Stress can cause shock which occurs when the blood circulating system shuts down. Shock and death occurs when substantial bleeding lowers the blood pressure. Exertion on the part of the fish while being played causes lactic acid to accumulate in the fish s muscles. This leads to blood acidification and a temporary disruption of many metabolic processes. Very high levels of lactic acid can cause the brain to start mixing up signals from other organs and may cause shock and death.
Survival is dependent upon blood acid levels returning to normal.
Usually if levels are not restored in 72 hours the fish will die. Stressed fish have an increased oxygen demand, but if oxygen can t reach the muscle tissue because of increased lactic acid levels, the fish becomes badly stressed and dies. Quick retrieval and capture reduces mortality rates by reducing muscular exertion and metabolic stress. Using light tackle for sport may increase mortality rates. This will increases catch and release mortality.