Chebel, F. (2018). Ecology, biology, morphometry and exploitation of the gilthead sea bream
Sparus aurata Linné, 1758 in the region of Skikda. PhD sciences thesis-ENSSMAL, Algeria.
Keywords: Ecology, biology, morphometry, exploitation, Sparus aurata, Skikda.
Abstract
The present work aims to contribute to a better knowledge of the ecology, biology,
morphometry and exploitation of the gilthead sea bream Sparus aurata Linné, 1758 in the
region of Skikda.
The biometric analysis of the gilthead sea bream, of the Skikda coasts, compared with that of
the same species of the Gulf of Annaba and the Algiers Bay, indicates the existence of very
highly significant differences between the three sites, as well as sexual dimorphism for a set
of 28 variables measured. A principal component analysis (PCA) clearly separated the three
populations of S. aurata from the three regions studied.
The structure of the community associated with the gilthead sea bream Sparus aurata
Linnaeus, 1758 of the Algerian east coasts is studied on the basis of data from the two
oceanographic campaigns "Thalassa 1982" and "ALDEM 2012" carried out in Algeria.
Determination of specific richness, specific diversity, equitability and use of abundance
distribution models revealed a young (immature) community with one or more species that
tend to dominate in number and weight. The ACP shows that in 1982, Mullus barbatus was
the most associated species with S. aurata. In 2012, Mullus barbatus remains the most
associated species with a significant presence of Trachurus trachurus and Pagellus acarne.
836 specimens of S. aurata of different size and weight ranges of the target species, harvested
from the commercial fishery from the Skikda area, were subjected to biological works on diet,
reproduction and growth to lead to the study of the exploitation of the species.
The inventory of prey ingested shows a significant diversification with 32 types of prey
distributed over different zoological groups. Decapods are the main preferential diet of S.
aurata, followed by Bivalves, Gastropods and Actinopterygii fishes. This food composition
seems to be different depending on the season, the sex and the size range of the individuals.
The reproduction of S. aurata was studied by considering: the reproductive cycle, the sex
ratio, the weight indices and the determination of the size at the first maturity. The numerical
proportion of males (68%) differs significantly from that of females (32%) (ε> 1.96, α = 5%).
The gonadosomatic (GSI) and hepatosomatic (HSI) indices of females and males indicate a
single reproduction period. This Spawning period ranges from December to January. The size
at first sexual maturity (Lm50) is 18.3 cm for males and 19.6 cm for females. In Algeria, the
present legislation stipulates a legal minimum catch size of 20 cm (Executive Decree 200486). This regulation is therefore appropriate for the gilthead sea bream.
The growth parameters (of the Von Bertalanffy model) of S. aurata are determined by
analysis of size structures. For all individuals, the linear growth model is:
(
)
The assessment of the current status of the mixed stock was performed using the multispecies
analytical approach of the Thompson and Bell model (1934). The latter showed an optimal
operating status of this mixed fishery in the study area. The model used therefore suggests not
to increase the fishing effort.
Sparus aurata Linné, 1758 in the region of Skikda. PhD sciences thesis-ENSSMAL, Algeria.
Keywords: Ecology, biology, morphometry, exploitation, Sparus aurata, Skikda.
Abstract
The present work aims to contribute to a better knowledge of the ecology, biology,
morphometry and exploitation of the gilthead sea bream Sparus aurata Linné, 1758 in the
region of Skikda.
The biometric analysis of the gilthead sea bream, of the Skikda coasts, compared with that of
the same species of the Gulf of Annaba and the Algiers Bay, indicates the existence of very
highly significant differences between the three sites, as well as sexual dimorphism for a set
of 28 variables measured. A principal component analysis (PCA) clearly separated the three
populations of S. aurata from the three regions studied.
The structure of the community associated with the gilthead sea bream Sparus aurata
Linnaeus, 1758 of the Algerian east coasts is studied on the basis of data from the two
oceanographic campaigns "Thalassa 1982" and "ALDEM 2012" carried out in Algeria.
Determination of specific richness, specific diversity, equitability and use of abundance
distribution models revealed a young (immature) community with one or more species that
tend to dominate in number and weight. The ACP shows that in 1982, Mullus barbatus was
the most associated species with S. aurata. In 2012, Mullus barbatus remains the most
associated species with a significant presence of Trachurus trachurus and Pagellus acarne.
836 specimens of S. aurata of different size and weight ranges of the target species, harvested
from the commercial fishery from the Skikda area, were subjected to biological works on diet,
reproduction and growth to lead to the study of the exploitation of the species.
The inventory of prey ingested shows a significant diversification with 32 types of prey
distributed over different zoological groups. Decapods are the main preferential diet of S.
aurata, followed by Bivalves, Gastropods and Actinopterygii fishes. This food composition
seems to be different depending on the season, the sex and the size range of the individuals.
The reproduction of S. aurata was studied by considering: the reproductive cycle, the sex
ratio, the weight indices and the determination of the size at the first maturity. The numerical
proportion of males (68%) differs significantly from that of females (32%) (ε> 1.96, α = 5%).
The gonadosomatic (GSI) and hepatosomatic (HSI) indices of females and males indicate a
single reproduction period. This Spawning period ranges from December to January. The size
at first sexual maturity (Lm50) is 18.3 cm for males and 19.6 cm for females. In Algeria, the
present legislation stipulates a legal minimum catch size of 20 cm (Executive Decree 200486). This regulation is therefore appropriate for the gilthead sea bream.
The growth parameters (of the Von Bertalanffy model) of S. aurata are determined by
analysis of size structures. For all individuals, the linear growth model is:
(
)
The assessment of the current status of the mixed stock was performed using the multispecies
analytical approach of the Thompson and Bell model (1934). The latter showed an optimal
operating status of this mixed fishery in the study area. The model used therefore suggests not
to increase the fishing effort.