Incidence and physiological consequences of decompression in smallmouth bass after live-release angling tournaments

Decompression can be an important problem for fish that are rapidly brought to the surface. The main objectives of this study were to (1) examine the incidence of external signs of decompression in smallmouth bass Micropterus dolomieu after live-release angling tournaments on lakes with different depths, (2) determine the physiological changes in smallmouth bass that exhibit external decompression signs, and (3) identify the best methodological approaches for evaluating this type of disturbance. Our results indicate that decompression does not cause problems for smallmouth bass when tournaments are held on relatively shallow lakes. However, when tournament anglers have access to deep water (> 5 m), significant numbers of smallmouth bass may exhibit decompression signs after these events. Decompression signs include swim bladder overinflation, increased plasma lactate, and increased activity of tissue enzymes in plasma. Tournament-caught smallmouth bass exhibiting external signs of decompression also experience internal physiological changes, including significant elevations in the plasma levels of intracellular enzymes (lactate dehydrogenase [LDH]; enzyme number 1. 1. 1.27: creatine phosphokinase [CPK]; 1 2.7.3.2; and aspartate aminotransferase [AST]; 2.6. 1. 1), red blood cell lysis, and a larger anaerobic disturbance after the weigh-in than observed in nondecompressed smallmouth bass. Additional laboratory experiments indicate that plasma AST activity may be the most useful indicator of the extent of tissue damage in decompressed smallmouth bass because it is highly correlated to plasma LDH and CPK levels but is not influenced by the blood sampling method.