Investigation of the physiological responses of Rutilus frisii fish to the stress caused by gill net

To investigate physiologic responses, the induced tensions and stress among Caspian Sea Rutilus frisii caused through gillnet fishing operations were evaluated using fixed gillnets deployed at a depth of 0.5 to 5 m along the shore. The blood samples of the fish trapped at zero, 1, 3, 6, 12, and 24hrs of entanglement were collected for examining their physiologic responses. Blood samplings were done at varying temperature (approximate 100c and 150c). Cortisol, plasma glucose and Heat Shock Protein (HSP70) levels were examined. The results indicated a direct link between stress and water temperature, suggesting higher blood sample values in warmer waters than those of in lower water temperature. In both temperatures, Cortisol contents showed significant differences in the blood samples obtained at all time intervals (P≤0.05). Cortisol accounted for 100% increase level. The amount of Plasma glucose and thermal shock protein (HSP70) did not show any significant difference between blood samples at time intervals (P≥0.05).The amount of plasma glucose and Heat Shock Protein (HSP70) showed a gradual increase, reflecting the impact of timing of stress on the above parameters. The fish perished after 18hrs of entanglement in gillnets. The fish mortalities began six hours following entanglement. This study shows that the acute gillnet-induced stress is highly lethal and that fish cannot tolerate stress and continue to survive for 18 hours in entanglement.