Barotrauma in Tournament Largemouth Bass and Comparison of Treatment Methods at Amistad Reservoir, Texas

Barotrauma typically occurs when fish are subjected to a decrease in ambient pressure, a result of being angled to the surface from deep water.  The condition has been implicated in reducing post-release survival of tournament black bass.  Afflicted fish experience over-inflated swim bladders resulting in hyper-buoyancy and the inability to remain submerged. Various treatments are used by tournament anglers and organizations to alleviate the condition. We conducted investigations in 2009-2010 involving largemouth bass at Amistad Reservoir, Texas, to formulate recommendations concerning barotrauma in tournament black bass.  Barotrauma incidence ranged from 34 to 68% for five tournament events, impacting an estimated 13,500 fish/year at the reservoir.  Between 6 and 24% of anglers/teams treated their fish for the condition prior to weigh-in, however the majority (68-93%) of afflicted fish were treated by tournament staff after weigh-in.  Barotrauma-afflicted fish left untreated experienced lower 3-d post-release survival than non-afflicted fish for two of the five tournaments.  However, the difference was minimal with survival averaging 81% for afflicted fish and 89% for non-afflicted fish.  None of the three treatment methods were effective for increasing survival of afflicted fish.  Fish receiving side fizzing or deep release experienced similar survival as control fish and mouth-fizzed fish experienced 14% lower survival. Survival was unrelated to timing of treatment (1 or 5 h) and level of training received by those performing fizzing treatments. Although treatment did not increase survival, we recommend that fish exhibiting barotrauma be treated for the condition using side-fizzing or deep-release because untreated floating fish near release sites are exposed to additional sources of mortality such as predation, sun exposure, and injury from boats.