Seasonal effect on lactate dehydrogenase and citrate synthase in snapper (Pagrus auratus)

The activities of two enzymes involved in metabolic energy production, lactate dehydrogenase (LDH) and citrate synthase (CS), were determined in the white trunk musculature of snapper, Pagrus auratus (Bloch & Schneider 1801), to determine whether the metabolic capacity reflects seasonal variations. LDH and CS activities for a population of wild fish were monitored on a monthly basis over a period of 1 year and correlated with body length and seasonal variation. Significant correlations were observed between enzyme activity and body length. Increased LDH activity may reflect energy demand for anaerobic burst swimming. In contrast, declining CS activity with increasing body length may indicate a reduction in energy generation. The seasonal variation of CS activity coincided with the somatic growth cycle, increasing from 1.18 U g(-1) white muscle in winter to 1.79 in spring and 1.78 in late summer, whereas LDH activity did not show a clear seasonal pattern. This information could be useful for tracking metabolic capacity in field specimens using simple biochemical analysis.