This coastal predator has opportunist food behaviour. It is nourished at seasonal
intervals on benthic preys, with a pronounced preference for the malacologic preys. While
growing, it widens its food spectrum but it does not completely abandon the preys which it
used to consume as youthful. The statistical comparison, by using the Spearman’s row
coefficient ( ), reveals the homogeneity of its food mode all along the year, whatever the sex
or the state of sexual maturity