Seasonal fluctuations in brain acetylcholinesterase activity and soluble protein content in roach (Rutilus rutilus L): A freshwater fish from northwest Russia

Seasonal fluctuations in brain acetylcholinesterase (AChE) activity and soluble protein (SP) content were studied over a 6-year period in roach (Rutilus rutilus L.) from Rybinsk Reservoir in Russia. There was a significant positive linear correlation between AChE activity and SP content in roach brain for all years (r = 0.49-0.95, p < 0.001). No correlations were found, however, between either parameter and sex, and adults or juveniles. Weak but significant (r = -0.02, p < 0.001) negative correlation was found between AChE activity and fish size. The data revealed two different seasonal patterns in both measures. During 1987, 1990, 1994, and 1995, enzyme activity and SP content were higher in summer than in winter, being associated with changes in water temperature. However, the highest values for both parameters in these years also were reported during spawning. An atypical seasonal pattern in both parameters was observed during Fall 1988 to Spring 1989. In this period, high values for both measures occurred during winter when water temperatures were lowest. (C) 1997 Elsevier Science Inc.