Abstract
This study is a contribution to the study of the spatio-temporal distribution and growth
biology of a teleost fish Hake Merluccius merluccius (Linnaeus 1758) in Bou-Ismail Bay.
The GIS was used in this work, to acquire, archive, enhance and present in a cartographic
form spatio-temporal databases from different trawling campaigns in a single repository in
order to establish a hake distribution model in Bou-Ismail bay. The temporal and bathymetric
variability of hake densities (ind ./h), biomasses (kg ./h), and demographic structures (sizes
and sexes) was studied using data from three trawling campaigns conducted between 1982
and 2004 at different bathymetric strata (50- 800 mètres) in Bou-Ismail Bay. Statistical
analyses were also used to identify the effects of 22 years of exploitation and depth on the
abundance and demographic structure of Merluccius merluccius. The results of these analyses
showed that the effect of the depth is significant, the highest concentrations of hake appeared
between 100 and 200 metres deep (probably correlated with the presence of nurseries), and
beyond 500 metres, hake has a limited abundance. The overexploitation of European hake has
had an impact on the demographic structure. Indeed, a very significant decrease in the average
and maximum sizes of individuals and in the proportion of females was observed during
1982, 2003 and 2004.
A growth of hake in Bay of Bou-Ismail, attests the hypothesis of rapid growth demonstrated
in other areas of distribution as well as the Mediterranean and the North Atlantique. Growth
follows a linear model size, fast among youth and decreases with age.
This study is a contribution to the study of the spatio-temporal distribution and growth
biology of a teleost fish Hake Merluccius merluccius (Linnaeus 1758) in Bou-Ismail Bay.
The GIS was used in this work, to acquire, archive, enhance and present in a cartographic
form spatio-temporal databases from different trawling campaigns in a single repository in
order to establish a hake distribution model in Bou-Ismail bay. The temporal and bathymetric
variability of hake densities (ind ./h), biomasses (kg ./h), and demographic structures (sizes
and sexes) was studied using data from three trawling campaigns conducted between 1982
and 2004 at different bathymetric strata (50- 800 mètres) in Bou-Ismail Bay. Statistical
analyses were also used to identify the effects of 22 years of exploitation and depth on the
abundance and demographic structure of Merluccius merluccius. The results of these analyses
showed that the effect of the depth is significant, the highest concentrations of hake appeared
between 100 and 200 metres deep (probably correlated with the presence of nurseries), and
beyond 500 metres, hake has a limited abundance. The overexploitation of European hake has
had an impact on the demographic structure. Indeed, a very significant decrease in the average
and maximum sizes of individuals and in the proportion of females was observed during
1982, 2003 and 2004.
A growth of hake in Bay of Bou-Ismail, attests the hypothesis of rapid growth demonstrated
in other areas of distribution as well as the Mediterranean and the North Atlantique. Growth
follows a linear model size, fast among youth and decreases with age.