What Happens After Release? Stress Physiology and Post-Release Mortality of White Marlin Caught in the U.S. Recreational Fishery

White Marlin are a highly migratory species that occur throughout temperate and tropical Atlantic waters and are the basis of a large sport fishery along the U.S. Atlantic coast with the vast majority of fish released after capture. Previous research has demonstrated that relative to standard J-hooks, circle hooks result in a significant decrease in post-release mortality of White Marlin; however, the relationship between fight time, physiological stress, and post-release mortality is not well understood. We examined post-angling physiological stress by sampling blood from 68 recreationally caught White Marlin of which 22 were additionally tagged with pop-up satellite archival tags (PSATs) to follow survival. Physiological data demonstrated that plasma glucose, sodium, potassium, and cortisol had a significantly relationship with fight time and plasma lactate and chloride increased significantly with fight time and water temperature. We inferred 3 mortalities (17%) from PSAT data and models demonstrated that plasma potassium was a significant predictor of mortality. Our results indicate that increased angling times and warmer water result in physiological stress in White Marlin; however, post-release mortality was not related to fight time and was marked by elevated potassium levels.