Various factors affect biomarkers in fish, both pollution-related and environmental. Determining those changes in biomarkers that can be attributed to each factor is thus crucial for the correct assessment of the overall condition of aquatic environments, because ignoring environmental influence may lead to a biased image of pollution. In this research, the effects of high hydrostatic pressure (HHP) on selected biomarkers, most of which are often measured in various pollution-related studies, have been studied in silver eel (Anguilla anguilla). For this purpose, two experiments were conducted, using a specially designed hyperbaric chamber system. In each of the experiments, 7 female fish were subjected to the HHP of 5MPa (corresponding to 500m depth) for 3 and 7days, respectively. The fish were kept in normoxic conditions and at constant temperature. A comprehensive battery of biomarkers were measured in the liver (EROD, GST, CAT, SOD, LP, POx, PY), and in gills (Na+/K+-ATPase), and relevant gross indices (HSI, GSI) were also calculated. Only a few biomarkers in the HHP groups statistically differed from control. In the 3day long experiment, a decrease was observed in hepatic LP and PY, and an increase in HSI. In the 7day long experiment, inhibition was found in LP, and induction in POx. No statistically significant changes were encountered in the other biomarkers, which suggest either fish adaptation to the HHP or lack of influence of HHP on these biomarkers.