engleski

Biochemical changes in coho salmon plasma following sea water adaptation

The transfer freshwater/seawater (FW/SW) of coho salmon as anadromous fish is one of the most delicate phases in their lives. During this time fish undergo a variety of morphological and physiological changes. In the Adriatic Sea temperatures and salinities are generally higher than that usually encountered in intensive salmon culture areas, such that growth rates may be optimised at certain times of the year. For this reason we observed in our investigations correlations between plasma electrolite and osmotic balance in coho salmon in the Adriatic Sea. The plasma biochemical parameters (glucose, Ca2+, Cl-, inorganic phosphate (IP) and K+) of two growth groups of coho salmon fry (1+ and 0+) were determined during the 8 days seawater challenge test in the season autumn/winter on four locations in the Adriatic Sea. Fish samples (n=10/time point) were taken in FW (0h), and after the transfer into the sea -1.5, -3, -6, and -12 hours, and also -1, -2, -4, and 8 days following the transfer. Glucose, Ca2+, Cl- and IP were determined by using CHEM-1 analyser, and K+ was determined by using flame photometry . Results: The results obtained show the differences in adaptability of both age-cathegories of the fish (1+ and 0+). Bigger and older coho salmon fry (1+) demonstrate greater tolerance to SW. Average values of Ca2+, Cl- , IP and K+after 8 days in the SW were higher (3.3 mmol/l, 140.8 mmol/l, 5.2mmol/l and 4.9 mmol/l) than those at the beginning of the investigation in FW (3.3 mmol/l, 119.2 mmol/l, 4.6mmol/l and 2.8 mmol/l). Plasma Cl- correlated positevely with condition factor and negatively with blood glucose concentration. This can be explained as a consequense of stress caused by the osmoregulatory adaptation but also as the result of change in energy metabolism.

coho salmon; sea water transfer; plasma electrolyte

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