Keeping Tourament Bass Alive
by Ralph Manns
Many researchers have reported finding that some black bass tournaments have high live-release survival rates of nearly 100 percent, while others have had as much as 60 percent total mortality. The almost universal conclusion is that tournaments in warm months kill more fish. Biologists have recommended short tournament hours, reduced limits, total aeration of livewells, and even abstinence from competitive fishing in summer months. Until recently, we had very little data identifying specific problems associated with livewells and ways to keep bass alive under summer conditions.
Oklahoma researchers* are providing more adequate guidance to competitors. Biologists studied the use of livewells in tournaments, and collected enough data to compare different livewell techniques. Tournament organizers were encouraged to use Weigh-in Kits developed by the Oklahoma Fisheries Research Laboratory and funded by Oklahoma fishing tackle manufacturers to standardize weigh-in affects on bass. Ice was used to cool waiting-line tanks 10oF when water temperatures exceeded 72oF, and salt was used to aid healing of fish slime. By standardizing weigh-in handling procedures, researchers reduced that variable as an uncontrolled influence on mortality, allowing valid comparisons of livewell procedures.
After weigh-ins, bass were held in soft nylon nets and any dead fish were tallied and removed . Control fish were captured by electrofishing, marked, and placed in nets with tournament-caught bass for comparison. Water temperatures and oxygen levels in boat livewells, were measured, and use of livewell chemical treatments and type and timing of pump/aerator operation was recorded. Livewells were manual or timer controlled, with flow-through or recirculating systems.
Some participants were instructed to operate livewell aerators/pumps continuously or at maximum timer setting. Others were given the same instruction, but were also asked to treat livewells with ice and salt , use constant recirculation of water, and to replace water only on a specific schedule. Preliminary tests identified an effective way to use ice in recirculating livewells containing 25-30 gallons of water and up to 15 pounds of bass. By adding an 8 pound block of ice at three hour intervals, livewells were cooled f rom 85oF to near 75oF. Each time ice was added, 50 percent of the livewell volume was exchanged with fresh 85oF water to reduce accumulations of metabolic wastes. The biologists were concerned about introducing chlorine from tap water used to make ice, but found no harmful effects. The small amount of chlorine in tap-water ice may actually reduce infections of fish.
Initial mortality in spring and summer tournaments was very low. Only 11 of 533 tournament-caught bass were dead at weigh-in. Immediate deaths averaged only 1.3 fish per event (1.6 percent) in spring, but increased to 3.5 fish (4.1 percent) in summer events. In three spring contests, total mortality averaged 2.9 percent with a maximum of 5.1 percent and no control bass died. But in summer, total mortality averaged 33.6 percent with a maximum of 43.3 percent.
Oxygen level in livewells modified survival. Bass taken from livewells containing high oxygen levels, more than 6.0 ppm oxygen , (average was 7.0 ppm) suffered only 35 percent post release mortality. But, 51 percent of bass from livewells below 6.0 ppm (average 4.3 ppm) eventually died. About 42 percent of the boats where livewells were run continuously had more than 6 ppm Oxygen, but only 28 percent of those with low oxygen used continuous operation.
For one tournament, weigh-in was held about 19 miles away from the water. Using two sets of scales, it still required two hours to weigh all fish. Twenty percent of the boats did not have, or were not using, recirculating aeration systems. Oxygen levels in livewells with recirculating/aerating systems averaged 6.7 ppm, while those without such equipment average 3.9 ppm, near the point that bass suffer from oxygen deprivation. When tested, continuous aeration increased dissolved oxygen levels from 5.0 ppm to 7.7 ppm.
Few of the control bass showed bacterial or fungal infections (1.7 percent), but 10.8 percent of the surviving tournament-caught bass had moderate to severe infections. Some of these may have died after the six-day holding period expired.
Anglers often believe bass float after death, but 53 percent of those that died were found at the bottom of the nets rather than floating. Fish dead more than 4 or five days often floated, but for typical live releases, fish that swam away would likely be destroyed by turtles and other scavengers and never float to reveal the full extent of post-tournament mortality.
