[Exogenous Sr2+ sedimentation on otolith of chum salmon embryos].

To explore the exogenous Sr2+ sedimentation on otolith of chum salmon embryos, chum salmon embryos were exposed to culture water contained Sr2+ at Sr2+ concentration of 50, 100, 200 or 400 mg . L-1 for 48 h to imitate Sr2+ sedimentation. After a culturing period of 12 d and 100 d, the otoliths of the chum salmon were taken to detect exogenous Sr2+ sedimentation with electro-probe microanalyzer (EPMA). The results showed that obvious deep red strontium signatures were produced in the otolith of chum salmon at different concentrations of Sr2+. The mean and extreme values of peak strontium area were not stable for the same Sr2+ dose, but the lowest of all the peak values was 35.1 times as much as that of control. Overall, the strontium value increased with the increase of Sr2+concentration. The strontium peak had no signs of abating after a culture period of 100 d. The results also showed that strontium was gradually deposited in the otolith, and had obvious hysteresis to immersion. Strontium sedimentation could also return to a normal level after the peak. These characteristics accorded exactly with the requirement of discharge tag technology, which indicated that exogenous Sr2+ was suitable in the marking of salmon otolith.

[Effects of salinity on haematological biochemistrical indices and liver tissue in juvenile Oncorhynchus keta].

In order to simulate the catadromous migration environment of the juvenile salmon (Oncorhynchus keta), five experimental groups containing different salinities (0, 5, 10, 15 and 20) were set up. The juvenile salmons with average body mass of (26.57 +/- 6.32) g and average full length of (14.44 +/- 1.05) cm were cultured for 130 days, and then the haematological biochemistrical indices was analyzed and the structure of liver tissue was observed to investigate the changes in physiological indices during the catadromous migration of juvenile salmon. The results showed that serum osmolality and the concentration of Na+, Cl- illustrated the same tendency with water salinity variation. Specifically, the serum Na+, C- and Mg2+ levels in the salinities of 15, 20 were significantly different from those in the salinity 5 and the freshwater and serum K+ in different salinities were all obviously lower than that in the freshwater. Also, the blood glucose level in salinity 10 was significantly higher than that in salinity 5 and 20, whereas total serum protein (TP), albumin (ALB) and globulin (GLB) levels all declined with the increase of salinity and the serum TP and GLB content in the freshwater group was remarkably higher than those in the salinity 15 and 20. There also existed an obvious discrepancy on total bile acids in freshwater group and the other salinity groups. The alanine aminotransferase (ALT) activity and aspartate aminotransferase (AST) activity in fresh water group were far different from those of the high salinity groups. Furthermore, in the low salinities (0 and 5), the liver cells of juvenile chum salmon partly broke down, and liver tissue was serious vacuolization. Collectively, the growth and survival rate had no significant difference in all groups and according to the physiological and biochemical indices, the appropriated salinity for juvenile chum salmon ranged from 10 to 20 during the catadromous migration.