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
*Gilliland, G. 1997. Evaluation of procedures to reduce
delayed mortality of black bass following summer tournaments.
Final Report, Federal Aid Grant # F-50-R, Fisheries Div.,
Oklahoma Dept. Of Wildl. Consv.
| Author Information.
Ralph Manns is a distinguished outdoor writer whose materials
appear in popular publications such as In-Fisherman
and other outdoor magazines. On the web, he is a contributor at
the Bass Fishing Home Page.
Ralph is a strong proponent of conservation and proper care of
the great bass fisheries and water resources that we must manage
and protect as anglers. His articles always encourage proper
handling of bass by anglers, in livewells, and during weigh-ins.
Email Ralph Manns at rmanns@peoplepc.com |
|
