Laboratorial experiments were carried out on juvenile and adults of A. latus to estimate and compare the effect of direct transfer from the control salinity of 1.5 psu to the different salinities of 1.5, 7.5, 15, 30 and 45 psu during the periods of 6, 24, 48 and 96hrs for short term effect experiments. Some physiological parameters (PCV, Osmotic pressure, muscles water content, total protein, glucose, sodium Na + , potassium K + and chloride Cl-) were tested in plasma of the two age stages. Results for all parameters showed a clear ability of adults to Osmoregulate and adapt a wide range of salinities ranged from 1.5 psu to 45 psu and explain why juvenile die at the salinity 45 psu after 48 hrs of transport by showing the insufficiency of juvenile to Osmoregulate and the high exhaustion of body activities in this salinity. The results indicated that the salinity increase caused an increase in plasma PCV, osmotic pressure, (sodium, potassium and chloride ions), total protein and glucose. Also, a decrease in water content of muscles of juvenile and adults. The time of 96 hrs was not enough for juvenile to reach the stable condition at high salinities, while adults showed more constancy at the end time of experiment in all salinities.

The study include the description of fish assemblage in Al- Saffia reservation during the period March 2006 to February 2007. Sixteen of osteichthyes species were obtained, the highest number of species 13 was recorded during July and the lowest 7 in November and January. The largest number of individuals collected was obtained during July (212) and the lowest in February (124). Four species formed 71.02% include Alburnus mossulensis 20.64 % Liza abu19.62 % Barbus luteus16.13 % Carassius auratus 14.46 %. The annual values of richness (D), diversity (H) and evenness (J) were 1.95 , 2.12 and 0.76 respectively .

Two experiments were carried out on fingerlings of Tilapia zillii to estimate the effect of direct transfer from the control salinity of 15 psu to the different salinities of 1.5, 7.5, 15 and 30 psu during the periods of 6, 24, 48 and 96 hrs for short term effect experiments, and after 56 days for long term effect experiment in the salinities of 1.5, 7.5, 15 and 30 psu. Some physiological parameters (P.C.V.; osmolality; water content; Na+, K+ and Cl-, ions; glucose; total protein) were tested in the two experiments. Results of PCV showed a direct proportion with salinity increase, the time (96 hrs) was enough to reach the stable state of PCV. Fishes reach a new stable range of PCV in the salinities of 1.5, 7.5 and 15 psu after 56 days from transfer. Fishes seem hyperosmotic in the salinities of 1.5 and 7.5 psu and hyposmotic in the salinities of 15 and 30 psu. Plasma osmolality of the blood was significantly greater at 30 psu than the control salinity (15 psu), while it was significantly lower in the salinities of 1.5 and 7.5 psu at the time 96 hrs. Plasma osmolality decreased to values close to those of the three salinities 1.5, 7.5 and 15 psu at the time 56 days, indicating a strong osmoregulatory capacity of T. zillii fish. Water content in the muscles of T. zillii had inverse relationship with salinity increase in short term effect experiment. It was decreased significantly (P ≤ 0.05) at the time 56 days from other times in the short term effect experiment at salinities 1.5, 7.5 and 15 psu. Sodium and chloride ions concentrations had a direct proportion with salinity increase in the short term effect experiment. After 56 days from transfer, sodium and chloride ions concentrations reached a stable state and had close values at the three salinities (1.5, 7.5 and 15 psu), Potassium concentration values had a direct proportion with salinity increase and the values decreased with time at all salinities. However, the potassium concentration had a lower value in contrast to sodium and chloride ions. Glucose concentrations in the plasma of T. zillii had a direct proportion with salinity increase after 96 hrs transfer to different salinities (1.5, 7.5, 15 and 30 psu). The glucose of plasma decreased significantly (P ≤ 0.05) at all salinities (1.5, 7.5 and 15 psu) at the time 56 days compared to its levels at times of short term effect experiment. Protein concentration in the plasma decreased significantly (P ≤ 0.05) in the three salinities (1.5, 7.5 and 30 psu) compared with the control salinity (15 psu) at the time 96 hrs of short term effect experiment. After 56 days from transfer, plasma protein values in the three salinities (1.5, 7.5 and 15 psu) had a significant increase from other times in the short term effect experiment at all salinities. The results indicated that the salinity increase caused an increase in PCV, osmotic pressure, plasma ions, glucose, total protein; of T. zillii plasma and decrease in water content of muscles and fish seemed hyperosmotic in the salinities of 1.5, 7.5 psu and hyposmotic in the salinities of 15, 30 psu, also the time of 96 hrs was not enough for fish to reach the stable osmotic pressure at all salinities.

Juveniles and adults of Acanthopagrus arabicus were studied to compare the effect of different salt concentrations (1.5, 7.5, 15, 30 and 45 psu) at 6, 24, 48 and 96 h on activities of the enzymes creatine kinase (CK) in gills, lactate dehydrogenase (LDH) in plasma and alkaline phosphatase (ALP) in intestine. CK and LDH were found to exhibit superior activity in adults compared to juveniles. All enzymes exhibited heightened activity with the increase in salinity and decreased activity with the passage of time in all salinities. Results showed that three enzymes exhibited excellent performance in adults than in juveniles.

The effects of Sudden and Gradual salinities stress on AST and ALT enzyme activity in Oreochromis aureus fingerlings were investigated in two separate experiments in this study. The fingerlings were suddenly transferred to five different set of salinities (5, 15, 25, 35, 45 psu) and gradually each one hour to seven set of salinities (5, 10, 15, 20, 25, 30, 35) psu in two replicate for each salinity for 72 hrs. Fish were killed after that and blood were taken from heart and putted in test tubes for serum separation and serum kept in freeze until doing measurements of AST and ALT enzymes. Results showed that all fishes were died in the salinity concentration 45 psu after 20 hrs of sudden transfer, while a 100% survival rate was recorded in other salinity concentrations. The salinity 45 psu was considered to be out of the O. aureus tolerance range. Findings showed a close correlation of AST and ALT concentrations with salinity increase in sudden and gradual transfer experiments as a result of the stress which occurred during fish acclimation to reach the homeostasis. The remarkable increase in serum ALT and AST of fish groups exposed to sudden transfer compared with gradual transfer groups reflect the better ability of these fishes to adapt in salinity changes of gradual transfer..