142
Royer, 2005 ; Ottersen et al., 2004 ; Cort, 1990 ). Furthermore, the size-weight analysis
confirmed that the growth of the BFT is allometric in favour of the total length. In addition, the
temporal analysis showed that there is a variation in total length according to the seasons, on
average between 146 and 181 cm in the spring season and between 244 and 255 cm in the
summer season.
The distribution of bluefin tuna along the Algerian coast is seasonal and governed by
several physical and chemical factors. Indeed, the high abundances of bluefin tuna have been
noticed in water masses with a seasonal variation in physical and chemical factors: first of all,
in the summer season, the temperatures of the water masses are obviously very high (on average
varies between 21.5 and 25.8°C), as is the salinity (on average varies between 36 and 39 psu).
And in the spring season, the water masses cool down due to the effect of the temperature drops
(on average from 12.8 to 16°c), also for the salinity drops on average from 35.4 to 37 psu. The
BFT has a high aerobic capacity (Royer, 2005e), the O2 concentrations in areas of high bluefin
tuna catches vary from 235.6 to 243 mmol.m-3 in the spring season and from 229 to 235.4
mmol.m-3 in the summer season. Chlorophyll (a) is the first link in the food chain and is used
to indirectly identify BFT schools. Average chlorophyll (a) concentrations in areas of bluefin
tuna overabundance are low, ranging from 0.11 to 0.14 mg.m-3 in spring and 0.15 to 0.23
mg.m-3 in summer. According to Teo et al. (Teo et al., 2007d), tagged adult BFT were located
in areas with relatively low surface chlorophyll concentrations. The average nitrate levels in
areas of high bluefin tuna catches vary between 0.01 and 0.04 mmol.m-3 in spring, and between
0.68 and 2.75 mmol.m-3 in summer. The nitrate factor can play the role of an indirect indicator
of the presence of bluefin tuna, as nitrate is a primordial nutrient in the development of the first
link in the trophic chain, phytoplankton populations; (Abboud-Abi Saab et al., 2005;Tham,
1998)Thunnus thynnus has the ability to swim in waters of high energy variability. Wave height
in areas of high catch averages 0.9-1.33m in spring and 0.49-0.62m in summer. Breeding BFT
move to areas with moderate wind speeds and areas with moderate eddy kinetic energy (Teo et
al., 2007d). The BFT has the ability to live in an environment of high variability with respect
to the speed of the sea current. Particularly in spring and summer, it prefers water bodies with
an average current speed ranging from 0.17 m/s to 0.3 m/s and 0.07 m/s to 0.15 m/s respectively.
Multiple linear regression analysis defined the best linear correction model equation (equation
1), chlorophyll a, dissolved oxygen, salinity and temperature explain 70.3% of the variability
in total BFT length. Environmental factors, namely: Temperature, Salinity, Chlorophyll a,
Current speed, Wave height, Dissolved oxygen, and Nitrate, are the determining factors of
bluefin tuna distribution along the Algerian coast.
Prospects: To achieve this, it is important to carry out this research on an adequate spatiotemporal scale, which can be applied to different stages of studies: data, analyses, modelling.
Projections and forecasts. Other variables must therefore be taken into account in the model to
explain variations in the total length of the species studied.
Acknowledgements
The authors would like to thank the researchers of the Laboratoire d'Océanographie Biologique
et Environnement Marin, Faculty of Biology of the Université des Sciences et Technologies
Houari Boumediene and the researchers of the Ecole Nationale Supérieure des Sciences de la
Mer et du Littoral of Algiers Algeria.
Royer, 2005 ; Ottersen et al., 2004 ; Cort, 1990 ). Furthermore, the size-weight analysis
confirmed that the growth of the BFT is allometric in favour of the total length. In addition, the
temporal analysis showed that there is a variation in total length according to the seasons, on
average between 146 and 181 cm in the spring season and between 244 and 255 cm in the
summer season.
The distribution of bluefin tuna along the Algerian coast is seasonal and governed by
several physical and chemical factors. Indeed, the high abundances of bluefin tuna have been
noticed in water masses with a seasonal variation in physical and chemical factors: first of all,
in the summer season, the temperatures of the water masses are obviously very high (on average
varies between 21.5 and 25.8°C), as is the salinity (on average varies between 36 and 39 psu).
And in the spring season, the water masses cool down due to the effect of the temperature drops
(on average from 12.8 to 16°c), also for the salinity drops on average from 35.4 to 37 psu. The
BFT has a high aerobic capacity (Royer, 2005e), the O2 concentrations in areas of high bluefin
tuna catches vary from 235.6 to 243 mmol.m-3 in the spring season and from 229 to 235.4
mmol.m-3 in the summer season. Chlorophyll (a) is the first link in the food chain and is used
to indirectly identify BFT schools. Average chlorophyll (a) concentrations in areas of bluefin
tuna overabundance are low, ranging from 0.11 to 0.14 mg.m-3 in spring and 0.15 to 0.23
mg.m-3 in summer. According to Teo et al. (Teo et al., 2007d), tagged adult BFT were located
in areas with relatively low surface chlorophyll concentrations. The average nitrate levels in
areas of high bluefin tuna catches vary between 0.01 and 0.04 mmol.m-3 in spring, and between
0.68 and 2.75 mmol.m-3 in summer. The nitrate factor can play the role of an indirect indicator
of the presence of bluefin tuna, as nitrate is a primordial nutrient in the development of the first
link in the trophic chain, phytoplankton populations; (Abboud-Abi Saab et al., 2005;Tham,
1998)Thunnus thynnus has the ability to swim in waters of high energy variability. Wave height
in areas of high catch averages 0.9-1.33m in spring and 0.49-0.62m in summer. Breeding BFT
move to areas with moderate wind speeds and areas with moderate eddy kinetic energy (Teo et
al., 2007d). The BFT has the ability to live in an environment of high variability with respect
to the speed of the sea current. Particularly in spring and summer, it prefers water bodies with
an average current speed ranging from 0.17 m/s to 0.3 m/s and 0.07 m/s to 0.15 m/s respectively.
Multiple linear regression analysis defined the best linear correction model equation (equation
1), chlorophyll a, dissolved oxygen, salinity and temperature explain 70.3% of the variability
in total BFT length. Environmental factors, namely: Temperature, Salinity, Chlorophyll a,
Current speed, Wave height, Dissolved oxygen, and Nitrate, are the determining factors of
bluefin tuna distribution along the Algerian coast.
Prospects: To achieve this, it is important to carry out this research on an adequate spatiotemporal scale, which can be applied to different stages of studies: data, analyses, modelling.
Projections and forecasts. Other variables must therefore be taken into account in the model to
explain variations in the total length of the species studied.
Acknowledgements
The authors would like to thank the researchers of the Laboratoire d'Océanographie Biologique
et Environnement Marin, Faculty of Biology of the Université des Sciences et Technologies
Houari Boumediene and the researchers of the Ecole Nationale Supérieure des Sciences de la
Mer et du Littoral of Algiers Algeria.