March 13, 2013
By Ralph Manns
In an extensive study of blood chemistry, post-release mortality, and behavior following release of tournament-caught largemouth bass, researchers found significant changes in blood chemistry as a result of stress, and that air-exposed fish took significantly longer to regain equilibrium or to leave release sites.* After 5 days, however, no released bass had died, even those exposed to air for as long as 13 minutes. This study was done at temperatures at 70°F or below, so these findings do not suggest largemouth bass can survive such treatment in warmer conditions. They do suggest that they survive air exposure better than previously believed.
A parallel study at similar water temperatures simulated angling and subsequent air exposure of largemouth and smallmouth bass for up to 10 minutes.** Again, no mortality occurred. There were similar changes in blood chemistry for the two bass species, but the behavior and recovery time of smallmouths were more affected by both exercise and air exposure than largemouths.
An earlier experiment of oxygen deprivation in largemouth and smallmouth bass indicated that smallmouths suffered more stress symptoms than largemouths and were more sensitive to hypoxia in all ways.*** Reducing time out of water is a good handling practice, but not as critical as once thought, particularly for largemouths.
* Thompson, L. A., S. J. Cooke, M. R. Donaldson, K. C. Hanson, A. Gingerich, T. Kleforth, and R. Arlinghaus. 2008. Physiology, behavior, and survival of angled and air-exposed largemouth bass. N. Am. J. Fish. Mgmt. 28:1059-1068.
** White, A. J., J. F. Schreer, and S. J. Cooke. 2008. Behavioral and physiological responses of the congeneric largemouth (Micropterus salmoides) and smallmouth bass (M. dolomieu) to various exercise and air exposure durations. Fish. Res. 89: 9-16.
***Furimsky, M., S. J. Cooke, C. D. Suski, Y. Wang, and B. L. Tufts. 2003. Respiratory and circulatory responses to hypoxia in largemouth bass and smallmouth bass: Implications for "live release" angling tournaments. Trans. Am. Fish. Soc. 132:1065-1075.
