Smallmouth Bass Kills, Livewell Oxygen Problems Every Summer

WEBSITE UPDATED               Tuesday June 22, 2022

Low dissolved oxygen saturation (DO Sat) in aerated livewells and bait tank transport water is the primary cause of summer tournament mortality/morbidity when fishermen overstock livewells. This tournament kill is always predictable.

Small mouth bass are extremely susceptible to the negative effects of hypoxia, high mortality/morbidity during live transport every summer, especially night tournaments and all-night transports in boat livewells and ice chest.

Low oxygen in aerated bass boat livewells kills smallmouth bass every summer, black bass are slightly more tolerant to low livewell summer oxygen problems caused by mechanical aeration. Livewell hypoxia mortality is bad during the day, but it is much worse during summer nights for smallmouths and live bait.

At night microscopic plants in environmental livewell water DO NOT PRODUCE OXYGEN WITHOUT SUNLIGHT and photosynthesis does not occur.  Plants produce no oxygen, the dissolved oxygen level plumets to deadly levels in aerated livewells at night.

Smallmouth/ Largemouth Tournament Bass Kills

SCIENTIFIC FACT: Smallmouth bass do die much quicker in low oxygen boat livewells than Largemouth bass. Smallmouth bass have less tolerance to acute and sustained livewell hypoxia. At night when environmental dissolved oxygen concentrations are lowest, aerated summer tournament boat livewells containing limits of fish are at serious risk of livewell suffocation.   Smallmouth bass die quickly in summer tournament conditions because they do not tolerate even minor livewell hypoxia. They are not like largemouth bass that are more resistant to sustained low oxygen levels in boat livewells.

Increased summer tournament kills can often be predicted by testing the dissolved oxygen saturations (dissolved oxygen meter) in tournament boat livewells upon arrival at the weigh-in site.  DO testing of in   fish bags and DO testing of weigh-in holding tanks and release boat hauling tanks.  Low dissolved oxygen in hot summer environmental water coupled with hooking fighting, landing, the all-day transports in a boat livewell low of oxygen and 3-5 minutes of exacerbating airtime during the weigh-in process and photo op is a tournament killer for smallmouth bass.   “How we caught the fish” speeches while displaying the fish to the public for photo-ops on stage add to deadly airtime and tremendous cellular oxygen debt. Recovery from this induced oxygen debt requires immediate re-oxygenation with pure oxygen, not air and a mechanical aerator.

Unlike a quick merciful death by a stunning desensitizing blow to the head or severed spinal cord, acute and chronic livewell suffocation is slower, more stressful, agonizing insult scientifically called hypoxia.   Hypoxia (medical) – Wikipedia, the free encyclopedia

Bass tournament fishermen and tournament directors know from experience that Smallmouth bass tournament mortality/morbidity is substantially greater than Largemouth bass mortality.  More aeration or bigger water pumps will not provide enough oxygen in slightly overstocked livewell full of smallmouth bass.

Dissolved oxygen saturation requirements for live Smallmouth and Largemouth bass transports have been scientifically tested, identified, established and practiced by all Federal, State, and private fish hatcheries throughout the USA as well as all international live fish transports for decades. Dissolved oxygen saturations are easily measured with a dissolved oxygen meter.

THE DILEMMA:   What’s a Tournament Conservation Director to do when DO saturation test in the contestant’s boat livewell water that’s full of fish is deadly low and the fish are dead, dying and suffocating?

The answer is simple, hiding in sun light… a logical fisherman would give the fish more oxygen of course.

THE FUNCTIONAL LIVEWELL RULE:  To enforce or not enforce this rule is a real “in your face problem” for tournament officials, State Fish and Game departments, State politicians and the media reporting the facts.

WHAT CAN ANY CONTESTANT OR TOURNAMENT OFFICIAL DO TO MAKE THIS LOW LIVEWELL OXYGEN PROBLEM AND HIGH SUMMER TOURNAMENT MORTALITY/MORBIDITY PROBLEM GO AWAY FOREVER?   Provide a safe continuous dose of supplemental oxygen into livewell water, administer enough oxygen to ensure minimal safe DO water quality and not suffocate the catch in summer tournaments. Provide the Best Tournament Fish Transport Care possible in boat livewells all day.

 “Respiratory and Circulatory Responses to Hypoxia in Largemouth Bass and Smallmouth Bass: Implications for ‘‘Live-Release’’ Angling Tournaments”


The results of the present study also have important implications for fisheries’ management. In our experience, hypoxia [low dissolved oxygen saturation during tournament captivity] is one of the most significant factors contributing to fish mortality during live-release angling tournaments.

When adequate precautions are not taken, hypoxia may occur at any of several different stages at these events, including live well holding, bag confinement, weigh-in air exposure, and the holding tanks of the live-release vessels used to disperse the fish at the end of the event.

Since angling tournaments normally target the largest fish in a given system, tournaments that include smallmouth bass should take extra precautions to ensure that sufficient oxygen levels are provided at each stage of the event.

In the future, tournament organizers and fisheries managers should develop guidelines for appropriate oxygen thresholds based on the needs of smallmouth bass, rather than those of largemouth bass, in regions where these two species coexist.

MAROSH FURIMSKY, Department of Biology, Queen’s University, Kingston, OntarioK7L 3N6Canada

STEVEN J. COOKE, Department of Natural Resources and Environmental Sciences,

University of Illinois and Center for Aquatic Ecology, Illinois Natural History Survey, Champaign, Illinois61820, USA

CORY D. SUSKI, YUXIANG WANG, AND BRUCE L. TUFTS*, Department of Biology, Queen’s University, Kingston, OntarioK7L 3N6Canada

Transactions of the American Fisheries Society 132:1065–1075, 2003

Copyright by the American Fisheries Society 2003


We thank Mr. Aaron Lerner, Director of Publications, American Fisheries Society, 5410 Grosvenor Lane, Bethesda, MD20814, ph: (301) 897-8616 (ext 231),  for granting permission to post the title, authors, excerpt, and link to the TAFS article on The Oxygen Edge™ website.

Summing it all Up

Scientific research, fish physiology facts and the application of scientific knowledge provide an opportunity for all catch and release tournament fishermen and tournament organizers to improve not only Bass Tournament Survival, but all freshwater and saltwater species survival.

It’s a personal choice to embrace or to reject the standard professional practices, techniques and technology necessary to ensure safe and effective live fish transport… to reverse and correct hypoxia within minutes after the fish is hooked, fought, captured and landed; and, ensure that safe dissolved oxygen saturations are sustained at professional hatchery standards throughout many hours of transport and captivity.