In four 1996 tournaments, anglers that received no instructions on livewell techniques or chemicals created the worst livewell conditions. Water temperatures in wells averaged 84oF and Oxygen levels averaged 4.7 ppm (lowest was 1.7 ppm and highest was 7.6 ppm). Total mortality was 32.2 percent. Anglers using continuous pumps, but no chemical additives, averaged 81.3oF with Oxygen levels averaging 6.1 ppm (lowest was 1.9 ppm). Total mortality was 21.6 percent. Anglers asked to use constant aeration , chemicals, and the three-time icing/replacement sequence had average livewell temperatures of 78.2oF, about 4 degrees less than lake surface temperature. Dissolved oxygen averaged 5.9 ppm, ranging from 3.0 ppm to 8.0 ppm. Total mortality was 18.0 percent. Fewer boats in this group had temperatures over 90oF or oxygen lower than 3.0 ppm, the lethal lower limit. Boats in the first two groups had maximum temperatures near 93oF oxygen below 1.7 ppm
The researchers note that fish released into the open lake may have slightly higher survival rates than those kept in nets. But, oxygen and temperatures at the nets were favorable to survival.
They conclude that to attain low post-release mortality rates at summer contests, all recommended procedures must be used in both the weigh-in line and individual livewells. "First aid" at weigh-ins didn't save bass that were mistreated and stressed in livewells.
Many anglers feared running down batteries, restricted pump usage, and assumed livewell equipment installed in modern bass boats worked . In 1995 events, 71 percent of anglers used automatic timers to cycle aeration pump operation., but recirculating systems that weren't turned on continuously didn't do the job when livewells contained several bass. The study reconfirmed high mortality rates at summer tournaments and revealed the fact that many bass anglers still don't take the possibility of post-tournament mortality seriously enough to use all available life-saving techniques.
Above 70oF, flow-through livewells must operate continuously to keep bass healthy. This technique maximizes oxygen and minimizes deaths. Boat makers are encouraged to install full-time operation switches in addition to intermittent timers and to make oxygen monitor systems available. The use of ice, closed livewells, and a three time water-replacement schedule further improve survival in summer.
Optimum livewell techniques help, but bass still die if weigh-ins aren't smooth and efficient. Fish must be kept in cooled, oxygenated water in the boats or holding tanks while awaiting the scales and handling time should be minimized.
Only 25 percent of Oklahoma contests are held from June though September, and it seems unrealistic to expect all groups to avoid summer events. Shorter contests and multiple weigh-ins help, but paper tournaments, where fish are measured and immediately released, are an even better option. Ralph Manns
by Ralph Manns
Many researchers have reported finding that some black bass tournaments have high live-release survival rates of nearly 100 percent, while others have had as much as 60 percent total mortality. The almost universal conclusion is that tournaments in warm months kill more fish. Biologists have recommended short tournament hours, reduced limits, total aeration of livewells, and even abstinence from competitive fishing in summer months. Until recently, we had very little data identifying specific problems associated with livewells and ways to keep bass alive under summer conditions.
Oklahoma researchers* are providing more adequate guidance to competitors. Biologists studied the use of livewells in tournaments, and collected enough data to compare different livewell techniques. Tournament organizers were encouraged to use Weigh-in Kits developed by the Oklahoma Fisheries Research Laboratory and funded by Oklahoma fishing tackle manufacturers to standardize weigh-in affects on bass. Ice was used to cool waiting-line tanks 10oF when water temperatures exceeded 72oF, and salt was used to aid healing of fish slime. By standardizing weigh-in handling procedures, researchers reduced that variable as an uncontrolled influence on mortality, allowing valid comparisons of livewell procedures.
After weigh-ins, bass were held in soft nylon nets and any dead fish were tallied and removed . Control fish were captured by electrofishing, marked, and placed in nets with tournament-caught bass for comparison. Water temperatures and oxygen levels in boat livewells, were measured, and use of livewell chemical treatments and type and timing of pump/aerator operation was recorded. Livewells were manual or timer controlled, with flow-through or recirculating systems.
Some participants were instructed to operate livewell aerators/pumps continuously or at maximum timer setting. Others were given the same instruction, but were also asked to treat livewells with ice and salt , use constant recirculation of water, and to replace water only on a specific schedule. Preliminary tests identified an effective way to use ice in recirculating livewells containing 25-30 gallons of water and up to 15 pounds of bass. By adding an 8 pound block of ice at three hour intervals, livewells were cooled f rom 85oF to near 75oF. Each time ice was added, 50 percent of the livewell volume was exchanged with fresh 85oF water to reduce accumulations of metabolic wastes. The biologists were concerned about introducing chlorine from tap water used to make ice, but found no harmful effects. The small amount of chlorine in tap-water ice may actually reduce infections of fish.
