SEASONAL-CHANGES IN SOME BLOOD-CHEMISTRY PARAMETERS AND IN RELATIVE LIVER AND GONAD WEIGHTS OF PIKE (ESOX-LUCIUS L) FROM THE RIVER DANUBE

Samples from a natural population of pike (Esox lucius L.) from the River Danube were used in a 12‐month study to determine seasonal variations in biochemical parameters of pike blood sera, hepatosomatic index (HSI) and gonadosomatic index (GSI). The ranges of enzyme activities for sample means were: aspartate aminotransferase (ASAT) 252.0–583.8 U 1−1, alanine aminotransferase (ALAT) 4.9–11 ‐2 U1 and alkaline phosphatase (AP) 39.5–91.8 U1−1. The ranges of other parameters analysed in serum were total protein 27.7–40.1 g 1 1, urea 0.57–l.52 mmol 1 1 and creatinine 21.2–118.6 μmol 1 1. The range of sample means for HSI and GSI were 1.28–4.16 and 0.07–20.2 respectively. Temperature ranged from 4.5 to 23.5°C. The activity of serum AP was positively correlated to water temperature in males only, while urea and creatinine showed a positive correlation to water temperature in individuals of both sexes. GSI was correlated significantly with HSI in females. Total protein reached the lowest values during the spawning period, while creatinine levels depended on both the sex and season. Copyright © 1992, Wiley Blackwell. All rights reserved