بعض الاستجابات الفسلجية لتغير الملوحة في سمكة البلطي الازرقOreochromis aureus (Steindacher, 1864) == Some Physiological Responses of Blue Tilapia Oreochromis aureus (Steindacher,1864) to Salinity Changes
Author name:
رافع عبد الكريم فارس
Supervisor name:
سمية محمد احمد
General topic:
Agricultural sciences
Specific topic:
Zoology - Fish And Marine Wealth
Degree:
Master
University:
University Of Basrah - Faculty Of Agriculture - Department Of Fish And Marine Wealth
Language:
Arabic
University location:
Basrah
First pages:
31T1788 - p.pdf
Abstract:
Tilapia (Oreochromis aureus) was used to investigate the effect of salinity on Osmoregulation and growth. One hundred ninety fish were collected from Al - Sweeb River / Qurna. Acclimation on laboratory conditions was done for 24 days. The abrupt salinity transfer experiment was done using the following salinities : 1.5, 5,10,15,20,25 and 30 g/l during 96 h. Survival rate was calculated and reached to 90% in salinity 20 g/l , while it decrease to 0% in salinity 25 g/l. LC50 was calculated and was 20.44 g/l. Gradual salinity increase was conducted and was shown that survival rate increased to 80% in salinity 30 g/l, while it was 0% in salinity 35 g/l. Growth experiment was conducted for 120 days using the following salinities : 1.5, 5,12g/l. the results showed that food intake decrease to 18%, 37%, 43% with increasing salinity to 5, 12 and 20 g/l (respectively) comparing with the control. The role of gut and muscles in water and ionic regulation, chloride cell aggregation in gills and operculum, oxygen consumption rate, energy usage was also studied during salinity acclimation.The results showed that water content decreased in the muscles to 80.1%, 79.58% during salinity increasing to 5 and 12g/l (respectively) comparing with the control. While the water content in the gut increased to 90.4% and 91.44% with increasing salinity to 5 and 12 g/l (respectively) comparing with the control (83.05%). Ionic content also affected with increasing salinity to 5 and 12 g/l , as Na+ concentration in the muscles increased to 30.33, 38.18 m Mol /kg tissue water (respectively) comparing with the control (19.14 m Mol/kg tissue water). While in the gut, Na+ increased to 34.02 and 42.26 m Mol/kg tissue water (respectively) comparing with the control (18.04 m Mol/kg tissue water). K+ concentration in the muscles also increased to 59.23 and 60.23 m Mol/kg tissue water when salinity increased to 5 and 12 g/l (respectively) comparing with the control (49.3 m Mol/kg tissue water). While in the gut ,K+ concentration increased to 68.61 m Mol/kg tissue water with increasing salinity to 5 g/l and decreased to 57.30 m Mol/kg tissue water in salinity 12 g/l ,comparing with the control.bWith increasing salinity, the percentage of chloride cells in the gill epithelia increased to 7.5% and 9.39% with increasing salinity to 5 and 12 g/l (respectively) comparing with the control (5.7%). In the Opercular epithelia the percentage of chloride cells also increased to 3.33% and 4.04% with increasing salinity to 5 and 12g/l (respectively) comparing with the control (3.07%).After 24 hours of salinity increasing to 5, 12 and 20 g/l, the rate and percentage of oxygen consumption increase to 267.71 mg/kg/h (17%), 306.38 mg/kg/h (34%) and 404.21 mg/kg/h (77%) (Respectively), comparing with the control (228.57 mg/kg/l). The increase in oxygen consumption rate was coincide with increasing in the rate and percentage of energy usage to 0.90 Kcal/kg/h (16%), 1.03 kcal/kg/h (33%) and 1.36 Kcal/kg/h (77%) with increasing salinity to 5, 12 and 20 g/l (respectively) comparing with the control (0.77 Kcal/kg/h).Food intake after four days of increasing salinity decreased to 2.27, 1.73 and 1.58 g/100 g fish when salinity increase to 5, 12 and 20 g/l, comparing with the control (2.76 g/ 100 g fish ).The results of the growth experiment after 120 days of transfer to higher salinities (5 and 12 g/l) showed that the growth rate was affected largely with salinity and temperature, as the weight of fish declined during the first 10 weeks when water temperature was ranged between 24 - 30o c , while significant increase in fish weight was recorded with increasing water temperature to above 30o c.The results of chemical compositions of the whole body at the end of the growth experiment showed a decrease in the fat and protein content with increasing salinity. This may be explained as the fish depend on body storage of protein and fat as