Initial mortality in spring and summer tournaments was very low. Only 11 of 533 tournament-caught bass were dead at weigh-in. Immediate deaths averaged only 1.3 fish per event (1.6 percent) in spring, but increased to 3.5 fish (4.1 percent) in summer events. In three spring contests, total mortality averaged 2.9 percent with a maximum of 5.1 percent and no control bass died. But in summer, total mortality averaged 33.6 percent with a maximum of 43.3 percent.
Oxygen level in livewells modified survival. Bass taken from livewells containing high oxygen levels, more than 6.0 ppm oxygen , (average was 7.0 ppm) suffered only 35 percent post release mortality. But, 51 percent of bass from livewells below 6.0 ppm (average 4.3 ppm) eventually died. About 42 percent of the boats where livewells were run continuously had more than 6 ppm Oxygen, but only 28 percent of those with low oxygen used continuous operation.
For one tournament, weigh-in was held about 19 miles away from the water. Using two sets of scales, it still required two hours to weigh all fish. Twenty percent of the boats did not have, or were not using, recirculating aeration systems. Oxygen levels in livewells with recirculating/aerating systems averaged 6.7 ppm, while those without such equipment average 3.9 ppm, near the point that bass suffer from oxygen deprivation. When tested, continuous aeration increased dissolved oxygen levels from 5.0 ppm to 7.7 ppm.
Few of the control bass showed bacterial or fungal infections (1.7 percent), but 10.8 percent of the surviving tournament-caught bass had moderate to severe infections. Some of these may have died after the six-day holding period expired.
Anglers often believe bass float after death, but 53 percent of those that died were found at the bottom of the nets rather than floating. Fish dead more than 4 or five days often floated, but for typical live releases, fish that swam away would likely be destroyed by turtles and other scavengers and never float to reveal the full extent of post-tournament mortality.
In four 1996 tournaments, anglers that received no instructions on livewell techniques or chemicals created the worst livewell conditions. Water temperatures in wells averaged 84oF and Oxygen levels averaged 4.7 ppm (lowest was 1.7 ppm and highest was 7.6 ppm). Total mortality was 32.2 percent. Anglers using continuous pumps, but no chemical additives, averaged 81.3oF with Oxygen levels averaging 6.1 ppm (lowest was 1.9 ppm). Total mortality was 21.6 percent. Anglers asked to use constant aeration , chemicals, and the three-time icing/replacement sequence had average livewell temperatures of 78.2oF, about 4 degrees less than lake surface temperature. Dissolved oxygen averaged 5.9 ppm, ranging from 3.0 ppm to 8.0 ppm. Total mortality was 18.0 percent. Fewer boats in this group had temperatures over 90oF or oxygen lower than 3.0 ppm, the lethal lower limit. Boats in the first two groups had maximum temperatures near 93oF oxygen below 1.7 ppm
The researchers note that fish released into the open lake may have slightly higher survival rates than those kept in nets. But, oxygen and temperatures at the nets were favorable to survival.
They conclude that to attain low post-release mortality rates at summer contests, all recommended procedures must be used in both the weigh-in line and individual livewells. "First aid" at weigh-ins didn't save bass that were mistreated and stressed in livewells.
Many anglers feared running down batteries, restricted pump usage, and assumed livewell equipment installed in modern bass boats worked . In 1995 events, 71 percent of anglers used automatic timers to cycle aeration pump operation., but recirculating systems that weren't turned on continuously didn't do the job when livewells contained several bass. The study reconfirmed high mortality rates at summer tournaments and revealed the fact that many bass anglers still don't take the possibility of post-tournament mortality seriously enough to use all available life-saving techniques.
Above 70oF, flow-through livewells must operate continuously to keep bass healthy. This technique maximizes oxygen and minimizes deaths. Boat makers are encouraged to install full-time operation switches in addition to intermittent timers and to make oxygen monitor systems available. The use of ice, closed livewells, and a three time water-replacement schedule further improve survival in summer.
Optimum livewell techniques help, but bass still die if weigh-ins aren't smooth and efficient. Fish must be kept in cooled, oxygenated water in the boats or holding tanks while awaiting the scales and handling time should be minimized.
Only 25 percent of Oklahoma contests are held from June though September, and it seems unrealistic to expect all groups to avoid summer events. Shorter contests and multiple weigh-ins help, but paper tournaments, where fish are measured and immediately released, are an even better option. Ralph Manns