myers fizzing san angelo 2010
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Barotrauma in Tournament-Caught Largemouth Bass At Amistad Reservoir and Comparison of Treatment Methods
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Barotrauma
•Primary Cause•Removing fish from the high-depth, high-pressure zone to the surface results in a substantial increase in the volume of air within a fish, which in turn, affects fish buoyancy
•External symptoms•swollen belly due to over-inflated air bladder•floating upside down•can not re-submerge•bulging eyes•everted stomach
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Air Bladder Function
•Compensate for pressure-depth relationship in water•pressure doubles for every 33 feet of depth•neutral buoyancy (conserve energy) •more air at deep depths and less at shallow depths
•Air exchange •circulatory system• rete mirabile•very slow •1 hour per 6 inches in depth
air bladder
rete mirabile
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•Fish released immediately after capture
-usually no barotrauma •Fish retained in live wells for later release
-high probability of barotrauma
•Barotrauma is highly specific to tournament-held fish
Barotrauma in Black Bass
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•What depth of capture results in barotrauma?
•Strong correlation between depth of capture and barotrauma
•However, capture depth is not a 100% accurate indicator of barotrauma
Although a fish air bladder is acclimated to a certain depth, fish regularly move up and down the water column to feed and in response to changing environmental conditions
Capture Depth and Barotrauma
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Depth
Barotrauma Treatments
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•Few agencies provide recommendations
•5 of 49 agencies•3 against and 2 promote venting
•Limited scientific study•Barotrauma impact on survival•Comparison of treatment methods
Tournament-weighed black bass
2004 2005 2006 2007 20080
10000
20000
30000
40000
50000•Tournament mortality puts considerable number of fish at risk
•30,000 fish/year at Amistad
•Lowering tournament mortality helps maintain high quality fisheries
Barotrauma
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How prevalent is Barotrauma at Amistad?
What percent of Amistad tournament anglers apply barotrauma treament to their fish?
How much does barotrauma affect survival of tournament-released bass?
Which of the treatment methods is best for increasing survival of affected fish?
Does timing of treatment influence survival of affected fish?
Does amount of experience in applying fizzing affect fish survival?
•Develop scientifically-based best management practices for treatment of tournament-retained black bass afflicted with barotrauma
Study Goal and Questions
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Study Methods
•Five Amistad tournaments in 2009•Assessed 3,625 actual tournament fish for barotrauma•Interviewed 900 anglers/teams•Determined 3-day post release survival of 433 fish•Fish were differentially marked by clipping fins•Stocked into large holding pens •Fish were held for 3-days•Fish were removed, identified according fin clips, and counted to calculate survival
8’ x 10’ x 37’ deep
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Methods•Barotrauma treatment experiments
•Spring 2009 and 2010•464 fish >14 inches collected by electrofishing •Each fish was individually tagged for later identification•Fish were stocked into cages and equally pressurized by lowering cages to 35’•After fish attained neutral buoyancy at 35’ cages were raised to induce barotrauma
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Methods
•Immediate release, no treatment, treatments•Treatment 1 or 5 hours after onset of barotrauma•Minimally trained and hands-on fizzers•Fizzing event data collected (blood, time, etc)•Fish stocked in large holding pens •3-d survival
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Incidence (%)
Event Mo Temp Fish Treat
Bass Champs
1 55 68 24
Bass Champs
2 58 34 17
BASS-Elite 3 60 46 6
FLW-Stren 5 80 35 7
Permian SIT
9 83 42 9
Results: Incidence of barotrauma and treatment
•On average, 45% of tournament-weighed fish at Amistad experience barotrauma
•45% of 30,000 fish/year is roughly 13,500 fish having barotrauma
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Survival (%)
3-day
Event Mo TempBT-neg
BT-pos
Bass Champs
1 55 98 93
Bass Champs
2 58 100 91*
BASS-Elite
3 60 100 93
FLW-Stren 5 80 80 83
Permian SIT
9 83 66 43*
*Chi-square
Results: Barotrauma impact on survival
•For 2 of the 5 tournaments, barotrauma fish had statistically significant lower survival than non-barotrauma fish
•On average, survival was 89% for fish not having barotrauma and 81% for fish having barotrauma
•Barotrauma does indeed negatively affect survival, 8% difference overall
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Survival (%): 3 day
Treatment2009
trial
2010
trialCombined
Controls 100 100 100
BT-Immediate release
100 100 100
BT-no treatment
97 97 97
BT-side fizz 97 97 97
BT-deep release
97 92 94
BT-mouth fizz 89 78 83*
Results: Comparison of treatment methods
*Chi-square
•Side-fizzed and deep-released fish experienced statistically similar survival (94-97%) compared to barotrauma fish not receiving treatment (97%)
•Mouth-fizzed fish experienced significantly lower survival (83%) than untreated barotrauma-fish (97%), suggesting that mouth fizzing lowered survival
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Survival (%): 3 day
Treatment 1 h 5 h
Deep release 94 94
Side fizz 100 94
Mouth fizz 81 86
*Chi-square
Results: Timing of treatment
•Timing of treatment was unrelated to survival regardless of treatment method. Fish survival was statistically similar for fish treated 1 hour versus 5 hours after barotrauma onset.
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Survival (%): 3 day
Treatment Minimal Hands-on
Side fizz 100 94
Mouth fizz 81 86
*Chi-square
Results: Fizzer experience
•For both fizzing methods, fish survival was statistically similar for minimally-trained and hands-on trained fizzers
•Level of training received by fizzers was unrelated to survival
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Survival (%)
Fizz type Blood No blood
Side 90 98
Mouth 43 89*
Results: Bleeding
*Chi-square
•Fish that were bleeding from the needle insertion site had lower survival than those that did not bleed, especially for mouth-fizzed fish.
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Results Summary
•45% of Amistad tournament fish had barotrauma, represents 13,500 fish/year
•6-24% of anglers/teams treated their fish during the tournament
•Barotrauma lowers survival of tournament fish, however by only 8%
•Side-fizzing and deep-release did not increase or decrease survival •Mouth-fizzing decreased survival by 14%
•Timing of treatment did not affect survival
•Level of fizzer experience did not affect survival
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Why did mouth-fizzing cause lower survival?
swim bladder
vertebral columnrete mirabile
fizzing needle
•Trauma to the rete mirabile•Close proximity of anterior kidney and vertebral column•Bleeding -anterior kidney
Anterior kidney
swim bladder
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Recommendations
•Although treatment did not increase survival, we recommend that fish be treated.
•Tournament anglers, organizations, and TPWD receive criticism when fish are floating at release sites. These fish appear dead to the untrained eye.
•Use side fizzing or deep-release as these did not lower survival. Mouth fizzing lowered survival.
•Although overall survival did not differ statistically speaking for timing of treatment, we recommend treatment be applied ASAP after onset of barotrauma.
•Side-fizzed fish treated within 1 hour had 100% survival.
•Only minimal training is necessary to successfully perform side fizzing•Fizzing instructions such as the ones we developed are likely sufficient for most anglers.
Differences exacerbatedDeep water
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Partners
Cooperators
Inland Fisheries staff