engleski

Aminotransferase responses of coho salmon (Oncorhynchuss kisutch, Walbaum) to sea water challenge test in relation to temperature and salinity

In the Adriatic environment, a decision regarding the most advantageous timing for smolt transfer may be more complex due to higher prevailing temperatures and greater salinities than seen for example in the Pacific. The blood, blood enzymes in particular, as reliable parameters for any metabolic activity, give an indication to the changes which might have caused them. The main objective of this study was to clarify how differently water temperature and salinity affect the apartate and alanin aminotransferase (AST and ALT) levels during sea water acclimation of coho salmon smolts. Challenge test was performed in the Adriatic Sea, Croatia (Cro) and Pacific seawater, Canada (Ca). Blood samples were collected fro eaqual numbers (n=7/time point) of two fish groups at regular predetermined intervals in fresh water (fw) and after entering seawater (sw) for up to 8 days. Enzymes AST and ALT were determined using Chem-1 analyzer. Higher temperatures and greater salinities in the Adriatic than in the Pacific were established. In fw plasma ALT values between Cro and Can coho were not statistically significant. After transfer to sw, ALT-Cro levels decreased and were lower to the 8th day. ALT-Can values decreased during the 24 hours post transfer and then slowly increased to the 8th day. No significant differences were found between AST-Can and AST-Cro levels at the beginning of the experiments in fw. After 8th day plasma-Can were significantly higher than AST-Cro levels (p<0.05). This can be explained as a consequence of stress caused by osmoregulatory adaptation but also as a result of exposure to different water tempreature and salinity.

coho salmon ; aminotransferase ; seawater transfer ; temperature ; salinity

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